Aviation week article on SpaceX reusability

[Robotbeat]

An expendable upper stage with a 9 meter fairing is a mental image in my mind.

How much extra payload does jettisoning the fairing add? 

…

Probably about 20 tons. And that applies to every orbit Starship can launch to. So to GTO or to escape velocity missions, that is huge. Doubling payload or even more.

Plus allows much larger payloads to be launched. Think like something similar to LUVOIR but without folding. Or a massive Skylab-like station. Or a huge but bulky solar array optimized for mass instead of stowage volume. Or a huge depot with more capacity than an entire Super Heavy booster. Or an in-space transfer vehicle for hundreds of people. Or an expandable habitat for thousands.

If you want to make a mega-telescope capable of 20m diameter or something exceeding any terrestrial scope.

[M.E.T.]

Currently, SpaceX has 13 active boosters. Additionally, there are 10 more boosters that have been spotted in either testing or transit.

It has been speculated that B1049 will be expended after it's next mission. Based on the available mission profile, it appears the 4 FH core boosters will be expended after their first launch as well.

The true number of launches with just the current boosters likely is between 80 and 160 - without SpaceX deciding to certify some of the later ones to 20 flights.

So counting it up, there are ninety-six flights left in the current thirteen active boosters.  That is if we assume an average of fifteen flights per booster.  And that doesn't include the new boosters that are in the pipeline or the side boosters which after supporting Falcon Heavy flights could be converted to regular Falcon 9 boosters.

Ninety-six flights will probably take SpaceX halfway through 2024. And it will be a whole lot more flights if we count the boosters that are in the production pipeline.

SpaceX is prepared to do a lot more flights on the Falcon 9.  I would say that they have definitely not assumed in the Falcon 9 production pipeline that the Starship will work.

And it's really eleven active boosters that have been responsible for the flights so far this year.  Booster 1949 last flew in September 2021.  It's supposed to be expended on its next flight this November.  And Booster 1069 just returned to flight a few days ago after an accident from a flight from last December(?).

https://twitter.com/elonmusk/status/1564994769826172929?s=21&t=Qr6mxKFx-RCkc1morHYO0g

[TomH]

Now this is surprising. I'd have guessed a longer coast would have given them more altitude and be beneficial. OTOH more booster damage due to earlier sustainer ignition makes perfect sense due to greater exposure to engine plume.

Coasting leads to an increase in gravity losses.

Correct. During the coast phase, the vehicle would be gaining altitude but also losing velocity that must be regained via the next stage. Think about throwing a rock straight up. Two things are happening as it approaches apex. It keeps getting higher and higher, but also is traveling slower and slower as gravity cancels out the energy your arm muscles put into it. Kinetic energy is changing into potential energy of elevation (which is then changed back to kinetic energy during descent.) The total acceleration a vehicle is undergoing at any point in time equals the positive acceleration coming from the engines minus the negative acceleration from gravity (known as gravity losses). During coast phase, there is no positive acceleration from engines, but you still have the cosine of one G decelerating the vehicle. From a performance perspective, you want coast to be as brief as possible. Since you want to recover and reuse the booster, you need enough coast time that the upper stage engine does not roast the booster. I am not sure how much thrust there is from ullage on both stages.

[M.E.T.]

Now this is surprising. I'd have guessed a longer coast would have given them more altitude and be beneficial. OTOH more booster damage due to earlier sustainer ignition makes perfect sense due to greater exposure to engine plume.

Coasting leads to an increase in gravity losses.

Correct. During the coast phase, the vehicle would be gaining altitude but also losing velocity that must be regained via the next stage. Think about throwing a rock straight up. Two things are happening as it approaches apex. It keeps getting higher and higher, but also is traveling slower and slower as gravity cancels out the energy your arm muscles put into it. Kinetic energy is changing into potential energy of elevation (which is then changed back to kinetic energy during descent.) The total acceleration a vehicle is undergoing at any point in time equals the positive acceleration coming from the engines minus the negative acceleration from gravity (known as gravity losses). During coast phase, there is no positive acceleration from engines, but you still have the cosine of one G decelerating the vehicle. From a performance perspective, you want coast to be as brief as possible. Since you want to recover and reuse the booster, you need enough coast time that the upper stage engine does not roast the booster. I am not sure how much thrust there is from ullage on both stages.

Probably absurd idea, for any number of reasons, but is there no benefit in briefly flipping the tail of the 2nd stage downwards by say 30 degrees to allow for immediate ignition upon separation, with the plume then directed mostly away from the separating booster?

For those few seconds the thrust will not be exactly in the intended direction, but you don’t have complete coasting either. Or does the inefficiency outweigh the benefits of a couple of seconds of extra partial thrust?

