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by

Michael A. Rampino

- US National Space Transportation Policy, 5 August 1994

On 18 May 1996, America took another small step toward maturity as a spacefaring nation. Under the scorching sun of the New Mexico desert, an attentive media corps readied their cameras. Ground and flight crews monitored consoles and waited for the latest global positioning updates to be received and processed. At 0812:02, a small, pyramid-shaped rocket, the McDonnell Douglas DC-XA, rose from its launch mount on a column of smoke and fire. Unlike today’s operational spaceships, this one landed on its feet after a 61-second flight with all its components intact. This ninth flight of the Delta Clipper experimental rocket was no giant leap for mankind given the limited capabilities of the vehicle, but it proved once again that reusable rockets are a reality--today.

Purpose. The US military must be prepared to take advantage of reusable launch vehicles (RLVs) should the NASA-industry effort to develop an RLV technology demonstrator prove successful. The focus of this research is an explanation of how the US military could use RLVs, by describing and analyzing two alternative concepts of operations.

Background. The most recent National Space Transportation Policy assigned the lead role in evolving today’s expendable launch vehicles (ELVs) to the Department of Defense (DOD). It assigned NASA the lead role in working with industry on RLVs. The United States Air Force (USAF), as the lead spacelift acquisition agent within the DOD, is an active participant in RLV development but with limited responsibility and authority since it is a NASA-led program. USAF leadership has maintained interest in the program, but has focused on ensuring continued access to space without incurring the technical risk of relying on RLV development. The USAF’s initiation of the evolved expendable launch vehicle (EELV) program reflects this approach.

As of this writing, the USAF, on behalf of DOD, is formulating and defining DOD requirements for an RLV in an effort to plan for a possible transition from ELVs to RLVs. Specifically, the NASA-USAF Integrated Product Team (IPT) for Space Launch Activities is currently examining "operational RLV DOD requirements." In addition, the USAF’s Phillips Laboratory started a Military Spaceplane Applications Working Group in August 1995 which may indirectly help identify DOD’s RLV needs. This research is intended to contribute to the ongoing process by describing how the US military should use RLVs.

Research Question. In order to help remedy the lack of specific DOD requirements for an operational RLV, this study will attempt to identify concepts of operations for military use of such a vehicle. Obviously, identifying concepts of operations requires addressing other issues along the way. For instance, the attributes of an operational RLV must first be identified to facilitate development of the alternative concepts of operations. If there are new missions enabled by the vehicle’s reusable nature, missions which are not feasible using ELVs or the Space Transportation System (STS, also known as the shuttle), they must be identified as well. Given the timeline of the RLV program, the year 2012 is a reasonable estimated date for the fielding of an operational system. This date will serve as the basis for analysis in this study.

Assumptions. Four assumptions are worth mentioning at the outset. T feasibility of RLV technology by 2012, a fiscally constrained space budget, and continued US government support for the growth and development of the spacelift industry (encouraging dual or triple-use of related facilities and systems) all seem to be conservative estimates. The fourth assumption could almost go unstated: that US national security strategy will continue to emphasize international leadership and engagement to further American political, economic, and security objectives.

Given the assumptions of fiscal constraint and a government policy of cooperation with and encouragement of the US commercial spacelift industry, any military RLV acquisition strategy will do well to take maximum advantage of possible dual- or triple-use opportunities and economies of scale. For instance, the US military could pursue development of a military RLV which would share design similarities (i.e., hardware components) with commercial RLVs to the greatest practical extent, minimizing military-unique design requirements and thereby lowering costs. Such an approach would also take advantage of the economies of scale possible if the commercial spacelift industry were to operate an RLV similar to the one manufactured for the military. Of course, this assumes there is a need for a military-unique RLV--not just military use of a commercially produced and operated RLV.

One answer to the research question proposed above might be that the DOD does not need RLVs. There may be no requirement for them. One way to confirm or deny this assertion is to examine the relevant requirements documentation.

Spacelift Requirements. An Air Force Space Command briefing on Mission Area Plan (MAP) alignments and definitions lists four functions for a "reusable spacecraft for military ops:" strike, transport, space recovery, and reconnaissance. However, the most recent Spacelift MAP takes a more conservative approach. Using the strategies-to-tasks methodology, the MAP documents five tasks of spacelift derived through the mission area assessment process: launching spacecraft, employing the ranges to support these launches, performing transpace operations, recovering space assets, and planning and forecasting government and commercial launches. Prioritized spacelift deficiencies are determined through mission needs analysis. These nine deficiencies are mainly cost-related concerns, but also include two capability related deficiencies: "cannot perform transpace operations," and "no DOD capability to perform recovery and return." The mission solution analysis concludes that the EELV is the number one priority in the mid-term (within 10 years) although RLVs, orbital transfer vehicles (OTVs), and a space-based range system are desirable in the longterm (within 25 years). The five key spacelift solutions are developing the EELV, completing range upgrades, cooperating with NASA in their RLV program, developing advanced expendable and reusable upper stage systems, and fielding space-based range systems. Although potential RLV applications in other mission areas such as reconnaissance and strike are discussed, these are seen as long-term (10-25 years) capabilities.

The fact that the USAF’s MAP for spacelift (DOD’s by default) does not aggressively pursue the potential of RLVs is not surprising. Being based on the strategies-to-task framework, the MAP process will not identify a deficiency or state a requirement when there is no existing higher-level objective or task calling for a capability. Further, the National Space Transportation Policy clearly identifies NASA as the lead agency for RLV technology demonstration, not the DOD (USAF). Finally, the USAF’s low-risk approach is understandable given the very real need to ensure continued access to space in support of national security requirements. The last time our country relied on a particular spacelift capability, the STS, major disruptions in access to space for national security payloads resulted. The 1986 Challenger accident combined with our national policy to emphasize use of the STS over expendable launch vehicles created a situation USAF spacelift leaders never want to see repeated. Given these factors, it is laudable that the spacelift MAP identifies transpace operations and recovery and return as capability deficiencies and foresees the use of RLVs in reconnaissance and strike missions. These two deficiencies will not be satisfied by EELV development, but they could be used to derive requirements for military use of an RLV.

CINCSPACE Desires. It is interesting to note that a different approach to generating requirements, a revolutionary planning approach, has identified RLVs as promising for broader military applications and sparked the interest of America’s most senior military space commander. In a recent message discussing implementation of the conclusions and recommendations of the Air Force Scientific Advisory Board’s New World Vistas study, General Joseph Ashy, Commander-in-Chief of United States Space Command (CINCSPACE) and Commander of Air Force Space Command, identified reusable launch vehicles as one of the most important technologies cited in the findings of this revolutionary planning effort. General Ashy identified the capabilities to "take-off on demand, overfly any location in the world in approximately one hour and return and land within two hours at the take-off base" as desirable. He further suggested reconnaissance, surveillance and precision employment of weapons as potential RLV applications.

Requirements Identified. For the purpose of exploring military RLV concepts of operations (CONOPS), this paper identifies spacecraft launch and recovery, transpace operations, strike (in and from space), and reconnaissance as potential RLV tasks. The first two tasks flow from the spacelift MAP. The second two tasks are not identified as tasks for spacelift in the MAP, probably because of the inherent near-term emphasis of the MAP, but may prove feasible with RLVs. Further, as shown above, they have been identified as potential RLV applications by the Commander-in-Chief of US Space Command.

Before developing and analyzing concepts of operations for military use of RLVs, current RLV concepts and attributes are summarized and hypothetical attributes of a notional RLV for use in military applications are suggested in the following section. Identifying these notional RLV attributes is a necessary step in the process of answering the research question; they are not intended to be the final word on military RLV design. Following the discussion of RLV concepts and attributes is a presentation of two concepts of operations. The two concepts are intended to roughly represent (1) the current vision of a military space plane and (2) a logical extension of the current RLV concept. An analysis of these concepts of operations follows those descriptions. The criteria used in the analysis include capability, cost, operations efficiency and effectiveness, and politics. The final section summarizes significant conclusions and recommends a course of action for the US military to pursue with respect to RLVs.

In order to facilitate CONOPS development and analysis, a summary of current RLV concepts and attributes, along with some hypothetical attributes of a notional RLV for use in military applications, is appropriate. These notional RLV attributes are not intended to serve as the final word on RLV design, as an endorsement of any particular company’s concept, or as a recommendation regarding whether an RLV should take off or land vertically or horizontally. Describing the attributes of an RLV is simply required to provide a basis for the subsequent analysis. Before stating these attributes, this section first presents an overview of the three RLV concepts proposed by Lockheed Advanced Development Company, McDonnell Douglas Aerospace, and Rockwell Space Systems Division, as well as the Black Horse transatmospheric vehicle (TAV) concept made popular by Air University’s SPACECAST 2020 project. Next, RLV attributes are discussed in terms of the requirements introduced earlier. Finally, the attributes of a notional RLV to be used for further analysis are presented.

