SECOND stage recovery speculation

[VolkerP]

Independent of Grendals post, I drew this old video up in a second browser tab before reading on in this thread.

So up to the 1:26 mark, SpaceX has delivered. The second stage does a deorbit burn. We have to see a powered landing of the Dragon capsule yet, and there is no information on the second stage features that should facilitate reuse. But patience pays...

 

[Grendal]

Independent of Grendals post, I drew this old video up in a second browser tab before reading on in this thread.

So up to the 1:26 mark, SpaceX has delivered. The second stage does a deorbit burn. We have to see a powered landing of the Dragon capsule yet, and there is no information on the second stage features that should facilitate reuse. But patience pays...

We have seen the Dragon 2 capsule do an abort and a powered hover. So there has at least been some progress. I'm thinking that SpaceX will use, with approval from NASA, some powered cargo landings on ISS supply runs. NASA seems to be working with SpaceX, as long as it doesn't jeopardize too much, for developmental experiments with reuse. I guarantee you that SpaceX will need to be rock solid with Dragon 2 landings before NASA ever allows astronauts to be involved. I would figure ten successful landings in a row before NASA would trust the system. That's just guesswork on my part though based on the 7 successful flights of the block 5 F9 before they let astronauts use the rocket.

As Elon says, stage 2 recovery will be a Hail Mary attempt. ITS will be the fully reusable system and designed from the ground up to be just that.

 

[malcolm]

Presumably if the second stage reaches orbital speeds there is the opportunity to time a de-orbit burn/choose a landing spot. Does it have to be on a barge?

Can you land with a vacuum engine/parachutes?

Interesting problem

 

[ItsNotAboutTheMoney]

Presumably if the second stage reaches orbital speeds there is the opportunity to time a de-orbit burn/choose a landing spot. Does it have to be on a barge?

Can you land with a vacuum engine/parachutes?

Interesting problem

Like the fairing (Stage 2 Subsection F ) they'll want it slow and with minimum damage.
Best hope: recover very wet stage 2 to see what damage the launch and de-orbit did, and then figure out a workable way to protect it.

A separate team will work on the giant bouncy castle.

 

[Grendal]

Like the fairing (Stage 2 Subsection F ) they'll want it slow and with minimum damage.
Best hope: recover very wet stage 2 to see what damage the launch and de-orbit did, and then figure out a workable way to protect it.

A separate team will work on the giant bouncy castle.

After a couple ocean attempts, they can go for a landing at LZ-1. The thing about stage 2 is that it can do an entire orbit of the planet before coming in exactly where SpaceX wants it to come in and land/splash down. The stage does not need to do any sort of boostback burn.

 

[ItsNotAboutTheMoney]

After a couple ocean attempts, they can go for a landing at LZ-1. The thing about stage 2 is that it can do an entire orbit of the planet before coming in exactly where SpaceX wants it to come in and land/splash down. The stage does not need to do any sort of boostback burn.

I think they'll need more than 2. Before SpaceX got to land Stage 1 on land they had demonstrated good control of location and speed with 6 or 7 other landing attempts.

 

[Grendal]

More news from Elon on twitter that occurred in response to a question about cost and reusability:

Fairing is ~$5M, but that should be reusable this year. Am fairly confident we can reuse upper stage too by late next year to get to 100%.

I think they'll need more than 2. Before SpaceX got to land Stage 1 on land they had demonstrated good control of location and speed with 6 or 7 other landing attempts.

I understand but SpaceX has proven time and time again that they have accuracy down. The company has never missed the ASDS or LZ-1 when they have tried for it. Now they will be showing accuracy and control over the fairings which are much harder to control than a powered controlled landing. NASA and the FAA seem to be giving some leeway to the company for now with no errors. So that is why I am guessing that just a couple of ASDS attempts (which can be near the port) or maybe even a New Mexico desert landing as proof of control for a second stage recovery attempt should be enough. Just me guessing though.

 

[ecarfan]

(Elon Musk tweet) "Am fairly confident we can reuse upper stage too by late next year to get to 100%."

That would be an amazing accomplishment if SpaceX can pull that off! I think they have been planning for that and working on it for awhile now, since it will require significant modifications to the 2nd stage no matter what approach they take.

 

[ecarfan]

This SpaceX video is several years old and shows how the 2nd stage might be recovered.,

 

[ItsNotAboutTheMoney]

(Elon Musk tweet) "Am fairly confident we can reuse upper stage too by late next year to get to 100%."

That would be an amazing accomplishment if SpaceX can pull that off! I think they have been planning for that and working on it for awhile now, since it will require significant modifications to the 2nd stage no matter what approach they take.

The first part ...

"Fairing is ~$5M, but that should be reusable this year. "

Hmm, I wonder if that confidence on Stage 2 is a result of examining the fairing?

 

[malcolm]

This SpaceX video is several years old and shows how the 2nd stage might be recovered.,

Thanks for the reminder

I wonder if it's possible to make grid fins out of heat shield materials or make them recessed into the sides of the stage - obviously they wouldn't deploy during re-entry but would need to survive it to be operational at lower altitudes. But maybe fins wouldn't be as effective at steering a much shorter stage and something else will be needed?

 

[Bobfitz1]

Thanks for the reminder

I wonder if it's possible to make grid fins out of heat shield materials or make them recessed into the sides of the stage - obviously they wouldn't deploy during re-entry but would need to survive it to be operational at lower altitudes. But maybe fins wouldn't be as effective at steering a much shorter stage and something else will be needed?

