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J Ransom & J E Pournelle, , "Access to Space: SSX", Cities in Space. 1991, ISBN 0-441-10591-2.
Also downloadable from to space ssx.shtml

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Access to Space: SSX
Jim Ransom

I know how to get the U.S. permanently into space. Write me a check for a billion dollars, give me a letter of credit for a second billion I probably won't have to spend, and get out of the way. I'll take the money and vanish into the Mojave desert, China Lake for preference, Edwards Air Force Base if 1 must; and in about four years I'll have a Single Stage to Orbit savable as well as recoverable and reusable spacecraft capable of putting about ten thousand pounds into orbit at costs of about five times the cost of the fuel the flight takes. Call it Space Ship Experimental, or SSX for short.

In round terms: the ship will weigh about five hundred thousand pounds full up, of which some fifty thousand pounds will be liquid hydrogen fuel. That sells for about four dollars per pound at present, but it would be no trick at all to produce it at well under two dollars per pound; it's a matter of the costs of energy to make and transport it. Liquid Oxygen ( LOX) is essentially free if you're making hydrogen in fuel quantities.

Airlines typically operate at about three times fuel costs. We'll say SSX operates at five times fuel cost; although you should understand that it takes about the same amount of fuel to fly a pound from the U.S. to Sydney, Austrialia as it does to put that pound in orbit; rocket engines, contrary to rumor, are extremely efficient.

SSX thus costs in the order of half a million dollars per flight - total operational cost - to put ten thousand pounds in orbit. Double that on general principles, and it's still one million dollars a flight for ten thousand pounds, or one hundred dollars per pound. Contrast that with NASA's tens of thousands for the shuttle.

We're not through. Once we have the ship flying, we work on the payload: we ought to be able to get that up to about fifteen thousand pounds on this size ship. Second, we work on those costs: we ought to be able to get them truly to four times fuel costs.

Even before we do that, though, understand that SSX operates both in vacuum and atmosphere: get one into orbit, and you can send another one up with fuel as payload. About twenty such flights fuels up to send SSX to the moon and back, leaving ten thousand pounds of payload on the moon, at a cost of twenty million dollars.

That's easily enough to supply a colony of five with plenty of safety factor: for example, one twenty million dollar annual flight would keep a Lunar Base going.

Is this wishful thinking? Not according to some hard eyed analysts. I've actually overstated the costs.

But what is this nonsense about giving Pournelle a billion dollars? Do I really think I could manage a project that large?

Actually, yes: it's a matter of picking the right team of bright young people and making them work twenty-six hours a day until the job is done. They can have their coronaries after SSX is flying. I know most of those we need, and I know of the rest. So, yes, I could do it. As to why China Lake, it's simple: I don't want to build an empire, and I don't want anyone who does. By putting the project in a place no one wants to live, you make the job more important than the empire.

Would this be an efficient operation, without fraud and waste? Probably not. It would merely get the job done.

Will they let me do it? Of course not. No one is going to hand a science fiction writer, even one who's a former aerospace scientist and who's been Chairman of the Citizens Advisory Council on National Space Policy for eight years, that kind of money and get out of the way. Not me, and not anyone else for that matter.

Then how can we build SSX?

One way is being done now: there's a Phase One Development contract out as I write this, and we have every reason to believe we can get funding to. complete the project. The total cost, given usual government management efficiencies to prevent fraud and waste, shouldn't run much over ten billion dollars, provided the contractor gets a priority, and is allowed to run this in "skunk works" mode, thus bypassing many of the procurement regulations. The job ought to be done in six years.

Will it be done that way? Probably not. It will probably be let as a normal contract in the usual way, and let under standard regulations. Can we build the ship that way? You bet. It shouldn't cost more than about twenty billion dollars, nor take more than eight years.

That's the way it will probably go - and it will be a bargain. It's a pity we won't be allowed to just take a team out to the desert and do it, but that's life.

Finally, there's the private route. It's possible that we could have a flying SSX for about two hundred million dollars as a private venture. Possible. I didn't say I could guarantee it for that. 1 can guarantee it for two billion dollars, even as a government project (under my rules). On the other hand, I've seen numbers, some of them developed by the Brothers Rhutan.

I sure wish I had two hundred million.