Definitions. The lexicon associated with RLVs can be confusing. Often, the term RLV is used interchangeably with terms such as SSTO, for single-stage-to-orbit; TAV, for transatmospheric vehicle; and MSP, for military spaceplane. Unfortunately, there doesn’t appear to be a consensus that these terms are interchangeable. The term RLV is not interchangeable with SSTO. A one-piece expendable rocket might also achieve orbit with a single stage, and a completely reusable multi-stage vehicle could be constructed. The term TAV tends to be used in connection with winged, aircraft-like vehicles which operate substantially in the atmosphere while maintaining some capability to reach orbit. The term MSP also carries the notion of an aerodynamic "plane." For the sake of clarity, the term RLV will be used here to refer to a completely reusable vehicle which is capable of achieving earth orbit while carrying some useful payload and then returning.

RLV Concepts. Three companies are currently participating in Phase I of the NASA-industry RLV program, the concept definition and technology development phase. One of these three will be selected to continue developing its RLV concept in Phase II of the program, the demonstration phase. NASA has scheduled source selection to be complete by July 1996. The winner of this source selection will develop an advanced technology demonstration vehicle, the X-33, which will be used to conduct flight tests in 1999. The focus of this second phase will be to demonstrate aircraft-like operations and provide enough evidence to support a decision on whether or not to proceed with the next phase in the year 2000. Phase III of the RLV program would include commercial development and RLV operations. The decision to enter Phase III will be a complex one. It will depend on Phase II results as well as many other contextual factors bearing on decision makers at the turn of the century. In keeping with the recommendations of NASA’s Access To Space Study, all phases of the RLV program are to be "driven by efficient operations rather than attainment of maximum performance levels."

All the RLV concepts are currently focused on satisfying the requirement to deliver and retrieve cargo from the international space station, Alpha (ISSA). This, perhaps artificially, drives a certain payload requirement (see Table 1). All three concepts use cryogenic propellants, liquid oxygen and liquid hydrogen, to achieve high specific impulse. Other common attributes are based on objectives of the RLV program, such as the mission life and maintenance requirements. The required thrust-to-weight ratio (F/W), specific impulse (I_sp), and mass fraction are based on current estimates and analysis. Current cost estimates are based on paper studies. The estimates vary widely and are affected by the size of the RLV, the number built, whether or not they are certified to fly over land, the basing scheme, other aspects of the concept of operations, and the acquisition strategy, to name just a few of the factors involved. For example, a smaller, lighter, and less capable (with respect to payload) RLV would presumably prove cheaper to build and face less technical risk in development.

Where the three RLV concepts diverge is in their propulsion systems and takeoff and landing concepts. Lockheed Advanced Development Company’s (LADC’s) RLV would be a lifting body using linear aerospike rocket engines as opposed to more traditional rocket engines with bell-shaped nozzles. The vehicle would takeoff vertically and land horizontally (VTHL). McDonnell Douglas Aerospace’s (MDA’s) RLV would be a conical reentry body using traditional bell-shaped nozzle rocket engines. The vehicle would takeoff vertically and land vertically (VTVL). Rockwell Space System Divisions (RSSD’s) RLV would be a winged body using traditional bell-shaped nozzle engines. Like the Lockheed concept, Rockwell’s is a VTHL vehicle (see Figure 1 for an artist’s concept of all three vehicles).

(Left to right: Rockwell, McDonnell Douglas, and Lockheed RLV concepts)

Black Horse. The Black Horse TAV concept was identified by Air University’s SPACECAST 2020 as the most promising spacelift idea evaluated by the team. The Black Horse is included here for comparison because is continues to be of interest to military spaceplane advocates and provides an interesting contrast to the concepts being explored under the NASA-led RLV program. However, this is not a fair comparison. The Black Horse does not come close to achieving the RLV payload capability (see Table 1). Also, some analysts have doubts about its technical feasibility. Even if Black Horse were technically feasible, the market for small payload launchers is highly competitive and includes the most operationally responsive of all expendable vehicles. This would likely limit Black Horse’s utility to only military missions, and perhaps just a subset of those.

The officially stated requirements for the RLV concepts currently being proposed do not include conducting military operations such as reconnaissance and strike (in and from space). As discussed above, there is growing support for developing a system that is capable of accomplishing these missions. It will be a great challenge to identify a system that (1) meets these military requirements, (2) does not require a great increase in the military space budget, and (3) satisfies civil (non-DOD government) and commercial needs.

Payload. The payload capability required of an RLV is a very important attribute. Determining the desired payload weight and size capability based on anticipated requirements for delivering and retrieving satellites and other cargo to and from orbit, flying reconnaissance payloads to space and back, and delivering weapons on the other side of the earth is not enough. Determining the desired payload weight and size must also be tempered by the technical risks, monetary costs, and operational costs which might be incurred as a result of establishing the payload requirement. The payload requirement drives the vehicle’s physical size, engine performance requirements, development cost, and other attributes. There is general, although not complete, consensus that a smaller RLV than currently conceived by NASA may be more feasible. An argument for the smaller vehicle can be made based on several factors.

First, the National Research Council’s recent assessment of the RLV Technology Development and Test Program indicated that scaleability of structures from the X-33 test vehicle to a full-scale RLV is an area of uncertainty. The report also concluded that "an increase of 30 percent or more" in current rocket engine performance will be required for the full-scale RLV. The X-33 engine will not satisfy full-scale RLV performance requirements, so development of a new engine will be required. The report estimates it will take a decade to develop. The report does not comment on the feasibility of developing a full-scale RLV, but identifies the necessary engine development as a "difficult challenge." These conclusions suggest that developing an RLV closer in size to the X-33 would minimize potential scaleability problems and reduce the requirement for increased engine performance. The result would be less technical risk.

Second, incurring less technical risk may also directly contribute to incurring less financial risk. If RLV development can avoid the need to develop engines with thrust-to-weight ratios of more than 75, then non-recurring costs may be reduced. Cost is an important consideration for both government and commercial funding. As discussed above, reducing the cost of access to space, not performance, is the primary driver for the RLV program.

Third, the greatest demand for launch services is not in the area of delivering 40,000 pound payloads to low-earth orbit (LEO). Recent forecasts show the greatest demand to be in the medium and small payload class, not more than 20,000 pounds to LEO, and less than 10,000 pounds to geosynchronous transfer orbit (GTO). These forecasts may indicate that sizing an RLV to compete in this market is more likely to result in a successful commercial development. Developing a less expensive vehicle which can satisfy commercial requirements as well as the majority of government requirements has the greatest potential for economic development. Of course, a larger RLV could deliver smaller payloads, perhaps more than one at a time, but it is not at all clear that using the larger RLV would be more efficient. The Titan IIIC, a large spacelifter originally designed to support launches of the Dynasoar spaceplane, never caught on as a commercial vehicle. The Ariane 5 was originally designed to launch the Europeans’ Hermes spaceplane which has since been canceled. It remains to be seen if the heavy-lift Ariane 5 can become a commercial success without government assistance.

An argument against developing a smaller vehicle can be made based on the fact that it would not satisfy all the government’s requirements. For instance, it might not be able to deliver the necessary cargo loads to the space station or launch the largest national security payloads. Some suggest that even commercial payload size is on the increase. This deficiency could be addressed in several ways. First, a large RLV could be developed after the smaller version, allowing more time for technology maturation and the development of an experience base with the smaller RLVs. In the interim, the large government payloads could be delivered using existing systems or the heavy-lift version of DOD’s EELV projected to be available in 2005. Second, the large payloads could, in theory, be made smaller, by taking advantage of miniaturization or by assembling modular components in orbit. Making payloads smaller may not be a panacea, especially for space station loads, but there is some evidence that the DOD is moving in this direction. Third, a technique referred to as a pop-up maneuver may be used to deliver large payloads with a smaller RLV. The pop-up maneuver is essentially a non-optimum staging maneuver in which the payload, with an appropriate upper stage, is deployed only a few thousand feet short of orbit. This maneuver can significantly increase the payload capability to orbit (or into an intercontinental ballistic trajectory). The pop-up maneuver requires the physical dimensions of the payload bay in the smaller RLV to be sized to accommodate the largest payloads the vehicle is planned to fly. It also forces the RLV to land downrange and be flown back to the primary operating base.

Cargo area dimensions for an RLV are under study, and recommendations vary considerably. NASA’s Access To Space Study considered payload bay lengths of 30 and 45 feet--large enough for space station cargo but still too small for some national security needs. The USAF’s Phillips Lab has proposed a 25-foot-long payload bay to satisfy military requirements. One RLV competitor, Rockwell, believes a 45 foot payload bay is needed even to accommodate "future generations of commercial satellites and their upper stages."

Propulsion and Mass Fraction. Propulsion and mass fraction are important attributes of an RLV, but are not stated as desired attributes here. The appropriate figures would result from design of an RLV to meet other requirements.

Takeoff and Landing Concept. An RLV’s methods of takeoff and landing are significant to the extent that they affect its operations. Obviously, the need for a runway limits basing and delivery access options. The VTHL vehicles will also require some means for erection prior to launch. On the other hand, even a VTVL vehicle will require some unique basing support, such as a 150-foot-square grate. Both approaches require cryogenic fuel facilities which are not typically available at most airfields. Perhaps more important than whether an RLV lands vertically or horizontally is the overall ease and simplicity of operations achieved through its design.

