Air University Review, January-February 1969

Future Space Booster Requirements

Major General Joseph S. Bleymaier, USAF

One major mission responsibility of the Air Force's Space and Missile Systems Organization (SAMSO) is the provision of launch capability for a large portion of the United States space effort. Almost three-fourths of the Free World's space launches to date have been accomplished by SAMSO-developed launch vehicles and SAMSO launch crews. Our total launch capability is, of course, a prime governing factor in the progress of our national space program as a whole. From the standpoint of both technology and economics, the launch vehicles constitute our "base for space."

The purpose of this article is to present, primarily from the Air Force vantage point, a broad, overall view of what the present United States space launch capability is, the general requirements that we in the Air Force foresee for the future, and the areas that are receiving particular emphasis in our approached to meeting these requirements.

present booster inventory

Historically, the growth of our space launch capability demonstrates the healthy philosophy that there is more than one way to put our space payloads into orbit. We have managed to develop during our first decade in space an extremely versatile stable of launch vehicles. Most of them are by now reasonably well known to those who have followed the United States space program consistently, so my review will be brief.

The NASA/DOD Scout provides a launch capability for our lightest payloads of up to 350 pounds for a 100-nautical-mile circular polar orbit

The Thor Standard Space Launch Vehicle (SLV-2), long since retired as an intermediate-range weapon system, is still giving yeoman service as a space booster. It as boosted a record number of space firsts for the United States and is especially remarkable for its exceptional adaptability, made possible by thrust augmentation and a variety of upper stages.

Among its adaptations are the Thrust-Augmented Thor (TAT) with Agena upper stage, and the Thrust-Augmented Long Tank Thor/Agena. Payload capability for 100-nautical-mile polar circular orbit of all versions of this launch system ranges from 1400 to about 2800 pounds.

The SLV-3 is a booster developed from the Atlas, first of the intercontinental ballistic missiles and one of our long-time workhorse boosters. The two versions of this launcher, used with the Agena and Centaur upper stages, can place an 8000- to 12,000-pound payload in low earth orbit. The man-rated Atlas D was the booster used to launch the Mercury manned space capsules.

The Titan IIIB/Agena is a combination of the Titan II Gemini core and the Agena upper stage, with a payload capability of 7500 to 9000 pounds.

The Titan IIIC (SLV-5) is the most powerful space launch system in our present military inventory. We actually have a "family" of versions of the Titan III, all of which are direct outgrowths of the Titan II ballistic missile. They are the launch systems on which we have the most active current development programs. The Titan III uses basically the same core as the Titan II, consisting of two stages, made structurally stronger to carry more payload weight. It has the same liquid-rocket engines and guidance systems. A third stage, or transtage, is added to the Titan IIIC to provide versatility in space. This stage consists of a control module housing all the guidance and attitude control equipment and. a propulsion module providing 16,000 pounds of thrust. The engines have multiple restart capability, which allows change of orbit plane and other complicated space maneuvers.

The Titan IIIC consists of the core vehicle and two added 120-inch solid rocket motors. These motors provide 2.4 million pounds of thrust at lift-off, and the vehicle can place 25,000 pounds into a 100-nautical-mile circular orbit. It can also boost 5000 pounds to escape velocity for such missions as moon shots. Most important, however, is its capability for synchronous equatorial orbit. It can put 2100 pounds into synchronous orbit and provide different velocities for a number of separate satellites. During the 1967-68 period the Titan IIIC has put into orbit military communications satellites, Vela nuclear detection satellites, and a variety of scientific spacecraft. Because of its demonstrated capability, the Titan IIIC was ordered into production during the summer of 1967 to provide space boosters for high-priority payloads over the next three years.

The Titan IIIM, now being developed as the booster for the Manned Orbiting Laboratory (MOL), is, in general, an uprated version of the Titan IIIC, minus the transtage. The system is man-rated, which entails more than usual redundancy and extensive modifications to allow maximum warning time for crew escape. The payload capability is being increased about one-third over the Titan IIIC by means of larger solid motors and uprated liquid-rocket engines.

The National Aeronautics and Space Administration's Saturn V launch system is being used in NASA'S Apollo program. It has the greatest payload capability of any booster now in the national inventory-between 250,000 and 280,000 pounds. From a national point of view, the Saturn V capability will undoubtedly be available to the Department of Defense should the requirement ever develop. Although it is difficult to foresee a military need for this payload capability, we must factor it into our long-range thinking as an available option. In doing so, we recognize that, short of building a Saturn V launch facility at the Western Test flange, utilization of this booster from the Eastern Test Range for polar orbit does carry a considerable penalty. With a required "dogleg" and the range safety limitations, deliverable payload to a polar orbit from the Eastern Range may be degraded by as much as 70 percent.

reliability of boosters

As indicated in this brief overview, which has included only major versions within each of the booster families, our present inventory of space boosters represents a wide range of versatile capabilities. In the first decade of the United States space effort, 1957 through 1967, these boosters successfully launched 514 spacecraft into earth orbit and 28 spacecraft into earth escape. These included launches of British, Canadian, French, and Italian spacecraft. This compares with a total of 284 successful space launches by the Soviets during the same period.

