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R Richardson, 1991, "Prospects for Inexpensive Space Transportation", B6.1. Presented at SPS'91 1991.
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Prospects for Inexpensive Space Transportation
R. C. Richardson

In this paper the author argues that it is now possible to reduce the cost of transportation from earth to low Earth Orbit by about 2 orders of magnitude. He explains why costs have been high until now, why these can be reduced dramatically, and what is now being done in America to do this. He concludes that this development, alone, should greatly improve the prospects of deploying economically viable solar power satellites ( SPS) and other space-based systems.

I. Background

Space is the most recent area that industrialized nations can exploit for economic, political, social, and security purposes. While technological progress opened up access to space over 35 years ago, even the most developed countries have only begun to realize the benefits for life on Earth that lie beyond this high frontier.

The era of discovery and exploration of near space should change into an era of economic exploitation by the onset of the next century. This will only come about, however, if two inter-related events take place. The first, is the opening up of space to free enterprise, and the second is technological realization of access costs that will permit the private sector to pursue profitable, large scale, business ventures in space. Only when affordable means of getting from Earth to near space and back, become available will the full economic potential of this new frontier be realized.

Until recently most U.S. space activities have been initiated and managed by government. One result of this has been that transportation costs tend to be buried in, or secondary to, the cost of the projects they support. And, since the objectives of the government's prograrns have been dictated primarily by national interests, such as security or intelligence gathering, they are paid for by the taxpayers and do not have to make a profit. As a result of this, there has been little or no real incentives for reducing transport costs other than in an overall national budgetary context.

While these priorities were logical and understandable in the cold war era, the failure of government funding to give a high priority to reducing lift costs has been one of the major impediments to the civil sector's development of this vast new area. Free enterprise space activities have to pay for themselves and turn a profit and transportation costs are obviously a major factor when it comes to meeting this basic requirement.

I suggest that all this is now about to change. The Cold War excuse for government monopoly of space developments is no longer valid. Obviously any dramatic reduction in travel costs would open up new economic possibilities in space. This would be to everyone's advantage. It would turn overly costly or marginal civil Sector ventures, that until now have been dreams or paper studies, into practical free enterprise projects. And, while governments will no doubt still have to pay for multi billion dollar, high risk, programs such as large power complexes like SPS, asteroid mining, or lunar bases, many less costly activities such as manufacturing in space, new communications systems, and even tourism should attract venture capital and result in industry initiatives.

In 1986 the U.S. National Commission on Space recommended "a U.S. commitment to create and operate systems and institutions to provide low cost access to the space frontier." (1) To achieve this goal they also recommended aggressive development of the technologies for reusable single stage to orbit ( SSTO) rocket launch vehicles. Last year a Committee appointed by the Vice President's Space Council to review the NASA space program also called for a new family of launch vehicles. (2)

Unfortunately, the development of econonzical launch vehicles has not been a matter of priority for either NASA or the USAF. This is no doubt partly due to the fact that neither organization has been specifically charged with helping free enterprise exploit space, and partly to a normal desire to protect their investments in the expensive older Shuttle and Expendable Launch Vehicle ( ELV) systems they now use. Fortunately, however, several of America's best known rocket engineers, The Citizen's Advisory Council on Space Policy and High Frontier, a national interest advocacy group in Washington, came together in 1989 to change this situation. Recognizing both the importance and feasibility of building cost effective SSTO rockets they insisted that the government take a more active role in developing these and this is now being done.

II. Possibilities For Cheap Lift

Ever since space became accessible, in 1958, the cost of transporting goods and people from Earth to low Earth orbit ( LEO) has been very high. It still is. Conservative calculations in 1988 U.S. dollars for each flight to LEO, equatorial plane, are now approximately $484.00 million on a Shuttle and $145.00 million on a Titan ELV. This works out to 10,803 $/lb on the shuttle and $3718 $/lb on Titans. (3) At these prices the United States spends between one half and one third of its space dollars simply to get to space. These prices have also been the principle barrier to the exploitation of~space for many potentially profitable commercial activities.

There is no insurmountable reason why travel to LEO need be so costly. By adopting a "new approach" to vehicle design, utillzing materials and engine technologies recently developed under the U.S. National AeroSpace Plane program (NASP) and designing our space transportation systems to be comparable in reliability, safety, and frequency of service, with commercial air, we should be able to reduce the above costs to under $500 per pound.