Cross-range Capability. The term cross-range capability, as used here, refers to the ability of an RLV to maneuver within the atmosphere upon its return from space. This does not include the ability of an RLV to change its orbital path while in space. An RLV’s ability to maneuver in space is a function of its propulsion system and available propellant. To some extent, an RLV may be able to trade payload weight carried for fuel increasing its ability to change its orbital path. However, given the mass fractions required of an RLV, trading all the payload capacity may still translate into very little out-of-plane maneuverability. The ability of an RLV to maneuver within the atmosphere is a different matter. It could be a significant advantage during contingencies requiring an abort while ascending or a change in landing location while returning from a mission. This capability could also prove very useful in military applications. For ascent contingency purposes, 600 nautical miles is adequate. If the vehicle must land at the same base from which it took off after one revolution around the earth, then a cross-range on the order of 1100-1200 nautical miles is required. The cross-range capability requirement for certain military missions could potentially be higher.

Turnaround Time. For commercial and civilian applications, this attribute is primarily an efficiency question. It will contribute to determining how many RLVs are needed and the nature of launch base facilities. For military missions, this attribute is not only related to efficiency, but effectiveness as well. Reconnaissance and strike missions in particular could be facilitated by shorter turnaround times. Related to turnaround time is the issue of responsiveness, how long it takes to prepare an RLV for launch. Again, military missions are likely to demand quicker response times.

Mission Life. This attribute is closely related to costs. Given the current uncertain state of RLV technology, it is hard to predict what a reasonable mission life would be, so the figure of 100 has been established. Some think a 500 mission life is a reasonable expectation. The frequency of required depot maintenance is also difficult to anticipate.

Other Attributes. There are several other attributes not yet addressed which can significantly affect RLV operations, such as the ability to operate in adverse weather conditions, and crew size. Today’s spacelift vehicles are severely constrained by weather, from lightning potential, to winds at altitude, to winds on the surface. Delays due to weather can add to the cost of operations and dramatically decrease responsiveness. A truly operational RLV, especially one which will conduct military missions, should be able to operate in all but the most extreme weather conditions. A truly operational RLV should also require smaller operations crews than are required by current systems. Today, thousands of people are employed in STS launch base operations at Kennedy Space Center. Unmanned, expendable launch vehicle operations at Cape Canaveral Air Force Station require hundreds of people to launch a vehicle. These figures should be well under 100 for an operational RLV. Finally, all payloads should use standard containers and interfaces to facilitate operations efficiency and responsiveness.

A review of current concepts under study and development in support of the RLV program provides reasonable bounds for requirements or desired attributes for a notional RLV which could be used to support military missions. At the same time, one of the assumptions underlying this paper is continued fiscal constraint. This assumption is the basis for a desire to maximize dual- or triple-use (i.e., military, civil governmental, and commercial use) of an operational RLV to the greatest extent practical. If more user requirements can be satisfied, especially those of commercial operators, it is more likely that funding will be available and that economies of scale can be achieved. Of course, trying to satisfy too many requirements with one vehicle could lead to failure. Defense procurement history is filled with programs that attempted to satisfy so many users that they failed to stay within budget, stay on schedule, or deliver the desired operational capability. With this caution in mind, the attributes of a notional RLV to be used as the basis for analysis are described below.

The notional RLV should be able to deliver 20,000 pounds to a circular LEO with an altitude of 100 nautical miles (see Table 2). This payload weight capability should also allow the vehicle to deliver commercial communications satellite-sized payloads to GTO, carry reconnaissance payloads on orbital or suborbital missions, and deliver significantly more weapons payload than today’s F-16 and F-117 fighter aircraft or as much as an SS-18 heavy intercontinental ballistic missile (ICBM). Its propulsion system’s attributes are not described or stated as requirements, but based on current RLV concepts the assumption is that cryogenic rocket engines will be used. The method of takeoff or landing is also not specified. To provide a basis for analysis it will be assumed that any RLV operating base will need no longer than a 10,000 foot runway. If a VTVL vehicle is pursued, this requirement might still exist in practice if it is necessary or desirable to supply an operating base rapidly using large transport aircraft. In any case, this assumption should not constrain choices of operating bases too severely. An RLV used for military applications must have shorter turnaround and response times than what might be necessary or desired for commercial and civil applications, but a nominal one-day turnaround, 12 hours for contingencies, and 6-hour response time do not seem unreasonable based on current concepts. Standard payload containers and interfaces would be used for all missions. Finally, mission life and costs are essentially accepted from the current concepts with one exception. Given the choice of an RLV with less payload capability, the cost figures are estimated to be in the lower end of the range established for a full-scale RLV.

The concepts being proposed for a full-scale RLV under the NASA-industry RLV program are driven by requirements which may not be completely compatible with requirements for a military RLV. The large, full-scale RLV may not target the spacelift market in the most economically viable way. Given the potential to reduce technical risk, save money, and more effectively target the vast majority of user requirements, these attributes for a notional RLV can serve as a basis for CONOPS development and further analysis.

This section presents an outline of two concepts of operations. The first concept, CONOPS A, is intended to be representative of military spaceplane advocates’ visions. It uses the notional RLV described in Table 2. CONOPS A attempts to make the fullest military use of the roughly half-scale RLV to accomplish not only traditional spacelift missions, but also the additional missions of returning payloads from orbit, transpace operations, reconnaissance, and strike (in and from space). The second concept, CONOPS B, is intended to represent a logical extension of the current RLV programs’ goals. It is based on the full-scale vehicle concepts currently being proposed under the RLV program (Table 1). CONOPS B also attempts to make expanded use of RLVs. The capabilities of each RLV used for analysis are summarized below (Table 3).

New systems, weapons, and technologies are usually fielded without the ultimate utility or best application (CONOPS) having been elaborated--the RLV may show its greatest application to have been unanticipated. An RLV may have to be built and operated for some time before its greatest utility is appreciated or the best methods of employment are discovered. In spite of this reality, describing a CONOPS for RLVs at this early stage is vital. Without defining how an RLV force is to be fielded, organized, and operated, its development is bound to be unguided by practical considerations and its utility is guaranteed to be limited.

Constraints and Assumptions. Each concept of operations is intended to conform to the same fiscal environment--they both live within the same budget. Due to this constraint, and as a result of cost estimates presented earlier, the two concepts of operations have different numbers of RLVs available. Since CONOPS A uses the half-scale RLV developed with less technical and financial risk, six are available for employment. Since CONOPS B uses the larger RLV developed with more technical and financial risk, four are available for employment. These figures are based on the development cost estimates presented earlier (Tables 1 & 2).

Overview. Each concept of operations is described in terms of its mission, systems, operational environment, command and control, support, and employment. The missions of spacelift (to and from orbit), transpace operations, reconnaissance, and strike (in and from orbit) contribute to the broader military missions of space superiority, precision employment of weapons, global mobility, and achieving information dominance. The systems description includes not only the RLVs, but also their associated ground systems and payloads. The operational environment addresses threats and survivability issues while command and control deals with command relationships as well as authority and responsibility for the mission and the people. Support addresses the numerous activities required to conduct successful operations. Finally, the employment discussion illustrates concepts of how the systems may be used throughout the spectrum of conflict, from peace to war and back to peace.

Mission. The missions of the RLV force are to conduct spacelift, transpace, reconnaissance, and strike operations. Spacelift operations include deployment, sustainment, and redeployment of on-orbit forces--earth-to-orbit, orbit-to-earth and intra-space transportation. Transpace operations involve delivering material through space, from one point on the earth’s surface to another. Reconnaissance missions are not limited to the earth’s surface, but include inspection of adversary space systems as well. Similarly, the strike mission may be accomplished against surface, air, or space targets. Strikes within space will likely be accomplished with directed energy, high power radio frequency (HPRF), or information weapons rather than explosive or kinetic impact weapons to minimize the chance of debris causing fratricide.

In peacetime, routine launch and recovery of spacecraft and reconnaissance will be the primary occupations of RLV forces. Exercises, training missions, and system tests will also be accomplished. During contingencies, requirements for responsive launch, transpace operations, and more frequent and responsive reconnaissance are likely. Contingencies may also include the need for heightened readiness to accomplish strike missions. During wartime, the full range of missions must be anticipated. Actions to achieve control of the space environment, such as reconnaissance and strike against adversary space systems, as well as surge launch and transpace operations will be conducted. RLVs may be called upon to accomplish prompt strikes against surface targets early in a conflict in an attempt to disrupt an adversary offensive. Once hostilities have passed the opening stages, RLV operations would continue, complementing the capabilities of forces from other environments. For example, strikes from space may enable attacks on targets which would otherwise be beyond the reach of air, land, and sea forces. Strikes from space may also enable attacks against targets deemed too heavily defended for non-space forces. Once hostilities have ceased, RLV forces may be called upon to conduct reconnaissance missions and provide a deterrent force so air, land, and sea forces may redeploy. RLV strike readiness could be maintained to ensure a prompt response if an adversary decided to take advantage of force redeployment and resume hostilities.

