Author Topic: Payload estimate for allowing routine re-entry  (Read 17238 times)

Online LouScheffer

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Payload estimate for allowing routine re-entry
« on: 04/28/2016 02:02 am »
Here's an estimate of how much less satellite mass would be required to make the re-entry burn routine.

According the SpaceX webcast, SES-9 was going about 2325 m/s at booster cutoff, about Mach 6.8.  There was a 17 second re-entry burn.  Each engine needs 270kg/sec, so that's 13.7t of fuel used.  Assuming an empty mass of 29t, 3t of fuel for the suicide slam, and a vacuum ISP of 311, then the delta v for the re-entry burn was 311*9.8*ln((32+13.7)/32) = 1086 m/s.  So the rocket was re-entering at about 2325 - 1086 = 1239 m/s, or about Mach 3.6 .  This is clearly marginal since Musk stated they did not expect it to survive re-entry. In practice, maybe it did or maybe it didn't.  It's not clear if the failure to restart one engine was a result of damage, too little fuel, or some other problem.

So how much margin do they need to make it work?  Given that it survived at all at Mach 3.6, Mach 2 should be OK with almost 6 times less peak heating and 3x less heating total. To get this they need to reduce the re-entry speed by about 550 m/s or so. Reserving more fuel for re-entry helps in two ways - booster cutoff will happen slightly earlier at a lower speed, and there is more fuel for the re-entry burn.  Since (from the point of view of the first stage) about 2/3 of the mass is shed at MECO (about 125t second stage, versus about 60t booster plus fuel), the second delta-V will be about 3x the first.  So about 137 m/s less at cutoff and a 412 m/s bigger re-entry burn.  A more careful calculation using the rocket equation give 121 m/s less boost and 429 m/s more burn.

So now the second stage has to provide 121 m/s more.  Assuming 111t fuel, 348 ISP, 5t empty,  5.3t SES-9, we get 348*9.8*ln(121.3/10.3) = 8410 m/s.  If we need 8530 m/s instead, that implies a 4900 kg or less payload.  For GTO payloads of this mass or less, SpaceX should  have all the margin needed to do a hot re-entry.
« Last Edit: 04/28/2016 02:05 am by LouScheffer »

Offline MarekCyzio

Re: Payload estimate for allowing routine re-entry
« Reply #1 on: 04/28/2016 01:42 pm »
1. What if you assume MACH 2.5 as safe speed? How does it change satellite's weight?
2. Do these numbers assume all GTO satellites will be deployed to orbit similar to SES-9? Is this a valid assumption?
3. Do these numbers assume 3 engine landing burn? Is there any way to recalculate this using single engine burn?
« Last Edit: 04/28/2016 01:42 pm by MarekCyzio »

Offline Doesitfloat

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Re: Payload estimate for allowing routine re-entry
« Reply #2 on: 04/28/2016 02:28 pm »
Couple years ago we were looking at the dry weight if stage 1 and the consensus was about 20t.  You use 30t. While I concede it gained some weight with legs and fins, I doubt it was 10 tons.  If your stage went on a diet to say 25t what difference would that make?

Offline AncientU

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Re: Payload estimate for allowing routine re-entry
« Reply #3 on: 04/28/2016 02:28 pm »
Thanks for the calculations, LouS.
Do you see 4,900 as clearly achievable and the margin between 4,900 and 5,300 'work required, but not impossible'?
Seems 5,300 is top of range that will be attempted, for now at least.
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Offline livingjw

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Re: Payload estimate for allowing routine re-entry
« Reply #4 on: 04/28/2016 04:54 pm »
Mach 3 - 3.5 should survive a reentry. SpaceX would have pushed both max reentry heat flux and minimum landing burn time. The high end of the former and the low end of the latter.
« Last Edit: 04/28/2016 05:00 pm by livingjw »

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #5 on: 04/28/2016 05:57 pm »
1. What if you assume MACH 2.5 as safe speed? How does it change satellite's weight?
It allows about 100kg more (5030 kg by my estimate)
Quote
2. Do these numbers assume all GTO satellites will be deployed to orbit similar to SES-9? Is this a valid assumption?
Yes.  This is a fair but not perfect assumption.  SES-9 went to a GEO-1775 m/s orbit.  That's just a little better than a standard transfer orbit from the cape, which is GEO-1800 m/s.  SpaceX could add about 100 kg and still make a minimal GTO.
Quote
3. Do these numbers assume 3 engine landing burn? Is there any way to recalculate this using single engine burn?
Yes, they assume a suicide slam as used on SES-9.  Subtract about another 300 kg payload to allow a regular, single-engine landing burn.  So a 4600 kg payload allows a safe re-entry and a regular landing.