[jimothytones]

You'd spend more time reorienting the S2/Fairing/spacecraft complex to a radial out-ish attitude using S2's very limited onboard gas RCS than you would just waiting to get some more distance from the booster. For a *very* marginal payload benefit, if any. TBH it would probably reduce your total available dV, at least on lighter payloads.

Heating and mechanical erosion from exhaust plume impingement decreases very rapidly with distance at the altitudes where F9 likes to stage. The performance advantage X is looking for when tweaking the timing of S2 ignition is measured in kilograms, not tons. It's worth fiddling with, but not really worth trying out any major operational changes.

[OTV Booster]

I agree it’d be smart to prepare a much bigger buffer of F9 capacity than Elon would probably prefer, but…

Keep in mind 42 is a minimum figure for available launches. I'm not sure how evenly the launches have been spread throughout the fleet. I think some of them are quite a bit lower, but it's not something I've tracked in detail, hence my question.  [EDIT Checked the F9 launch list on Wiki. It reckons they are at about 178 launches so far, so between 6-7 launches per booster left on average. Given some are within 2 launches of their 15 launch limit that confirms my feeling that the launches have been quite unevenly allocated, for whatever reasons]

As I noted for other launch companies having 42 launches available would be good for years of launches but SX's cadence is much higher than most (all?) others.

Docking Starship to ISS is not very different from docking Shuttle to ISS.

Given that it's about 13m longer than shuttle and designed to carry about 4x the mass of Shuttles payload bay (even if it came to orbit with only Shuttle's payload level) it's mass properties, such as 2nd moment of area, are going to be very different than Shuttles.

That's important because of the loads put on the docking adapter. I think of it as a pool cue. The sharp end is at the adapter but the heavy end is at the other end of the cue, only the heavy end is now 13m further away, able to excert much more torque on that interface.

Obviously with enough RCS control authority and fast enough acting control systems these issues can be overcome, if the will is there to do so.

We'll find out when Starship makes orbit. Starship docked to ISS will be quite a sight. 

I'm late to the party, but have to comment. The difficulties in docking the SS to the ISS may be more profound than you expect.


The Shuttle aft bulkhead, between the cargo bay and the engine bay was a massive slab of titanium, hogged out leaving reinforcing ribs and attachment bosses. The stringers and beams leading forward from it attached to the bulkhead between the cargo bay and the crew cabin. This box assembly had to be strong enough to resist buckling and twisting from wing loading during EDL. In other words, that front bulkhead had to be pretty strong too.


This front bulkhead is where the air lock and docking port lived. If the Shuttle had a bit of torque to feed into the connection, this very strong bulkhead is what would be loaded. Probably the second strongest point on the shuttle. Maybe the third after the wing spar attachments.


The SS has no comparable strong point. One could be designed in but it would have to load into the hull structure and spread the load widely in an area not designed for loads of that type. The shuttle probably needed extra reinforcement too but it would have been loading into a relatively small structure already designed to be rigid and already designed to load into a strong box structure.


I see only two solutions. 1) Reinforce some or all ships. 2) Drop the idea and stay with Dragon.


There's a lot to be said for staying with dragon and F9. It's known to be reliable, NASA is comfortable with it and I think I saw something about NASA contracting for more dragon flights, or planning on it. When the next contract is up, if SX has started phasing out the F9, is the time to renegotiate on the basis of NASA either paying enough to make a legacy system worth SX's time or paying enough to justify special mods to SS. It's not bait and switch. It's a new set of conditions.

[john smith 19]

The Shuttle aft bulkhead, between the cargo bay and the engine bay was a massive slab of titanium, hogged out leaving reinforcing ribs and attachment bosses. The stringers and beams leading forward from it attached to the bulkhead between the cargo bay and the crew cabin. This box assembly had to be strong enough to resist buckling and twisting from wing loading during EDL. In other words, that front bulkhead had to be pretty strong too.

This front bulkhead is where the air lock and docking port lived. If the Shuttle had a bit of torque to feed into the connection, this very strong bulkhead is what would be loaded. Probably the second strongest point on the shuttle. Maybe the third after the wing spar attachments.

Exactly. IMHO any point you can reasonably put a docking port is still going to have a substantial portion of the vehicle mass a substantial way from it, giving the ability to excert serious torque on that docking port.

I see only two solutions. 1) Reinforce some or all ships. 2) Drop the idea and stay with Dragon.