Last year, the prospects of doing this within a few years time were sufficiently persuasive to cause the U.S. Defense Department's Strategic Defense Initiative Office (SDIO) to allocate $15 million towards the development of a prototype, SSTO, rocket transport. This work is now well underway led by four major U.S. aerospace corporations and their findings to date are very optimistic.

Today there seems to be general agreement among most of our space experts and engineers that the technology exist to build several types of reusable, low cost SSTO rockets that can be made to operate much like conventional aircraft. Many of those now working with this program are confident that this would reduce the cost of transportation into space by at least 2 orders of magnitude. With only a 4 vehicle fleet this would bring space transportation costs to LEO to well under $500.00 per/lb and per flight costs to about $8 Million.

The SDI contracts call for demonstration vehicles by the mid 1990s and first generation operational vehicles to be flying before the turn of the century. If successful cost reductions of this magnitude could generate an economic revolution in space activities greater than that brought about by jet aircraft. In any event, they will make large space systems such as SPS much easier to deploy and more cost effective, hence more attractive to pursue whether by governments or private investors.

III. Why is Cheap Lift Now Possible?

The initial reaction of most audiences to predictions of such dramatic cost reduction in the near term is incredibility. The first question is invariably, "if this is true why haven't governments involved in space operations done this long ago, or at least moved towards achieving these cost goals?" While it is not the purpose of this paper to detail and defend the specific technologies that now make this possible, a brief answer to this question seems pertinent to persuading those of you now advocating and planning for future space projects, such as SPS systems, not to be discouraged by the current high costs associated with their deployment.

The high transportation costs faced by space operations today can be broken down into two broad categories in terms of their origin. The first are those attributable to technological reasons and the second are those that stem from the circumstances surrounding the initial space race in the late 1950s and early 1960s.

In the first case - that of technological limitations - the possibility of building low cost, effective, transportation systems was limited by the types and weights of structural materials available in the 1950s and 1960s. It was also limited to a lesser degree by rocket engine technology.

In the second case - the circumstances - the urgency to keep up with Soviet space developments for national security led to using what were essentially modified military munitions - ICBM's with saddles on them - to get into space quickly instead of developing transportation vehicles optimized solely for transportation purposes.

These two conditions led to the development, use, acceptance, and almost standardization of multiple-stage, wholly or partly expendable, rocket systems which were derived from munitions with all their associated risks and costs. Even when technological advances in materials, in the 1970s, started to make single-stage recoverable, reusable, and relatively safe lift systems interesting a combination of resistance to change and demands for ever heavier payloads kept governments from exploiting these advances to develop new types of launch vehicles until now. Once billions have been committed to any one approach to doing anything it is inherently difficult for those involved to start over at the expense of risking their expertise and making the systems they have been accustomed to using.

Another major factor in the high cost of space travel has been that associated with the operations and maintenance (O&M) of the munitions derived systems. Literally, field armies of people are now required to service and operate these. It has been estimated that it takes over 15,000 employees to refurbish, assemble, test, launch and safely supervise and operate a Shuttle flight. This compares to a U.S. airline average of 140 people per aircraft and some 400 people per aircraft for the most sophisticated military systems such as our Blackbird Fleet. Such personnel costs, when coupled with the low turn around rates of shuttles and throw away features of expendable rocket launcher are obviously major factors in their high operating costs.

To minimize costs vehicles designed for any transportation mission, including access to and from space, must benefit from simple designs for ease of maintenance and servicing, provide a reliable abort capability throughout their flight regime in the event of non catastrophic failures, and have turn around times equivalent to aircraft. The new family of SSTO transports we are now developing will meet these criteria.

By some estimates failures on today's launch fleet nearly double national costs of space launches. SSTO rockets can potentially reduce these losses due to their intrinsic reliability. Design now under consideration can lose one main engine and complete their mission or loose two and still safely abort, similar to conventional aircraft. Given these capabilities the savings in insurance alone become substantial.

If the new vehicles are not only designed for safety in all operating regimes but also for rapid refaeling, ground processing, and turn around, and to be able to operate with minimum use of unique base facilities and equipment such as assembly buildings and gantries, the potential cost savings are very great. All this can now be done and with existing technology.