Meanwhile, a description of SSX; the ship that could take us all into the Endless Frontier.

SSX: Spaceship Experimental
Spaceship: A vehicle designed for travel in space; not a converted missile.
Experimental: Inexpensive and rapidly developed to gather operational data.

The United States does not have access to space. The tragic events of January 28, 1986, burned the image of a forked smoke plume suspended in a deep blue sky into our memories. The loss of the Space Shuttle Orbiter Challenger, its seven person crew, and communications satellite payload in a fiery launch accident was the inevitable consequence of an unforgiving design pushed beyond its limits. Since Challenger, the United States has suffered one Delta, one Atlas, and two Titan expendable launch vehicle accidents.

Yes, we are launching Space Shuttles again, but our access to space is neither assured nor affordable. Placing a satellite in orbit using the Space Shuttle or an expendable launch vehicle costs more than the satellite's weight in gold! The premium to insure the launch of a communications satellite is currently about twenty percent of the cost of the satellite. It does not require a degree in math and training as an actuary to calculate the expected loss rates from this premium.

Today, United States space transportation is about as dangerous and unreliable as the first years of the United States Air Mail operations in the 1 920s. Air transportation became reliable through the development of better fuels, better engines, and most important, better aircraft designs. With the arrival of the Boeing 247 and the Douglas DC-3, air transportation became reliable and affordable. These new transport aircraft could cruise above the worst weather near the ground, avoiding the hazards of fog and downdrafts while keeping the passengers comfortable. The streamlined DC-3 could carry twenty-one passengers fast and economically enough to make a profit (air mail contracts subsidized the early airlines).

Space transportation is less affordable now than air trans portation was in 1920. No adult United States citizen can expect to fly into space in their lifetime, unless they possess special scientific or technical skills required by the government and can pass rigorous medical screening. A wealthy American might take advantage of an offer by the Soviets to fly a single individual into orbit to visit the Mir space station for ten million dollars in hard currency. There are no space barnstormers and no five dollar rocket rides at the county fair.

SSX can give us assured, affordable access to space.

Spaceship Experimental ( SSX)

The Spaceship Experimental ( SSX) program will demonstrate a true reusable launch vehicle designed for reliability and low-cost operation. The SSX design is easy to flight test and fundamentally safe. Due to its design simplicity, modularity, and use of demonstrated technology, SSX can be developed by a streamlined "Skunk Works" program office in less than five years at a total program cost of under one billion dollars.

SSX is a Single-Stage-to-Orbit ( SSTO) vehicle. Unlike the Space Shuttle and other current launch vehicles, the SSX does not drop off any booster stages or payload shrouds on its way into orbit. The SSX has only one stage to assemble, prepare, operate, and refurbish. The SSX expends only propellants.

To carry a useful size payload, into orbit with only one stage, the SSX uses high-energy liquid hydtogen and liquid oxygen propellants, a lightweight structure, and a high-performance engine system. The SSX propellants are nontoxic. The SSX is a short, squat, round vehicle with the internal tanks close to spherical in shape and thus lighter in weight than those of long, slender rockets. The Space Shuttle and other rockets have a small base area; to get the necessary thrust levels, the Shuttle must use high-pressure rocket, engines. The large base diameter of the SSX permits the use of a plug nozzle (or aerospike) which consists of many small, lower-pressure engines mounted in a ring around the base of the vehicle. As the SSX reaches high altitude, the engine exhaust gases push against the entire base of the vehicle and produce an engine performance equal to that of the Space Shuttle.

The SSX is Vertical Takeoff and Vertical Landing ( VTOVL) like a helicopter. The SSX reenters base first just as the Apollo capsule did twenty years ago. The base area must have a thermal protection system to protect it from the hot engine gases during ascent, and the same system serves double duty keeping the SSX vehicle cool during reentry. Now almost empty of propellants, the SSX vehicle weighs only a tenth as much as it did at takeoff. Once it reaches the lower layers of the atmosphere, the SSX has a terminal velocity of only a few hundred miles an hour and is approaching the ground at exactly the same rate as the Space Shuttle does before landing. The SSX fires its engines, brakes to a stop just above the ground, hovers for several seconds to permit final adjustments in landing site, and sets down on its landing gear.

