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" Solid-fuel rockets can't easily be shut down on command. "
Henry Spencer
Command
Shut
Down
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" Trying to build a spaceship by making an aeroplane fly faster and higher is like trying to build an aeroplane by making locomotives faster and lighter - with a lot of effort, perhaps you could get something that more or less works, but it really isn't the right way to proceed. "
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" Is manned space exploration important? Yes - not least because it simply works much better than sending robots. "
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" Progress requires setbacks; the only sure way to avoid failure is not to try. "
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" If your goal is to change the world, you can't start by doing things the same old way because it sells better. "
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" 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. "
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" Testing a parachute drop of a heavy object is not simple. "
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" 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. "
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" 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. "
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Group
Tests
Small
" 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. "
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Test
Chance
Escape
" Rocket engines generally are simpler than jet engines, not more complicated. "
Henry Spencer
Complicated
Than
Rocket
" 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. "
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Earth
Apollo
Voice
" The Apollo programme of the 1960s had some weight problems, too; in particular, the lunar lander needed some fairly drastic weight-reduction work. "
Henry Spencer
Apollo
Work
Weight
" 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. "
Henry Spencer
Virtue
Launch
Connection
" 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. "
Henry Spencer
Serious
Spectacular
Fail
" 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. "
Henry Spencer
Enough
Women
NASA
" 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. "
Henry Spencer
Long
People
Progress
" 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. "
Henry Spencer
First
Doing
Years
" 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. "
Henry Spencer
Sleep
Mission
Small
" 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. "
Henry Spencer
Money
Impossible
Off
" As plans for the first lunar landing started to be made, nobody had really thought about who would be out first. "
Henry Spencer
Nobody
Plans
First
" 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. "
Henry Spencer
Probability
Past
Failure
" The demise of Constellation is not the death of a dream. It's just the end of an illusion. "
Henry Spencer
Just
Illusion
End
" 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. "
Henry Spencer
Work
Goals
Support
" 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. "
Henry Spencer
More
People
Earth
" Historically, the U.S.'s big launchers fly seldom enough that their costs are dominated by annual upkeep of facilities and staff, not by the actual cost of each launch. The expensive part is maintaining the launch capability, not actually conducting launches. "
Henry Spencer
Big
Cost
Costs
" 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. "
Henry Spencer
Space
Moon
Cheap
" 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. "
Henry Spencer
Flight
Real
System
" 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. "
Henry Spencer
Moon
World
Questions
" Foul-ups in testing are not uncommon, especially when the test setup is being tried for the first time. "
Henry Spencer
First Time
Test
Testing
" SpaceX does seem to have had a run of bad luck, with its first three launches all failing. "
Henry Spencer
Bad Luck
First
Three