IV. Correcting the High Costs

During the 1980s massive U.S. government spending on developments programs, such as the National AeroSpace Plane programs (NASP) and Strategic Defense Initiative (SDI) have produced and tested light weight, re-usable, structures able to both contain cryogenic propellants and withstand the heat of re-entry. The advanced materials these research programs have brought about are ideally suited to SSTO rockets.

Since empty weight drives development, production, and operating costs on both air and space systems the potential for even greater cost reduction should increase as SSTO rocket technology and operations mature. Graphite epoxy, aluminum lithium, titanium metal matrix composites, and aluminum honeycomb panels are now off the shelf materials available to build propellant tanks and space structures. This has all but solved the earlier SSTO weight problems.

By designing for reliability, safety, a minimum of support personnel, and an economical flight rate the SSTO transport will be more like a commercial aircraft than a space booster. Conventional boosters normally now operate with reliabilities of 94% to 96%. The SSTO transports, using multiple levels of backup capabilities to provide intact abort, and including escape- ejection mechanisms for catastrophic failure, should have 99.9% reliability. These safety features also allow progressive flight testing Ilke aircraft thus increasing reliability and reducing gold plating and redundancy requirements.

Unlike ELVs which throw away everything on each flight, or even Shuttles which toss off tanks and other parts, the SSTO's only expendables will be fuel and propellants used for control along with life support expendables if needed. When one adds to this flight rates of once or twice weekly that spread fixed costs over large numbers of flights cost reduction in the order of 60% over conventional launchers are achievable.

There appear to be no insurmountable problems in devising engines to meet the SSTO requirements. More than adequate progress has been made in rocket engine thrust to weight ratio in recent years. The problem has been the configurations best suited to meet the abort specifications. Current proposals envision engines ihat can be easily maintained and are structurally efficient. When these are clustered in groups of up to ten modules, each with self contained pumps, combusters, and nozzles, they will provide the necessary redundancy for safe operations, engine out capabilities, and ease of engine change. Modifications to existing engine designs appear to be adequate to demonstrate the first SSTOs even though improved engines made specifically for SSTO operations, will no doubt be built for use in operational systems. All engines will be liquid fueled. Most proposals plan to use inexpensive H2-O2 although other fuels are being examined.

We have never before built a rocket ship that you could save if you had an engine failure, and bring it back, repair it, and fly it again. As a result, the problem with engines for first generation SSTO space transports is more one of configuration and throttling of the multiple engine systems required to meet abort and landing requirements rather than one of needing any new developments in thrust to weight ratios.

Looking ahead, it now appears that the inherent scalability of rocket vehicles combined with use of advanced technologies will support larger payloads in later generation vehicles. Even if the SSTO vehicles now being designed can be scaled up to heavy lift payloads in later generations this may or may not prove to be necessary. Instead it seems likely that standardized, reliable, vehicles with twenty to fifty thousand pound lift capabilities should cause payload designers to adjust to their use rather than pay exhorbitant additional costs for larger specialized loads. This is especially true when quick responses and rapid turnaround capabilities will make it easier to assemble structures in space.

V. Making this Happen

Theory as to what can now be done is fine but counting on it being done in order to plan projects that depend on it calls for some evidence that the reduced costs forecast will in fact be realized and in what time frame. Obviously this is what SPS designers are likely to be most interested in.

It is now clear that first generation demonstration space transports able to provide cost effective transport at under $400 per pound, and possibly less, will fly before the turn of the century. This is based not on confidence in the paper proposals and theories of SSTO advocates but on the fact that, at long last, their initial development and demonstration is underway having been funded and contracted for by our Defense Departments SDI organization in early 1990.

While there is still debate as to the specific characteristics and architecture of these specialized

space transports, and what their initial payload capabilities will be, all those involved appear to be convinced there are no technological problems not readily resolvable. The SDI contractor programs are now approaching their Phase II task - that of designing a full, or possibly sub scale vehicle. In Phase II, which will start this summer assuming it is adequately funded, one or more orbital or sub-orbital vehicles will be built and tested.

The key requirements these mnst meet are:

  1. A medium payload to orbit of 15,000 to 20,000 lbs including crew members;
  2. A turn around time of 7 days or less with surge capability and no more than 350 mandays of support per flight;
  3. High reliability: short flights with an engine out, all altitude abort and crew ejection.