Systems. Six RLVs with the attributes described earlier are available (Tables 2 and 3). Payload capabilities include a wide range of systems all using a standard container and interface. Spacecraft, reconnaissance payloads, and weapons dispensers use the same standard container to ensure simplicity and ease of RLV operations. For surface attack, weapons options include maneuverable reentry vehicles which may contain a variety of munitions and guidance systems depending on the nature of the targets to be struck. For strikes within space, weapon options include directed energy, HPRF, and information munitions. In-flight vehicle operations and control may be affected remotely; however, the vehicle is capable of executing all missions based on programs loaded prior to takeoff. The ability to operate autonomously helps minimize the force’s vulnerability to electronic warfare and enhances in-flight security. Communication for purposes such as in-flight operations and control and payload data transfer is available throughout the mission primarily through space-based tracking and data relay spacecraft, though line-of-sight communication with ground stations is possible. RLV self-defense capabilities include its ability to use maneuver and speed to avoid threats, and on-board electronic and optical countermeasure systems which can operate autonomously and through remote control. The vehicle’s thermal protection system gives it some inherent passive defense against lasers. As with vehicle operations and control, in-flight payload operations and control may be affected remotely. The payload functions can also be executed based on programs loaded prior to takeoff. The two primary operating bases are located in Florida and California. Four alternate bases may be used as necessary. Two of the alternate bases are located on the coasts--one each on the East and West coasts. The other two alternate bases are located in the US interior. The alternate bases may be used in the event of contingencies such as those related to system malfunction, extremely severe weather, or threats to primary base physical security. RLV units and personnel also have the capability to establish a contingency base at virtually any airfield in the world with a runway length capable of accommodating large jet-powered aircraft. Other space systems necessary for RLV operations besides the tracking and data relay satellites already mentioned include communications satellites, warning satellites, and space surveillance systems.

Operational Environment. The operational environment of the RLV currently contains few direct threats. However, the proliferation of technology, particularly rocket, spacecraft, and directed energy technology, combined with the increasing importance of space operations to warfighting success indicates that more threats are likely to develop. It would be tempting to follow the air power theorist Guilio Douhet’s example from the 1920s and predict there will be no way to defend against an RLV attack, but this is not likely to be the case. The world’s leading spacefaring nations, America and the former Soviet Union, have already demonstrated the capability to attack spacecraft using ground-based and air-launched kinetic impact weapons as well as co-orbital kinetic impact systems. Lasers and other directed energy devices may also present threats in the RLVs operational environment. When in flight, the RLV’s on-board defensive systems and inherent maneuverability and speed make it difficult for adversary weapon systems to prevent mission accomplishment. The fact that an adversary has to detect the RLV’s launch, predict its orbit, pass that information on to its defense force, and then execute an anti-RLV mission would require a high degree of technological sophistication and operational capability. Striking an RLV will be more complicated than a typical anti-satellite (ASAT) mission where the spacecraft’s orbit is well established, predictable, and less likely to be altered. However, even if an RLV in flight poses a difficult target for an adversary, its associated command and control centers, communications links, and bases are vulnerable to enemy attack. This vulnerability drives the need for warning and other intelligence support, an autonomous operations capability, active and passive operating base defenses, and redundant systems. Secure, anti-jam, low-probability-of-intercept, communications connectivity provides some measure of protection for in-flight vehicle and payload operations and control when autonomy is not acceptable. Assuming vehicle autonomy and security measures for necessary communication links are achieved, the system’s greatest vulnerability will be at the operating base. The existence of alternate bases and the capability to establish contingency bases mitigates this vulnerability when combined with active and passive base defense measures.

Command and Control. RLV forces are divided between military and commercial organizations. During peacetime, four of the six RLVs available are operated by a commercial organization engaged primarily in providing spacelift services. This company also provides commercial remote sensing services. The remaining RLVs are operated by the US military under the Combatant Command (COCOM) of the Commander-in-Chief, United States Space Command. The military RLVs conduct very little spacelift during peacetime to avoid any real or perceived competition with the US commercial spacelift industry. They primarily conduct reconnaissance while training for and exercising their strike and transpace missions.

During times of heightened tension or war, the National Command Authority may direct mobilization of some or all of the commercial RLV fleet based on existing government-industry agreements. These RLVs may then be modified as necessary to conduct military missions. This mobilization of commercial RLVs is necessary to avoid requiring commercial organizations and their employees to accept the increased risk, hardship, and discipline required of military RLV missions. In a war, RLVs used in direct military action or in support of military operations, along with their associated systems, facilities, and personnel, will likely be targeted by the enemy. When CINCSPACE is acting as the supporting CINC to a geographic CINC, RLV forces may be put under the tactical control (TACON) of the Joint Force Commander (JFC) to ensure the most effective use of these systems in direct support of the theater campaign plan. For air and surface strike missions, the Joint Force Air Component Commander will normally direct the use of RLV forces. CINCSPACE directs the use of RLV forces supporting the campaign for space superiority and conducting transpace missions. RLV forces may be used to help wage a campaign for space superiority by conducting strikes and reconnaissance within space, spacelift, and strikes against surface-based elements of an adversary’s space force. The JFC resolves any disputes over apportionment and allocation of RLV forces.

Support. Intelligence support for RLV forces covers a broad range of requirements. Operating base threats must be assessed and threat information provided continuously. Such information will drive defense status and relocation from prime to alternate bases or deployment to a contingency base. RLV surface strike missions will require extensive intelligence support, similar to that required to accomplish precision strikes with today’s air forces or missiles. Strikes in space will require extensive space surveillance support. Some space surveillance information may actually be collected by the RLV itself, but it will require support from systems or a network with broader and continuous coverage of the near-earth environment. Mission planning will require not only the information just described, but very capable computer hardware and software to process planning information inputs and to generate mission programs for in-flight payload and vehicle operations. Security of operating bases is paramount. The greatest threats may come from terrorists or an adversary’s special forces. In this regard, security requirements will be similar to today’s requirements to protect high-value assets at DOD bases in the continental US--except that the threats will have evolved by the year 2012. Logistics support is simplified to the greatest extent practical. Organizational-level maintenance actions at the operating bases are accomplished by military enlisted maintenance technicians organic to RLV units. The primary RLV base on the East coast is home to RLV unit headquarters.

Employment. During contingencies and war, RLV operations consist of three phases: readiness planning, mission planning, and execution. Readiness planning requires being responsive to world events and direction from higher headquarters to maintain a specified readiness posture. At the highest state of readiness, RLVs may be maintained on alert to respond within 6 hours for surge spacelift, transpace, reconnaissance, or strike missions. The RLV force’s ability to execute specific missions within 6 hours may be constrained by factors beyond the control of the RLV force. For instance, orbital dynamics may dictate an appropriate launch time for a particular spacecraft deployment, space strike, or space reconnaissance mission that falls beyond the 6 hour response time--the RLV may be available, but physics will require waiting longer to execute the mission. Maintaining alert at the highest state of readiness impacts RLV availability to conduct routine missions. Mission planning is conducted once a hypothetical or actual mission tasking is received. Mission planning is conducted by the RLV unit, nominally within one hour for any mission, taking full advantage of the support outlined above. Mission planning includes payload selection and generation of mission programs to be loaded prior to takeoff, assuming the specified mission has not been previously planned and stored for later use. The execution phase of RLV operations includes final launch preparations, launch, flight operations, and recovery. Recovery is normally at the base from which the sortie generated. System malfunctions, extremely severe weather, or threats to base security may drive recovery at another base. Transpace operations may require establishment of a contingency base and operations from that location. RLV recovery is followed by immediate preparation for subsequent missions. Deployment to an alternate or contingency base may be directed by higher headquarters or the local RLV unit commander.

Mission. The missions of the RLV force are to conduct spacelift, transpace, reconnaissance, and strike operations. The CONOPS B RLV force of four full-scale vehicles is commercially operated. Given the full-scale RLV’s longer turn-around time relative to the notional CONOPS A RLV, its utility for reconnaissance and strike missions during contingencies and war is diminished, but not eliminated. Further, its completely commercial operation complicates use of the RLV fleet in direct military actions. Nevertheless, this CONOPS does include strike operations for completeness and to provide a basis for subsequent analysis.

During peacetime, routine launch and recovery of spacecraft and remote sensing will be the primary occupation of the RLV fleet. During contingencies, requirements for responsive spacelift, transpace operations, and surface reconnaissance are likely. Actions to achieve control of the space environment, such as reconnaissance and strike against adversary space systems, are also likely to be required. During war, surface strike missions may be conducted. Once hostilities have ceased, RLV forces may be called upon to conduct reconnaissance missions and maintain some level of strike readiness.

Systems. Four RLVs with the attributes described earlier are available (Tables 1 and 3). Payload capabilities are similar to those described for the CONOPS A RLV in that they all use a standard container and interface, but the weight and size of CONOPS B payloads is larger. In-flight vehicle operations, communications, self-protection systems, and payload operations are the same. The basing scheme includes the same two primary operating bases. There are no designated alternate bases, but the operators have the capability to establish a contingency operating base at virtually any airfield in the world with a runway length capable of accommodating large jet-powered aircraft.