Offline cambrianera

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Re: Payload estimate for allowing routine re-entry
« Reply #6 on: 04/28/2016 06:01 pm »
Couple years ago we were looking at the dry weight if stage 1 and the consensus was about 20t.  You use 30t. While I concede it gained some weight with legs and fins, I doubt it was 10 tons.  If your stage went on a diet to say 25t what difference would that make?

Here you can find why.
http://forum.nasaspaceflight.com/index.php?topic=37304.msg1358917#msg1358917
Number stated was approximate, and not clear if considering landing fuel or not; nevertheless it is the best number we have.
Oh to be young again. . .

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #7 on: 04/28/2016 06:01 pm »
Couple years ago we were looking at the dry weight if stage 1 and the consensus was about 20t.  You use 30t. While I concede it gained some weight with legs and fins, I doubt it was 10 tons.  If your stage went on a diet to say 25t what difference would that make?
If the stage goes on a 25t diet (hopefully not a crash diet), then the calculated performance allows a slightly higher payload - perhaps 5000 kg with a safe re-entry and a suicide slam, or 4700 kg with a safe re-entry and a "normal" landing.

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #8 on: 04/28/2016 06:21 pm »
Thanks for the calculations, LouS.
Do you see 4,900 as clearly achievable and the margin between 4,900 and 5,300 'work required, but not impossible'?
Seems 5,300 is top of range that will be attempted, for now at least.

Well, the 4900 figure had a safe re-entry, but still a suicide slam.  Getting rid of the slam completely costs about another 300 kg.  So I'd say 4600 kg should be clearly achievable - safe re-entry and already-proven landing.  5300 kg seems very marginal, though worth a try.   If I had to guess, after the system is characterized and all the bugs worked out, I'd say 5000 kg or less, they will expect to recover.  5001-5300 kg, they'll try, but not with high expectations.  5301-6500 kg, pure expendable - don't bother to send the barge.

Online envy887

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Re: Payload estimate for allowing routine re-entry
« Reply #9 on: 04/28/2016 06:51 pm »
Thanks for the calculations, LouS.
Do you see 4,900 as clearly achievable and the margin between 4,900 and 5,300 'work required, but not impossible'?
Seems 5,300 is top of range that will be attempted, for now at least.

Well, the 4900 figure had a safe re-entry, but still a suicide slam.  Getting rid of the slam completely costs about another 300 kg.  So I'd say 4600 kg should be clearly achievable - safe re-entry and already-proven landing.  5300 kg seems very marginal, though worth a try.   If I had to guess, after the system is characterized and all the bugs worked out, I'd say 5000 kg or less, they will expect to recover.  5001-5300 kg, they'll try, but not with high expectations.  5301-6500 kg, pure expendable - don't bother to send the barge.

Or (hopefully) do send the barge, because the other two cores are landing at home.  ;D

Offline nadreck

Re: Payload estimate for allowing routine re-entry
« Reply #10 on: 04/28/2016 07:11 pm »
Thanks for the calculations, LouS.
Do you see 4,900 as clearly achievable and the margin between 4,900 and 5,300 'work required, but not impossible'?
Seems 5,300 is top of range that will be attempted, for now at least.

Well, the 4900 figure had a safe re-entry, but still a suicide slam.  Getting rid of the slam completely costs about another 300 kg.  So I'd say 4600 kg should be clearly achievable - safe re-entry and already-proven landing.  5300 kg seems very marginal, though worth a try.   If I had to guess, after the system is characterized and all the bugs worked out, I'd say 5000 kg or less, they will expect to recover.  5001-5300 kg, they'll try, but not with high expectations.  5301-6500 kg, pure expendable - don't bother to send the barge.

Or (hopefully) do send the barge, because the other two cores are landing at home.  ;D

Actually I believe all 3 can go home up to 7t and from 7 to 10 the barge goes out for the centre core
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline MarekCyzio

Re: Payload estimate for allowing routine re-entry
« Reply #11 on: 04/28/2016 07:36 pm »
Yes, they assume a suicide slam as used on SES-9.  Subtract about another 300 kg payload to allow a regular, single-engine landing burn.  So a 4600 kg payload allows a safe re-entry and a regular landing.

So it looks like SpaceX will try to master 3 engine landing as it gives significant mass increase compared to any other approach. It will be interesting to see what they decided to do for JCSAT-14.

Offline MarekCyzio

Re: Payload estimate for allowing routine re-entry
« Reply #12 on: 04/28/2016 07:38 pm »
Or (hopefully) do send the barge, because the other two cores are landing at home.  ;D

There is no place to land two cores. And it does not look like SpaceX is builiding Landing Zone 2 - we have not seen any environmental studies yet.

