Posts by Vincent Cate

NASA inks deal for Shuttle replacements

space tethers - not space elevators

You can build space tethers with the ropes we have today. They are much shorter and cheaper and could toss a payload every 90 minutes. We can make a reusable rocket that gets to the speed needed to hand-off to the tether. So the time Space Elevators take materials that we may never get, or at least not in the next 30 years. If an elevator takes a couple weeks to life a payload you only get 25 per year and amortizing your capital costs over a few trips means each one is going to cost a lot. As we get better and better ropes, the rocket part of a space tether can do less and less.

Humans should not ride on solids

Solid rockets can not be turned off if anything starts to go wrong. Liquids can be much safer.

"As an aside, Von Braun had said that no human should ever ride on solid rockets. They were just too dangerous. One in twenty-five blew up due to defects. They could not be stopped once lighted and thus had the potential for a major loss of life." (before challenger)

http://msl1.mit.edu/ESD10/block4/4.3_-_Challenger.pdf

"I tend to consider solid rocketry a branch of fireworks rather than transportation."

-- Henry Spencer

Private ventures, like spacex.com, will have much safer and cheaper rockets for humans before NASA gets this big dangerous solid finished, and so it will probably not see much use.

-- Vince Cate