Operational Environment. The operational environment of the RLV is much as described under CONOPS A, except it is less hostile. The apparently civilian, and thus less threatening, nature of peacetime RLV operations would minimize the provocation of hostile action against the vehicles by potential adversaries. Refraining from exercising the RLV fleet in strike operations during peacetime could help to de-emphasize any potential military applications. Exercising strike operations would obviously hurt the RLV fleet’s peaceful appearance, although it would undoubtedly improve the operators’ proficiency to execute the mission. Unfortunately, regardless of whether or not the RLV fleet is used for strike missions, threats from ASAT-like systems as described above for CONOPS A are still likely to exist. Further, as long as the RLV fleet is used in even indirect support of military operations (e.g., surge launch of spacecraft used to support military surface or air operations), it will be a potential target of enemy action.

Command and Control. The RLV force is owned and operated entirely by a commercial organization. The company provides spacelift and remote sensing services for government and commercial customers. US government agreements with the RLV operator include a measure of military oversight and involvement to ensure the RLV force is ready and available to conduct missions in support of national security objectives in peace and in war. The systems are never operated by military personnel, but mobilization agreements allow for close military direction of activities during contingencies and war. The Secretary of Defense may approve mobilization of the RLV fleet during contingencies and war for the purposes of conducting spacelift and transpace operations in support of national security requirements. The President must approve any use of the RLV fleet for strike missions. When mobilized, CINCSPACE exercises COCOM over RLV assets. CINCSPACE also retains operational control (OPCON) and TACON of all RLVs given the fleet’s high value and few numbers. When strike operations are to be conducted, military personnel must be present to provide a measure of positive control.

Support. Intelligence support to RLV forces is much the same as under CONOPS A. Logistics support requirements are less stringent due to decreased readiness required for deployment and mission accomplishment. Maintenance actions are accomplished entirely by civilian personnel. There is no requirement for military personnel to be trained and certified in maintenance or operations tasks. Military personnel simply develop tasks and oversee their execution by the commercial civilian operators. The only exception is with respect to strike missions. Military personnel working with RLV operators must be trained and proficient in implementing positive control measures for RLV strikes. Military personnel are assigned to a detachment collocated with the RLV operator’s headquarters.

Employment. During contingencies and war, RLV operations will be responsive to national security requirements. If directed by the Secretary of Defense, the RLV fleet will be mobilized to conduct surge spacelift and transpace operations. These operations would be conducted in the same fashion as peacetime RLV operations, but with close military coordination. SECDEF mobilization of the RLV fleet will require the civilian operators to meet contingency turn-around and response times of 24 and 12 hours, respectively. CINCSPACE will direct tasks and priorities for the fleet once mobilized. CINCSPACE, in conjunction with the supported CINC if CINCSPACE is playing a supporting role, will determine whether or not RLV strike operations are warranted and request Presidential approval as appropriate. If use of the RLV fleet for strike missions is approved, measures will be taken to ensure military control of these operations.

This section presented an outline of two concepts of operations. The first concept, CONOPS A, attempts to make the fullest military use of the roughly half-scale notional RLV to accomplish not only traditional spacelift missions, but also the additional missions of returning payloads from orbit, transpace operations, reconnaissance, and strike (in and from space). CONOPS A is intended to represent military spaceplane advocates’ visions. The second concept, CONOPS B, based on the full-scale vehicles currently being proposed under the RLV program, also attempts to make expanded use of RLVs, but their application is inhibited by design attributes and completely commercial operation. CONOPS B is intended to represent a logical extension of the current RLV program’s goals.

The criteria used to analyze the concepts of operations described above include capability, cost, operations efficiency and effectiveness, and politics. Capability analysis includes all the required mission areas: spacelift, reconnaissance, strike, and transpace operations. Cost analysis addresses operating base, ELV augmentation, and transpace operations costs, as well as the potential for technology maturation to reduce development costs. Operations efficiency and effectiveness analysis discusses the impact of using cryogenic propellants, deployment operations, and overall system reliability. Political analysis examines the suitability of each CONOPS in both the international and domestic environments.

Each concept of operation described above was intended to satisfy all RLV mission requirements: spacecraft launch and recovery, reconnaissance, transpace operations, and strike (in and from space). Each CONOPS does meet these requirements but, as a result of the differences in the attributes of the vehicles used in each CONOPS and the way in which they are organized, deployed, and employed, their capabilities in each mission area vary to some degree. This variation in the extent to which each CONOPS satisfies mission requirements is examined below.

Spacelift. Both CONOPS provide dramatically improved spacelift capability from a responsiveness perspective. The most responsive of today’s spacelifters requires a minimum of two months from call-up to launch compared with less than a day for either RLV described here. However, when considering spacelift payload capability the two RLVs are not equal. The half-scale RLV used in CONOPS A (RLV-A from here forward) may not necessarily meet all users’ needs from a payload weight and size perspective. If a smaller RLV is developed, an alternative lift means might be required, such as a heavy ELV, if a particular payload can’t be downsized.

At 8.5 meters (28 feet) long and 2724 kg (about 6,000 pounds) unequipped, the US components of the ISSA would fit within the dimensions of RLV-A, not to mention that they will have already been deployed long before the first operational flight of an RLV. However, NASA is concerned about minimizing the number of visits to the space station to avoid disrupting microgravity materials processing work. NASA also has concerns about accommodating the crew module envisioned for transporting US astronauts to and from the station. These concerns appear to be driving a desire for the large payload capability of current RLV program concepts. Another factor behind the large payload requirement is the desire to capture the large national security payloads that currently fly on the Titan IV expendable rocket in the interest of pursuing further reductions in life-cycle costs. It is difficult to predict whether or not these payloads will be lighter and smaller in the future. However, if we plan on building vehicles big enough to carry the largest payloads, it is easy to predict that payload designers will take advantage of the capability.

If large national security payloads cannot, or will not, be downsized, they could be lifted on the heavy version of the DOD’s EELV, predicted to be available in 2005. If large space station payloads cannot, or will not, be downsized, they could be lifted on the heavy version of EELV as well. Large Russian rockets could also be used. In fact, launching into the ISSA orbit from the Baykonour cosmodrome in the former Soviet republic of Kazakstan instead of Cape Canaveral, the planned launch base for American ISSA missions, provides more than a 35 foot per second velocity advantage to the relatively high-inclination orbit, 51.6 degrees. This higher-inclination orbit is the same as that currently used by the Russian space station Mir, which was launched and is resupplied out of Baykonour. Another alternative might be launching large space station payloads on the Ariane 5. The Europeans plan to develop their own manned Crew Transfer Vehicle as part of their participation in ISSA. The Ariane 5 will be able to lift 18,000 kilograms (about 39,600 pounds) to LEO, which is comparable to the payload capacity of the Titan IV.

A final, but not least significant, consideration is the need to return large payloads from orbit. While the Russians or French might happily provide return-from-orbit services using their Soyuz capsule or Crew Transfer Vehicle, respectively, will they be large enough for the loads coming back from the station? As stated above, they might if we plan on using these vehicles and size the return payloads from ISSA appropriately, but certainly won’t if we plan to use a larger vehicle.

Reconnaissance. Some may question the need to use an RLV for reconnaissance given the US ability to perform space-based reconnaissance of the Earth’s surface using satellites. However, there may be times when the element of surprise is desired and not likely to be obtained using existing on-orbit assets. It is conceivable that a potential adversary might have enough information about US space-based reconnaissance systems to effectively implement operations security measures and avoid detection. Another motivation for using an RLV in a reconnaissance role is the need for responsiveness. Given a fast breaking contingency, RLVs may provide a quick response not attainable with on-orbit spacecraft, manned aircraft, or UAVs. For instance, a low-orbiting remote sensing spacecraft might not have a given location on the Earth’s surface within its field of view until several orbits have passed. Manned aircraft and UAVs may not allow overflight of a location deep within the target country’s territory.

With respect to reconnaissance within space, one might pose a similar question about the utility of RLVs. There are undoubtedly other systems which can perform space surveillance. Paul Stares, in The Militarization of Space, claims that the USAF attempted to develop a satellite inspection system (SAINT) in the earliest days of the space age. It was canceled in 1962, but Stares suggests the US ability to survey space was not degraded since advances in ground-based sensors made by the mid-1960’s facilitated the gathering of a great deal of data. This may be true, but on-orbit reconnaissance may allow for more detailed as well as active inspection of spacecraft in LEO. Reconnaissance of payloads in higher orbits, such as geosynchronous earth orbit (GEO) or Molniya orbits, may require reducing the reconnaissance payload weight or may have to be conducted from a greater distance. This reconnaissance capability might also support strike missions in space with pre-strike target information and post-strike battle damage assessment inputs.

