Author Topic: SpaceX Starship : First Flight : Starbase, TX : 20 April 2023 - DISCUSSION  (Read 511623 times)

Online ugordan

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Will this Starship have a heatshield on it?

It better if they're really planning on a "soft ocean landing".

Offline snotis

Yes full heatshield - needs to survive re-entry because they want to softly land it in the water looks like.

Will this Starship have a heatshield on it?

Online DaveS

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Admittedly, I only have a KSP-level knowledge of orbital mechanics, so please gently educate me if I'm wrong here.

Can this actually complete a full orbit? Looking at the times (SECO @ 521, Ship Splashdown @ 5420) I'm having a hard time seeing how they launch from Boca Chica, orbit all the way around past Boca Chica, and then make it another 300 degrees around to Kauai.

Assuming the answer is "No, it doesn't go all the way around"... Will this achieve orbital velocity and then do a de-orbit burn? Or will it just be a very long ballistic trajectory? (The lack of a second burn of the second stage would suggest it's the later.)
Remember, they're last east-ward, so you're going to pass over Kauai first before making landfall over CONUS and heading back over TX.
« Last Edit: 05/13/2021 09:20 pm by DaveS »
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Offline nacnud

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So , since it's getting real , What could be the final orbit of Starship after insertion. Will they keep it low to minimise TPS heating for the time being , also since the landing (or splashdown) is 90 minutes after liftoff , from Boca TX to Hawaii in eastward direction could mean the it will complete a single orbit before re-entering.

Also will they be testing the R-Vacs for the first time in Orbit?

I think the flight will be suborbital, but only just, like a shuttle eternal tank. Then you can target the landing zone even if the raptors fail to complete the deorbit burn.

Edit: Also starship landing occurs at T+90 minuets, so exactly like an ET
« Last Edit: 05/13/2021 09:23 pm by nacnud »

Offline mmonce

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Any data or informed estimates of the projected altitude of Starship when it passes over the Florida Strait? I live in SW FL and wonder if it's worthwhile to invest in a decent set of binoculars and hope for favorable weather.

Offline AC in NC

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Doesn't sound like there's going to be any booster hops.  ;D

You got lucky on that one.  The argument was still wrong 2 or more years ago when SS was carbon composite.   :P

Online Jeff Lerner

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If they splash Starship, how will they be able to see how well the complete set of tiles performed ??..presumably they will be damaged on impact with the water ...

Offline Lars-J

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So , since it's getting real , What could be the final orbit of Starship after insertion. Will they keep it low to minimise TPS heating for the time being , also since the landing (or splashdown) is 90 minutes after liftoff , from Boca TX to Hawaii in eastward direction could mean the it will complete a single orbit before re-entering.

Also will they be testing the R-Vacs for the first time in Orbit?

I think the flight will be suborbital, but only just, like a shuttle eternal tank. Then you can target the landing zone even if the raptors fail to complete the deorbit burn.

Edit: Also starship landing occurs at T+90 minuets, so exactly like an ET
I think it will be fully orbital. And it is going further than the ET… that impacted in the Indian Ocean.

Offline jimvela

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If they splash Starship, how will they be able to see how well the complete set of tiles performed ??..presumably they will be damaged on impact with the water ...

If it survives entry to the point where it hits the water more or less intact, then the biggest test of whether the heatshield will work at all is answered. 

I'd imagine they would have observing assets in place to try and assess the reentry as well.
« Last Edit: 05/13/2021 09:44 pm by jimvela »

Offline scr00chy

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If they splash Starship, how will they be able to see how well the complete set of tiles performed ??..presumably they will be damaged on impact with the water ...

If they actually get to the landing part, that will mean the tiles worked. That's probably good enough for the first ever reentry attempt.

Offline nacnud

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I think it will be fully orbital. And it is going further than the ET… that impacted in the Indian Ocean.

True, I wonder how much it would fly a lofted re-entry to reduce max heating temperature or a depressed entry to reduce heating time.

I'm guessing a lofted reentry, which would lengthen the flight distance, but its just a guess.

Offline 2megs

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Admittedly, I only have a KSP-level knowledge of orbital mechanics, so please gently educate me if I'm wrong here.

Can this actually complete a full orbit? Looking at the times (SECO @ 521, Ship Splashdown @ 5420) I'm having a hard time seeing how they launch from Boca Chica, orbit all the way around past Boca Chica, and then make it another 300 degrees around to Kauai.

Assuming the answer is "No, it doesn't go all the way around"... Will this achieve orbital velocity and then do a de-orbit burn? Or will it just be a very long ballistic trajectory? (The lack of a second burn of the second stage would suggest it's the later.)
Remember, they're last east-ward, so you're going to pass over Kauai first before making landfall over CONUS and heading back over TX.

I thought that was what I was saying?

Headed east from Boca Chica, Kauai is about 294 degrees around the earth, plus another 22.5 degrees for the rotation of the earth during those 5420 seconds. A just-barely-sub-orbital ballistic trajectory can get them there very naturally in that timeline.