One particularly noteworthy aspect of the launch record has been the increasing reliability of our launch systems over the years. During the period 1958 through 1960, of 59 attempts to place earth satellites in orbit 29 failed. In 1967, out of 82 attempts, 77 were successful. Some of our workhorse boosters have become almost as reliable as milk trains. The Thor has achieved an unequaled record of 123 consecutive successful launches-almost four years of 100 percent reliability. Overall reliability of the Atlas SLV-3 launch system is better than 96.5 percent.

We have had 39 consecutive successful Atlas launches. Moreover, the excellent reliability record of the Titan IIIC, a relative latecomer to the booster inventory, is heartening evidence that the rising level of reliability is not simply a matter of practice making perfect in the course of a long operational experience with one or two booster types. Rather it is a direct reflection of greatly improved reliability of components and parts, the kind of integral, built-in reliability that can be passed along to future systems.

gaps in present capability

In spite of the basic soundness of our present launch vehicle inventory, however, gaps do still exist in our capability, and we are continually investigating the possibilities for next-generation launch vehicles. Our emphasis is on boosters to meet possible future needs that cannot be met by current launch systems and on concepts that could significantly improve the economics of space launch operations.

The major capability gaps in our present inventory are between the payload capability of the Titan IIIC/Saturn In (approximately 25-30,000 pounds) and the payload capability of the Saturn V (approximately 250,000 pounds).

In addition, we are interested, of course, in all concepts in any part of the payload spectrum that could give significant lower launch costs, including partial and fully reusable systems.

the 100,000-found booster-a requirement?

For the past several years both NASA and the Department of Defense have done a great deal of work in investigating concepts within the 35,000-to 250,00-pound range. A letter written in September 1967 by Mr. James Webb, NASA Administrator, to Secretary of Defense Robert McNamara provides a good summary of this interest:

Perhaps of longer term importance is the question of whether either of w (NASA or DOD) or both will need a 100,000 pound payload, and the most efficient way to boost it into orbit. I believe both DOD and NASA have the possibility of focusing on a useful payload at about this level (100,000 pounds in orbit), but we believe we both will need a great deal more information, accumulated over months or years, before we can be sure that such an effort is justified. The payload needs probably govern whether the Department of Defense or NASA should be assigned the responsibility for the development of a new booster.

The actual degree and immediacy of our need for a 100,000-pound booster is still a subject for lively debate, as we accumulate the data essential to future decision. Even detailed study of projections of current mission does not give us a definitive answer to the question. Projections of future systems do not always show a need for greater payload capability than that currently in hand, primarily because mission planners consistently tend to plan future systems around existing launch vehicle capability. Especially in today's climate of increasingly stringent requirements for justification, review, and re-review of proposed programs, the payload planner does not want to propose a system keyed to a launch capability that does not currently exist or is not at least firmly programmed. There is little doubt, however, that if the larger payload capability were to be developed, payload planners would be quick to put it to good use.

It is undoubtedly true also that with increasing sophistication our space systems tend to grow progressively heavier. One fairly typical example of this has been the course of development of the Vela nuclear detonation detection satellites. The eight satellites orbited in pairs to date represent four progressive steps in the capabilities and sophistication of the systems. Each of the first pair, orbited in October 1963, weighed 520 pounds. The fourth pair, orbited in April 1967, had greatly improved mission capabilities and weighed 730 pounds apiece, a weight increase of roughly 40 percent.

We can anticipate also other factors that will tend to increase the weight of our space payloads. The trend, for instance, is increasingly toward satellites capable of what might be called "predigestion" or "boiling down" of data gathered, before transmission to the surface control centers. The ideal is to have as much as possible of the preliminary data processing accomplished within the satellite itself. Even with microminiaturized components, the penalty for shifting a greater part of the processing function into space is added weight.

A number of approaches are currently being made to the 100,000-pound booster capability. The Air Force is studying the use of 156-inch-diameter solids, and NASA has done work in 260-inch-diameter solids. Studies are being made of the possibilities of down-rating the Saturn V and up-rating the Saturn IB. And we have been considering the use of current engines and stages in a variety of combinations.

