Consequently, the Board has levied a requirement that the whole Shuttle system be retested and requalified by 2010. This would be impossibly expensive, given that many of its components and fuels are so old and dangerous that they would have to be replaced.

So NASA finally has an unofficial but hard deadline beyond which no shuttles will fly. In the next six years, NASA has to develop at least one and possibly two new spaceships to support the crew exchange and supply needs of the International Space Station.

What will these new vehicles be like? One thing is now certain: they won't be any kind of "spaceplane", even if "Orbital Space Plane" still lingers as the official name of the development program. Like Count Zeppelin's airships, the spaceplane blindly perpetuates the habits and traditions of a previous technology (seafaring/aviation) in a new medium (air/space) which actually requires a completely fresh concept.

Like the zeppelin, the spaceplane can be just barely made to work with an immense amount of skilled labor and public funding, but is so inefficient and dangerous that it would never compete with a vehicle designed specifically for the new medium of space from a clean sheet of paper.

The basic problems with airplane-like designs are numerous and crippling. Many of these problems are so bad that the Space Shuttle's engineers and flight controllers (the only people who deal with a real nuts-and-bolts spaceplane instead of an idealized fantasy vehicle) have developed well-justified phobias about them. These phobias were well in evidence during the doomed last flight of Columbia, and made significant but little-noted contributions to that catastrophe.

Compromise shape: The spaceplane concept originated back before there was any experimental data base on hypersonic velocities. Since airplanes had progressively become more streamlined as speeds increased, it was assumed that sharp needle-nosed designs would suffice for orbital returns.

When the first wind-tunnel tests were made in the early 1950s, it turned out that blunt rounded shapes are needed at orbital entry velocities to minimize aerodynamic heating.

Consequently, the Shuttle orbiter is a compromise design, just blunt enough to survive the early stages of reentry, but still shaped enough like an airplane to "glide" subsonically at an angle of 20-25 degrees.

It is this compromise shape that causes extremely high heating rates at the wing leading edges, and dictated the use of the extremely brittle RCC material at these points.

Inefficient packing: Spaceplane designers have to find internal volume for many components of odd shapes that can't be changed. The Shuttle's double-delta wing was adopted partly to house the landing wheels. As the unsuitability of wing+fuselage designs have become apparent, spaceplane designs have tended to converge with those of capsules.

This convergence has resulted in a family of lifting-body designs where fuselage and wings are integrated. These shapes are very awkward and difficult to utilize efficiently.

A major reason for the dismal failure of the X-33 was the need to store its cryogenic fuels in complex multilobed tanks which proved overweight and impossible to fabricate.

Unstable aerodynamics: It has proven very difficult to find configurations that are inherently stable over the immense speed ranged a winged RV must endure (M25 to M0.3).

The Shuttle and most other winged spacecraft designs rely heavily on active stability augmentation by computers, and could not survive a computer failure in many flight regimes. Active control also requires a source of hydraulic power during reentry, which the Shuttle obtains from a battery of hydrazine-fueled turbines that frequently catch fire or explode.

Windows: Since subsonic airplanes have windows at the front with pilots looking out, most spaceplanes have them also. But of course the front is the worst possible place for a window on any hypersonic vehicle subjected to intense frictional heating. Only by flying most of the reentry at a high angle-of-attack can the Shuttle windshield be kept from melting. This is a particularly clear example of a pointless tradition. There is really no need for forward vision on Shuttle, since most in-orbit tasks occur "above" or "behind" the crew cabin, and the pilots don't manually fly the vehicle during reentry or landing.

Landing gear: The nose-up entry protects the windshield, but exposes the bottom of the spaceplane to maximum heating. On a ballistic RV, this area is always solid and unbroken. On a spaceplane, the belly must be pierced by three large doors for the landing gear. This inherent vulnerability is why the Shuttle engineers obsessed about the foam having struck Columbia's left main gear door and neglected the possibility of a strike on the leading edge.

