Abort options for Starship and Starship/SuperHeavy

[ulm_atms]

Has anyone just plain asked Elon what Raptor's dead stopped to 100% thrust speed is?  I figure it is not something classified or anything and he is usually good about answering those types of questions.

Best I got out of the Raptor engine thread search here was ~2 seconds.  That's fast...but not fast enough for a lot of abort reasons.

[Lee Jay]

Has anyone just plain asked Elon what Raptor's dead stopped to 100% thrust speed is?  I figure it is not something classified or anything and he is usually good about answering those types of questions.

Best I got out of the Raptor engine thread search here was ~2 seconds.  That's fast...but not fast enough for a lot of abort reasons.

It's different with every version and probably with every sub-version.  They're still actively messing with Raptor so there is definitely no definitive answer to that question.  Plus, you may not need 100%.  If 0-90% is 500ms and 0-100% is 1500ms, it may be important to know that.

[envy887]

Has anyone just plain asked Elon what Raptor's dead stopped to 100% thrust speed is?  I figure it is not something classified or anything and he is usually good about answering those types of questions.

Best I got out of the Raptor engine thread search here was ~2 seconds.  That's fast...but not fast enough for a lot of abort reasons.

It's different with every version and probably with every sub-version.  They're still actively messing with Raptor so there is definitely no definitive answer to that question.  Plus, you may not need 100%.  If 0-90% is 500ms and 0-100% is 1500ms, it may be important to know that.

The previously posted graph gives a pretty good idea how fast the MCC comes up to pressure, and that's only a couple hundred ms or so to reach 300 bar.

What it doesn't tell us is when the preburners lit... But the preburners can't run at any substantial speed without building pressure in the MCC, so it probably wasn't long.

I would expect that with some optimization they could get an emergency startup sequence that reaches full thrust in under 200 ms, but there aren't a ton of scenarios where a few hundred ms is the difference between a failed abort and a successful one.

Edit: I lost a decimal somewhere, so multiply those by ten. This post is correct: 2.9 seconds to 290 bar, including 1 second hanging around at 150 bar.

The closest I've seen was this graph Elon tweeted recently. Pixelcounting from 0 to 290 bar says 2.9s. So at least that. But it was a test, maybe they went slower than usual.

[TheRadicalModerate]

The closest I've seen was this graph Elon tweeted recently. Pixelcounting from 0 to 290 bar says 2.9s. So at least that. But it was a test, maybe they went slower than usual.

I'd feel better about that chart if 0ms was correlated with some particular event.

[rsdavis9]

Has anyone just plain asked Elon what Raptor's dead stopped to 100% thrust speed is?  I figure it is not something classified or anything and he is usually good about answering those types of questions.

Best I got out of the Raptor engine thread search here was ~2 seconds.  That's fast...but not fast enough for a lot of abort reasons.

There is a tweet from elon.
Sub second is all I remember. (maybe like .3s)
Try searching through his tweets.

[steveleach]

Has anyone just plain asked Elon what Raptor's dead stopped to 100% thrust speed is?  I figure it is not something classified or anything and he is usually good about answering those types of questions.

Best I got out of the Raptor engine thread search here was ~2 seconds.  That's fast...but not fast enough for a lot of abort reasons.

There is a tweet from elon.
Sub second is all I remember. (maybe like .3s)
Try searching through his tweets.

I found this from 30 Dec 2019...

Spin start from COPVs so the ox & fuel turbines spool up super fast in unison. A precise start with full flow staged combustion is very important

[TheRadicalModerate]

[Update for stupid arithmetic error.]

Best I can tell, relative escape acceleration of a minimally-loaded Starship, with just enough prop to reach LEO and do EDL in an emergency, is going to be about 3G.  If you figure a 5-second¹ warning time (the "uh-oh-to-boom" interval),  the difference between 0.3s and 2.9s to full power is the difference between 33.2m of separation and 6.6m:  26.6m, or half a Starship length. [Always helps to multiply 3G by 9.8.] is 70m 260m [yet another arithmetic braino], 325m vs. 65m.   Figure the center of the explosion is 40m from the separation plane.

Question: which is worse, the overpressure or the shrapnel hitting a bunch of complex turbomachinery or the LOX dome?  (I'm thinking overpressure, but that assumes that the LCH4 dome on the SH is likely to remain intact during the explosion.

Another question:  What are the best estimates for sea-level thrust for both the RSL2 and the RVac2?

__________
¹Remember, the little-boom-to-big-boom interval on the Amos-6 explosion was about 3.5s.

[andrewmcleod]

On the plus side, the presumably robust top of the booster (made so for hot staging) may help protect the ship from booster-created shrapnel (along with the debris-clearing power of the ship's six active Raptor engines)...

Activation of the FTS immediately after separation may help prevent too much boom (or help slow the booster and debris down).

[TheRadicalModerate]

On the plus side, the presumably robust top of the booster (made so for hot staging) may help protect the ship from booster-created shrapnel (along with the debris-clearing power of the ship's six active Raptor engines)...

Activation of the FTS immediately after separation may help prevent too much boom (or help slow the booster and debris down).

I guess you could still have ricochets of tank-wall shrapnel off the tower, but that's getting to be a fairly low-probability event.

[Twark_Main]

[Update for stupid arithmetic error.]

Best I can tell, relative escape acceleration of a minimally-loaded Starship, with just enough prop to reach LEO and do EDL in an emergency, is going to be about 3G.  If you figure a 5-second¹ warning time (the "uh-oh-to-boom" interval),  the difference between 0.3s and 2.9s to full power is the difference between 33.2m of separation and 6.6m:  26.6m, or half a Starship length. [Always helps to multiply 3G by 9.8.] is 70m 260m [yet another arithmetic braino], 325m vs. 65m.   Figure the center of the explosion is 40m from the separation plane.