Extensive feasibility studies have been made of a joint NASA-non intermediate launch vehicle for operation in the mid-1970s which might include as its third stage a lifting-body vehicle with variable-sweep wings for controlled landing on airfields. An alternate possibility for the third stage would be an Apollo-like space capsule. Its payload capability would be somewhere between that of the Titan III and the Saturn V. Choice of configuration would depend upon mission developments. No decision has yet been made concerning actual development of such a booster.

However, there are Titans with potential growth that could fill in existing gaps in our booster payload capabilities. The prime candidate among these is the Titan IIIG, which uses increased-diameter core stages one and two and 156-inch-diameter strap-on solid motors. This launch vehicle is designed to boost approximately 100,000 pounds into low earth orbit.

An intermediate step to the 100,000-pound-capability Titan III involves substituting a first-stage large-diameter liquid core and retaining the existing stage two and the 120-inch solid rocket motors. A good deal of work has been done on this concept, and it appears to be a relatively low-cost development that could yield a payload capability on the order of 42,000 pounds.

continuing progress in applicable technology

Meanwhile, pending major programming of any next-generation booster development, work continues in supporting research and technology that can provide the basis for new booster capabilities. Among other projects, for example, the Air Force Rocket Propulsion Laboratory, under a contract from the Space and Missile Systems Organization, has completed a number of static firings of 156-inch-alameter motors configured as the first, second, and third stages of a multipurpose space or ballistic vehicle. These tests demonstrated the potential of large submerged ablative nozzles, high burn-rate propellants, and omniaxial liquid-injection thrust vector control for large solid motors. All of these offer promise for application to large boosters of the future.

Another of our recent developments is a new tungsten alloy with greatly improved strength and ductility. The alloy has a strength of over 75,000 pounds per square inch at 3500 degrees Fahrenheit. A tungsten alloy with such properties, in addition to tungsten's high melting point, has excellent potential as a structural material for space power plants and rocket engines.

the economics of space launches

The economic aspects of space launches have always been a major determinant of our booster planning and a primary consideration in our projections for space payloads themselves. Indeed, there is some evidence as we start our second decade in space, in a climate of unprecedentedly tough competition for government funds, that the high cost of space operations-much of it directly attributable to launch costs-is to some extent pricing progress out of the market.

Launch costs are subject to many variables, and the range of cost per pound of space payload is wide. Unquestionably, launch costs are decreasing with time, as more efficient launch vehicles are introduced and as increasing traffic volume permits a broader sharing of fixed costs. For the 1970s we anticipate a delivery cost to low altitudes of approximately $450 to $500 per pound. Delivery to the synchronous equatorial orbit -is about 10 times more costly, roughly $4000 to $5000 per pound.

Of the numerous approaches to reducing space launch costs, one is continued improvement of the reliability of our boosters to prevent failures-a route on which we are making good progress, as I noted earlier. Another means of reducing costs is major extension of the life of the spacecraft. We have found that we can feasibly increase spacecraft orbital life by a factor of two to ten. This means that we can accomplish our mission over a given time period with fewer spacecraft and fewer hunch vehicles, resulting in savings of about 45 percent.

We can also reduce costs by the use of multimission spacecraft, that is, by combining the function of three to five single-mission spacecraft in one "package". This procedure is particularly attractive for the high-cost synchronous equatorial orbit, where it could reduce program costs from 25 to 50 percent.

Our studies have indicated further that multiple launches of spacecraft on a single launch vehicle could give total program savings of up to 55 percent. The Titan IIIC has this multiple-launch capability. With it we have orbited as many as eight separate payloads in one launch.

Reusable boosters and re-entry vehicles, using either present technology and hardware or more advanced concepts, do offer definite promise, but the initial development expense will be high. Such systems must provide a flexible capability, have relatively low non-recurring costs, and provide significant recurring-cost savings, to allow development costs to be amortized over a reasonably short period of time.

designing for minimum cost-the BDB

One unusually challenging approach to the booster cost problem represents a 180-degree divergence from our traditional thinking with respect to space launch systems. Customarily we have designed for minimum weight and maximum performance. We use the finest lightweight alloys. We demand the highest order of skills in design, production, test, and retest, to get results that are the utmost in precision and sophistication. Since 1965 we have been studying the potential of a new concept of designing for minimum costs, and the result may be a new breed of launch vehicle, known unofficially in the family as the "Big Dumb Booster."

Our thinking on the BDB is dictated by the realization that, in general, minimum weight, minimum cost, and maximum reliability of subsystems cannot all be achieved simultaneously. Instead, trade-offs must be made among these requirements to produce a compromise vehicle design of minimum cost. For instance, if we use heavier hardware, of lower unit cost and inherently higher reliability, then greater simplicity of design becomes possible. Subsystems can then be substantially reduced. Tolerances can be increased optimally. A propulsion system can be selected which results in a lower propellant mass fraction but does not require structural complexity, high-speed machinery, a multitude of parts, supporting subsystems, and/or high launch service costs.

