Discussion of plan for flight 5

[sanman]

FST update:

This thread is for speculation / discussion of what SpaceX might do on flight 5. Actual testing/flight preparations belong in the separate thread:

https://forum.nasaspaceflight.com/index.php?topic=60799.0


In the NSF chat, they were holding a poll asking if IFT-5 would be another water landing, or if they'd try a catch attempt.

Whether it happens on IFT-5 or a later flight, it still seems so radical to go from a water landing to a mechazilla catch.
Is there no way to try anything in between, as an intermediary step?

With a tower catch, there are so many things that could go wrong.
Even if the Booster functions correctly, the Chopsticks themselves could screw it up.

How can they more thoroughly & realistically test the Chopsticks before taking on the risk of a live SuperHeavy Booster?

[FutureSpaceTourist]

https://twitter.com/esherifftv/status/1799064516191526933

Will we see a catch on Flight 5 of Starship?
Let's ask Elon.

[sanman]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

[sanman]

Will we see a catch on Flight 5 of Starship?
Let's ask Elon.

Wow, that's pretty radical. Talk about flying by the seat of your pants. 

I hope they don't end up with another Rock Tornado fiasco -- because that could ground flights for awhile, as it gets sorted out with the FAA.

Should make for exciting footage either way, though.

[Herb Schaltegger]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

A lot of NSF members seem to have some kind of catch-tower obsession. There is no indication SpaceX is remotely interested in that kind of thing. It hasn’t appeared in any rendering; it hasn’t been discussed by SpaceX at all; and the concept isn’t mentioned in any of the now-extensive regulatory and licensing documentation.

Let it go, folks. If SpaceX pivots to a catch-only tower, it would likely only occur in the wake of a failed capture damaging a launch mount significantly, not because a bunch of space nerds on the internet seem to want it.

[DanClemmensen]

Will we see a catch on Flight 5 of Starship?
Let's ask Elon.

Wow, that's pretty radical. Talk about flying by the seat of your pants. 

I hope they don't end up with another Rock Tornado fiasco -- because that could ground flights for awhile, as it gets sorted out with FAA.

Clearly it's a calculated risk. If it succeeds, they may gain 2 months (assuming a 2-month-flight cadence now). If you fail, you lose the four months it takes to repair the damage  (or maybe more).

They took a similar chance on IFT-1, and lost the bet. The damage repair in that case added about four months to the cadence, which was about 4 months at the time.

[rsdavis9]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

A lot of NSF members seem to have some kind of catch-tower obsession. There is no indication SpaceX is remotely interested in that kind of thing. It hasn’t appeared in any rendering; it hasn’t been discussed by SpaceX at all; and the concept isn’t mentioned in any of the now-extensive regulatory and licensing documentation.

Let it go, folks. If SpaceX pivots to a catch-only tower, it would likely only occur in the wake of a failed capture damaging a launch mount significantly, not because a bunch of space nerds on the internet seem to want it.

Remember the catch tower doesn't have a launch mount.
The launch mount survives 33 raptors thrusting down at it. Whats a measly booster with a little fuel going to do to it.
Either way one of the towers get a little toasted.

[Herb Schaltegger]

Will we see a catch on Flight 5 of Starship?
Let's ask Elon.

Wow, that's pretty radical. Talk about flying by the seat of your pants. 

I hope they don't end up with another Rock Tornado fiasco -- because that could ground flights for awhile, as it gets sorted out with FAA.

Clearly it's a calculated risk. If it succeeds, they may gain 2 months (assuming a 2-month-flight cadence now). If you fail, you lose the four months it takes to repair the damage  (or maybe more).

They took a similar chance on IFT-1, and lost the bet. The damage repair in that case added about four months to the cadence, which was about 4 months at the time.

Another aspect to trying a catch on Flight 5: it would require a specific modification to the Launch License, which itself has already been modified to allow multiple flights, but only to the extent they follow the Flight 4 mission profile. As I read this, a catch attempt would necessitate at least some minimal further regulatory review. From a pragmatic engineering standpoint, especially if you are serious about developing a fully reusable launch system, I think you’d want to be able to iterate on the Ship TPS, especially around the hot gas flap hinge seals, as rapidly as possible, while also tweaking Booster Raptor startup issues before trying a catch which might wreck your OLM and prevent a rapid launch cadence.

[Perchlorate]

Will we see a catch on Flight 5 of Starship?
Let's ask Elon.

Wow, that's pretty radical. Talk about flying by the seat of your pants. 

I hope they don't end up with another Rock Tornado fiasco -- because that could ground flights for awhile, as it gets sorted out with FAA.

Clearly it's a calculated risk. If it succeeds, they may gain 2 months (assuming a 2-month-flight cadence now). If you fail, you lose the four months it takes to repair the damage  (or maybe more).

They took a similar chance on IFT-1, and lost the bet. The damage repair in that case added about four months to the cadence, which was about 4 months at the time.

