Starship heat shield

[john smith 19]

Zack Golden reasonably arrives at the conclusion that the tile damage from the 6 engine Raptor test was caused by debris from the test stand.

Implications for taking off from Mars, but not for taking off from Earth.

Which suggests that there should be action around the base to either strengthen the concrete or overlay it with steel plate preping for the next flight.

That should be pretty visible. Has anyone seen this?

  "the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....

Don't forget S25. It has to go through ambient, cryo, thrust and static fire tests too. The sub-orbital pads need an upgrade if they want to SF 6 Raptors again.

And if Raptors ongoing development work include upgrading the thrust level without it whatever debris got blown up by them starting up is going to happen worse, without something being done to the pad.

So has anyone noticed anything?

[Barley]

  "the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....

Then I guess the question becomes "Does the launch pad differ from the static fire pad?" IE Heavier concrete layers, steel plates laid down etc.

That would suggest that unexpected high levels of pad debris was the issue with the missing tiles.

IIUC It looks to me that the super-heavy pad has a much taller "milk stool", eyeballing it 6m to 30m, at least for some of the mockups.  So perhaps they've already learned the lessons and made the changes.

OTOH they will need somewhere to static fire SS (Static firing Starship atop the booster is not a good idea) so some changes may be needed to the static fire pad.

[RamsesBic]

  "the next flight" will see Starship atop the booster not on the suborbital pad. Static fires of course.....

Then I guess the question becomes "Does the launch pad differ from the static fire pad?" IE Heavier concrete layers, steel plates laid down etc.

That would suggest that unexpected high levels of pad debris was the issue with the missing tiles.

IIUC It looks to me that the super-heavy pad has a much taller "milk stool", eyeballing it 6m to 30m, at least for some of the mockups.  So perhaps they've already learned the lessons and made the changes.

OTOH they will need somewhere to static fire SS (Static firing Starship atop the booster is not a good idea) so some changes may be needed to the static fire pad.

The risk of debris hitting tiles when the ship is stacked on the booster is near zero.
The booster has no tiles that need protecting.
The "problem" is static fire tests of ships on the sub-orbital stands. I am sure they are going to do something to solve the problem before the next SF test with 6 Raptors. Installing better mounts for cameras on the legs of the stand might also give them better images and avoid causing unintentional brush fires.

[adrianwyard]

*Technically* I suppose they could suspend Starship from the chopsticks at the correct height for the QD to attach. With no booster below that would give plenty of clearance for a static fire and guarantee no debris would reach the tiles  (This is joke.)

I find it fascinating we've not seen any evidence of flame diverters (which they use at MacGregor) for the test mount or main launch table. Even rolling in a small one like used for the V2 would presumably help?

Either way the key challenge for the heat shield is not static fire debris but launch vibration. (Mars landings are of course another matter entirely.)

[RamsesBic]

An alternate method could be to shield the ship rather than protect the ground. It could for example be a much wider ring on top of the stand, or protecting walls around the ship (the lower sections at least.
I am pretty sure they are giving all such alternatives careful thought and will chose the most practical.

[OTV Booster]

So, we're seeing static fire tile damage that looks to be unavoidable without heroic efforts. An alternative reason for tile challenged builds? Do all the ground testing without tiles then install tiles before mounting SS on SH?


It looks like they are planning on some throwaways to get StarLink v2 going but maybe this makes makes long term sense.

[adrianwyard]

Adding bespoke debris/blast shields to the test mount to protect the flaps and lower edge of the starship doesn't sound that difficult in the scheme of things. Then any resulting tile loss would be due to startup vibrations, so somewhat indicative of what will happen on an actual flight.

[RamsesBic]

So, we're seeing static fire tile damage that looks to be unavoidable without heroic efforts. An alternative reason for tile challenged builds? Do all the ground testing without tiles then install tiles before mounting SS on SH?


It looks like they are planning on some throwaways to get StarLink v2 going but maybe this makes makes long term sense.

I would not call some upgrade of a stand a "heroic effort" by any means.

[john smith 19]

I find it fascinating we've not seen any evidence of flame diverters (which they use at MacGregor) for the test mount or main launch table. Even rolling in a small one like used for the V2 would presumably help?

