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SpaceX Starship Flight 4 (www.spacex.com)

submitted 5 months ago by llamacoffee to c/[email protected]

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The fourth flight test of Starship could launch as soon as June 5, pending regulatory approval.

The fourth flight test turns our focus from achieving orbit to demonstrating the ability to return and reuse Starship and Super Heavy. The primary objectives will be executing a landing burn and soft splashdown in the Gulf of Mexico with the Super Heavy booster, and achieving a controlled entry of Starship.

To accomplish this, several software and hardware upgrades have been made to increase overall reliability and address lessons learned from Flight 3. The SpaceX team will also implement operational changes, including the jettison of the Super Heavy’s hot-stage following boostback to reduce booster mass for the final phase of flight.

Flight 4 will fly a similar trajectory as the previous flight test, with Starship targeted to splashdown in the Indian Ocean. This flight path does not require a deorbit burn for reentry, maximizing public safety while still providing the opportunity to meet our primary objective of a controlled Starship reentry.

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[–] llamacoffee 4 points 5 months ago (2 children)

So no in-space engine relight just as we heard recently, but the interesting addition of jettison of the hot stage ring. I really hope that's temporary!

I also LOVE to see that they want to attempt to relight the raptors and do the flip of Starship survives entry! I wonder how confident they are that it will.

Also in an update, SpaceX noted that both booster engine issues and RCS on IFT-3 were caused by filter blockages and clogged valves. Kind-of fascinating that's still happening, but I have high hopes they will solve that soon!

[–] clothes 4 points 5 months ago (1 children)

The lack of vacuum relight is really interesting - I thought that was the biggest barrier to a "real" orbital flight with a payload that can start offsetting development costs.

But yes, everything else about this flight plan is exciting!

[–] [email protected] 2 points 4 months ago (1 children)

My guess would be that they figure the engineering to get that to work is simple enough that they skipped the risk of it messing up the much more challenging and interesting test of reentry. They already relight Merlin engines in a vacuum routinely so they're experienced with that, even though Raptor's a very different engine I bet there's plenty of similarities there.

[–] clothes 2 points 4 months ago* (last edited 4 months ago)

I think I've come to a similar conclusion after IFT-4. Reusability is the top priority, not a stretch goal like with Falcon-9. As such, the expected value of testing reentry is a lot higher than that of orbital maneuvering.

What an insanely aggressive development approach!

[–] [email protected] 4 points 5 months ago* (last edited 5 months ago) (2 children)

I find it interesting that the hot stage jettison is after the boostback burn. That implies to me that the purpose of the jettison isn't for weight reduction. I wonder if there are aerodynamic control reasons to jettison the hot stage.

I also wonder if the hot stage ring is expected to sustain enough damage to be a single use part anyway.

[–] llamacoffee 5 points 5 months ago* (last edited 5 months ago)

The renders for Starship V2 have a dramatically redesigned hot stage mechanism. My guess is as good as any, but it's possible the current HSR is so bulky and has nothing in common with the future version that they feel it's actually more representative to throw it away.

[–] [email protected] 1 points 4 months ago

I saw a video by CSI Starbase that speculated that during IFT3 the hot stage ripped off in an uncontrolled manner due to failure of the latches holding it in place. Since the latched-on nature of the interstage is a temporary measure anyway they may have figured "who cares, we're not trying to make this bit work so just throw it away so we can properly test the stuff we do want to do."