There's a lot to be said for staying with dragon and F9. It's known to be reliable, NASA is comfortable with it and I think I saw something about NASA contracting for more dragon flights, or planning on it. When the next contract is up, if SX has started phasing out the F9, is the time to renegotiate on the basis of NASA either paying enough to make a legacy system worth SX's time or paying enough to justify special mods to SS. It's not bait and switch. It's a new set of conditions.

True.  Those do look like the major options. And this is certainly nothing like the sort of bait-n-switch that Boeing did with XS-1

It's nearest parallel is ULA's wish to migrate all launches to Vulcan but still having contractual obligations DIVH. 

Economically (and let's not forget Musk has a degree in Economics as well as Physics) SX's best path is total shut down of the F9/FH operation, once SS shows it can get to and return from orbit.

The joker is of course wheather the 15 flight maximum is an economic or a physical limit imposed by the flight conditions and if it takes longer SS to prove out that SX expect. SX say it's the former, so if SS needs more testing then that's not a problem as they just raise the limit.

As always time will tell.

[TomH]

....I see only two solutions. 1) Reinforce some or all ships. 2) Drop the idea and stay with Dragon.


There's a lot to be said for staying with dragon and F9. It's known to be reliable, NASA is comfortable with it and I think I saw something about NASA contracting for more dragon flights, or planning on it. When the next contract is up, if SX has started phasing out the F9, is the time to renegotiate on the basis of NASA either paying enough to make a legacy system worth SX's time or paying enough to justify special mods to SS. It's not bait and switch. It's a new set of conditions.

Add to this, Elon wants to retire F9 and Dragon ASAP. Also, if Russia does abandon ISS, it will require significant effort to keep it functioning. With that being the case, Elon may consider the whole thing not worth the risk. (A risk that is beyond engineering risk and more the risk of what the very unpredictable and unreliable Russians will do.)

It's like a really bad marriage, especially if one party is just playing mind games. Sometimes therapy is futile and divorce is the better option.

[Robotbeat]

SpaceX will STILL need a docking port for Dragon, Orion, and Gateway. I don’t buy that shuttle was uniquely reinforced and Starship can’t be.

[su27k]

Also even if Starship doesn't dock with ISS, it'll need to dock with commercial stations, so the ability to dock with space station is kind of a requirement. I think Nanorack already mentioned Starlab can be serviced using Starship.

[OTV Booster]

New Dragon contract.

https://arstechnica.com/science/2022/09/nasa-will-pay-boeing-more-than-twice-as-much-as-spacex-for-crew-seats/

Main point: SX is now contracted for 14 more Dragon missions.

Another point in favor of keeping F9 in service is ground support. It's all there. It works. It's ready to go. It doesn't intrude on SS operations (yet).

SS has a lot on its development plate. EDL, refueling and Artemus, not to mention human rating. It looks like ISS is toast in 7+ years and NASA has all the missions contracted. There will most probably be private Dragon flights. Number unknown.

SS docking will have to be developed for Artemus, private stations and by reasonable extension SX internal use, but not for ISS.

[MP99]

Now this is surprising. I'd have guessed a longer coast would have given them more altitude and be beneficial. OTOH more booster damage due to earlier sustainer ignition makes perfect sense due to greater exposure to engine plume.

Coasting leads to an increase in gravity losses.

Correct. During the coast phase, the vehicle would be gaining altitude but also losing velocity that must be regained via the next stage. Think about throwing a rock straight up. Two things are happening as it approaches apex. It keeps getting higher and higher, but also is traveling slower and slower as gravity cancels out the energy your arm muscles put into it. Kinetic energy is changing into potential energy of elevation (which is then changed back to kinetic energy during descent.) The total acceleration a vehicle is undergoing at any point in time equals the positive acceleration coming from the engines minus the negative acceleration from gravity (known as gravity losses). During coast phase, there is no positive acceleration from engines, but you still have the cosine of one G decelerating the vehicle. From a performance perspective, you want coast to be as brief as possible. Since you want to recover and reuse the booster, you need enough coast time that the upper stage engine does not roast the booster. I am not sure how much thrust there is from ullage on both stages.

Probably absurd idea, for any number of reasons, but is there no benefit in briefly flipping the tail of the 2nd stage downwards by say 30 degrees to allow for immediate ignition upon separation, with the plume then directed mostly away from the separating booster?

For those few seconds the thrust will not be exactly in the intended direction, but you don’t have complete coasting either. Or does the inefficiency outweigh the benefits of a couple of seconds of extra partial thrust?

I think Elon may have discussed something related.

Starlink is released by spinning the vehicle end over end, which moves the sats away gently via centri-whatever forces.

He said same for staging SS, which would leave the bottom of SS and top of Booster rotating away from each other.

