Nov07
The Maturity Of The Space Shuttle
on November 7, 2012 at 10:28 amSome thoughts from Wayne Hale. It was always an experimental system, and NASA is making exactly the same mistake with the SLS. If anything, they’re compounding it with the low flight rate.
And the real, total system, every time it flew, it flew right down the center of the envelope.
This
Great post. Thanks for sharing it.
And with SLS, unlike Shuttle, the SRBs won’t be recovered, meaning that much less data about their performance will be collected. I suppose there’s one bright side to this. Is an SRB blows up someday, people won’t be able to point a finger at NASA management and say it ignored all of the data from previous flights showing there was a problem — because there won’t be any such data!
This points out the extreme difficulty of operating expendable vehicles, because they can’t be properly tested unless we increase the development cost by nearly an order of magnitude.
Also, it raises the question of whether or not we’ll ever truly be able to have launch systems that can be declared operational in the same sense as aircraft. Consider what it means to test the corners of the envelope in an airplane. Generally speaking unless you’re testing supersonic aircraft the worst case scenario is that the plane will become uncontrollable for a while or it will stall or go into a spin. The vast majority of these things are fairly easily recoverable.
But when you move to the hypersonic, high dynamic pressure, high thrust world of rocketry everything changes. The land outside the envelope isn’t filled with stalls and spins, it’s filled with explosions, vehicle disintegration due to aerodynamic forces, excursions toward the bounds of range safety, and in general catastrophic loss of the vehicle. A properly reusable vehicle can be used to test vastly more of the problem space in the operating envelope but there are still a great many corners of the envelope that will be expensive to test due to the near certainty of losing the vehicle. Which also means that we don’t dare test those corners with manned vehicles.
We’ll certainly be able to do far better than we have done but it’ll be a long time before launch vehicles can be as well tested and as well trusted as airplanes.
Also, it raises the question of whether or not we’ll ever truly be able to have launch systems that can be declared operational in the same sense as aircraft. Consider what it means to test the corners of the envelope in an airplane. Generally speaking unless you’re testing supersonic aircraft the worst case scenario is that the plane will become uncontrollable for a while or it will stall or go into a spin. The vast majority of these things are fairly easily recoverable.
It’s worth noting that airplanes weren’t operational in that sense for a while too. Space launch is a different beast, but I think there’s a lot of room for reliability and safety improvements once we get a higher launch rate.