[somenameforme]

During the Starline abort test only 2 of the 3 parachutes opened, and that was a pad abort test - no SRBs!! NASA not only calling that a "success", but a sufficient success to move onto crewed testing was about the moment I lost all faith in Bridenstine being different. Immediately after leaving office he picked up a cushy consulting type gigs for various aerospace/defense companies (aka Boeing et al). Shocker.

For those who might not know SRB = solid rocket booster. Boeing uses them, SpaceX doesn't. An SRB is basically like a giant firecracker. You light it and it starts burning and doesn't stop until its done. It poses substantial safety concerns in the case of an accident where you need to abort the flight. But they're cheap, extremely powerful, and relatively simple contrasted against liquid fuel engines.

[philwelch]

While I share your reservations with solid rockets as a main propulsion system on a manned rocket, it turns out they are well suited for launch escape systems themselves for some of the same exact reasons: they’re simple and powerful.

[nordsieck]

> While I share your reservations with solid rockets as a main propulsion system on a manned rocket, it turns out they are well suited for launch escape systems themselves for some of the same exact reasons: they’re simple and powerful.

Interestingly, both Crew Dragon and Starliner have eschewed SRB based LES/LAS systems for liquid fueled hypergolic ones. You can tell this because neither capsule has a "puller" on the nose like Apollo/Orion does.

[philwelch]

Yeah, that is an interesting decision, especially since hypergolics represent a completely different set of risks. But they are extremely reliable for this application.

[tekla]

Failure of 1 chute was designed for, though yes, it wasn't a great look.

> It poses substantial safety concerns in the case of an accident where you need to abort the flight

SRBs are in general very safe, which is why they're still used for human rated rockets.

[somenameforme]

Well we shall see I suppose. SRB's go back to the Apollo era and NASA safety qualifications often come down to 'are you doing what we've done before'? Hence them refusing to even consider SpaceX retropulsive crew landings, even though that would be a huge step forward.

I would also observe that NASA has a relatively poor safety record contrasted against the Soyuz (which has not lost crew since 1971 in spite of flying more manned missions), and one of the few completely catastrophic crashes we have had, Challenger, was directly related to the SRB. In either case, I expect variance is playing a much larger role than most might appreciate.