Either way the key challenge for the heat shield is not static fire debris but launch vibration. (Mars landings are of course another matter entirely.)

I remember seeing images of this and have always wondered why they were'nt more use than huge, heavy flame trenches.

Thanks for providing the image.

[InterestedEngineer]

I find it fascinating we've not seen any evidence of flame diverters (which they use at MacGregor) for the test mount or main launch table. Even rolling in a small one like used for the V2 would presumably help?

Either way the key challenge for the heat shield is not static fire debris but launch vibration. (Mars landings are of course another matter entirely.)

I remember seeing images of this and have always wondered why they were'nt more use than huge, heavy flame trenches.

Thanks for providing the image.

Because you can't easily service underneath a stand which has flame trenches.

That conversation really belongs in the Facilities and Fleets section, here's a convenient link to the start of that conversation:

https://forum.nasaspaceflight.com/index.php?topic=54355.msg2411243#msg2411243

[AC in NC]

So, we're seeing static fire tile damage that looks to be unavoidable without heroic efforts. An alternative reason for tile challenged builds? Do all the ground testing without tiles then install tiles before mounting SS on SH?
It looks like they are planning on some throwaways to get StarLink v2 going but maybe this makes makes long term sense.

I would not call some upgrade of a stand a "heroic effort" by any means.

OK.  But that has absolutely nothing to do with what OTV said.

[Dr.Unhold]

I believe this argument has been made several times before on this thread, but in the light of all the talk about focussing on optimizing the test stand to avoid damages:
The ground tests on sub-par stands also serve as good testing grounds for landing/starting on unprepared terrain. Certainly, SS is a long way away from regularly landing in such environments (maybe moon being an exception). But think about what you can learn early on about making your engines/vehicle more robust. You might even pick up some easy fixes that substantially reduce the damages in these kind of environments, when you have experience (=data). And how to collect better data on this than on a ship that might not even fly, sits on the ground and can be easily inspected..
So the process of finding a good enough (sub-)orbital test stand and launch pad has synergies with arriving at a more robust system.

[OTV Booster]

Adding bespoke debris/blast shields to the test mount to protect the flaps and lower edge of the starship doesn't sound that difficult in the scheme of things. Then any resulting tile loss would be due to startup vibrations, so somewhat indicative of what will happen on an actual flight.

How indicative is an open question. Being close to the ground is acoustically different than being on top of SH. There's a lot of acoustic energy being reflected back up. It's conceivable that when stacked during an SH live fire a whole new set of problems will show up. I hope not but that's why the test.

[john smith 19]

I believe this argument has been made several times before on this thread, but in the light of all the talk about focussing on optimizing the test stand to avoid damages:
The ground tests on sub-par stands also serve as good testing grounds for landing/starting on unprepared terrain. Certainly, SS is a long way away from regularly landing in such environments (maybe moon being an exception). But think about what you can learn early on about making your engines/vehicle more robust. You might even pick up some easy fixes that substantially reduce the damages in these kind of environments, when you have experience (=data). And how to collect better data on this than on a ship that might not even fly, sits on the ground and can be easily inspected..
So the process of finding a good enough (sub-)orbital test stand and launch pad has synergies with arriving at a more robust system.

That is a very interesting trade.

On the one hand it improves your chance of a rugged TPS for the Mars landing, but on the other it could seriously damage an otherwise perfectly good SS that could make orbit and land safetly on a concrete pad, but now won't 

Also you get that  TPS testing for free (apart from the pad repairs). 

OTOH the key goal right now is simply to get to (and back from) orbit in the first place.

That has to be the enabling step to get every SS programme moving.

[InterestedEngineer]

I believe this argument has been made several times before on this thread, but in the light of all the talk about focussing on optimizing the test stand to avoid damages:
The ground tests on sub-par stands also serve as good testing grounds for landing/starting on unprepared terrain. Certainly, SS is a long way away from regularly landing in such environments (maybe moon being an exception). But think about what you can learn early on about making your engines/vehicle more robust. You might even pick up some easy fixes that substantially reduce the damages in these kind of environments, when you have experience (=data). And how to collect better data on this than on a ship that might not even fly, sits on the ground and can be easily inspected..
So the process of finding a good enough (sub-)orbital test stand and launch pad has synergies with arriving at a more robust system.