Offline Kabloona

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Re: Payload estimate for allowing routine re-entry
« Reply #13 on: 04/28/2016 09:12 pm »
Yes, they assume a suicide slam as used on SES-9.  Subtract about another 300 kg payload to allow a regular, single-engine landing burn.  So a 4600 kg payload allows a safe re-entry and a regular landing.

So it looks like SpaceX will try to master 3 engine landing as it gives significant mass increase compared to any other approach. It will be interesting to see what they decided to do for JCSAT-14.

JCSAT-14 mass has not been published yet that I know of, but based on data from Gunter's Space Page, I estimate it at 4300 kg, which would make it a comfortable single-engine landing burn.

Offline Lar

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Re: Payload estimate for allowing routine re-entry
« Reply #14 on: 04/28/2016 09:20 pm »
Or (hopefully) do send the barge, because the other two cores are landing at home.  ;D

There is no place to land two cores. And it does not look like SpaceX is builiding Landing Zone 2 - we have not seen any environmental studies yet.
We hear very conflicting things on this ... and discussion of whether there will be more places to land is off topic for this thread.

Could we adjourn that to https://forum.nasaspaceflight.com/index.php?topic=36513 (the eastern range landing zone thread)? I'll reply there.
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Offline Dmitry_V_home

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Re: Payload estimate for allowing routine re-entry
« Reply #15 on: 04/30/2016 09:46 am »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

Offline Zed_Noir

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Re: Payload estimate for allowing routine re-entry
« Reply #16 on: 04/30/2016 11:07 am »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities
Thanks for the info, Dimtry.

Updated performance figures from the SpaceX website

F9     28800 kg   to   LEO
          8300 kg   to   GTO
          4020 kg   to   MTO

FH    54400 kg   to   LEO
        22200 kg   to   GTO
        13600 kg   to   MTO

Wow, the F9 have the same lift as the Delta IV Heavy with the RS-68A to LEO in the expandable mode. Does this mean that the Delta IV Heavy can be dispense with for polar missions out of VAFB? :o

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #17 on: 04/30/2016 02:15 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

Wow - 8300 kg to GTO.  I did not see that coming.

5500 kg recoverable makes sense.  They almost recovered SES-9 at 5300.  With a slightly less aggressive GTO, 5500 seems doable.

But 8300 kg is a lot.  We know that SES-9 had a 17 second re-entry, and a roughly 6 second landing, both with 3 engines.  So an expendable could have perhaps 8 more seconds of 9-engine booster burn.  We know that near cutoff the booster is accelerating at 4-5 Gs, so that's maybe 350 m/s more for expendable.

But with a 121t starting mass (after fairing jettison), a 5t empty mass, and a 348 ISP, going from 5.5t to 8.3t means 800 m/s less.  That's too much to reach GTO with only 350 m/s more from the first stage.  A lower empy mass for the second stage only makes this discrepancy worse.

So I'm guessing it's the trajectory.  It must be that ANY recoverable trajectory, not just RLTS, involves more initial lofting, perhaps to get the first stage out out of the atmosphere so it can turn around.  If SpaceX is not recovering, the first stage goes more horizontal and builds up more orbital velocity, and stages at a lower altitude.  This reduces the gravity and pitch losses. 


Offline Rebel44

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Re: Payload estimate for allowing routine re-entry
« Reply #18 on: 04/30/2016 03:16 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

Wow - 8300 kg to GTO.  I did not see that coming.

5500 kg recoverable makes sense.  They almost recovered SES-9 at 5300.  With a slightly less aggressive GTO, 5500 seems doable.

But 8300 kg is a lot.  We know that SES-9 had a 17 second re-entry, and a roughly 6 second landing, both with 3 engines.  So an expendable could have perhaps 8 more seconds of 9-engine booster burn.  We know that near cutoff the booster is accelerating at 4-5 Gs, so that's maybe 350 m/s more for expendable.

But with a 121t starting mass (after fairing jettison), a 5t empty mass, and a 348 ISP, going from 5.5t to 8.3t means 800 m/s less.  That's too much to reach GTO with only 350 m/s more from the first stage.  A lower empy mass for the second stage only makes this discrepancy worse.

So I'm guessing it's the trajectory.  It must be that ANY recoverable trajectory, not just RLTS, involves more initial lofting, perhaps to get the first stage out out of the atmosphere so it can turn around.  If SpaceX is not recovering, the first stage goes more horizontal and builds up more orbital velocity, and stages at a lower altitude.  This reduces the gravity and pitch losses.

