Originally Posted by
ryan1234
I actually like the liquid as opposed to solid... "solid" tends to burn a bit faster and does not usually have the ability to restart (except for the hybrid)....great for ballistic missles, hard to manage to precision aerial vehicles. Solid fuel seems at first glance to be easier to engineer... but looking more closely requires specific design characteristics for a manned vehicle (without boosters) that would need specific control inputs among other things.
As far as safety goes, I would favor a liquid fuel.... once a solid goes uncontrolled, that's it, game over.
Liquid fuel engines are VERY complex, and often stressed right to the engineering limits (no 150% ultimate load).
Look at recent history...I can't recall any solid fuel booster failures in the last two decades, but there have been numerous, recent, major malfunctions of liquid engines.
Even the shuttle Challenger booster did not fail...it leaked, but it continued to function normally. The leak ignited the liquid fuel tank.
The military invariably uses solid boosters in all applications for reliability and safety...the only justification for the cost and risk of liquid is if you have to get something heavy into orbit, or move it around once you get there.