General Falcon and Dragon discussion (Thread 15)

[Comga]

Latest update in my EELV launch rate comparison chart with SpaceX's 200th flight.  Asterisks:

- EELV - yes this is a dated term
- SpaceX's 200th flight - I am counting the Heavy yesterday (not included in the chart) as 201st as I am counting the on-ground Amos anomaly as a failed launch, due to the destroyed payload. 
- Really fascinated to see how much faster the Vulcan can debut than the launchers depicted here.  They have a very ambitious first-year launch rate queued up...

Equally as instructive is the lower left corner covering the first few years.
Even Falcon 9 took several years to get rolling.
People on this forum who think any of the new rockets in development will bolt out of the gate should examine this carefully.

(It also would be interesting to see expanded data, say 10X, for the first five or so years.
It could be added to the graph by offsetting it by +100 and using faint lines of the same color)

[LouScheffer]

There is little economic incentive to recover the center core.

No, it is physics and not economics.

I agree it's economics, not physics.  The second stage can recovered - it's pretty straightforward.  But it costs considerable delta-V.  The question is whether there are enough missions at that performance point to make it worthwhile.  I don't think there are, and here's why.

First, the bread and butter mission for FH is direct GEO injection.  A stock, recoverable, F9 stages at about 2200 m/s on a GTO mission.  An FH with an expendable center core stages at about 4000 m/s.  That extra 1800 m/s, by coincidence, is just about what the second stage needs to circularize a direct GEO injection. So any payload that an F9 (recoverable) could put into GTO, a FH, with no core recovery, can put into GEO.  Any substantial delta-V penalty will rule this mission out.

Next, the delta-V loss for recovering the center core is about 600 m/s.  This can be shown to be consistent as follows:  First, this would mean a cutoff speed of 3400 m/s if a disposable core is 4000 m/s.  The entry burn has to get down to 1500 m/s.  So the delta-v required is about 1900 m/s, as opposed the usual 700 m/s.  This implies a mass ratio (at an ISP of 348), of exp(1900/(348*9.8 )), or 1.75.  At the end of the entry burn the mass needs to be about 32 tonnes (27 empty + 5 fuel for the landing).  So about 23.9 tonnes of fuel are needed for this burn.

Now, how much delta V does this cost?  This is the delta V added by burning the last 23.9t of fuel.  But we need to add 5t more, since if we are not doing the entry burn we don't need the landing burn either. So between the entry+landing fuel, and the neither-entry-nor-landing fuel, and assuming the upper stage+payload is 120t, our initial mass is 32*1.75+120t, and our final mass is 27+120t. Therefore our sacrificed delta-v is 348*9.8*ln((32*1.75+120)/(27+120)) = 611 m/s, consistent with our initial estimate.

So if SpaceX recovers the center core of FH, they will only get about 1200 m/s more than a barge-recovery F9.  But that's not enough to cover the primary mission of FH, which is direct GEO insertion for the DoD.  A better GTO orbit would be nice, but it does not seem to be compelling to comsat folks (and they can get the first 400 m/s of this with an expendable F9).  So FH center core recovery is considerable work for few customers, which is why I believe SpaceX does not offer it.

[Alvian@IDN]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

[woods170]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

Correct.

FH Center Core recovery was already tried 3 times, with one of the 3 attempts fully successful (only after the successful barge landing did the second FH center core topple due to heavy sea states, but the ASDS landing was successful)

The third of those attempts was extremely challenging due to the much higher entry heating (compared to the previous 2 missions), which was above what the FH center core was designed for. The fact that it still made it back all the way to the immediate vicinity of the ASDS, despite severe entry damage to the engine section, was a miracle in itself. But the entry heating had burned through the base heat shield, damaging critical hardware to control and steer the center engine. SpaceX had already predicted that the chances of recovering the center core of the STP-2 mission were low. And they were right.

The performance requirements for the "stage 1 portion" of the fourth and fifth FH missions were even greater than those for the previous three missions, meaning that the center cores of those missions came in even hotter than the one for STP-2.

But that by no means rules out recovery of the FH center core on future missions. It all depends on the balance between the performance requirements laid down by the customer and what the customer is willing to pay for the launch. If the customer wants maximum performance AND is willing to pay the premium for expending the core stage, than SpaceX will expend the core stage.