Strike. Accomplishing strikes using RLVs is technically feasible. However, to be militarily useful, the vehicles should be able to deliver significant weapons payloads. With respect to surface strike, it appears RLV-A can deliver as much payload as a typical modern fighter. RLV-B can deliver as much weapons payload as a B-2 Spirit stealth bomber. Obviously, there are additional considerations besides payload weight when analyzing surface strike capability. Response and turn-around times have a dramatic effect on the usefulness of RLVs for surface strike missions. Both RLVs could deliver initial strikes earlier than B-2s. Due to RLV-A’s quicker response time and shorter turn-around time, it compares favorably with the strike capability of a cost-equivalent number of B-2s conducting strikes over a two-day period even though RLV-A’s payload capability is roughly half that of the B-2 (Table 4 and Figure 2). RLV-B, on the other hand, cannot compare as favorably through this same period despite its relatively large payload capability (Table 4 and Figure 2). The B-2s’ strike capability exceeds that of both RLVs over a three-day period.

 

Figure 2: Cumulative 2,000 Pound Weapons Delivery Within Three Days

Strike in space using RLVs is also technically feasible. Both concepts include the capability to strike adversary spacecraft. The means used and type of strike are only limited by the creative development of strike mission payloads. For instance, RLV space strikes might be accomplished in a manner which minimizes debris and affects only a specific subsystem on board the target spacecraft. Information strikes causing disruption of adversary communications and command and control, or aimed at deception, might also be conducted. Strikes against spacecraft in high Earth orbits, such as GEO or Molniya orbits, may require reducing the strike payload weight or be conducted from a greater distance.

Transpace Operations. As defined earlier, transpace operations involve transportation through space from one point on the earth’s surface to another. The requirement for this capability is not very well defined. One might easily doubt its feasibility except that any RLV capable of recovering and returning payloads from orbit will have an inherent capability to deliver cargo from one location on the earth to another. Putting aside cost considerations for the moment, a major factor in assessing the feasibility of transpace operations is the ability to establish an RLV operations base at the pick-up and delivery points. Experience with the sub-scale, sub-orbital McDonnell Douglas Aerospace DC-X can only hint at what an operational RLV operating base might look like. The base established for DC-X (now called the DC-XA in its modified form) operations at White Sands Missile Range includes propellant facilities, electrical power facilities, vehicle control systems, and connections. The propellant facilities include liquid oxygen, liquid hydrogen, gaseous helium, and gaseous nitrogen storage tanks, transfer lines and control systems. The vehicle control systems include ground control systems and a "real-time data system" to collect, store, and display vehicle data centrally before, during, and after flight. The real-time data system also provides a means for operator intervention, if necessary, and allows for receipt, processing, and loading of autonomous flight operations programs. While an operational RLV design should include operations efficiency considerations, any RLV operating base will certainly require very large propellant facilities and associated equipment. Given that a full-scale RLV, such as RLV-B, will require about 100 times more propellant than the DC-X, the propellant facilities will not necessarily lend themselves to quick and easy transport. In this sense, RLV-A may have some advantage in that its propellant facilities would be smaller than RLV-B’s. Obviously, RLV-A also has less payload weight capability. Without a clear definition of requirements for transpace operations, it is difficult to evaluate this trade-off between the two CONOPS.

Base Operating Costs. CONOPS A is sensitive to base operating costs. CONOPS A includes two primary and four alternate bases as well the capability to establish a contingency base. CONOPS B simply has two primary bases with a capability to establish contingency bases. Launch base costs for today’s fleet of expendable rockets may not be a good indicator of future RLV launch base costs given the objectives of the RLV program. This is fortuitous since today’s launch bases are expensive to operate. Operating the US’s largest and busiest launch base, Cape Canaveral, and its associated range costs about $160 million a year. Experience with the DC-XA is also difficult to use as a basis for estimation since the vehicle is very much smaller and less capable than an operational RLV. The DC-XA launch base also uses existing facilities and equipment at White Sands Missile Range. Nevertheless, industry sources estimate it will cost roughly $50 million to setup an RLV operating base, at a minimum. Using this figure, CONOPS A’s operating base costs may be estimated at $200 million more than CONOPS B’s.

ELV Augmentation. CONOPS A may also require ELV augmentation if large space station and national security payloads are not downsized. The Moorman Study reported that simply shrinking the size of the RLV payload bay from 45 to 30 feet might cost an extra $26.6 billion in ELV costs through the year 2030. Employing foreign heavy lift vehicles could reduce this cost.

Transpace Operations. It is unclear that transpace operations will be economical. If one accepts the program goal of delivering payloads to orbit for $1,000 per pound, then the same estimate may be used for the cost per pound of delivering cargo from one point on the earth’s surface to another using an RLV. Sending cargo internationally, say from New York to Seoul, using an express package delivery service ranges from about $50 per pound for a 1 pound box to $5.70 per pound for a 100 pound box. Sending loads by military airlift is less expensive, but takes longer. For example, shipping a 20,000 pound load on military airlift from Dover Air Force Base in Delaware to Ramstein Air Base in Germany will cost $1.079 per pound and take 3.1 days, if the cargo is given the highest priority. Such costs make it unlikely that RLV cargo delivery will be economically attractive. Whether or not RLV cargo delivery will be militarily useful remains to be seen.

Technology Maturation. A recurring theme in studies related to the RLV program is the idea that program costs can be reduced through technology maturation. A technology development program targeted against specific high-risk areas executed before system development and acquisition can mitigate the technical and financial risks. Advancing the technology readiness of a system from "concept design" to "prototype/ engineering model" prior to entering full scale development can lower development costs by more than 40 percent. Phase I of the RLV program is intended to include demonstration of the maturity level of candidate technologies. The X-33 flight demonstrations at the end of Phase II represent an attempt to demonstrate technological maturity levels. However, the major recommendations of the National Research Council’s recent review of RLV technology indicate a need for more vigorous development of propulsion technology. There is a government-industry effort currently underway that can help address this issue. The Integrated High Payoff Rocket Propulsion Technology (IHPRPT) program has goals for booster, orbit transfer, spacecraft, and tactical propulsion systems. Noteworthy booster cryogenic propulsion goals include achieving a "mean time between removal" or "mission life" of 20 for reusable systems by the year 2000, an improvement of 3 percent in I_sp by 2010, and an increase of 100 percent in the thrust-to-weight ratio by the year 2010. Unfortunately, funding levels for this program have not increased in spite of the start of the RLV program and recommendations by high-level studies to increase funding in this area. Given the critical nature of propulsion technology development to the success of the RLV program and US spacelift competitiveness in general, it is surprising IHPRPT funding has not been raised to the recommended levels.

Cryogenic Propellants. Although cryogenic propellants are the most potent propellant, they are not ideal for operations efficiency and effectiveness. A good historical basis for this assertion is the Atlas missile’s short life as an ICBM. It was relegated to a spacelift-only role in 1965 after being an operational ICBM for less than six years because it was not well suited to the responsive operations and reliability required of an ICBM. The extreme caution needed in fueling the missile immediately before launch kept it from ever meeting its required 15-minute reaction time. It also suffered from a host of reliability problems, many related to its propulsion system. The Atlas was quickly followed by the Titan and Minuteman. The Titan ICBM, using hypergolic propellants, could stay propellant loaded since hypergolics didn’t need constant refrigeration. The Minuteman, using solid propellants, provided outstanding responsiveness and reliability.

The legacy of the Atlas missile’s operational life as an ICBM may provide a caution when contemplating the development of an operational RLV with a goal of high reliability and low operations costs. It may be even more relevant when considering the military use of an RLV that drives quicker turn-around and response times. Today’s Atlas spacelift vehicle outfitted with a cryogenic Centaur upper stage requires cryogenic propellant loading about two hours prior to launch, well within the response time specified for either RLV-A or RLV-B. During test flights in July 1995, the DC-X required a similar timeline for propellant loading and was prepared to demonstrate an 11-hour turn-around time. While these timelines seem to bode well for an operational RLV, there is no denying the relative complexity of cryogenic propulsion systems compared with hypergolic or solid alternatives. This complexity will make achieving RLV operations efficiency and effectiveness goals a challenge.

Deployment. The nature of cryogenic propellants also drives complexity in the RLV operating base. This complexity will challenge designers and operators faced with the problem of how to build, deploy, and operate an RLV contingency base. Ideally, such a base will be deployable by air. This is particularly true in CONOPS A, where dispersion for security and increased responsiveness for military missions is required. As mentioned above, this contingency base capability will also be a key to transpace operations. Power and propellant systems are likely to comprise the majority of the weight and bulk required to be moved. Lessons may be learned from efforts within the USAF to develop multifunction support equipment for aircraft maintenance. Being able to reduce the number of operating base support equipment pieces, as well as their size, could ease mobility requirements. It could also lead to a decrease in the number of personnel required to deploy and reduce the cost of outfitting a contingency RLV operating base. Winston Churchill once said of the Royal Air Force that, "except in the air, it is the least mobile of all the armed services." If the deployability of the RLV force is neglected it might suffer a similar criticism.