The payload sits in a large-diameter shroud atop the vehicle. The payload is away from the engines, reducing noise and vibration loads. Once the SSX reaches the desired orbit, the shroud opens, the payload is released, and the shroud closes again for reentry.

The SSX will have low flight costs because it is completely reusable and capable of rapid reflights. The low-pressure engines sustain less wear than high-pressure engines like those on the Space Shuttle. The SSX expends no hardware and has only one stage to handle.

The SSX is designed to be highly reliable in operation. One or more engines can fail on the pad at liftoff and the vehicle can still reach orbit. If necessary, the SSX can hover to burn off propellants and then land vertically. It does not need to achieve any minimum velocity or altitude - SSX can land safely at any point in its ascent trajectory. The SSX is a savable rocket.

The SSX is designed for low-cost, rapid development. The engine components are based on existing designs. Each engine module is small compared to those on the Space Shuttle and Titan, reducing the amount of propellant required for development and permitting the use of smaller test stands. The SSX shape is simple aerodynamically; it is very similar to the Apollo Command Module for which tons of test and operational data exist. The incremental flight test program will begin with hover flights and move progressively up in altitude to orbit, just like testing a new jet airliner. The SSX comes back every time, unlike past rockets where test flights expended most or all of the expensive hardware. Finally, the SSX is designed to have a modest but useful payload capability to keep development and facilities costs down.

The name Spaceship Experimental emphasizes the similarity to air transport development. Aerospace engineer Maxwell Hunter coined the name SSX to recall the days of experimental aircraft development at Edwards Air Force Base when hardware was built, flown, and rebuilt incorporating the flight test data in less than a year.

SSX and Current Space Operations

United States space operations can smoothly and quickly make the transition to using production SSX launch vehicles. The SSX design has inherently more reliability and lower operations costs than the current generation of space launch vehicles. Within two years after the first production SSX rolls off the line, SSX vehicles can take over the launch of at least a third of all U.S. national security, civilian, and commercial payloads.

Launch Site Support

The SSX is designed to be easy to launch from limited launch facilities. The broad base area spreads the vehicle exhaust gases over a wider area thantraditional space boosters, thus reducing launch pad heating and erosion rates. SSX does not use solid rocket motors, thus it has low water deluge requirements for launch pad protection and acoustical load suppression. The short squat vehicle shape eliminates the need for large gantries and towers. For payload integration, the unfueled SSX vehicle could be roIled in and out of a modest-sized integration building, or the SSX vehicle could be serviced with a rolling payload changeout derrick plus environmental shelter. The short large-diameter payload compartment is easier to handle than the long multi-section shrouds used on the Titan IV.

New launch sites will be much easier to establish for SSX than any current space booster. The SSX liquid oxygen and liquid hydrogen propellants are nontoxic and the vehicle is modest in size, significantly reducing any environmental impacts. The intact abort capability plus highly reliable design will permit rapid FAA certification for the SSX to overfly populated areas during ascent, giving SSX an all-azimuth launch capability. For higher inclination orbits, SSX could be launched from Colorado Springs to take advantage of the higher altitude and resulting reduction in air drag losses.

Existing Payloads

Assuming an initial certified payload capability of four tons into polar low-earth orbit, the SSX can immediately launch most spacecraft now flown on the Delta, Titan II, and Scout boosters. The SSX offers a larger payload volume and lower acceleration, vibration, and acoustical loads than these boosters. Unlike the Space Shuttle, the SSX launch and landing loads are all longitudinal, and no structural modifications will be necessary to payloads designed for expendable vehicles to fly them on an SSX.

The SSX combination of low cost per launch, operational flexibility, and high-surge capability are ideally suited to the support of national security missions. The. Strategic Defense Initiative space-based interceptor system and the related Brilliant Pebbles concept are both perfect candidates for launch on SSX. Lower-cost tactical support satellites (also known as CINCSats) could be flown at low cost on the SSX, with fewer size and weight constraints than the small, solid-propellant launch vehicles now proposed for the job. SSX launch vehicles can fly from dispersed launch sites into the crucial high-inclination orbits using their all azimuth launch capability. Previous Air Force studies have shown that a complete liquid oxygen/liquid hydrogen propellant production systemcan be airlifted on a C-5B pallet to a site and then. hooked up to electrical and natural gas supplies. Using the SSX vehicle tanks for storage, such a system could support two or more flights per week.