Based on updated numbers at SX website, Merlin engines are again getting more powerful - so less gravity losses during whole flight should help somewhat (and maybe other improvements).

Offline woods170

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Re: Payload estimate for allowing routine re-entry
« Reply #19 on: 04/30/2016 03:39 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

Wow - 8300 kg to GTO.  I did not see that coming.

5500 kg recoverable makes sense.  They almost recovered SES-9 at 5300.  With a slightly less aggressive GTO, 5500 seems doable.

But 8300 kg is a lot.  We know that SES-9 had a 17 second re-entry, and a roughly 6 second landing, both with 3 engines.  So an expendable could have perhaps 8 more seconds of 9-engine booster burn.  We know that near cutoff the booster is accelerating at 4-5 Gs, so that's maybe 350 m/s more for expendable.

But with a 121t starting mass (after fairing jettison), a 5t empty mass, and a 348 ISP, going from 5.5t to 8.3t means 800 m/s less.  That's too much to reach GTO with only 350 m/s more from the first stage.  A lower empy mass for the second stage only makes this discrepancy worse.

So I'm guessing it's the trajectory.  It must be that ANY recoverable trajectory, not just RLTS, involves more initial lofting, perhaps to get the first stage out out of the atmosphere so it can turn around.  If SpaceX is not recovering, the first stage goes more horizontal and builds up more orbital velocity, and stages at a lower altitude.  This reduces the gravity and pitch losses.

Based on updated numbers at SX website, Merlin engines are again getting more powerful - so less gravity losses during whole flight should help somewhat (and maybe other improvements).
It has been suspected for a long time that SpaceX sandbagged the initial performance numbers of Merlin 1D and Falcon 9. The new performance figures seem to confirm this: now that SpaceX has a good number of missions of both the 1.1 and the FT under it's belt they likely have more confidence in the final performance figures.

Offline Oli

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Re: Payload estimate for allowing routine re-entry
« Reply #20 on: 04/30/2016 04:46 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

28.8t to LEO doesn't seem possible. Future version with Raptor upper stage?

Offline Dmitry_V_home

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Re: Payload estimate for allowing routine re-entry
« Reply #21 on: 04/30/2016 05:00 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

28.8t to LEO doesn't seem possible. Future version with Raptor upper stage?

I think, everything is much simpler. Perhaps, 28800 kg are a mass of payload together with the second stage in a parking orbit (that is before 2nd ignition of the engine of the second stage). In this case 8300 kg into GTO quite real figure for the expendable rocket.
« Last Edit: 04/30/2016 05:40 pm by Dmitry_V_home »

Offline Oli

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Re: Payload estimate for allowing routine re-entry
« Reply #22 on: 04/30/2016 05:08 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

28.8t to LEO doesn't seem possible. Future version with Raptor upper stage?

I think, everything is much simpler. Perhaps, 28800 kg are a mass of payload together with the second stage in a parking orbit (that is before yvtory ignition of the engine of the second stage). In this case 8300 kg into GTO quite real figure for the expendable rocket.

Yeah that could work out.

Offline sewebster

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Re: Payload estimate for allowing routine re-entry
« Reply #23 on: 04/30/2016 05:40 pm »
But with a 121t starting mass (after fairing jettison), a 5t empty mass, and a 348 ISP, going from 5.5t to 8.3t means 800 m/s less.  That's too much to reach GTO with only 350 m/s more from the first stage.  A lower empy mass for the second stage only makes this discrepancy worse.

So I'm guessing it's the trajectory.  It must be that ANY recoverable trajectory, not just RLTS, involves more initial lofting, perhaps to get the first stage out out of the atmosphere so it can turn around.  If SpaceX is not recovering, the first stage goes more horizontal and builds up more orbital velocity, and stages at a lower altitude.  This reduces the gravity and pitch losses.

The orbit probably won't be as "high" as for SES-9 either, but I doubt that makes up the difference (I forget the calcs on the extra dV they gave it).

Offline sewebster

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Re: Payload estimate for allowing routine re-entry
« Reply #24 on: 04/30/2016 06:08 pm »
I think, everything is much simpler. Perhaps, 28800 kg are a mass of payload together with the second stage in a parking orbit (that is before 2nd ignition of the engine of the second stage). In this case 8300 kg into GTO quite real figure for the expendable rocket.
By the same logic should be linked 54 tons to LEO and 22 tons to GTO for FH then.

Would they really quote numbers like that? Maybe I don't understand it, but it seems like an irrelevant number to a customer...?

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #25 on: 04/30/2016 06:42 pm »
What if the customer wants a better orbit (such as the GEO-1500 m/s that Ariane can provide) ?