[LouScheffer]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

The third of those attempts was extremely challenging due to the much higher entry heating (compared to the previous 2 missions), which was above what the FH center core was designed for. The fact that it still made it back all the way to the immediate vicinity of the ASDS, despite severe entry damage to the engine section, was a miracle in itself. But the entry heating had burned through the base heat shield, damaging critical hardware to control and steer the center engine. SpaceX had already predicted that the chances of recovering the center core of the STP-2 mission were low. And they were right.

I think this was another in the long line of landing experiments performed after the primary mission was complete.  I think SpaceX calculated the mission did not require the full performance of the center core, but on the other hand did not leave enough fuel for the full re-entry burn they would need.  But they gave it a try with what fuel they had left, fully suspecting the aerodynamic heating would be too much.  But in any case it's a data point for the upper envelope of re-entry conditions.

But that by no means rules out recovery of the FH center core on future missions. It all depends on the balance between the performance requirements laid down by the customer and what the customer is willing to pay for the launch

Agreed.  I don't think there are many missions that need a FH but don't need (or don't want to pay for) full performance.  But if such a customer materializes, SpaceX would be happy to recover a center core.   Or it might take more than one such customer, since there is some additional overhead - sending the barge so far downrange (costly in terms of time), octo-grabber mods, and so on.

[LouScheffer]

The third of those attempts was extremely challenging due to the much higher entry heating (compared to the previous 2 missions), which was above what the FH center core was designed for. The fact that it still made it back all the way to the immediate vicinity of the ASDS, despite severe entry damage to the engine section, was a miracle in itself. But the entry heating had burned through the base heat shield, damaging critical hardware to control and steer the center engine. SpaceX had already predicted that the chances of recovering the center core of the STP-2 mission were low. And they were right.

I would argue that this was not a miracle - it's exactly what you would expect.  That's because it's the entry burn and the grid fins that target the barge.  The heating that damaged the engine occurred after the re-entry burn is complete, and there is no indication the grid fins failed.  So although the landing burn could not happen due to engine damage,  the stage was already on course to land very near the ASDS.

[DanClemmensen]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

I think SpaceX is perfectly capable of recovering the center core for a certain class of mission profiles. I feel that the number of missions that can economically use these profiles during the remaining life of FH may be zero. That is, those profiles are on the FH launch price sheet, but nobody will buy one. Those are my "conjectures". On the other hand, your "conjecture" is that such a customer exists. I have no reason to believe that my conjecture is better than yours, or vice versa.

[abaddon]

Latest update in my EELV launch rate comparison chart with SpaceX's 200th flight.  Asterisks:

- EELV - yes this is a dated term
- SpaceX's 200th flight - I am counting the Heavy yesterday (not included in the chart) as 201st as I am counting the on-ground Amos anomaly as a failed launch, due to the destroyed payload. 
- Really fascinated to see how much faster the Vulcan can debut than the launchers depicted here.  They have a very ambitious first-year launch rate queued up...

Equally as instructive is the lower left corner covering the first few years.
Even Falcon 9 took several years to get rolling.
People on this forum who think any of the new rockets in development will bolt out of the gate should examine this carefully.

(It also would be interesting to see expanded data, say 10X, for the first five or so years.
It could be added to the graph by offsetting it by +100 and using faint lines of the same color)

Attached, I just did it separately.

[Comga]

Wow
Look at how tight is the grouping around two years out.
If anyone thinks some new rocket will launch more than five additional times in the three years after the debut, they have to justify why that particular team will be so much faster than the historical records.

That says that a rocket debuting in, say, 2024, won't have more than 6 launches by 2027.
By that point Falcon 9 might have over 500 launches.  (But Starship etc. etc. )

note: by using the full data sets in the new graph, the lines end sloping up to the next launch.
"Forward leaning"
Looking at the points, at the end of the second year, four rockets had launched two additional times, and the fifth only once.
At the point Falcon 9 had 18 launches, ~4.8 years, Atlas V and Ariane 5 had 9 each.
It took SpaceX less than 5 years to double the historic launch rate for new rockets.
And that with only Falcon 1 as a previous development.

[Stan-1967]

Wow
Look at how tight is the grouping around two years out.
If anyone thinks some new rocket will launch more than five additional times in the three years after the debut, they have to justify why that particular team will be so much faster than the historical records.

....snipped....

