I’ve not written much about NASA’s planned “Orbital Space Plane” (OSP) program because, for various reasons, I’ve thought it beside the point. I’ll explain why shortly.
It’s just the next stage in a continuing progression of abortive plans to either replace or complement the space shuttle that have been put forth for over a decade and a half. Of course, with the loss of a quarter of the essentially irreplaceable shuttle fleet three months ago with the Columbia disaster, the matter has taken on a seeming new urgency.
The OSP is viewed as an admission that (at least for our government space agency) the more grandiose plans for “Shuttle II” were unrealistic, with the failures of (among other things) the National Aerospace Plane, and the X-33 fiasco.
Instead, because the government (mistakenly) perceived that, as a result of these program failures, fully-reusable space transports were not achievable, they decided to back off to nascent plans of forty years ago–to place a reusable entry vehicle on top of an expendable launch system.
The original concept for this was called Dynasoar–a winged vehicle that would provide access to space on a rocket, and then return to earth to land on a runway. In fact, it was the first concept for manned space, predating Mercury, but it was cancelled in 1963.
But the dream never died. NASA’s OSP program is just the latest reincarnation of this ancient desire for a small, flexible winged passenger transport system.
Wings were desired because they provide much more accurate and precise control over landing locations, and a much more gentle touchdown (an important factor if the vehicle is to serve as an ambulance for ill or injured crew).
Winged entry vehicles have disadvantages as well, however. The guidance and navigation requirements are more exacting, because the vehicle must enter at precisely the right angle, with little margin for error, to avoid the kind of overheating and stresses that apparently destroyed Columbia in February. Moreover, the heat loads on wing leading edges are much higher than a more distributed load over a broad surface (such as a ballistic capsule) would be, so the thermal protection requirement is much more stringent. As we saw with Columbia, the thermal protection system was the ultimate “Achilles heel” for winged entry vehicles, and at this point, given that recent experience, it’s almost certainly one of the highest areas of technical risk, with extreme implications for safety.
Due to these and other factors (some of which are inherent to NASA’s way of doing business), resulting in absurdly high estimates (perhaps in excess of ten billion dollars) for cost and schedule to develop such a system, the agency has now been led to look at something simpler and less costly, albeit less capable and flexible as well.
The latest news is that NASA is looking back to Apollo as a concept for near-term crew access to and from space. The idea is to use a ballistic entry vehicle, that we know works well, based on the Apollo command module concept. Just how much of that original design would be used is still to be determined, as the article in the link shows, but at a minimum, the vehicle would employ the same outer mold line, or body shape, as the original capsules that returned our astronauts safely from the Moon several times in the late sixties and early seventies, with a great deal of margin in the thermal protection system.
There are many trade studies to be done, including whether or not to attempt to come up with a way of bringing it down on land rather than (as was done in Apollo) in the ocean, and how reusable to make the system, in which the type of thermal protection system will be the largest factor. Apollo used an ablative system, in which the insulation actually charred and came off in thin layers, carrying the heat away with it. This approach may make sense for the new vehicle as well, if such a shield can be made cheaply and easily changed each mission, but fully reusable shields employing more modern materials will be considered as well.
Such a system, with its greater forgiveness of guidance failures (demonstrated by the mishap on the Soyuz entry vehicle last week, in which the landing was hundreds of miles off target, and much harder than planned, due to a computer malfunction) might well be more robust than a more sophisticated space plane, in which a similar failure might have resulted in loss of vehicle and crew.
But as I said at the beginning of this column, I consider the whole issue personally moot, even if (in defiance of the long history of such programs) it turns out to be technically successful, because it is all based on a flawed premise–that we as a nation know what we want to accomplish in space, and that is to continue to send a few government employees up to a space station each year, and that we don’t mind spending billions of dollars per year to do so.
No one should be deluded that OSP in any form will reduce the costs of access to space, though it may make it moderately safer than the shuttle. No system that costs billions of dollars to develop and is used only a few times a year will ever even pay for itself, as we’ve seen with shuttle itself. And if we phase out shuttle, we will be back to a single, fragile infrastructure for getting people to and from space.
As long as the space agency’s and Congress’ focus remains on their own institutional and political needs, rather than on those of the nation, and they continue to ignore the yearning of millions of people for space activities of their own, we will continue to squander billions on a mission to nowhere.
And sadly, that too would be “back to the future.”