Slashdot Mirror
Orbital Space Plane Problems
FTL writes "NASA's next big step in space (after getting the remaining Shuttles flying again) is the construction of the Orbital Space Plane. It is a small vehicle designed to transport people to and from ISS. Jeffrey Bell takes a close look at OSP in this article and comes to the conclusion that it will result in yet another crippled vehicle. Sounds like what people were saying about the Shuttle's problems back when it was being designed."
The X-prize is suborbital. Still, supporting a similar orbital prize may very well be a good idea.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Orbital Space Plane @ orbital.com
Orbital Space Plane @ globalsecurity.org
Actually, during the late 1980's there were some serious studies of building a small spaceplane that could be launched from the top of a modified 747-200.
Essentially, the 747-200 would be fitted with a de-rated version of the Space Shuttle main engine, which will allow the 747 with the spaceplane on top to do a steep 35 degree climb to around 50,000 feet. The spaceplane, which has a small external fuel tank attached, would then launch at that altitude and fire its engines (essentially 3-4 RL-10's used by the Centaur upper stage) for a 7 minute flight to orbit. Because the launch happens at 50,000 feet, there is no need for the spaceplane to lug along a big load of propellant fuel, and that means it could carry a load as large as seven crew members or its equivalent weight in cargo to the International Space Station. I can envision by 2014 crews will visit the ISS either by using this new spaceplane or much-updated versions of the Soyuz spacecraft; ISS consumables and future extensions to the space station will be brought up by lifting them to orbit on uprated versions of the Atlas V and Delta IV Heavy rockets plus updated versions of the Russian Proton rocket.
Your entire comment makes the rather broad assumption that air density is the same at sea level, 10km and 150km. I'm kind of thinking it drops pretty quickly.
.000460, air density at sea level is .002377, so air density at 45,000 feet is about 1/5 that of sea level (google rocks, chart 1).
It saves quite a bit of fuel because there is significantly less drag at 10km than there is at sea level. 10km would be, what, pretty much 35 thousand feet, but the service ceiling of an unmodified 747 is 45,000 feet (google owns you).
Air density at 45,000 feet is
So, if the 747 dropped the payload at 45,000 feet, and the payload gained altitude at a good rate, it would require significantly less rocket fuel than taking off from the ground. In addition, the payload could have smaller fuel tanks, which means smaller pipes, less structure and less insulation to fall off and ding a wing.