I'm not disagreeing with the premise, & I think the odds of Starship following that trend are favorable.  However I think Starship has conditions not comparable to the other vehicles, and at least has the non zero probability of bucking the trend.  The burden of justification for that statement is significant, but here is what I see:

All the vehicles on the graph, with the exception of F9, had fairly limited manifests coming out of the design stage.  There was no basic need to ramp launch rate any faster.  The launch market also had other vehicles for the overall industry manifest.  F9 had a very large manifest, and it took some time for F9 to build it's flight rate.  I am amazed F9 compared so closely to the other EELV's given the novice nature of SpaceX at the outset.

None of the other vehicles purposely designed & engineered a system to deliver the type of launch rates Starship could be capable of.  None had a factory churning out cores and upper stages as has been built by SpaceX in TX.  That alone is a huge differentiator in the metrics of scaling the launch rate.

Finally, none of the comparison rockets had re-use capability at the outset.  F9 took time to develop that, and it's flight rate certainly diverged after 2017 from comparable rockets. That is a data point that argues that reusable rockets are statistically different.

I look at this under the lens of "means, motive, opportunity".  Can SpaceX perform the task, do they want to perform the task, have they given themselves a chance to succeed with their engineering and manufacturing decision?

Lastly, do any of the older rockets from the 50's & 60's defy that chart?  Atlas, Delta, Titan, & their variants?  That era may have instructive comparisons

[JayWee]

I'm not disagreeing with the premise, & I think the odds of Starship following that trend are favorable.  However I think Starship has conditions not comparable to the other vehicles, and at least has the non zero probability of bucking the trend.  The burden of justification for that statement is significant, but here is what I see:
...
I look at this under the lens of "means, motive, opportunity".  Can SpaceX perform the task, do they want to perform the task, have they given themselves a chance to succeed with their engineering and manufacturing decision?
...

People should always remember that, as of now, Starship already has around ~600 flights (Starlink V2) on its manifest. That's a pretty *big* driving force.

[DeimosDream]

People should always remember that, as of now, Starship already has around ~600 flights (Starlink V2) on its manifest. That's a pretty *big* driving force.

While I agree with your conclusion that Starship has a driving urgency its worth noting that the FCC rejected the scenario that would have required 600 flights. SpaceX was only approved for 7,500 Starlink V2 satellites, which at ~75/launch (scaling from F9 to a conservative 100t Starship payload) 'only' implies about 100 flights manifested for Starship by Starlink V2.

Wow
Look at how tight is the grouping around two years out.
If anyone thinks some new rocket will launch more than five additional times in the three years after the debut, they have to justify why that particular team will be so much faster than the historical records.

To get 50% completion of their Gen-2 constellation by the end of 2028 SpaceX will need 50+ Starship launches within 6 years, a feat which required 8 years with Falcon 9. To make it SpaceX is going to have to be at least 33% faster to ramp up than they were with their own record setting F9. That's at least 7 additional times in the first three years to be where F9 was at year-4. SpaceX has had practice beating historical trends with F9, so that doesn't seem unreasonable.

Neutron would also be a good candidate for exceeding historical trends. Rocket Lab has the twin advantages of first being a fast follower able and willing to apply F9's booster reuse lessons from the start and second has significantly more Electron flight experience than SpaceX had Falcon-1 experience.

[LouScheffer]

Here is estimated performance of all Falcon variants to high energy orbits.  I started with the Nasa performance estimator, which offers 4 Falcon versions - F9 RTLS, F9 ASDS, FH boosters recovered, and FH fully expended.  I requested C3=10, since all boosters can do do that, so I get a chart of for the four variants.

Next, I looked at what C3 each can achieve with a 2000 kg payload (which all can do).  Using a single payload mass means the second stage performance is identical.  So we can work back to the booster variation.  For convenience, I converted each C3 to a velocity at a (160 km) LEO altitude:


Rocket        C3@2000kg  m/s at LEO   delta
F9 RTLS              -3  10912        ----
F9 ASDS              12  11579        667
FH RTLS+ASDS         37  12612        1700
FH all expend        83  14320        3408

The next step is to interpolate for the versions not shown (F9 expended, FH RLTS side expend center, and FH ASDS side expend center).  From the expended F9s late last year, we know that expending the booster gains about 400 m/s.  We know that on ArabSat-6 (RLTS side, core recovered) the booster cut off at 10730 km/hr, where on USSF-67 it was about 14500 km/hr (roughly 1000 m/s greater).  Finally, we can deduce that the difference between FH ASDS sides and FH-expend-all will be small, less than the 400 m/s of the F9.  I'm guessing about 250 m/s by the following logic:  The entry burn (20 sec, 3 engines) and landing burn (30 sec, one engine) total about 90 engine-seconds.  That's 10 seconds for 9 engines, and the FH is only accelerating at about 2.5 Gs at the point (extrapolating from the RTLS trajectory, which we have seen).  This gives us our final estimated curve.