Reliability. Air Force Space Command’s Draft Operational Requirements Document (ORD) for the EELV, dated 31 March 1995, defines reliability as "the ability of the spacelift system to successfully accomplish its intended mission." The ORD defines reliability of the schedule or dependability separately as "the ability of the system to consistently launch . . . when planned." The Moorman Study identified three factors which affect spacelift system reliability: complexity, flight rate, and design stability. Considering these factors, one can see evidence of their impact in today’s spacelift systems. The Delta II, the least complex system, has the highest reliability, 100% over the last five years, compared to 84.2% and 85.7% for the Atlas and Titan, respectively. The Delta also has the highest flight rate and the most stable design of today’s expendable systems. The message for RLV development is clear: keep system complexity down, flight rate up, and design stable. The second item, flight rate, may be achieved by capturing the largest share of the launch market practical and/or capitalizing on military applications. The third item, design stability, is aided by requiring standard payload containers and interfaces. Current RLV program competitors already include a standard payload container and interfaces as a key design element.

Unfortunately, the National Research Council’s warning about the need for vigorous propulsion system development may indicate danger ahead for RLV reliability. One of the reliability problems today’s spacelifters face is their lack of performance margin. A robust design approach in the RLV program could avoid this pitfall and lead to increased reliability. Rather than focusing on eliminating variation in performance, a requirement when operating a system with no performance margin, a robust design approach would minimize the effects of variation in performance. If the RLV is designed to be a high-performance system without any performance margin, then the operators will be in the same position as today’s spacelift operators--reliability goals will not have been achieved. This would seem to indicate the desirability of building a system with plenty of propulsion power for its intended operations. As current RLV concepts plan on milking existing engine (SSME or RD-0120) derivatives for their last ounce of capability this will result in fielding a full-scale RLV always operating at its performance limits. In this respect, RLV-A may offer some advantage, as the smaller vehicle is not likely to push propulsion performance requirements to the extent that a full-scale vehicle will.

Any potential lack of reliability is also directly related to cost in that the cost of failure is typically high in the spacelift business. The ability of an RLV to abort and land back at its base during ascent or descent may minimize the cost of failure in flight. However, any unreliability can cause delays which increase costs, although they do so less dramatically than a catastrophic in-flight failure. If an in-flight RLV failure does occur, its cost will be considerably higher than that of losing one of today’s expendable spacelifters.

Finally, as highlighted by the Atlas missile’s ICBM experience, reliability is a key attribute of military weapon systems. As much as cost, reliability will determine whether or not RLVs can successfully perform military missions.

International. No RLV capabilities or operations described in either CONOPS A or B would violate international treaties. To some, this may be surprising. Since the dawn of the space age the popular image of space activities has been that they are peaceful and non-military. This image has been reinforced by governments, including the US government, to help guarantee the use of space for unimpeded reconnaissance. As such, there are international laws and treaties such as the Limited Test Ban Treaty (1963), the Outer Space Treaty (1967), and the ABM Treaty (1972), which restrict military space activities. However, RLV forces can live within these treaties as long as they are not used to carry weapons of mass destruction, conduct antiballistic missile (ABM) testing, deployment, or operations, or interfere with "national technical means (space intelligence systems)" which are being used to verify treaty provisions during peacetime. This is not an exhaustive list of prohibitions, but highlights the main areas of caution for RLV military applications.

Treaties and law are not the only international political concerns related to RLVs. Developing such a dramatic new military weapon capability could appear threatening to other states. It is conceivable that other nations would resent the US’s ability to strike from space or within space with little or no warning. They might respond to this threat by developing similar capabilities, or by developing ASAT or anti-RLV weapons. If deployment of an RLV force were perceived as an attempt to extend American global hegemony it could encourage other states to form alliances against the US. Political scientist Stephen M. Walt suggests that this sort of balancing mechanism led to a favorable balance of power for the US during the Cold War. The Soviets appeared threatening to other states, which drove them into the US camp. Given its completely commercial operations and more inhibited use in strike operations, CONOPS B might prove less threatening and minimize the appearance of US aggressiveness relative to CONOPS A. On the plus side, RLVs could be used for conventional strikes with the range and nearly the promptness of ICBMs, but without the nuclear baggage. Assuming the RLV force would never test or employ nuclear weapons, there should be no international concern about the start of a nuclear conflict with the launch of an RLV.

Domestic. Domestically, one concern which must be addressed is the potential US political concern associated with ASAT deployment. While this would certainly not prohibit RLV development and use in spacelift, reconnaissance, and transpace operations, it might complicate development of a strike capability. If the prohibition stands, strikes in space will not be possible. Surface strikes might be allowed under the ban, but Congress would have to be convinced that the system would not operate in an ASAT role.

On the executive side of the government, NASA Headquarters direction that the RLV must replace the Space Shuttle comes across loud and clear. While this is understandable, viewing an RLV as a shuttle replacement can be detrimental in three ways. First, it can be detrimental if it limits the designers’ and planners’ imagination. Second, it could be detrimental if the shuttle replacement paradigm leads simply to swapping RLVs for space shuttle orbiters, but retaining the same dated concept of operations and support facilities. Third, it could be detrimental if it forces the RLV to accommodate the same large payload sizes and weights as the space shuttle without an objective evaluation to consider if there are better options.

Outside of the government, industry requires profit to survive. NASA leaders have experienced frustration in their attempt to get the private sector to fund a significant share of RLV development costs. NASA administrator Daniel Goldin recently criticized the X-33 contractors for their "lack of courage to step up to the plate and make it happen." The two-stage X-34 demonstration vehicle program has already been a casualty in the effort to encourage industry to fund reusable launch vehicle technology. The contractor team of Orbital Sciences and Rockwell International "withdrew from development of the X-34 launch vehicle after determining it wouldn’t be commercially viable." The reality of industry’s motivation for profit should not be surprising. It indicates that unless government is willing to fund the RLV program completely itself, the design will have to be commercially viable.

It is not likely that the government will completely fund the RLV program. The current budget environment is severely constrained and it can be expected to remain this way for the foreseeable future. Both the public and the Congress want a frugal government. The NASA budget in particular is on a downward trend. In fiscal year 1995, the programmed NASA budget for the year 2000 was $14.7 billion. The fiscal year 1997 program cut NASA’s year 2000 budget down to $11.6 billion. The DOD budget has suffered from the same trend and the future appears to offer little relief. In short, support is not likely to be found for an expensive RLV development effort reminiscent of Cold War-era space and defense programs. RLVs will have to be developed with industry contributions. Again, commercially viability will dictate development investment and timelines.

Using capability, cost, operations efficiency and effectiveness, and politics as a framework for analyzing RLV concepts of operations yields several insights. First, capability analysis indicates either RLV can be used as a multi-role space superiority weapon. Each CONOPS provides for spacecraft deployment, spacecraft sustainment, reconnaissance of the space realm, and strike within space as well as to the surface--key capabilities for controlling the space environment. CONOPS A may require augmentation with large ELVs given its use of the smaller RLV-A. CONOPS B may provide less flexibility and strike utility given its longer response and turn-around times. CONOPS A may have the advantage in transpace operations given the potential for RLV-A requiring smaller propellant facilities and the accompanying relaxation of mobility requirements.

Second, cost analysis indicates advantages and disadvantages for each CONOPS. CONOPS A will be sensitive to operating base costs, and may require the additional expense of maintaining access to space for heavy payloads using ELVs. It is difficult to imagine either CONOPS providing economically competitive transportation from one point on the earth’s surface to another, but there may be some military utility for such missions in the distant future. CONOPS B may suffer in development costs because RLV-B is more likely to push the limits of technology, thus failing to take full advantage of the cost reductions possible through technology maturation. Related to this observation is the final conclusion of cost analysis--funding for propulsion technology development should be increased.

Third, operations efficiency and effectiveness analysis indicates cryogenic propellants will present a challenge to designers and operators. While these propellant systems offer high specific impulse, they do not lend themselves to simplicity and ease of operations. Fortuitously, today’s cryogenically propelled systems meet the required timelines for either CONOPS. Deployability will be a challenge as well. Power and propulsion systems for RLV forces will likely be physically large. Efforts to decrease the size and amount of support equipment will ease the deployment burden. Reliability is perhaps the most important attribute within the operations efficiency and effectiveness category. Conclusions drawn from the analysis indicate RLV-A may have the advantage of wider performance margins and greater reliability assuming no major propulsion technology breakthroughs are made.

Fourth, political analysis indicates a tougher environment at home than internationally for RLVs. Neither CONOPS violates international treaties or laws, although it might be in America’s best interest to soften the RLV’s military appearance, perhaps an advantage for CONOPS B. Domestically, the Congressional ASAT ban would prohibit the use of RLVs for strike missions in space, and complicate attempts to use them for strikes to the surface as well. The domestic fiscal environment poses the greatest difficulty for RLV development. NASA cannot afford to foot the entire bill for an RLV fleet, and industry will only fund what market analysis indicates is a profitable venture. The DOD is also unlikely to fund RLV development independently.

General Schriever, a powerful force behind early developments in US military missile and space capabilities, was premature in predicting the importance of space battles, although the future may prove him correct. Given the increasing importance of space support to recent battles on the land and sea, as well as in the air, his emphasis on achieving space superiority may be more appropriate today. However, it is ironic to read General Abrahamson’s words of almost thirty years later. These remarks reflect the view of the top leader in development of the largest and most lethal space weapon system ever seriously considered for deployment. Yet he chose to emphasize the need for responsive and cost effective space transportation, not weapons, as the key to future space activity of any kind. It is also interesting to note that the program which may be credited with inspiring the current pursuit of reusable rockets, the McDonnell Douglas DC-X, was started by General Abrahamson’s organization.

