During the last fifty years the United States has spent billions trying to develop a cost-effective space plane. Most of these efforts were abandoned as failures. Only two space plane designs were built and used. The first was the 1980s manned Space Shuttle and the more recent unmanned X-37B.
In the 1990s NASA spent nearly a billion dollars on the proposed Lockheed X-33, a single-stage to orbit space plane. That effort failed and was canceled in 2001. The next year the U.S. Air Force proposed a joint effort with NASA to develop a more practical Military Space Plane. This effort would develop tech that could also be used by NASA for a Space Shuttle replacement and other military and civilian programs. Two different space vehicle programs would cost more than building extra copies of a single design. The first part of the new Space Plane effort would be the SOV, or Space Operations Vehicle. This would be a large booster rocket, possibly two stages initially and ultimately one stage, that would put an SOV into orbit. SOV was meant to put several different payloads in orbit. These would include the SMV, or Space Maneuver Vehicle: This might be a small, reusable, manned orbiting vehicle able to conduct any of several missions and then land at a military airbase. Not really designed to launch satellites, this could be used as a reconnaissance platform in a conflict.
Another SOV payload would be the OTV or Orbital Transfer Vehicle. This was a manned spacecraft designed to launch and service satellites. It would be able to land at very long runways.
Then there was the MIS or Modular Insertion Stage: This was an unmanned expendable upper stage booster designed to put satellites into orbit. In theory, during a crisis, the Air Force could use a stockpile of SOVs with these MIS stages to rapidly deploy more military satellites.
Finally, there was the CAV or Common Aero Vehicle. This was taken into the upper atmosphere by the SOV but would skip along the upper atmosphere rather than travel in space exclusively. It would be used to rapidly deliver precision weapons. In theory, the CAV could replace the B-2 bomber on 16,000-kilometer missions, conducting them in a fraction of the time.
One object of the MSP concept was to cut down the time required to plan and launch any kind of payload. Back then it could take six months to get a payload and a space shuttle to match and launch something into orbit, even if you are willing to change the pre-set schedule for the space shuttle fleet. The MSP would, in theory, be able to conduct a launch within three or four weeks of somebody deciding that a given payload was needed. In some cases, such as putting a manned recon platform into orbit, such a launch could take place within a few days.
The Space Shuttle program was a success as it put a manned spacecraft into orbit where it could maneuver and perform tasks like inspecting and repairing satellites in orbit. In some cases, a small enough satellite could be brought back to earth for repairs and upgrades and launched again. The Space Shuttle program flew 133 manned missions between 1981 and 2011, with two shuttles lost in fatal accidents. That was enough to end the program, which was already in trouble because of the cost, about $100 million per launch.
Even before the Space Shuttle program ended NASA and the Air Force began a program of developing satellites and SLVs (Satellite Launch Vehicle) that could do the same work. The NASA program began in 2007 and continues. Another solution is also about to fly as a Space Plane (by Radian) aircraft similar to the Space Shuttle, but one that can take off like an aircraft and under its own power and reach orbit. There the crew can inspect and repair satellites in lower orbits. This Space Plane then leaves orbit and lands like the Space Shuttle did. Until the Radian Space Plane came along, no one had come up with a manned Space Plane design that could get itself into orbit on its own with a useful load and then land like an aircraft.
The Space Shuttle was retired because it was the most expensive way to get stuff into orbit. Satellites sent up via the Space Shuttle cost $25 million a ton to put in orbit. The Russians and Chinese did it for under $10 million a ton using old but reliable single-use rockets as SLVs. But insurance can more than double that cost if there have been a number of recent failures. That is what happened with Russian and Chinese boosters. The Space Shuttle failure rate was two percent, which was similar to most Western satellite launchers. This keeps more reliable and expensive American and European SLVs in business.
The price competition has become more intense because the Americans have developed and are increasingly using SpaceX (Space Exploration Technologies Corporation) SLV technology. The SpaceX reusable rockets, which repeatedly returned to earth and landed intact under their own power, fundamentally changed the SLV business because these rockets are refurbished and used again and again. This saves a lot of time and money.
Radian, like SpaceX, takes full advantage of new technology to make their Space Plane design work. Several venture capital firms are supplying money so Radian can prove its concept works. Technically, the Radian Space Plane is a reusable SSTO (single stage to orbit) aircraft that can carry a crew of five and up to 2.3 tons of cargo into orbit. Radian has developed a new rocket engine that can be mounted in the rear of a space plane like a jet engine, but without the air intake, and generate 200,000 pounds of thrust. The Radian One space plane has three of these engines and, with the help of a high-speed reusable sled, is carried down a long runway until it is near lift-off speed, at which time the rocket engines ignite, taking the space plane into LEO (low earth orbit).
Efforts like SpaceX inspired the Radian space plane effort. Both projects used the latest tech to do the improbable. With SpaceX it was a booster that could return to earth under its own lower, deploy stabilizing struts and land as science fiction rockets hand long done. SpaceX was funded by a single investor, a wealthy and successful engineer who understood the reusable rocket tech and got it to work. SpaceX revolutionized the SLV industry with some of its boosters already remaining in service after a dozen launches and landings. Larger models of Radian One can put more people and cargo into orbit and return safely and economically for another mission. Radian expects its first space plane to require only two days of maintenance before another mission. Even if Radian One does not work, it should definitely prove that the basic concept is closer to success.