Next, we double check with known missions.  Arabsat-6 had an apogee of 90,000 km and an inclination of 23^o.  That works out to be about roughly 3000 m/s above LEO, or C3=-5.  It massed 6500 kg.  This is compatible with sides RTLS, core ASDS, which was used.  USSF-67 was direct to GEO.  This is 1800 m/s more than GTO which is about 2470 m/s.  Converting to C3 gives C3=24 (which will be true for all direct GEO missions.  They are quite hard.)  Mass was 3750 kg.  This is slightly more than can be done while recovering the center core, explaining the expendable.  Finally we know Europa Clipper was spec'ed at 6060 kg, C3=42.  This needs full power - even catching the sides on ASDS won't work.  And indeed, it's scheduled as fully expendable.

Overall, SpaceX has built quite a dial-a-rocket system.

[oldAtlas_Eguy]

Historical trends. NOTE historical trends started very different to what the settled down to later. See the old chart dated 1965 and be blown away by the ramp up and launch rate. Atlas (the first stainless steel rocket) had a fantastic mass production line that churned out not only tanks but rocket engines as well. The estimate on engine production was close to 200/yr at one point.

If you will notice the curve actually increases faster than the F9 one. That is almost completely because of the fantastic production rates >75 per year in 1957 for the Atlas D and E and 1960 for continuation of Atlas D and production of Atlas F. Launch rates on Atlas E's shot up because they were ICBMs that were deactivated in 1960 and replaced by silo sited Atlas F's. They were used for many different both suborbital and orbital tests and actual small spy sat launches. The remainder of the E's and F's were removed from storage in the 70's through until the 90's and used at Vandenberg to launch spy and NOAA polar orbit sats. Atlas stainless steel rockets tanks and their engine sets were produced continuously from 1957 through the 1990's.

[DanClemmensen]

Historical trends. NOTE historical trends started very different to what the settled down to later. See the old chart dated 1965 and be blown away by the ramp up and launch rate. Atlas (the first stainless steel rocket) had a fantastic mass production line that churned out not only tanks but rocket engines as well. The estimate on engine production was close to 200/yr at one point.

If you will notice the curve actually increases faster than the F9 one. That is almost completely because of the fantastic production rates >75 per year in 1957 for the Atlas D and E and 1960 for continuation of Atlas D and production of Atlas F. Launch rates on Atlas E's shot up because they were ICBMs that were deactivated in 1960 and replaced by silo sited Atlas F's. They were used for many different both suborbital and orbital tests and actual small spy sat launches. The remainder of the E's and F's were removed from storage in the 70's through until the 90's and used at Vandenberg to launch spy and NOAA polar orbit sats. Atlas stainless steel rockets tanks and their engine sets were produced continuously from 1957 through the 1990's.

High launch rates, but also very high failure rates. That was apparently in the "try it, it might work" era of rocket design. Looks a lot like Boca Chica in 2019.

[Comga]

Wow
Look at how tight is the grouping around two years out.
If anyone thinks some new rocket will launch more than five additional times in the three years after the debut, they have to justify why that particular team will be so much faster than the historical records.

....snipped....

I'm not disagreeing with the premise, & I think the odds of Starship following that trend are favorable.  However I think Starship has conditions not comparable to the other vehicles, and at least has the non zero probability of bucking the trend.  The burden of justification for that statement is significant, but here is what I see:

All the vehicles on the graph, with the exception of F9, had fairly limited manifests coming out of the design stage.  There was no basic need to ramp launch rate any faster.  The launch market also had other vehicles for the overall industry manifest.  F9 had a very large manifest, and it took some time for F9 to build it's flight rate.  I am amazed F9 compared so closely to the other EELV's given the novice nature of SpaceX at the outset.