The key to such a booster is, of course, the propulsion system, and some few further low-cost developments in propulsion technology will be necessary before the minimum-cost launch vehicle can become a practical reality. As it is now shaping up, the propulsion system would utilize storable, bipropellant pressure-fed stages having single ablation-cooled engines, the simplest of designs. The first stage may be designed for recovery from the sea after launch and refurbishment for reuse.

We think that with such a "large economy size" booster, payloads in the 40,000-pound class could be put into low polar orbit for less than $100 per pound, without first-stage recovery and with low production rates. If we can eventually accomplish first-stage recovery and certain other design-cost savings, it seems entirely possible that this cost can be cut by more than one-half.

We do have a healthy variety of opinion within our own house concerning the best approaches to minimum cost. The Big Dumb Booster, as a frankly revolutionary about-face from the deeply ingrained perfectionism of traditional aerospace design, generates both great enthusiasm and some uneasiness among Air Force engineers and those of the aerospace industry. There is little doubt, however, that the concept of which the BDB is a principal example today-design for minimum cost-must be a main current of our thinking on future space boosters,

The economic factor is particularly important with respect to the development of vehicles with new payload capabilities that will fill the existing gaps in our inventory, most notably within the 40,000- to 250,000-pound range. Because we have been designing space payloads within the restrictions of the launch capability actually in-being, the annual number of payloads in this class will be relatively small at first. If a new booster is to survive the stringent cost-effectiveness evaluation that will precede its approval, it must indeed be designed from the outset for rock-bottom minimum cost.

There can be no doubt, however, that the 100,000-pound booster, or something in the general neighborhood of that capability, is our next logical major step in booster development. How long it will be in coming depends upon many factors. Not the least of these are the tightening squeeze on space funds-especially evident in the lowered 1969 civilian space budget-and the unfortunate loss of momentum in advance space programming. The pacing factor is not, as it was in the early days, the state of the art; it is the state of the budget and the resultant necessarily cautious slowdown of the complex machinery of program decision and approval. Even existing booster designs are feeling the pinch. Production of the Saturn IB and Saturn V, at the upper range of our present payload capability, has been slowed down in an attempt to prevent an abrupt falloff in the production facilities, from feast to famine, when existing contracts are completed.

potential advantages of mid-range boosters

Development of some new mid-range booster capability, without undue delay, could definitely contribute to the improvement of our military space posture. It could open the way for more ambitious, more cost-effective space endeavors; more sophisticated and reliable mission equipment; more manned capability; longer orbital life of our space systems, manned and unmanned; greater mission versatility and flexibility, including the capability to maneuver systems in space; more multimission spacecraft and multiple-payload launching of space systems; and reusable spacecraft which, instead of being expended in one mission, could be used over and over again.

In conclusion, we have in-being at the present time an exceptionally flexible booster inventory with an excellent record of accomplishment in the first decade of the space age. We have made steady gains in the reliability and the cost effectiveness of our space launch systems and have marked the frail for continued improvements in the future. Gaps do exist in our launch capabilities. We are giving particular emphasis and study to the possibilities of highly cost-effective boosters with payload capabilities in the mid-range from approximately 40,000 to 100,000 pounds. This capability is important to the optimum development of space systems of the immediate future. No program has as yet been specifically approved and funded for the development of such a booster; certain growth models of the Titan III could provide the most immediate solution. In the present economic atmosphere, establishment of any such program depends primarily upon our ability to design a system of provable exceptional cost effectiveness. We are investigating all concepts that appear to offer promise for future launch systems of this nature. And we are pushing forward with the advanced technology that can make such systems, when their development does become feasible, very significant additions to our capability for the exploration and utilization of space.

Space and Missile Systems Organization, AFSC


Contributor

Major General Joseph S. Bleymaier (B.A., University of Texas) is Deputy Director, Manned Orbiting Laboratory (MOL) program, and heads the MOL Systems Office at AFSC's Space and Missile Systems Organization (SAMSO), Los Angeles. He enlisted in 1941, was commissioned in 1942, and served as aerial gunnery officer on 25 combat missions with 11th Bomb Group (H), Seventh Air Force, Pacific Theater, 1943-45. Postwar assignments have been Deputy for Test Operations, Air Proving Ground, 1946-50; Assistant Director, Command Support Division, Deputy for Development, Hq USAF; at Hq Air Research and Development Command, 1952-58, became Assistant Director of Astronautics; with AF Ballistic Missile Division, later Space Systems Division; and as Commander, AF Western Test Range, from 1965 until his present assignment in 1967. General Bleymaier is a graduate of Air Command and Staff College and Air War College.

Disclaimer

The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.


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