By my estimate, this requires about 450 m/s more a basic GTO (needs an apogee about 100,000 km).  Using the assumptions that the second stage starts at 121t after fairing jettison, 5t empty mass, then to get the extra 450 m/s:

If a re-usable launch can do 5500 kg to GEO-1800, then it can do 4000 kg to GEO-1500.

If an expendable launch can do 8300 kg to GEO-1800, it can do 6600 kg to GEO-1500.

Offline sewebster

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Re: Payload estimate for allowing routine re-entry
« Reply #26 on: 04/30/2016 07:10 pm »
What if the customer wants a better orbit (such as the GEO-1500 m/s that Ariane can provide) ?

By my estimate, this requires about 450 m/s more a basic GTO (needs an apogee about 100,000 km).  Using the assumptions that the second stage starts at 121t after fairing jettison, 5t empty mass, then to get the extra 450 m/s:

If a re-usable launch can do 5500 kg to GEO-1800, then it can do 4000 kg to GEO-1500.

If an expendable launch can do 8300 kg to GEO-1800, it can do 6600 kg to GEO-1500.

Doesn't it need 300 m/s to go from GEO-1800 to GEO-1500?

Offline rocx

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Re: Payload estimate for allowing routine re-entry
« Reply #27 on: 04/30/2016 07:31 pm »
Doesn't it need 300 m/s to go from GEO-1800 to GEO-1500?
Nope, the GEO-xxx numbers refer to the amount of delta-V needed at apogee burn. Due to the beautiful mathematics of orbital mechanics, to reduce this amount (by reducing the inclination) you need more delta-v at transfer orbit insertion.
Any day with a rocket landing is a fantastic day.

Online LouScheffer

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Re: Payload estimate for allowing routine re-entry
« Reply #28 on: 05/01/2016 12:45 am »
What if the customer wants a better orbit (such as the GEO-1500 m/s that Ariane can provide) ?

By my estimate, this requires about 450 m/s more a basic GTO (needs an apogee about 100,000 km).  Using the assumptions that the second stage starts at 121t after fairing jettison, 5t empty mass, then to get the extra 450 m/s:

If a re-usable launch can do 5500 kg to GEO-1800, then it can do 4000 kg to GEO-1500.

If an expendable launch can do 8300 kg to GEO-1800, it can do 6600 kg to GEO-1500.

Doesn't it need 300 m/s to go from GEO-1800 to GEO-1500?
Yes, if you apply the delta-V at apogee.  But doing this has several drawbacks.  You need to do a three-burn mission, where the second stage burns once for parking orbit, once for GTO, then again at apogee after about a 6 hour coast.  And even if you can do this, the booster will end up in a very ugly orbit - too high to decay naturally, and too much delta V to de-orbit, and crossing the altitude of other orbits.

But the booster can help another way that does not have these problems.  With a more powerful second burn, it can put the payload into a less-inclined orbit with a much higher apogee (making plane changes easier).   Now the booster is not doing anything it would not do anyway, just more doing it more strongly, and the booster ends up in an orbit that will decay naturally (something like 375x100,000 km, typically).  But it's not as efficient, and takes about 450 m/s more oomph to save the payload 300 m/s of maneuvering.

Offline John Alan

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Re: Payload estimate for allowing routine re-entry
« Reply #29 on: 05/01/2016 07:08 am »
I would sure like to see the full price sheet including the expendable modes...  ???

I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
And you will pay dearly for that last 2.5mt...
Still... if you can't design a bird under these generous weight points...  ::)

And... are the listed prices with no choice new or used?.. Extra for new required?

I bet the full price sheet being used for new launch orders NET 2018 is VERY interesting...  ;D  ;)

On edit..
My thinking is SpaceX is keeping pricing about the same as in the past... BUT changing the terms...
Get everyone used to reusable S1 as the norm...
Put the increased profit into funding BFR and the infrastructure to support it...
They already are the lowest cost provider in the world... so why lower prices even more...
my opinion...  ;)
« Last Edit: 05/01/2016 07:25 am by John Alan »

Offline Zed_Noir

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Re: Payload estimate for allowing routine re-entry
« Reply #30 on: 05/01/2016 08:05 am »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

28.8t to LEO doesn't seem possible. Future version with Raptor upper stage?

I think, everything is much simpler. Perhaps, 28800 kg are a mass of payload together with the second stage in a parking orbit (that is before 2nd ignition of the engine of the second stage). In this case 8300 kg into GTO quite real figure for the expendable rocket.

