An eligible replacement for the Space Shuttle is the Delta Clipper. It was originally developed and built in 1991-1993, and was completed as the DC-X. The DC-X was a joint venture between the United States Air Force, and was intended to be a one third scale prototype of an RLV proposed by the Strategic Defense Initiative Organization (SDIO).
A primary goal of the Delta Clipper project was to show that an RLV was possible, and that the RLV could be operated in a manner similar to a commercial airliner. That meant that the Delta Clipper team was attempting to develop a spacecraft that could be flown very often, with little maintenance required between flights. The team succeeded in running the Delta Clipper from a much smaller building than the Space Shuttle uses. Figure 2 below shows the Vehicle Assembly Building (VAB) that supports the Space Shuttle. The VAB is also where much of the between flight maintenance is performed. The VAB is a very specialized building, but it is also very massive; the American flag on the building is approximately the size of a football field. On the other hand, Figure 3 shows the support garage that the Delta Clipper team used to service and maintain the DC-X. The difference between the two buildings couldn’t be bigger.
Another way in which the DC-X could be operated in a manner similar to a commercial airliner was its long-term storage capabilities. At one point during the testing, the Delta Clipper project was temporarily halted due to budget cuts, and the engineers of the project turned the delay in funding into an experiment. The engineers built a makeshift shelter around the DC-X on its launch pad, and left it that way for some months. When the engineers returned from their prolonged break, the shelter was taken down, and the DC-X tested for flight readiness. The engineers determined that the spacecraft could be prepared and ready for a flight within a week.
The Delta Clipper’s flight profile was also much simpler than the Space Shuttle’s is. Figures 4 and 5 below show the mission profiles for the Space Shuttle and the Delta Clipper, respectively. The Space Shuttle’s mission profile is as follows. First, the Shuttle takes off, and then the solid rocket boosters are disengaged, and dropped into the ocean, from where they must be recovered later. Next, the fuel tank is detached and dropped. Then the Shuttle enters orbit, where it performs its mission. Finally, the Shuttle reenters the earth’s atmosphere, and lands at one of the few places where the runway is long enough to accommodate it. The Delta Clipper, on the other hand, has a much simpler profile. The Delta Clipper takes off, enters orbit without dropping any fuel tanks or boosters, where it carries out its mission. Then, the Delta Clipper de-orbits and reenters the atmosphere, where it could land anyplace that has a decently size concrete pad.
The simplicity of the Delta Clipper’s flight plan isn’t its only selling feature; it also takes a very short time to build, and is cheap enough to build several Delta Clippers for each of the Space Shuttle’s launches. Even though the DC-X was just a subscale prototype, a full-sized Delta Clipper would still cost less to build than it costs to launch the Space Shuttle once. The original DC-X was completed in 21 months by a team of 100 people, and cost a grand total of $60 million, built completely of off-the-shelf parts [3]. After the build phase, the US Air Force completed 8 flight tests. During the fifth flight test, the vehicle demonstrated its automatic landing capabilities; after a small leak in the fuel lines caused an explosion, the vehicle initiated an automatic landing sequence and settled itself to the ground safely. The DC-X was also designed to have an engine-out capability comparable to the characteristic of the same name of commercial airliners.
Later on, NASA acquired the Delta Clipper program and changed the name to DC-XA. NASA installed experimental fuel tanks and better reaction control systems, reducing an already light vehicle’s weight by 620 kilograms. NASA then conducted 4 flight tests and 2 static engine tests.
The effort required to resurrect the Delta Clipper program wouldn’t be very great. Many tests showing the proof that the concept works have already been conducted, and the vehicle’s capabilities have already been proven. Therefore, the Delta Clipper is simply a space vehicle nearly ready for use. All that remains is some final testing, building a full-size vehicle, and then putting the spacecraft to work.
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A primary goal of the Delta Clipper project was to show that an RLV was possible, and that the RLV could be operated in a manner similar to a commercial airliner. That meant that the Delta Clipper team was attempting to develop a spacecraft that could be flown very often, with little maintenance required between flights. The team succeeded in running the Delta Clipper from a much smaller building than the Space Shuttle uses. Figure 2 below shows the Vehicle Assembly Building (VAB) that supports the Space Shuttle. The VAB is also where much of the between flight maintenance is performed. The VAB is a very specialized building, but it is also very massive; the American flag on the building is approximately the size of a football field. On the other hand, Figure 3 shows the support garage that the Delta Clipper team used to service and maintain the DC-X. The difference between the two buildings couldn’t be bigger.
The Delta Clipper’s flight profile was also much simpler than the Space Shuttle’s is. Figures 4 and 5 below show the mission profiles for the Space Shuttle and the Delta Clipper, respectively. The Space Shuttle’s mission profile is as follows. First, the Shuttle takes off, and then the solid rocket boosters are disengaged, and dropped into the ocean, from where they must be recovered later. Next, the fuel tank is detached and dropped. Then the Shuttle enters orbit, where it performs its mission. Finally, the Shuttle reenters the earth’s atmosphere, and lands at one of the few places where the runway is long enough to accommodate it. The Delta Clipper, on the other hand, has a much simpler profile. The Delta Clipper takes off, enters orbit without dropping any fuel tanks or boosters, where it carries out its mission. Then, the Delta Clipper de-orbits and reenters the atmosphere, where it could land anyplace that has a decently size concrete pad.
Later on, NASA acquired the Delta Clipper program and changed the name to DC-XA. NASA installed experimental fuel tanks and better reaction control systems, reducing an already light vehicle’s weight by 620 kilograms. NASA then conducted 4 flight tests and 2 static engine tests.
The effort required to resurrect the Delta Clipper program wouldn’t be very great. Many tests showing the proof that the concept works have already been conducted, and the vehicle’s capabilities have already been proven. Therefore, the Delta Clipper is simply a space vehicle nearly ready for use. All that remains is some final testing, building a full-size vehicle, and then putting the spacecraft to work.