Comments on: Most recent engine test on eighth Starship prototype had issues

By: Diane Wilson

Diane Wilson — Sun, 15 Nov 2020 21:31:55 +0000

@LocalFluff,

So far, through all the Starship prototypes, they’ve mounted all of the Raptors while on the launch pad. So that’s routine. “Rocket surgery,” if you will, as opposed to rocket science. This is the second Raptor swap-out on SN8.

They really do need all three engines working for the 15km hop. In addition to launch, they’re also planning to test parts of the entry and landing profile. Flipping from vertical to almost horizontal at the top of that 15km will require two working Raptors.

No real details on the problem, yet, but discussion over on NasaSpaceFlight has focused on issues with heat and vibration in the confined area under the Starship as a possible root cause. Apparently this is a normal part of rocket development for multiple-engine rockets.

By: LocalFluff

LocalFluff — Sun, 15 Nov 2020 21:15:20 +0000

@Diane Wilson
Installed today!? Can they just change it on the launch pad as if it were a flat tire on a car? I suppose that if it weren’t a prototype with no more than three engines, they could’ve launched anyway with only one broken engine.

“Engine rich exhaust” meaning that parts of the engine hardware flew out together with the burning fuel. No problem!

By: Diane Wilson

Diane Wilson — Sun, 15 Nov 2020 20:27:32 +0000

A replacement Raptor is being installed today, so I expect to see static fires this week. Assuming the static fires pass, I expect the 15km hop sooner rather than later.

Keep in mind the speed of their prototyping cycle. I would almost call SN8 “expendable.” It’s an engineering test article, and there’s a limit to how much they can learn from it on the ground. I also would not expect the first 15km hop to be successful; there are too many unknowns that can only be understood from flight data. SN9 is nearly complete, and could probably be on the launch pad (they have two, just in case SN8 destroys one), and ready for SN9 static fires in two or three weeks.

By: LocalFluff

LocalFluff — Sun, 15 Nov 2020 17:24:20 +0000

@Brad, I can’t imagine SpaceX fiddling with a non-working launcher for a decade, when they’ve come so far already. With their track record and efficient learning curve I’d be surprised if Starship doesn’t (because of technical problems) put its first hardware in orbit next year or 2022.

But they do require quite some other kinds of hardware and preparations before launching people to Mars on a 30 months or so long trip. I don’t believe that will be done this decade. A test or preparatory launch to Mars can only be made every 26 months, and they need more than one.

By: Brad

Brad — Sat, 14 Nov 2020 18:51:26 +0000

Unless this turns out to be a minor problem, that probably kills any hopes for a 15 km alt. test flight this year.

Problems are bound to crop up during development of something as novel as the Starship Mars transportation system. So many people though have unrealistic high expectations of the rate of success. I think it will take SpaceX twice as long to get Starship working compared to their aspirational timeline. Meaning the first manned Starship to Mars landing is more likely to launch during 2031 than 2026.

Even so, 2021 should be a pretty exciting year to watch Starship. Probably a lot of test launches and a lot of crashes too!