Musk confirm the correct payload to LEO is 22800 kg for the Falcon 9 on twitter plus more performance stats updates :o
Quote
Elon Musk ‏@elonmusk  7h7 hours ago
@elonmusk F9 LEO payload on capabilities page (correct figure on main page) should be 22,800 kg
Quote
Elon Musk ‏@elonmusk  2h2 hours ago
F9 thrust at liftoff will be raised to 1.71M lbf later this year. It is capable of 1.9M lbf in flight.
Quote
Elon Musk ‏@elonmusk  2h2 hours ago
Falcon Heavy thrust will be 5.1M lbf at liftoff --  twice any rocket currently flying. It's a beast...
twitter link


Offline Prettz

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Re: Payload estimate for allowing routine re-entry
« Reply #31 on: 05/01/2016 04:21 pm »
I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
Oh no. Now all the satellite manufacturers will have to stop building GEO satellites heavier than 8 tons. Thanks a lot, SpaceX.

Offline The Amazing Catstronaut

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Re: Payload estimate for allowing routine re-entry
« Reply #32 on: 05/01/2016 04:35 pm »
I would sure like to see the full price sheet including the expendable modes...  ???

I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
And you will pay dearly for that last 2.5mt...
Still... if you can't design a bird under these generous weight points...  ::)


Uhm, I'm not sure where you're coming from.

If SpaceX decided to maddeningly charge monolithic magniloquent machiavellian mountains of unmannerly moolah for payloads over eight tonnes to GTO, then Falcon Heavy is out of a job.
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Offline John Alan

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Re: Payload estimate for allowing routine re-entry
« Reply #33 on: 05/01/2016 05:36 pm »
I would sure like to see the full price sheet including the expendable modes...  ???

I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
And you will pay dearly for that last 2.5mt...
Still... if you can't design a bird under these generous weight points...  ::)


Uhm, I'm not sure where you're coming from.

If SpaceX decided to maddeningly charge monolithic magniloquent machiavellian mountains of unmannerly moolah for payloads over eight tonnes to GTO, then Falcon Heavy is out of a job.

My point was they WILL pay the cost of thrown away stages in 2018 verses cost included up till now...
SpaceX will use prices to drive the market to accept reuse as the new norm... they have to, my opinion..

On edit...
Example quote (WAG on my part)... customer has 8mt bird they want launched to Geo...
That will be $90 mil on a FH... our choice new or used stages...
Or say $100 mil on a used core F9 expendable with used stage... (barn is full, on sale)
All new... that will be $125 mil please...

Now... Customer has a 22.3mt bird they want sent to Geo...  :o
Sure... FH full expendable... we can do that for you...
That will be (WAG) $175mil our choice new or used and $250mil all new...

My point was... SpaceX was on a mission to be low cost provider and get re-usability working...
NOW(as of 2018) they will pivot to still be low cost provider... BUT increase profits to fund BFR and Mars...

That was my whole point...
They are going to be able to (in effect) charge by the m-ton instead of by the launch vehicle...
and that 5.5mt weight point is now the cheapest cost to weight value point in the market...
 ;)
« Last Edit: 05/01/2016 06:10 pm by John Alan »

Offline The Amazing Catstronaut

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Re: Payload estimate for allowing routine re-entry
« Reply #34 on: 05/01/2016 05:43 pm »

My point was they WILL pay cost of thrown away stages in 2018 verses cost included up till now...

They do anyway - it's factored into the launch cost as with every other LV.

Perhaps I'm misunderstanding your point.

Edit: Do you mean that reusability pricing will become the norm, and that current rates will be charged only for expended launch?
« Last Edit: 05/01/2016 05:44 pm by The Amazing Catstronaut »
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Offline John Alan

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Re: Payload estimate for allowing routine re-entry
« Reply #35 on: 05/01/2016 06:16 pm »

My point was they WILL pay cost of thrown away stages in 2018 verses cost included up till now...

They do anyway - it's factored into the launch cost as with every other LV.

Perhaps I'm misunderstanding your point.

Edit: Do you mean that reusability pricing will become the norm, and that current rates will be charged only for expended launch?

Yes... (to your edit above)... reusablity is now required to get back to past pricing points...
I edited my own post to clarify this point... two posts above...
« Last Edit: 05/01/2016 06:19 pm by John Alan »

Offline mme

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Re: Payload estimate for allowing routine re-entry
« Reply #36 on: 05/01/2016 07:23 pm »

My point was they WILL pay cost of thrown away stages in 2018 verses cost included up till now...

They do anyway - it's factored into the launch cost as with every other LV.

Perhaps I'm misunderstanding your point.

Edit: Do you mean that reusability pricing will become the norm, and that current rates will be charged only for expended launch?