Future Payloads

The attributes of the SSX offer benefits for the designers of future spacecraft. The larger payload volume can eliminate the requirement for some deployment operations by permitting the launch of a spacecraft with these appendages already extended. The. relatively low 3-G maximum longitudinal acceleration level during ascent plus the use of large-diameter structural interface adapters will reduce spacecraft launch loads. Spacecraft can be checked out while still attached to the SSX and returned to earth if any critical problems are detected. With the high SSX mission reliability, spacecraft program managers can have the same high confidence in the space launch portion of their launch operations as they do today in the transport of their spacecraft from the factory to the launch site in a cargo aircraft.

The SSX vehicle has a higher mass-fraction than the Centaur upper stage. After refueling in orbit from other SSX vehicles or an orbital fuel depot, an SSX could boost a payload into geosynchronous or Molniya orbit. The SSX could then deboost and return using aerobraking into low earth orbit or reenter and land, leaving no discarded upper stage or other debris.

Manned Operations

The intact abort capability of the SSX plus its inherent reliability will make SSX passenger certification a very similar process to that of commercial air transports. The certification process will include the same methodical testing of the flight and performance envelope of the SSX as currently used to certify a commercial jetliner. The vertical takeoff and vertical landing SSX design plus the low flight costs will permit an extensive test series with dozens of test flights.

The initial payload capacity of the SSX will permit the launch of a three to six person module similar to the Apollo Command Module into low-altitude earth orbits. The SSX vehicle will provide the thermal protection and propulsion systems for the attached crew module. Recent studies of similar manned modules include a Crew Emergency Rescue Vehicle (CERV) for Space Station Freedom performed by NASA contractors and an independent concept for a Multi-Role Capsule performed by members of the riechnical staff of British Aerospace. Such a module can include a working airlock assembly for crew transfer to other manned vehicles and to support extravehicular activity (EVA).

The combination of SSX and passenger module can supplement the Space Shuttle to allow more frequent crew rotation for Space Station Freedom. The operational flexibility, low cost, and rapid turnaround of the SSX vehicle will easily support both medical and emergency evacuation of Space Station Freedom crew members without incurring the development and operations costs of the proposed CERV.

Afterword to Access to Space: SSX

Lest anyone get the wrong idea, I had no hand in the design of SSX. The concept has a long and honorable history, with contributions from a great number of people. It's very hard to give credit here: how do you separate those who thought up technical features, those who recognized their importance, and those who integrated them into a new design?

What I can claim credit for is chairing a meeting of the Citizens Advisory Council on National Space Policy at which the SSX was chosen as the proper ship for those who want to focus on citizen access to space. I was then part of the team that carried that concept to Vice President Quayle and helped convince him that the concept was worth an independent evaluation.

All of which is preparatory to a pitch: the L-5 Society has merged with the National Space Society (NSS), and has become yet one more part of the NASA cheering section. NSS now seems to have the typical Washington attitude that nothing of importance happens outside the Beltway, and nothing can be done without the government. As for me, as I watch The Incredible Shrinking Space Station, the redesigns of things that weren't broken, and the general bureaucratic CYA attitude, I am convinced that NASA is the problem, not the solution.

Recall Dick Rhutan patting Voyager's wing after his historic flight: "See what free men can do," he said.

Well, we're going to try. Jim Ransom, Phil Chapman, and some of the other old L-5 enthusiasts have started The Lunar Society. The Society exists; it has a legal charter. It isn't precisely looking for members, but we'll take them. We prefer people who want to do something.

There's no big membership-services group, because the organization has no full-time employees. If you want to register, it costs one hundred dollars, and the only thing you get for that money is our personal guarantee that we won't waste the money. If you're interested, the address is: The Lunar Society, 3960 Laurel Canyon Blvd., Suite 372, North Hollywood, CA 91604 (see footnote). Please don't write to ask for "information." We don't have any fancy brochures. Just hard-working people trying to put a colony on the moon - in our lifetimes.

J Ransom & J E Pournelle, , "Access to Space: SSX", Cities in Space. 1991, ISBN 0-441-10591-2.
Also downloadable from to space ssx.shtml

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