Henry Spencer
Henry Spencer
Henry Spenceris a Canadian computer programmer and space enthusiast. He wrote "regex", a widely used software library for regular expressions, and co-wrote C News, a Usenet server program. He also wrote The Ten Commandments for C Programmers. He is coauthor, with David Lawrence, of the book Managing Usenet. While working at the University of Toronto he ran the first active Usenet site outside the U.S., starting in 1981. His records from that period were eventually acquired by Google to provide...
NationalityCanadian
ProfessionScientist
CountryCanada
Large solid rockets have never been a very good way to build launchers that might have crews on top, especially because of the problems in getting the crew away from a failing launcher.
Developing expendable rockets is always going to be painful and expensive. Throwing the whole rocket away on each attempt not only costs a lot, it also hampers figuring out just what went wrong because you don't get the rocket back for inspection.
Solid-fuel rockets can't easily be shut down on command.
Claiming that solid rockets are necessary for a heavy-lift launcher is obvious nonsense.
Sometimes people wonder why aeroplanes are so cheap and rockets are so expensive. Even the most superficial comparison shows one obvious difference: aeroplane engines use outside air to burn their fuel, while rockets have to carry their own oxidisers along.
Reusable rockets promise much easier testing because you should usually get them back, and you can debug as you go rather than having to get everything perfect the first time.
Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular.
Past experience, on the shuttle and the Titan rockets, suggests that large multi-segment solid rockets have a probability of failure of 0.5 to 1 per cent.
Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it's hard to make it pay off - Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap.
The key virtue of orbital assembly is that it eliminates the tight connection between the size of the expedition and the size of the rockets used to launch it.
Technically and financially, it might still make sense to give up on Ares I and simply write off the money spent on it, but politically, that's probably impossible.
Sometimes a malfunctioning test setup actually gives the tested system a chance to show what it can do in an unrehearsed emergency. During a test of an Apollo escape system in the 1960s, the escape system successfully got the capsule clear of a malfunctioning test rocket.
It's true that Apollo 10's lander was overweight. Late in the craft's development, it became clear that its ballooning weight was endangering the whole mission.
In the long run, it's impossible to make progress without sometimes having setbacks, although people who get lucky on their first attempt sometimes forget this.