Yes... (to your edit above)... reusablity is now required to get back to past pricing points...
I edited my own post to clarify this point... two posts above...
I do not think that is not correct.  SpaceX have publicly stated that they think that with reuse, the price of an F9 will drop to the $40 million dollar.   FH prices may assume booster reusability since expending them offers limited benefit.

I think people have overestimated customer's reluctance about flying on previously flown rockets.  SES is chomping at the bit to fly on a reused booster.  They publicly low-balled the offer at $30 million, but that doesn't mean they are concerned.  It just means they want a deal.  If they were afraid of used boosters, they would not accept even a free ride.  Their satellites cost 100s of millions to make and take years to build.  They will only launch if they are confident that the risk is low and they have already publicly stated that when SpaceX is convinced it's safe, they will gladly book one.

Edit:  References -

- Parabolic Arc Article: http://www.parabolicarc.com/2016/03/11/shotwell-spacex-reduce-launch-costs-30-percent-reusing-stagde/
- SES-9 Mission Briefing:
« Last Edit: 05/01/2016 07:29 pm by mme »
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Offline ChrisGebhardt

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Re: Payload estimate for allowing routine re-entry
« Reply #37 on: 05/01/2016 10:02 pm »
Gentlemen, somebody can comment on new figures on the website SpaceX?
http://www.spacex.com/about/capabilities

Wow - 8300 kg to GTO.  I did not see that coming.

5500 kg recoverable makes sense.  They almost recovered SES-9 at 5300.  With a slightly less aggressive GTO, 5500 seems doable.

But 8300 kg is a lot.  We know that SES-9 had a 17 second re-entry, and a roughly 6 second landing, both with 3 engines.  So an expendable could have perhaps 8 more seconds of 9-engine booster burn.  We know that near cutoff the booster is accelerating at 4-5 Gs, so that's maybe 350 m/s more for expendable.

But with a 121t starting mass (after fairing jettison), a 5t empty mass, and a 348 ISP, going from 5.5t to 8.3t means 800 m/s less.  That's too much to reach GTO with only 350 m/s more from the first stage.  A lower empy mass for the second stage only makes this discrepancy worse.

So I'm guessing it's the trajectory.  It must be that ANY recoverable trajectory, not just RLTS, involves more initial lofting, perhaps to get the first stage out out of the atmosphere so it can turn around.  If SpaceX is not recovering, the first stage goes more horizontal and builds up more orbital velocity, and stages at a lower altitude.  This reduces the gravity and pitch losses.

Based on updated numbers at SX website, Merlin engines are again getting more powerful - so less gravity losses during whole flight should help somewhat (and maybe other improvements).
It has been suspected for a long time that SpaceX sandbagged the initial performance numbers of Merlin 1D and Falcon 9. The new performance figures seem to confirm this: now that SpaceX has a good number of missions of both the 1.1 and the FT under it's belt they likely have more confidence in the final performance figures.

But what were the original (or last released) performances numbers we had for Falcon 9 FT?  Does anyone have those or can someone point me to them?  I'd be nice to have to compare for this article I'm working on.

Cheers,
Chris G.

Offline mvpel

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Re: Payload estimate for allowing routine re-entry
« Reply #38 on: 05/01/2016 11:26 pm »
But what were the original (or last released) performances numbers we had for Falcon 9 FT?  Does anyone have those or can someone point me to them?  I'd be nice to have to compare for this article I'm working on.

Chris, if you use the Internet Archive's Wayback Machine, there's snapshots of the specs page for Falcon 9 going back to July 15, 2013:

Capture Summary for www.spacex.com/falcon9

The earliest capture in 2013 shows this:

Quote
Launch Site:   Cape Canaveral Air Force Station
    
Mass to Low Earth Orbit (LEO):   13,150 kg (29,000 lb)
Inclination:   28.5 degree
    
Mass to Geosynchronous Transfer Orbit (GTO):   4,850 kg (10,692 lb)
Inclination:   27 degree

... all for the low, low price of $54 million.
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Offline dorkmo

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Re: Payload estimate for allowing routine re-entry
« Reply #39 on: 05/02/2016 10:20 am »
i made this chart a while back. i could have done a better job but yeah.

https://docs.google.com/spreadsheets/d/1gfcyWNtavUeN6p9AeXkloTSJY4fOEa3sBOQM8jORSio/

Offline HMXHMX

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Re: Payload estimate for allowing routine re-entry
« Reply #40 on: 05/02/2016 03:32 pm »
i made this chart a while back. i could have done a better job but yeah.

https://docs.google.com/spreadsheets/d/1gfcyWNtavUeN6p9AeXkloTSJY4fOEa3sBOQM8jORSio/

And in 2005, the Falcon 5 was $12M and the F9 was $18M, from memory.  (I was trying to buy two F5's at the time.)