Tires: Letting rubber tires soak in vacuum for weeks and then putting them through reentry only inches away from the belly tiles is asking for trouble. It is no wonder that the Columbia's controllers feared a tire failure and were preparing to order the crew to bail out once they reached subsonic velocity. Again, a inherent flaw in the spaceplane concept distracted the controllers' attention from what was really happening.

Irrational seating: The airline-style seating in spaceplanes is correct for launch, with the acceleration in the most favorable orientation (eyeballs-in). However, upon reentry, the lift forces on a winged vehicle are in an unfavorable direction (eyeballs-down) and the drag forces are even worse (eyeballs-out). It would be logical to recline or even turn around all the Shuttle's seats before reentry. This isn't done because it would prevent the pilots from looking out the windshield and pretending that they, not computers, are flying the vehicle.

Massive overweight: All this unnecessary baggage of wings, flaps, hydraulics, APUs, wheels etc. makes a winged or lifting-body design about three times heavier than a capsule design, and therefore at least three times more expensive to launch.

Restricted landing capability: The spaceplane can land only on a few long runways or dry lakes, whereas a parachute-landing vehicle can come down anywhere in the ocean. It is strange that both the US and Russia ignore this and weigh down their manned spacecraft with extra systems to allow land recoveries. NASA has two seagoing recovery ships that it rents out for the long idle months between Shuttle launches. Even an emergency ditching is impossible for most spaceplane designs due to their high landing speed and AOA.

Lack of development potential: Winged RVs can barely cope with entry from LEO; they have never been considered as return modules for lunar or deep-space missions where far more reentry energy must be dissipated. The 1967 Apollo CM was considerably over-designed for its mission and could cope with any likely Mars return trajectory. And by 1980 we had the Galileo probe RV that survived a direct ballistic entry into Jupiter's atmosphere.

Booster incompatibility: A spaceplane mounted on an expendable booster is like an arrow with the feathers at the front. It requires massive tailfins or expanded control authority from its engines to avoid swapping ends during launch. The EELV boosters would have to be significantly redesigned and consequently, requalified to launch a spaceplane.

Poor abort capability: During the later stages of a typical rocket ascent, the booster is traveling at nearly orbital altitudes but still well below orbital speeds. If the booster fails and the spaceplane pulls away from it safely, it is now on a very steep reentry path.

Unless it has an impossibly high hypersonic Lift/Drag ratio, it will be unable to pull out of this steep dive before reaching the thick lower atmosphere and will be destroyed by excessive heating and/or g-forces.

This problem was first discovered during the development of the X-20 Dyna-Soar spaceplane in the early 1960s. It can be ameliorated by having the booster pitch over more quickly and reaching orbital velocity at a lower altitude.

However, this safer ascent path is much less efficient and places increased aerodynamic stress on the booster. While published documents do not confirm this, it's possible that this problem accounts for the adamant refusal of the designers of the ESA's Hermes spaceplane to include any escape rocket system, and the removal of such a system from the Shuttle late in its development cycle.

This last issue was also a show-stopper for NASA's original pre-Columbia concept of a winged and wheeled Orbital Space Plane. After Columbia, it is impossible to imagine the US Congress funding any manned vehicle that lacks a robust launch abort capability. And given the launch azimuth from the Cape to the ISS and the ascent profiles of the EELVs, there really is no viable launch-abort option for the OSP except a water-landing capsule with an escape tower.

NASA HQ has communicated this decision to the three competing contractor teams in its usual deceptive way by advancing the operational date from 2010 to 2008. Five years is just not long enough to develop a completely new design. So it is no surprise that the London-based magazine The Engineer reports that both Boeing and Lockheed-Martin have abandoned their winged designs and will propose Apollo-derived semi-ballistic capsules for the OSP competition. Clearly this program needs a name change -- perhaps OST for "Orbital Space Transport" as suggested in a press release by Florida Rep. Bill Weldon.

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