The SSTO fleet is being designed to be both man and non man rated and flight certified from the onset just like commercial aircraft. We are looking for the option of deploying a fleet of these mini vans by the turn of the century. The first fleet is being funded and developed by SDI in order to reduce deployment costs for Brilliant Pebbles, the space based layer of SDI's defenses. Many believe that if and when it demonstrates the ability to meet the goals I have outlined new transportation service companies will enter the space travel field and industry will compete to provide these with the low-cost, safe, and reliable vehicles they will be shopping for. The SSTO promises to become the Space DC-3 or 747 of the 21st century.

VI. Additional Advantages

One major advantage that SSTO transport will enjoy over existing expendable systems lies in their flexibility when it comes to both launch and recovery sites. Because the new transports drop nothing on their way to orbit and back, and are capable of returning to base or continuing on their missions under emergency abort conditions, and need no highly specialized and exotic ground facilities, they will be able to operate off inland bases as well as on the coast with no more risk to those below than presented by today's aircraft. This in itself will reduce costs for their users if not their operators.

The availability of inexpensive specialized space transports will not necessarily obsolete heavy lift vehicles such as the Shuttle. It could however change their role somewhat. Shuttle vehicles while expensive, complex, and risky as transports to and from space also serves as space laboratories once in orbit. While criticized as a cost effective transport its usefulness to do more than merely carry people and equipment is unquestioned. In this last role the longer it could stay in orbit the more cost effective it will become. The only limiting factors here are resupply of expendables, replacement of crews, and removal of waste. If a cheap transport SSTO rocket can act as a ferry for resupply the shuttles could stay in orbit for weeks or more on tests and tasks of the type envisioned for the space platform. Those of us who advocate the new SSTO transport systems have not persuaded NASA of this yet but we are working on it!

Another important characteristic of the family of SSTO vehicles now on the drawing board is their likely versatility once in space. Unlike Shuttles or expendable rockets if refueled in orbit they can operate effectively anywhere in cis-lunar space as well as land on the Moon. This suggests that even first generation models will be able to deliver cargo beyond LEO if refuelled in space. As such they should eliminate the need for secondary lift systems-space tugs-to do this for solar energy projects like SPS

VII. In Summary

We now have a new family of space transports under development that should provide reliable, low cost transportation to and from low Earth orbit. This should make the frontier of space affordably accessible for the benefit of all friendly nations and establish a new space highway over which space comrnerce can flourish. This system is currently referred to as single-stage-to- orbit ( SSTO) space transportation vehicle. The SSTO will initially be a medium lift (10 to 20 thousand pounds of cargo) low mass, reusable, transport that can be scaled up for heavy launch requirements in later models.

By being designed for ease of maintenance, efficient vehicle ground service systems, automated mission planning, and containerized payloads the new space transports can be regularly turned around in a few hours or days depending on mission needs and fleet sizes.

These vehicles can now be built by taking advantage of new, lightweight proven structural material design. This should result in vehicles able to deliver payloads as a ratio to their empty weight, comparable to today's aircraft. By keeping down empty weight and operations and maintenance costs and personnel requirements, and emphasizing reusability and saveability these transports will greatly decrease travel costs to and from space.

There is no reason why the new family of SSTO vehicles cannot be operational by the late 1990s. Their availability should open up space not only to the private sector for commercial ventures but also to the public by making activities such as tourism economically feasible. They will also obviously change government attitudes appropriating moneys for obtaining new sources for vital resources from space such as solar energy or rare metals on asteroids. This will create new opportunities for adventure and open up new industries and new sources for creating wealth and/or providing cost effective national security for spacefaring nations on

  1. U.S. National Commision on Space, 1986 Report, Dr. Thomas Pavne, Chairman, Washington, DC.
  2. Report of Advisory Committee on the Future of the U.S. Space Program, December 1990, U.S. Government Printing Office, Washington, DC 20402.
  3. Steve Hoeser, " The Cost Impact of True Spaceships", Journal of Practical Applications in Space, Vol.1, No.4, High Frontier, Inc., 2800 Shirlington Road, Suite 405A, Arlington, VA 22206.
R Richardson, 1991, "Prospects for Inexpensive Space Transportation", B6.1. Presented at SPS'91 1991.
Also downloadable from for inexpensive space transportation.shtml

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