Belief is no substitute for arithmetic.

MS-DOS isn't dead, it just smells that way.

A bit of tolerance is worth a megabyte of flamming.

If you lie to the compiler, it will get its revenge.

Solid-fuel rockets can't easily be shut down on command.

Testing a parachute drop of a heavy object is not simple.

C++ is the best example of second-system effect since OS/360.

Those who do not understand Unix are condemned to reinvent it, poorly.

Rocket engines generally are simpler than jet engines, not more complicated.

Altruism is a fine motive, but if you want results, greed works much better.

Politics /n/: from 'poly ticks', short for 'many small bloodsucking insects'.

Progress requires setbacks; the only sure way to avoid failure is not to try.

Programming graphics in X is like finding the square root of PI using Roman numerals.

Claiming that solid rockets are necessary for a heavy-lift launcher is obvious nonsense.

SpaceX does seem to have had a run of bad luck, with its first three launches all failing.

The demise of Constellation is not the death of a dream. It's just the end of an illusion.

To err is human, but to really screw things up requires a design committee of bureaucrats.

Foul-ups in testing are not uncommon, especially when the test setup is being tried for the first time.

Spaceflight, especially in the Mercury spacecraft, clearly wasn't going to be much like flying an airplane.

If your goal is to change the world, you can't start by doing things the same old way because it sells better.

Is manned space exploration important? Yes - not least because it simply works much better than sending robots.

As plans for the first lunar landing started to be made, nobody had really thought about who would be out first.

Since SpaceX's very beginnings, they have talked about recovering and reusing at least the first stages of their rockets.

In a small spacecraft, it was hard for the other two guys to sleep when the on-duty man was talking to Mission Control regularly.

The Moon may not be quite as appealing as Mars, but it's still a complex and poorly understood world, with many questions still unanswered.

The Apollo programme of the 1960s had some weight problems, too; in particular, the lunar lander needed some fairly drastic weight-reduction work.

Liquid oxygen is one of the cheapest manufactured substances on Earth. In large quantities, it costs pennies per kilogram - cheaper than milk or beer.

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.

One of the headaches of high-tech test programmes is having to debug the test arrangements before you can start debugging the things you're trying to test.

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.

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.

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.

My one concern is that when money gets tight, it's easy to cut R&D funding that isn't tied to a specific project - look at what's happened to NASA's aviation research.

The communications delays between Earth and Mars can be half an hour or more, so the people on the ground can't participate minute by minute in Mars surface activities.

Speaking of photography, while the Apollo 8 crew shot hundreds of photos, there was one that got everybody's attention: a blue-and-white Earth rising over a gray moonscape.

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.

In the first few years, it was at least plausible to come in in the morning and read all the Usenet traffic that had come in, and 15 minutes later be off doing something useful.

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.

Not until the space shuttle started flying did NASA concede that some astronauts didn't have to be fast-jet pilots. And at that point, sure enough, women started becoming astronauts.

NASA has never had a problem finding capable people to be astronauts. NASA's problem was, and still is, finding ways to cut the list of capable applicants down to a manageable length.

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.

The original specifications for Apollo navigation called for the ability to fly a complete mission, including a lunar landing, with no help from Earth - none, not even voice communications.

In 1960-61, a small group of female pilots went through many of the same medical tests as the Mercury astronauts and scored very well on them - in fact, better than some of the astronauts did.

Sure, there were hopes that Constellation's systems could later be adapted to support more ambitious goals. But Apollo had those hopes, too. It didn't work in 1970, and it wasn't going to work in 2020.

On the technical side, Apollo 8 was mainly a test flight for the Saturn V and the Apollo spacecraft. The main spacecraft system that needed testing on a real lunar flight was the onboard navigation system.

The Orion capsule uses an escape system quite like that of the Apollo spacecraft in the 1960s and 70s: an 'escape tower' containing a solid-fuel rocket that will pull it up and away from Ares I in a pinch.

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.

If I must be ruled by larcenous bullies, I much prefer that they be located far away. Local bullies know far more about me and my doings than faraway bullies sitting in offices in Washington, and can oppress me far more effectively.

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.

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