Another aspect to trying a catch on Flight 5: it would require a specific modification to the Launch License, which itself has already been modified to allow multiple flights, but only to the extent they follow the Flight 4 mission profile. As I read this, a catch attempt would necessitate at least some minimal further regulatory review. From a pragmatic engineering standpoint, especially if you are serious about developing a fully reusable launch system, I think you’d want to be able to iterate on the Ship TPS, especially around the hot gas flap hinge seals, as rapidly as possible, while also tweaking Booster Raptor startup issues before trying a catch which might wreck your OLM and prevent a rapid launch cadence.

So probably keep Flight 5 like Flight 4 and address other issues, while immediately beginning to seek a license for Flight 6 with a tower catch.

[DanClemmensen]

Another aspect to trying a catch on Flight 5: it would require a specific modification to the Launch License, which itself has already been modified to allow multiple flights, but only to the extent they follow the Flight 4 mission profile. As I read this, a catch attempt would necessitate at least some minimal further regulatory review. From a pragmatic engineering standpoint, especially if you are serious about developing a fully reusable launch system, I think you’d want to be able to iterate on the Ship TPS, especially around the hot gas flap hinge seals, as rapidly as possible, while also tweaking Booster Raptor startup issues before trying a catch which might wreck your OLM and prevent a rapid launch cadence.

So probably keep Flight 5 like Flight 4 and address other issues, while immediately beginning to seek a license for Flight 6 with a tower catch.

My guess: if they are crazy enough to try the catch on IFT-5, then they have already informally discussed this with FAA and are ready to formally request the modification as soon as whatever already-agreed analyses are complete.

It's hard to see how FAA would agree to let them catch at BC, ever. To me, it looks like the tank farm is too close to the tower, so the maximum credible accident would be pretty spectacular and would have off-site environmental consequences. However, I have no information at all on how these decisions are made. At the other end of the spectrum, FAA might conclude that the maximum credible accident will only affect SpaceX assets and is not a danger to people or the environment, so even destruction of the  tower is not a mishap.

[steveleach]

Another aspect to trying a catch on Flight 5: it would require a specific modification to the Launch License, which itself has already been modified to allow multiple flights, but only to the extent they follow the Flight 4 mission profile. As I read this, a catch attempt would necessitate at least some minimal further regulatory review. From a pragmatic engineering standpoint, especially if you are serious about developing a fully reusable launch system, I think you’d want to be able to iterate on the Ship TPS, especially around the hot gas flap hinge seals, as rapidly as possible, while also tweaking Booster Raptor startup issues before trying a catch which might wreck your OLM and prevent a rapid launch cadence.

So probably keep Flight 5 like Flight 4 and address other issues, while immediately beginning to seek a license for Flight 6 with a tower catch.

My guess: if they are crazy enough to try the catch on IFT-5, then they have already informally discussed this with FAA and are ready to formally request the modification as soon as whatever already-agreed analyses are complete.

It's hard to see how FAA would agree to let them catch at BC, ever. To me, it looks like the tank farm is too close to the tower, so the maximum credible accident would be pretty spectacular and would have off-site environmental consequences. However, I have no information at all on how these decisions are made. At the other end of the spectrum, FAA might conclude that the maximum credible accident will only affect SpaceX assets and is not a danger to people or the environment, so even destruction of the  tower is not a mishap.

I don't understand how a catch incident can be worse than a launch incident (in terms of impact, not likelihood), and they are risking the launch incident every flight anyway.

[baking]

So probably keep Flight 5 like Flight 4 and address other issues, while immediately beginning to seek a license for Flight 6 with a tower catch.

I think they want to try an engine re-light for a deorbit burn.  It's a necessary step before Starlink deployment.

[steveleach]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

They are building another tower, but they clearly don't see the point in not building another OLM to go with it. That makes sense to me, as it gives them a lot more flexibility, and flexibility is more valuable to them than any savings from not having it. I guess there might be a short period in which the second tower is capable of catching but they haven't completed the launch mount though.

I also don't think that they'll wait until they have the second tower before attempting a catch; that's just not very SpaceX.  If the catch fails and they need to wait for tower 2 to be ready before flight 6 then they are no worse off than if they'd waited anyway, and if it doesn't fail (or the failure doesn't make tower 1 unusable) then they have gained a load of time.

[Keldor]

Another aspect to trying a catch on Flight 5: it would require a specific modification to the Launch License, which itself has already been modified to allow multiple flights, but only to the extent they follow the Flight 4 mission profile. As I read this, a catch attempt would necessitate at least some minimal further regulatory review. From a pragmatic engineering standpoint, especially if you are serious about developing a fully reusable launch system, I think you’d want to be able to iterate on the Ship TPS, especially around the hot gas flap hinge seals, as rapidly as possible, while also tweaking Booster Raptor startup issues before trying a catch which might wreck your OLM and prevent a rapid launch cadence.

So probably keep Flight 5 like Flight 4 and address other issues, while immediately beginning to seek a license for Flight 6 with a tower catch.

My guess: if they are crazy enough to try the catch on IFT-5, then they have already informally discussed this with FAA and are ready to formally request the modification as soon as whatever already-agreed analyses are complete.