That is a very interesting trade.

On the one hand it improves your chance of a rugged TPS for the Mars landing, but on the other it could seriously damage an otherwise perfectly good SS that could make orbit and land safetly on a concrete pad, but now won't 

Also you get that  TPS testing for free (apart from the pad repairs). 

OTOH the key goal right now is simply to get to (and back from) orbit in the first place.

That has to be the enabling step to get every SS programme moving.

Starting to get OT here, but at what point in this hypothesis does Gwynn Shotwell call up Musk as ask "hey about those Starlink v2 satellites we need to make revenue next year", they build a more robust test stand so they can test actual orbital launches

[john smith 19]

Starting to get OT here, but at what point in this hypothesis does Gwynn Shotwell call up Musk as ask "hey about those Starlink v2 satellites we need to make revenue next year", they build a more robust test stand so they can test actual orbital launches

Hasn't she already done so?

That was my point. Leave the sub orbital stand alone and if damages a SS that's a learning experience, or upgrade  and push harder to get to orbit to begin with.

My instinct is that the importance of TPS exceeds engines. There's a Raptor (or  should we call it Raptor II?) thrust level that will get SS to orbit. Anything above that --> more payload. A design that's not hitting 100% of theoretical performance is not a show stopper.

But underperfoming TPS --> Vehicle will (or probably will) fail to survive re-entry. And that stops everything, unless you want to sacrifice every SS.

BTW I just remembered that someone can only have 5 launches from this site.  Has anyone tracke how many they have left?  I would have guessed they would have pushed for at least 12 to allow (potentially) 1 a month to iterate the design.

[eriblo]

I personally think the "Mars does not have landing pads/launch pads/whatever so Starship won't need it" meme is a bit premature, especially with regard to TPS.

Permanent and expanding presence on Mars requires that Starship is fully successful on Earth first and that the tech is somewhat transferable, not the other way around.

We do not even know if the current TPS is at all relevant to Mars launches. If it works well on Earth it will probably work for Mars EDL as well, especially for slow-transfer-and-quite-possibly-one-way cargo Starships.

However, returning from Mars will be a tougher entry than any crewed vehicle has done so far. I fully expect the crew transfer ships to have a heavily modified if not completely different TPS.

[OTV Booster]

Starting to get OT here, but at what point in this hypothesis does Gwynn Shotwell call up Musk as ask "hey about those Starlink v2 satellites we need to make revenue next year", they build a more robust test stand so they can test actual orbital launches

Hasn't she already done so?

That was my point. Leave the sub orbital stand alone and if damages a SS that's a learning experience, or upgrade  and push harder to get to orbit to begin with.

My instinct is that the importance of TPS exceeds engines. There's a Raptor (or  should we call it Raptor II?) thrust level that will get SS to orbit. Anything above that --> more payload. A design that's not hitting 100% of theoretical performance is not a show stopper.

But underperfoming TPS --> Vehicle will (or probably will) fail to survive re-entry. And that stops everything, unless you want to sacrifice every SS.

BTW I just remembered that someone can only have 5 launches from this site.  Has anyone tracke how many they have left?  I would have guessed they would have pushed for at least 12 to allow (potentially) 1 a month to iterate the design.

Uh, I thought that was five launches per year. Does anybody have that at their fingertips?

[john smith 19]

Uh, I thought that was five launches per year. Does anybody have that at their fingertips?

Sorry, that indeed should have been 5/year. That could seem generous in early development, but now with whole stage 1s and 2s built it would seem quite restrictive.

Could they have just one left that they are holding in reserve to try and make orbit before the year ends? Not quite a SS to Mars, but a good way to close out 2022. In which case they'd want every possible failure mode closed off (AFAP) before using it.

[tbellman]

Sorry, that indeed should have been 5/year. That could seem generous in early development, but now with whole stage 1s and 2s built it would seem quite restrictive.

Could they have just one left that they are holding in reserve to try and make orbit before the year ends? Not quite a SS to Mars, but a good way to close out 2022. In which case they'd want every possible failure mode closed off (AFAP) before using it.

Which universe are you from where 5 - 0 = 1?  There hasn't been a single orbital launch of Starship, or even attempt at orbital launch, so how could there be only one left out of five?