None of the other vehicles purposely designed & engineered a system to deliver the type of launch rates Starship could be capable of.  None had a factory churning out cores and upper stages as has been built by SpaceX in TX.  That alone is a huge differentiator in the metrics of scaling the launch rate.

....snipped....

Ha!
To be honest, my comments were not made with Starship in mind.
It was primarily about New Glenn and Vulcan, which has a long list of launches ULA hopes to make in 2023 despite the debut launch occuring in February or March (maybe).
Starship has every chance of bucking the trend for all the reasons you state.
Because SpaceX does things differently.

[oldAtlas_Eguy]

Historical trends. NOTE historical trends started very different to what the settled down to later. See the old chart dated 1965 and be blown away by the ramp up and launch rate. Atlas (the first stainless steel rocket) had a fantastic mass production line that churned out not only tanks but rocket engines as well. The estimate on engine production was close to 200/yr at one point.

If you will notice the curve actually increases faster than the F9 one. That is almost completely because of the fantastic production rates >75 per year in 1957 for the Atlas D and E and 1960 for continuation of Atlas D and production of Atlas F. Launch rates on Atlas E's shot up because they were ICBMs that were deactivated in 1960 and replaced by silo sited Atlas F's. They were used for many different both suborbital and orbital tests and actual small spy sat launches. The remainder of the E's and F's were removed from storage in the 70's through until the 90's and used at Vandenberg to launch spy and NOAA polar orbit sats. Atlas stainless steel rockets tanks and their engine sets were produced continuously from 1957 through the 1990's.

High launch rates, but also very high failure rates. That was apparently in the "try it, it might work" era of rocket design. Looks a lot like Boca Chica in 2019.

Yes very similar to the F9 1st stage recovery attempts at first. Try try again.

But the other item of the limits of payloads had a definite affect on launch rates once reliability went up. Effectively slowing the launch rates in the later 60's.

So the prior 3 years of flight testing for Starship equivalent to the F1 flight testing years. And now passing into the equivalent  F9 orbital flight testing with this year the fourth one for Starship means that the curves are not that different except that depending on difficulties incurred in reaching orbit and in the recovery of boosters will govern eventual ramp up of flight rates as will the addition of more vehicle production facilities i.e. KSC.

[alugobi]

but also very high failure rates.

Remember that quote from The Right Stuff:  "People have begun to say that our rockets always blow up."

[LouScheffer]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

I think SpaceX is perfectly capable of recovering the center core for a certain class of mission profiles. I feel that the number of missions that can economically use these profiles during the remaining life of FH may be zero. That is, those profiles are on the FH launch price sheet, but nobody will buy one. Those are my "conjectures". On the other hand, your "conjecture" is that such a customer exists. I have no reason to believe that my conjecture is better than yours, or vice versa.

Such missions certainly exist, or at least have existed.  For example, the original Psyche needed a C3 of 15-18 for a mass of 2800 kg. This is beyond what an expendable F9 could do, but well within the range of a FH with a recovered core.  (The new Psyche trajectory, judging by pictures, has a greater initial apohelion and may need an expendable core.  But I have not seen any numbers.)

[DanClemmensen]

Those people that recently believe center core recovery will never happen just because two recent missions expended it have no idea that they're sinking ever deeper into conjectures & not believing in so called "coincidences"

I think SpaceX is perfectly capable of recovering the center core for a certain class of mission profiles. I feel that the number of missions that can economically use these profiles during the remaining life of FH may be zero. That is, those profiles are on the FH launch price sheet, but nobody will buy one. Those are my "conjectures". On the other hand, your "conjecture" is that such a customer exists. I have no reason to believe that my conjecture is better than yours, or vice versa.

Such missions certainly exist, or at least have existed.  For example, the original Psyche needed a C3 of 15-18 for a mass of 2800 kg. This is beyond what an expendable F9 could do, but well within the range of a FH with a recovered core.  (The new Psyche trajectory, judging by pictures, has a greater initial apohelion and may need an expendable core.  But I have not seen any numbers.)

OK, we have an existence proof for one mission, maybe, and there may be more. Let's move the goalposts slightly. I think we need a mission that has RTLS for the side boosters and a downrange recovered core. If you want to recover all three downrange, you need another ASDS, and I feel that there will not be enough missions to justify its cost. Again, this is a gut feeling, not a quantitative analysis, so I may be wrong.