Having derived RLV requirements, described RLVs and their attributes, elaborated two concepts of operations, and analyzed those CONOPS, conclusions may now be drawn in attempt to answer the initial research question. These conclusions are followed by recommendations and a summary of the research.

RLVs Have Military Potential. It is clear from both the CONOPS and the subsequent analysis that RLVs have potentially important military applications. In many ways, they can provide a multi-role tool to help achieve the space superiority General Schriever discussed almost forty years ago. An RLV’s potential for accomplishing strike missions, especially to the surface, will be higher if turn-around and response times are shorter. Increasing the tempo of operations can make the force appear larger. Military missions also benefit from RLVs with greater cross-range capability allowing the kind of operations described by General Ashy. Taking full advantage of RLVs’ spacelift capabilities may require a paradigm shift in spacecraft design, deployment, and sustainment. The launch on demand strategy possible with an RLV is not in fashion today. Successful implementation of such a strategy will support space superiority, but will require spacecraft ready to launch on short notice and ready to operate immediately upon deployment in orbit. These requirements could motivate development of cheaper, single-mission satellites since it may not be feasible to build and store billion-dollar multi-mission satellites, or to expect them to be operational immediately upon deployment. Capitalizing on the RLV’s ability to recover and return payloads, or to service them on orbit, would similarly require satellite design changes.

RLV Design Effects. The potential impacts of RLV sizing have been addressed throughout this paper. There is no unanimity regarding the proper size for an operational RLV. Nevertheless, many argue that the current size identified for a full-scale RLV as part of the NASA-led program involves high technical risk which means high financial risk as well. This study has suggested that derivatives of current propulsion systems will not deliver the performance levels required, or if they do deliver, there will be no performance margin and reliability will suffer. This assessment may be supported or proven false by further technology development and demonstrations. But due to the limited objectives of the X-33 flight tests, even these demonstrations may fail to give developers and investors the necessary confidence to go full-scale. Perhaps the best course of action with respect to this issue is to ensure marketing analysts, developmental engineers, and operators remain in the closest contact to ensure the best RLV size is chosen.

The choice of RLV size must also be informed about the negative consequences and opportunity costs associated each option. This study suggests that choosing smaller, cheaper RLVs can provide savings to apply towards a larger fleet and more bases. With such a force structure we can accomplish militarily significant activities to an extent not allowed by the choice of a smaller fleet and fewer bases. However, choosing a more militarily useful RLV design and force structure could result in negative consequences for commercial and civil operators. A more militarily useful RLV design might include increased thermal protection system requirements to facilitate the greater cross-range capability needed to takeoff and land at the same base after one orbit. It may also require the additional weight and cost of on-board self-protection systems. Meeting these requirements will not be cost free. Whether the costs are in dollars, weight, or volume, trade-offs will have to be made.

Propulsion Technology Development Required. One way to mitigate some of the challenges faced in developing a full-scale RLV is to pursue propulsion technology development more vigorously. Regardless of the size chosen for an operational RLV, advances in thrust-to-weight ratios such as the 100% increase sought in the Integrated High Payoff Rocket Propulsion Technology program can dramatically decrease technical and financial risk. Such efforts should be funded at the full level recommended by the Moorman Study. An investment of $120 million per year pales in comparison to the potential cost of developing an RLV. A lack of investment in propulsion technology development up-front is bound to prove penny wise and pound foolish.

Top Priority Must Be Cheap and Responsive Space Access. While RLVs have tremendous potential to perform military missions well beyond simply conducting spacelift, an objective evaluation of priorities leads to other conclusions. The US military possesses tremendous strike and reconnaissance capabilities through existing and planned land, sea, and air systems. Space-based reconnaissance has also been conducted since the dawn of the space age. What the US military, and the entire nation, does not possess is cheap and responsive space access. General Abrahamson’s words quoted above were prophetic. Less than a year after his address, America’s space access program literally crashed as result of poor policy choices and a string of accidents that left the US with a grounded STS fleet, and a limited and unreliable ELV fleet. Talk of achieving space superiority is cheap. We first have to have access to the space realm before we can begin to gain superiority there.

Three recommendations are offered here. First, the US military, especially the USAF, is already a participant, but it should become more active in the RLV program. If, as this study assumes, today’s fiscally constrained environment continues, the US military will not have the luxury of independently developing an RLV fleet. Accordingly, the US military will have to blend its requirements in with those of other users in order to pursue militarily significant applications. The current focus of the RLV program appears to be on NASA and commercial requirements. There is an implicit assumption that whatever is developed will spin-on some military capability. If the US military is a passive participant in the RLV program, then the assumed spin-on capabilities may be limited or non-existent. Military requirements must be defined and stated if America is to develop a triple-use, rather than merely dual-use, RLV fleet. If the current fiscally constrained environment does not continue, then active participation in the current program is still warranted. An investment in defining military RLV requirements now will reap dividends should the time come when a military-unique RLV force can be developed.

Second, whether or not America develops a dual-use or triple use RLV fleet, or two fleets with one being military-unique, she should not do so before the technology is ready. If this study’s assumption that RLV technology will become operationally feasible by 2012 does not prove valid, then RLV development should not be pursued until the technology matures. The current RLV program appears to include this tenet, but NASA may be tempted to seek high-risk development in order to acquire a shuttle replacement. For that matter, military spaceplane advocates may desire a similar approach in pursuit of a seemingly invincible weapon. Both parties undoubtedly have America’s best interests at heart, but could lead us to squander our treasure in pursuit of a dream not yet ready to be realized. Careful evaluation of progress at each step in the program is the prudent course. The earliest opportunity confidently to assess the merits of developing an operational vehicle will not come until the turn of the millennium.

Third, regardless of the embryonic state of reusable rocket technology, it is not too early for the US military to think deeply about the implications of their operational use. If operational RLVs become a reality, there will be serious implications for warfighting strategy, force structure planning, training, and doctrine. Concepts of operations should be developed in more depth and breadth than this study could achieve. In this regard, the analytical criteria used in this paper may prove to be a useful framework for evaluating new RLV CONOPS. Another way to support preparation for the birth of operational RLVs is to keep military people active in the flight test programs. Today’s DC-XA flight tests include uniformed personnel from the USAF’s acquisition command. It is not too soon to include operators and maintenance personnel in this activity. One of the often-heard objectives of the RLV program is to develop aircraft-like operations. An excellent way to pursue this worthy goal would be to leverage the experience of seasoned military aircraft maintainers. A handful of senior crew chiefs working with RLV developers and test teams may provide helpful advice on how to establish efficient RLV generation and recovery systems and procedures. At the same time, these crew chiefs would also be developing a knowledge base for future military planning and operations.

The US military must be prepared to take advantage of reusable launch vehicles should the NASA-led effort to develop an RLV demonstrator prove successful. The focus of this research was an explanation of how the US military could use RLVs by describing and analyzing two concepts of operations. Four assumptions which guided the research are worthy of mention. First, the estimate that RLV technology will become operationally feasible by 2012 is reasonable. Second, a fiscally constrained environment will continue. Third, the US government will continue to support growth and development of the US commercial spacelift industry and encourage dual-use, or perhaps triple-use, of related facilities and systems. Fourth, the US Government’s national security strategy will continue to emphasize international leadership and engagement to further its political, economic, and security objectives.

Before developing and analyzing concepts of operations for military use of RLVs, requirements were stated: spacelift, reconnaissance, transpace operations, and strike (in and from space). Then, to provide a basis for CONOPS development and analysis, current RLV concepts and attributes were summarized, and hypothetical attributes of a notional RLV for use in military applications were suggested. Following discussion of RLV concepts and attributes, two concepts of operations were presented and subsequently analyzed. The criteria used in the analysis included capability, cost, operations efficiency and effectiveness, and political considerations (Table 5).

Four major conclusions resulted from the analysis. First, RLVs have military potential. Second, design choices for an operational RLV will have effects on risk, cost, capability, and operations efficiency and effectiveness, the choice of a larger vehicle being accompanied by more risk. Third, increased investment in propulsion technology is warranted. Fourth, the top priority for the RLV program, even from the DOD perspective, should remain cheap and responsive access to space.

Three recommendations were offered. First, the US military should become a more active participant in the RLV program. Second, America should not pursue development of operational RLVs before the technology is ready. Third, and finally, it is not too early for the US military to think deeply about the implications of operational RLVs for warfighting strategy, force structure planning, training, and doctrine.

The small steps being taken by the DC-X Delta Clipper-Experimental in the New Mexico desert today may be recognized in coming years as having warmed and strengthened our muscles for the giant leap into an "exciting and vital future in space activities of all kinds." America and her military must be prepared for that future.

This work was accomplished in partial fulfillment of the Masters Degree requirements of the School of Advanced Airpower Studies, Air University, Maxwell AFB, AL, 1996.

Advisor: Major Bruce M. DeBlois, Ph.D.

Reader: Dr Karl Mueller