NASA Grounds Space Shuttle Fleet

Rytsarsky writes "This story (Reuters) at MSNBC explains why NASA has grounded the fleet. They have been grounded 'indefinitely after finding small cracks in propellant lines on the main engines of two shuttles.' This will 'delay the scheduled July 19 launch of shuttle Columbia.' Good thing this was caught before something catastrophic happened."

Comments

Time to move on

[lindsayt]

Further proof that the Shuttles are dying and their time has passed. They're unnecessarily big, wasteful, and difficult to maintain. That's not to say that I have a replacement or that I'm smug enough to believe I know better than the rocket scientists though...

NASA has been crippled by budget cuts and the deadweight of maintaining technology that was designed 25 years ago (remember, the Enterprise test flights were in and around 1980, and by then the design was mainly done). Perhaps it's time for us to revisit Chuck Yeager's opinion that we should not use deadlift rockets but should instead fly into space. I've heard that the shuttle uses up more fuel to go the first 100 feet than a packed 747 uses for its entire flight. Now, if we could use a graceful system like horizontal launch to first break the inertia, then a rocket boost up in the 10K-30K feet range (3KM-10KM roughly) would be much more efficient and allow heavier cargo and more people in the same space as our current shuttles.

The rumor is that Chuck Yeager was struck down in the first place because of the political reality that rockets were more impressive and seemed a radical break with past technology, not because of superior lifting ability. I don't know that to be true however...

Re:Time to move on

[medcalf]

It's actually remarkably difficult to get from the surface (or subsurface) of the Earth into space. There's a reason that they compare the difficulty of things to "rocket science". The payload is typically less than 10% of the weight lofted, with the rest being fuel/oxidizer (for simplicity, henceforth "fuel") and structure. And of that, most of the weight is oxidizer. The more you want to lift, the more fuel you need. But adding fuel adds the weight of both fuel and the structure to contain it. This means that you need more fuel to lift it. Eventually, you find a nice place where you can lift the appropriate payload and fuel and structure. If, that is, you can build something that big - depends on the payload size and orbit (which together determine the amount of energy needed to loft the payload), launch pads, assembly buildings and so forth. It's difficult and it's expensive.

Are there other ways to do this than big chemical rockets? You bet. You can use nuclear rockets, like the NERVA program. You can build a rocketplane (hybrid rocket/jet). There are other options (lifting under a balloon, for example), but they are not very attractive, for a variety of reasons.

Nuclear rockets are great from a technical standpoint. If you used minimal shielding (to minimize the weight while still protecting the cargo) and didn't care about radioactive exhaust, you could theoretically launch more for less, given the high specific impulse of the engines and the lack of oxidizer, which together make up for the weight of the reactor vs. a traditional rocket. Practically, this won't happen for political reasons, though nuclear rockets may some day be lifted into space as payload, then used to move things around.

Pathfinder takes a nice approach: put both jets and rockets onto the ship, and take off without oxidizer. The ship would use the jets to fly up to a tanker, which would provide the oxidizer. The ship would then separate from the tanker, point up and light the rockets. Since no oxidizer is carried to get through the majority of the atmosphere, the total weight of the ship is much less (it needs less structure to hold oxidizer, because it uses less oxidizer). The oxidizer is carried up by a tanker, which is airbreathing, and the net effect is to be much more efficient. You could argue whether or not to carry the rockets and jets both, or just to carry rockets, and enough oxidizer to get up to tanking altitude. There are advantages and disadvantages to either.

The other nice thing about this approach is that you have built an airplane. It can be tested incrementally, and can be fully reusable with minimal refurbishment between flights. It can self-ferry to whatever airport is appropriate for whatever mission it is going to fly, and could land at any large airport that can provide the fuel of your choice (probably kerosene). The problem with this approach is that it's never been done, and there is no real constituency to do it. Unless a private company like Pioneer Rocketplane manages to get the necessary funding, or a government suddenly decides to anger its current spaceflight constituency in order to boost a doubtful new spaceflight constituency, the concept won't get tested.

The end result of all of this is that it is unlikely that the current situation will change, and it is unlikely that a shuttle-like system will ever be built to replace the shuttle. We'll continue to use disposable rockets for most things, with huge failure rates, and refurbish the shuttles until we decide that manned spaceflight is too hard for us to do, the precedents of history notwithstanding.