Cheers, Martin

Sent from my Lenovo TB-X606X using Tapatalk

[FutureSpaceTourist]

Current booster reuse status, following Starlink launch few hours ago:

twitter.com/_rykllan/status/1566656119921147904

#SpaceX's #Falcon9 & #FalconHeavy flightworthy boosters as of Sep 5, 2022

https://twitter.com/_rykllan/status/1566656128402046976

Statistics of #SpaceX's #Falcon9 & #FalconHeavy booster missions as of Sep 5, 2022

[john smith 19]

Current booster reuse status, following Starlink launch few hours ago:

Interesting.

So B1051,1058 and 1060 are the flight leaders.

It'll be interesting to see what happens when they reach 15 flights.

[AmigaClone]

Current booster reuse status, following Starlink launch few hours ago:

Interesting.

So B1051,1058 and 1060 are the flight leaders.

It'll be interesting to see what happens when they reach 15 flights.

From the article in the original post.

The decision to requalify the boosters for 15 flights was a natural outgrowth of the ongoing evolution of the Block 5. “Every flight, we’re continuously inspecting, learning and then reapplying those lessons to either changing the design, a manufacturing process or our inspection methods across the fleet and into the next flights,” says Kiko Dontchev, SpaceX vice president for launch.

SpaceX has three classes of inspections: A class is performed for every mission; B class involves periodic maintenance, which is now performed every sixth or seventh flight; and C class, the most thorough maintenance process, is used for the fleet life-leaders and for all crewed missions.

I suspect that SpaceX might do a more intensive inspection on at least B1058 and B1060 in view of potentially requalifing those boosters and the ones that follow to 20 flights. I'm not certain if B1051 would also undergo that inspection or not.

[john smith 19]

I suspect that SpaceX might do a more intensive inspection on at least B1058 and B1060 in view of potentially requalifing those boosters and the ones that follow to 20 flights. I'm not certain if B1051 would also undergo that inspection or not.

Well Musk is saying 100 launches next year so that number of flights is not nealy as much leeway as it appeared. Looking to get the fleet up to 20 each would be a sensible precaution.

We'll see.

[DanClemmensen]

I suspect that SpaceX might do a more intensive inspection on at least B1058 and B1060 in view of potentially requalifing those boosters and the ones that follow to 20 flights. I'm not certain if B1051 would also undergo that inspection or not.

Well Musk is saying 100 launches next year so that number of flights is not nealy as much leeway as it appeared. Looking to get the fleet up to 20 each would be a sensible precaution.

We'll see.

This also depends on how many of Elon's launches are Starship. If he magically hits 30 Starship launches, he only has 70(!) F9/FH to worry about.

[wannamoonbase]

I suspect that SpaceX might do a more intensive inspection on at least B1058 and B1060 in view of potentially requalifing those boosters and the ones that follow to 20 flights. I'm not certain if B1051 would also undergo that inspection or not.

Well Musk is saying 100 launches next year so that number of flights is not nealy as much leeway as it appeared. Looking to get the fleet up to 20 each would be a sensible precaution.

We'll see.

This also depends on how many of Elon's launches are Starship. If he magically hits 30 Starship launches, he only has 70(!) F9/FH to worry about.

It's been 6 years to get to a SS/SH on the OLM.  I would love to be wrong, but I think SS will be in the single digits in 2023 and maybe even 2024.

F9/FH are going to be carrying the mail in 2023.

[AmigaClone]

I suspect that SpaceX might do a more intensive inspection on at least B1058 and B1060 in view of potentially requalifing those boosters and the ones that follow to 20 flights. I'm not certain if B1051 would also undergo that inspection or not.

Well Musk is saying 100 launches next year so that number of flights is not nealy as much leeway as it appeared. Looking to get the fleet up to 20 each would be a sensible precaution.

We'll see.

I suspect it will take a combination of certifying at least some of the boosters to 20 flights and converting some FH side boosters to F9 to reach that goal of 100 Falcon 9 launches. Note that booster B1052 flew twice as a FH side booster and this year has flown 5 times as a Falcon 9, so it's something that's been done with a Block 5

[john smith 19]

It's been 6 years to get to a SS/SH on the OLM.  I would love to be wrong, but I think SS will be in the single digits in 2023 and maybe even 2024.

F9/FH are going to be carrying the mail in 2023.

That's my view as well.   

The simple fact is it's 116 days to 2023 and SS has not reached orbit yet.

Obviously it could launch tomorrow, and the era of Starship will have finally dawned, but it could just as easily stay on the ground till next year.

I'm not really clear what the delay is at this point. The economics from SX's PoV are get SS to orbit and start winding down the whole expendable infrastructure.