Holy unreadable corrections, Batman!   

I'm finding it hard to unambiguously discern which number is supposed to replace which previous number. Can this wording be clarified, ideally omitting the bogus numbers entirely?

[Starmang10]

anyways so i basically just proved that the ship basically tried to save itself during the explosion *check my “essay” in the discussion threat 3 of the flight test on it*, any ideas on what wouldve happened had it not exploded?

[meekGee]

[Update for stupid arithmetic error.]

Best I can tell, relative escape acceleration of a minimally-loaded Starship, with just enough prop to reach LEO and do EDL in an emergency, is going to be about 3G.  If you figure a 5-second¹ warning time (the "uh-oh-to-boom" interval),  the difference between 0.3s and 2.9s to full power is the difference between 33.2m of separation and 6.6m:  26.6m, or half a Starship length. [Always helps to multiply 3G by 9.8.] is 70m 260m [yet another arithmetic braino], 325m vs. 65m.   Figure the center of the explosion is 40m from the separation plane.

Holy unreadable inline corrections, Batman!

I honestly can't figure out which number is supposed to replace which previous number. Can this wording be clarified, or ideally re-written without including any bogus numbers at all?

Not seeing it, but is this a case of TapAtalk not showing strike-throughs?

[Twark_Main]

Not seeing it, but is this a case of TapAtalk not showing strike-throughs?

I do see the strike-throughs. The wording is just unnecessarily tortuous and difficult-to-follow.



Edit: f**k it, I'll just Cunningham it... 

Ahem!  Fellow Internet-ers, your attention please!!  I am 100% sure that TRM definitely meant this:

"Best I can tell, relative escape acceleration of a minimally-loaded Starship, with just enough prop to reach LEO and do EDL in an emergency, is going to be about 3G.  If you figure a 5-second¹ warning time (the "uh-oh-to-boom" interval),  the difference between 0.3s and 2.9s to full power is the difference between 325m of separation and 65m:  260m.  Figure the center of the explosion is 40m from the separation plane."

[spacenut]

I still think SpaceX should get the rocket working to orbit first, at least perfect the booster and booster landing.  Then get Starship to orbit by launching Starlinks.  Then master the return and landing.  By that time, they may have a good confidence level to not need an abort option.  Many launches of Starlinks, a fuel depot, tanker, lunar Starship for NASA.  By that time it should be safe enough to launch humans.  I still also think the landing is the hardest part, not abort, once it gets to launching.  Landing from space will be harder than a booster landing. 

[TheRadicalModerate]

Not seeing it, but is this a case of TapAtalk not showing strike-throughs?

I do see the strike-throughs. The wording is just unnecessarily tortuous and difficult-to-follow.



Edit: f**k it, I'll just Cunningham it... 

Ahem!  Fellow Internet-ers, your attention please!!  I am 100% sure that TRM definitely meant this:

"Best I can tell, relative escape acceleration of a minimally-loaded Starship, with just enough prop to reach LEO and do EDL in an emergency, is going to be about 3G.  If you figure a 5-second¹ warning time (the "uh-oh-to-boom" interval),  the difference between 0.3s and 2.9s to full power is the difference between 325m of separation and 65m:  260m.  Figure the center of the explosion is 40m from the separation plane."

Looks right to me.

I often make changes for typos and clarity without an audit trail, but I feel funny about leaving unlogged math corrections, on the outside chance that somebody relied on them.

Hey, it was nothing a sed script couldn't fix...

[JayWee]

Would something like this work as an escape capsule?

https://twitter.com/NASASpaceflight/status/1690473479433310208

[InterestedEngineer]

Would something like this work as an escape capsule?

https://twitter.com/NASASpaceflight/status/1690473479433310208

the bottom dome is very odd indeed

[Stan-1967]

Can't wait to see how & if the landing thruster ring attaches below this ogive section, as well what they do with the cargo space above the LOX/CH4 section. Will there two separate pressurized sections with an airlock?

Will the rocket gods really smile & we get to see a "Stoke Aerospace" style aerospike beneath this ogive section?

Interesting indeed, as this type of configuration has been proposed before as a more viable crew escape option vs. trying to abort with a fully fueled SS with the Raptors.

[TheRadicalModerate]

the bottom dome is very odd indeed

It's a pressure dome.  Looks like a full-up prototype of the LSS crew module.

I haven't pixel-counted: is that the full ogive section, or just a portion of it?  I'd guess that it would fit onto the cylindrical portion of the payload bay, likely with a tunnel (or two) into the airlocks on the "garage" deck.

In answer to the original question, it's too big and heavy for an escape system.  It also doesn't have any canards, which would be required for an EDL-capable escape system.

Is the door how crew ingress for launch?  Seems pretty unlikely to be the hatch/elevator on the garage deck.

[InterestedEngineer]

the bottom dome is very odd indeed

It's a pressure dome.  Looks like a full-up prototype of the LSS crew module.

I haven't pixel-counted: is that the full ogive section, or just a portion of it?  I'd guess that it would fit onto the cylindrical portion of the payload bay, likely with a tunnel (or two) into the airlocks on the "garage" deck.

In answer to the original question, it's too big and heavy for an escape system.  It also doesn't have any canards, which would be required for an EDL-capable escape system.

Is the door how crew ingress for launch?  Seems pretty unlikely to be the hatch/elevator on the garage deck.

Does SS need a pressure dome for 1 bar differential?