But there's no trajectory that can complete a full orbit (i.e. 360 degrees east from Boca to go past Boca again), and then go another 294 + 22.5 degrees east to Kauai, and still fit that timeline.... right?

So I'm assuming this can't complete a full orbit. IMO that's for the best on the first flight, no risk of stranding a Starship in a low unstable orbit, re-entering at an unpredictable place.

(If I'm wrong here, help me understand what the orbit could be.)

Online oldAtlas_Eguy

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The FCC doc specifically states orbit not suborbital. As well as a reentry burn executed by the SS.

Offline nacnud

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The FCC doc specifically states orbit not suborbital. As well as a reentry burn executed by the SS.


Thanks, didn't realise there was a PDF as well, only saw the tweet!

Offline Lars-J

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Admittedly, I only have a KSP-level knowledge of orbital mechanics, so please gently educate me if I'm wrong here.

Can this actually complete a full orbit? Looking at the times (SECO @ 521, Ship Splashdown @ 5420) I'm having a hard time seeing how they launch from Boca Chica, orbit all the way around past Boca Chica, and then make it another 300 degrees around to Kauai.

Assuming the answer is "No, it doesn't go all the way around"... Will this achieve orbital velocity and then do a de-orbit burn? Or will it just be a very long ballistic trajectory? (The lack of a second burn of the second stage would suggest it's the later.)
Remember, they're last east-ward, so you're going to pass over Kauai first before making landfall over CONUS and heading back over TX.

I thought that was what I was saying?

Headed east from Boca Chica, Kauai is about 294 degrees around the earth, plus another 22.5 degrees for the rotation of the earth during those 5420 seconds. A just-barely-sub-orbital ballistic trajectory can get them there very naturally in that timeline.

But there's no trajectory that can complete a full orbit (i.e. 360 degrees east from Boca to go past Boca again), and then go another 294 + 22.5 degrees east to Kauai, and still fit that timeline.... right?

So I'm assuming this can't complete a full orbit. IMO that's for the best on the first flight, no risk of stranding a Starship in a low unstable orbit, re-entering at an unpredictable place.

(If I'm wrong here, help me understand what the orbit could be.)

My assumption is that Starship will reach orbital velocity, but will not complete a full orbit. (if that makes sense - similar to Gagarin's flight)

And with the total flight time being ~90 minutes, it makes sense. The first 9-10 minutes is just acceleration to orbital speed. Which leaves 80 mins afterwards, and then subtract the re-entry slowdown time. It seems to add up.
« Last Edit: 05/13/2021 09:57 pm by Lars-J »

Offline neoforce

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The FCC doc specifically states orbit not suborbital. As well as a reentry burn executed by the SS.


Thanks, didn't realise there was a PDF as well, only saw the tweet!

PDF doesn't explicitly say re-entry burn:

Quote
It will achieve orbit until performing a powered, targeted landing

Offline joek

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If they splash Starship, how will they be able to see how well the complete set of tiles performed ??..presumably they will be damaged on impact with the water ...
If it survives entry to the point where it hits the water more or less intact, then the biggest test of whether the heatshield will work at all is answered. 
I'd imagine they would have observing assets in place to try and assess the reentry as well.

Agree. Expect both SH booster and SS will end up in the water. These are pathfinders. SpaceX does not need to recover them intact (as much as that might be desirable) to get much of the data they need to proceed to the next step... for which intact recovery will be the next step.

Patience everyone. Simply getting SH/SS launched and SS into an orbital reentry profile is a giant step forward.

Offline Lars-J

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If they splash Starship, how will they be able to see how well the complete set of tiles performed ??..presumably they will be damaged on impact with the water ...
If it survives entry to the point where it hits the water more or less intact, then the biggest test of whether the heatshield will work at all is answered. 
I'd imagine they would have observing assets in place to try and assess the reentry as well.

Agree. Expect both SH booster and SS will end up in the water. These are pathfinders. SpaceX does not need to recover them intact (as much as that might be desirable) to get much of the data they need to proceed to the next step... for which intact recovery will be the next step.

Yes. But I fully expect there to be boats in both places ready to safe/recover/scuttle landed hardware that is bobbing around in the ocean.
« Last Edit: 05/13/2021 09:59 pm by Lars-J »

Offline Barry Brisco

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Is there any chanche to see SS flip, if it makes through reentry, via a non SpaceX camera?
There won’t be any non-SpaceX cameras out in the ocean 100kM northwest of Kauai. My guess is that a Starlink antenna will be installed on the SS and the flight will be live streamed.

The SN15 test flight appears to be the first time the vehicle had a Starlink antenna in place. The stream certainly did not work very well, but the problems should be correctable.

Offline joek

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...
But there's no trajectory that can complete a full orbit (i.e. 360 degrees east from Boca to go past Boca again), and then go another 294 + 22.5 degrees east to Kauai, and still fit that timeline.... right?

So I'm assuming this can't complete a full orbit. IMO that's for the best on the first flight, no risk of stranding a Starship in a low unstable orbit, re-entering at an unpredictable place.
...

Correct.  However, they do not necessarily need to complete a full orbit to get the data they need (at least at this point).

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