No engineering knowledge here - just gut feeling. What's amazes me is how well stage 1 grid fins are able to help guide the long first stage at two or more periods during reentry and landing. I would think that doing the same for stage 2 (after the hottest period during reentry) would be easier for a shorter cylindrical shape.

 

[Nikxice]

Phenolic Impregnated Carbon Ablator (PICA) is a mouthful, but this material will likely be put to use as part of any Falcon second stage reentry profile. The SpaceX guy with the most knowledge in this area is named Dan Rasky. I found an article related to this topic published two years ago in Space News.

SpaceX Leaves Searing Impression on NASA Heat Shield Guy

For anyone further interested, here's a link to an eight minute interview with Rasky from a year ago. He is keen to emphasize just how rapidly SpaceX is able to develop and test prototype materials.

 

[Grendal]

The whole series of 16 with Dan Rasky is spectacular:

For the rest, go to YouTube and search for "Dan Rasky." There is a page for the whole series.

1. Introduction
2. Cost Estimation - SpaceX just does things in better and cheaper ways
3. History of Cost Plus Contracting
4. Non-traditional Requirements Development
5. Build Where the Talent Resides
6. Start-ups Organizational Structure - Best under 160 people
7. Importance of Co-Location -
8. SpaceX Collaborative Work Environment
9. Mentor & Apprentice Work Model
10. SpaceX Use of Sparse Matrix Engineering
11. Applying software design process to aerospace
12. SpaceX Rapid Prototyping Design - Posted by Nikxice
13. Non-traditional Requirements Development
14. Blue Origin's Unique Engineering
15. SpaceX Collaborative Design Approach - great Elon story!
16. Aligning Incentives, Flat Business, Collaborative Design

I can't recommend this series enough to get an idea of how Elon, SpaceX, and Tesla work.

 

[favo]

There's a playlist for COTS: Dan Rasky.

 

[Ludus]

Second stage reuse doesn't have to be universal to be very valuable to SpaceX. It would have more margin to play with on FH flights. SpaceX is coming up on deploying thousands of its own satellites in an Internet Constellation. These will likely be launched on FH in a very standardized process with very regular launches. In a few years these FH launches may be half of all SpaceX launches. Just being able to recover and reuse the second stage for these launches would be a major savings straight to the bottom line. SX can't pass the costs on to a customer so every dollar saved counts. Even if all customer paid launches and all launches on single core F9 are still expendable S2, this would be important.

 

[Bobfitz1]

After a couple ocean attempts, they can go for a landing at LZ-1. The thing about stage 2 is that it can do an entire orbit of the planet before coming in exactly where SpaceX wants it to come in and land/splash down. The stage does not need to do any sort of boostback burn.

Grendel you say in this post that for Stage 2 no boost back burn is needed. Does that mean that bleeding off the stage's much high velocity is all accomplished by the air resistance and associated heating of stage 2 reentry? If I've got that part right, then only enough extra fuel would need to be boosted by first stage to allow Stage 2 to slow it's much lower mass down to a gentle landing. Has anyone done calculations as to how much add'l weight of stage 2 fuel would be necessary? And could that extra first stage payload weight fit within the Block 5's higher payload to orbit limits? Thanks.

 

[Grendal]

Grendel you say in this post that for Stage 2 no boost back burn is needed. Does that mean that bleeding off the stage's much high velocity is all accomplished by the air resistance and associated heating of stage 2 reentry? If I've got that part right, then only enough extra fuel would need to be boosted by first stage to allow Stage 2 to slow it's much lower mass down to a gentle landing. Has anyone done calculations as to how much add'l weight of stage 2 fuel would be necessary? And could that extra first stage payload weight fit within the Block 5's higher payload to orbit limits? Thanks.

A boostback burn would be unnecessary and unwanted. It only makes any sense if most of velocity is burned off with air resistance just like a capsule. A booster can have up to three burns: boostback, reentry, and landing. A second stage would probably limit that to just one: the landing burn. If a booster needs about 7% of the fuel for recovery then I'd think that a second stage with only one burn would need about 5%. However, you have to consider that there will be additional weight to begin with that isn't there now. So if it is only 5% for landing there would be extra fuel used in the boost phase.

While I'm glad to see SpaceX attempt this and hope that it all works out. I really hope to see them stabilize and finalize their designs to an extent. That way they can focus on getting their payloads into orbit with no anomalies. Keep in mind that both anomalies were second stage issues. There are still plenty of areas more critical that need focus and direction. They have FH coming up, Commercial Crew, and Dragon 2. Personally I think Dragon 2 landings are far more critical than recovering a second stage. Thereafter, the company has the immense job of building and testing ITS. The company needs a stabilized design for military launches and Commercial Crew. It will be interesting to see what they do. I would expect that stage two recovery attempts will be attempted on easy launches like CRS missions.

 

[jkn]

Grendel you say in this post that for Stage 2 no boost back burn is needed. Does that mean that bleeding off the stage's much high velocity is all accomplished by the air resistance and associated heating of stage 2 reentry? If I've got that part right, then only enough extra fuel would need to be boosted by first stage to allow Stage 2 to slow it's much lower mass down to a gentle landing. Has anyone done calculations as to how much add'l weight of stage 2 fuel would be necessary? And could that extra first stage payload weight fit within the Block 5's higher payload to orbit limits? Thanks.

Boost back is not needed, because 2. stage can fly around Earth. 2. stage has so much speed, that it must be slowed down by heat shield. It would take too much fuel to slow down from orbital speed. I have an idea how this should be done, but I have not done calculations.