Offline airider

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Re: Payload estimate for allowing routine re-entry
« Reply #41 on: 05/04/2016 11:42 pm »
I think, everything is much simpler. Perhaps, 28800 kg are a mass of payload together with the second stage in a parking orbit (that is before 2nd ignition of the engine of the second stage). In this case 8300 kg into GTO quite real figure for the expendable rocket.
By the same logic should be linked 54 tons to LEO and 22 tons to GTO for FH then.

Would they really quote numbers like that? Maybe I don't understand it, but it seems like an irrelevant number to a customer...?

SpaceX will run numbers and sims specific and unique to each payload, orbit desired, and customer using a lot more and better data than any on this board or the general public will have at our disposal.

The only "truth" I've seen published so far is that SpaceX doesn't reveal any absolutes about performance and I wouldn't either since the real answer, per payload is, "it depends".

Honestly this whole discussion is really rather silly because SpaceX probably doesn't know for sure themselves (since they don't fly their spacecraft to the absolute maximums) and they want to ensure they can give the customer a reasonable probability of success, which means they back-off from trying to "push it" (which is why they've been able to incrementally "add" performance from the same engines over time as real flight performance verifies how well, or poorly things work).

Based on this, I consider any attempts at estimating success by "arm chair orbital mechanics" to be "Kentucky Windage" attempts and should be treated as such.

Offline Impaler

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Re: Payload estimate for allowing routine re-entry
« Reply #42 on: 05/06/2016 08:34 am »
I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
Oh no. Now all the satellite manufacturers will have to stop building GEO satellites heavier than 8 tons. Thanks a lot, SpaceX.

Sat masses will keep going up and SpaceX will have to keep improving their GTO performance numbers to keep up.  Ariane 5 which made it's mark with dual launches is now increasingly having to pair one runty sat at a low fair with one big one because the sizes have grown so large.  I expect BFR to be dual or triple launching 15 mt Satellites as part of it's commercial manifest as that will be the size of GEO birds by that time.

Offline SwissCheese

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Re: Payload estimate for allowing routine re-entry
« Reply #43 on: 05/06/2016 09:38 am »
I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
Oh no. Now all the satellite manufacturers will have to stop building GEO satellites heavier than 8 tons. Thanks a lot, SpaceX.

Sat masses will keep going up and SpaceX will have to keep improving their GTO performance numbers to keep up.  Ariane 5 which made it's mark with dual launches is now increasingly having to pair one runty sat at a low fair with one big one because the sizes have grown so large.  I expect BFR to be dual or triple launching 15 mt Satellites as part of it's commercial manifest as that will be the size of GEO birds by that time.

No company would want to rely on a single provider for launching its birds, so do not expect any satellite weighing more than the maximum capacity of the second provider.

Offline cartman

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Re: Payload estimate for allowing routine re-entry
« Reply #44 on: 05/06/2016 09:39 am »
Stage separation according to webcasts (screenshots taken the moment the numbers stopped rising)
sat:           speed       altitute   time   weight     delivered orbit
SES-9:      8325km/h 64.5km 2:40m 5,271 kg    334 x 40648 km x 27.96
JCSAT-14: 8354km/h 66.3km 2:40m 4,696.2kg  189 x 35957 km x 23.70

« Last Edit: 05/06/2016 09:54 am by cartman »

Offline Zed_Noir

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Re: Payload estimate for allowing routine re-entry
« Reply #45 on: 05/06/2016 10:14 pm »
I bet you will now pay dearly if you want to exceed the 5.5mt or 8.0mt to GTO caps posted online...
In effect... they just raised prices IF you dare exceed these listed payload points...
Satellite designers just got a new weight target they must be under at all cost... 5.5mt or 8.0mt...
Oh no. Now all the satellite manufacturers will have to stop building GEO satellites heavier than 8 tons. Thanks a lot, SpaceX.

Sat masses will keep going up and SpaceX will have to keep improving their GTO performance numbers to keep up.  Ariane 5 which made it's mark with dual launches is now increasingly having to pair one runty sat at a low fair with one big one because the sizes have grown so large.  I expect BFR to be dual or triple launching 15 mt Satellites as part of it's commercial manifest as that will be the size of GEO birds by that time.

No company would want to rely on a single provider for launching its birds, so do not expect any satellite weighing more than the maximum capacity of the second provider.

Don't think there will be any satcom bigger than about 10 mT. Anything bigger will be like one of those orbital communication platforms in the Sci-Fi novels of the 1960's. Something like a Mir sized GEO platform with lots of modular transponder suites that can be replaced.

But we are getting off topic.  :-X

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