It's hard to see how FAA would agree to let them catch at BC, ever. To me, it looks like the tank farm is too close to the tower, so the maximum credible accident would be pretty spectacular and would have off-site environmental consequences. However, I have no information at all on how these decisions are made. At the other end of the spectrum, FAA might conclude that the maximum credible accident will only affect SpaceX assets and is not a danger to people or the environment, so even destruction of the  tower is not a mishap.

The tank farm is basically empty by the time of launch.  It only holds enough fuel for a single launch, which of course has been pumped over into the vehicle and mostly used up as we get to the point of booster landing.  Yes, there are residuals, as well as some amount of margin to cover boiloff under various flight delay scenarios, but the vast majority of the contents of the tanks is gone.

[matthewkantar]

-They are building a second tower at Starbase.
-SpaceX has said the Starbase facility is for manufacturing and testing,  not for routine launch operations
-imo, that means they are planning  on lumping up the towers a few times during landing experiments.

[Vettedrmr]

With a tower catch, there are so many things that could go wrong.
Even if the Booster functions correctly, the Chopsticks themselves could screw it up.

How can they more thoroughly & realistically test the Chopsticks before taking on the risk of a live SuperHeavy Booster?

Up front, THIS IS ASSUMPTION:  I read during the IFT-4 prep that the reason for the booster to land closer to the launch site in a "virtual landing" was to enable the booster and chopsticks to communicate with each other to coordinate the closing of the chopsticks while the booster was hovering.  I know that the chopsticks were closed immediately after booster splashdown per. NSF's feed, so I (here's that word again) assume that took place.  If that's so,  IDK what additional intermediate step you'd take before making the attempt.

[meekGee]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

They are building another tower, but they clearly don't see the point in not building another OLM to go with it. That makes sense to me, as it gives them a lot more flexibility, and flexibility is more valuable to them than any savings from not having it. I guess there might be a short period in which the second tower is capable of catching but they haven't completed the launch mount though.

I also don't think that they'll wait until they have the second tower before attempting a catch; that's just not very SpaceX.  If the catch fails and they need to wait for tower 2 to be ready before flight 6 then they are no worse off than if they'd waited anyway, and if it doesn't fail (or the failure doesn't make tower 1 unusable) then they have gained a load of time.

Ship catch-only towers make the most sense for high launch rate operations, when infrastructure is functioning near capacity, since numerically there are twice as many landings as there are launches, and the ship landings are asynchronous.  (Occurring at odd times, and requiring varying types of payload processing)

There is a small amount of value for a catch tower during development (as a risk reducer during landings) but there is a higher value for a second full tower as a risk mitigator in case of launch damage.

I'm sure SpaceX view launches as higher risk operations than landings, and that's why we're not hearing about catch-only towers rn.

[alugobi]

Musk says things when he's excited.  When he calms down, and with advice from cooler heads, he'll see that they need to tune the landing more.  They'll waste the v. 1 boosters doing this.

[steveleach]

Also, I was thinking that they should build another tower without any OLM. That tower would be used just for the catch.

So, launch from the existing tower, and then catch with the other tower which doesn't have any OLM.
At least then you're not risking so much valuable infrastructure.
You should then do a number of flights that way, before attempting things on the full Stage Zero.

They are building another tower, but they clearly don't see the point in not building another OLM to go with it. That makes sense to me, as it gives them a lot more flexibility, and flexibility is more valuable to them than any savings from not having it. I guess there might be a short period in which the second tower is capable of catching but they haven't completed the launch mount though.

I also don't think that they'll wait until they have the second tower before attempting a catch; that's just not very SpaceX.  If the catch fails and they need to wait for tower 2 to be ready before flight 6 then they are no worse off than if they'd waited anyway, and if it doesn't fail (or the failure doesn't make tower 1 unusable) then they have gained a load of time.

Ship catch-only towers make the most sense for high launch rate operations, when infrastructure is functioning near capacity, since numerically there are twice as many landings as there are launches, and the ship landings are asynchronous.  (Occurring at odd times, and requiring varying types of payload processing)

There is a small amount of value for a catch tower during development (as a risk reducer during landings) but there is a higher value for a second full tower as a risk mitigator in case of launch damage.

I'm sure SpaceX view launches as higher risk operations than landings, and that's why we're not hearing about catch-only towers rn.

We're straying off topic so we should probably move to facilities and fleets, but it just seems limiting to me to build towers without launch mounts: what do you gain by limiting the tower to catching only? And I don't think "twice as many landings" is particularly relevant, because a single tower can catch twice per launch, even if it isn't catching the same ship that launched with the booster.

[steveleach]

Musk says things when he's excited.  When he calms down, and with advice from cooler heads, he'll see that they need to tune the landing more.  They'll waste the v. 1 boosters doing this.

While this is entirely possible, it is also possible that he'll convince those cooler heads that their caution doesn't actually benefit anything in the long run.

For example, they may say "we need to do more to protect the tower", and he might respond with "why? its an old design that we're going to rip apart anyway once tower 2 is built". 

Alternatively, there might not even be a debate, just some due diligence followed by collective agreement that data showed that the tower could have caught the flight 4 booster just fine if they had attempted it.