Why did North Korea’s rocket launch fail?

Electronic Products ^ | 4/18/12 | JEFFREY BAUSCH

[jesseam]

Re: That’ll do wonders for the esprit de corps of the bunch tasked with designing/launching the next one.

The beatings will continue until moral improves

[Gandalf_The_Gray]

It’s a lot easier to precisely control a liquid fueled rocket, plus you probably get better energy density. The advantage of solid fuel is that it is a “sealed round”, you take it off the shelf and shoot it. Liquid fuel needs maintenance and lead time to fuel. Soviet ICBMs were liquid fueled and were nightmares in terms of maintenance.

Precise control of a liquid fueled rocket is somewhat problematic, most are designed to run flat out and do not allow throttling back thrust output. They do allow cutting thrust completely but do not allow a restart. Solid fueled rockets may be controlled by employing thrust reverser's and case pressure venting.

Yes, the energy density is better with liquid fuels but when you take into account the added mass of the plumbing and turbo pumps with their own fuel supply and ancillary hardware, the actual advantage is not that much.

Your summery of the advantages/disadvantages is on the button except you left something out. The probability of failure of a mechanism is directly proportional to the number of parts making up the assembly (for want of a nail...). Yes, maintenance can help ease the problem but in the final analysis complexity is the death of reliability.

US missile technology started with solid fuel (Honest John, Pershing) moved to liquid fuel (Redstone, Atlas, Titan) and back to solid fuel (Polaris, Minuteman, and various "Standard" Missiles) with some Titan variants being hybrids with hypergolic main engines and solid boosters. Problems with hypergolic fuel led the US to go solid across the board (a dropped wrench caused a Titan to explode in it's silo and toss it's nuclear package 800 feet it the air w/no damage!).

Regards,
GtG