Author Topic: FH payload to Mars, when fully re-usable  (Read 14086 times)

Offline LouScheffer

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FH payload to Mars, when fully re-usable
« on: 02/11/2018 03:20 pm »
The FH just put the roadster, estimated at 1250 kg, on an orbit with Mars apogee.   But the first launch left a lot on the table.   How much can a recoverable FH lift to Mars?

First, it appears the first flight used a very tame throttle profile, with the center core not even at full thrust for liftoff, and only 30 seconds of single-core operation after separation.  A more aggressive throttle up at liftoff, then further down during 3 booster flight,  could save more fuel for after booster sep, giving some of the benefit of cross-feed.  A crude guess indicates they could get perhaps 500 m/s more staging velocity with this.

Second, SpaceX had the ASDS close to shore.   Putting it further out means no boostback burn.  Another crude guess indicates they could get 500 m/s from this.

Of course, they cannot use all 1000 m/s for increased staging, since they need to save some for slowing down the booster so not to fry it on entry.   This trades off about 4:1, since the booster mass is about 1/4 of the whole stack near staging.   So perhaps they can increase the staging velocity by 800 m/s, then slow the booster by the same amount, then land fully downrange.

Now plugging in some estimates for the second stage (ISP=348, empty mass 4.5t, fuel = 111.5t) gives the delta-V for a 1.25t payload.   If the second stage can provide 800 m/s less, it can loft about 3t instead of 1.25t.

Finally, there is some improvements that are hard to estimate.  Block 5 will increase the thrust, which will decrease the gravity losses.  Also there is no 6 hour coast on a normal Mars injection.  The total firing time of the second stage on the first FH mission was shorter than usual by about 23 seconds.   Some of this might be no need to throttle for this payload, but a lot might be boiloff.  This could result in a large increase in capability - even 10 more seconds of firing could contribute 500 m/s or so.

So all things combined, it would not surprise me if FH could loft 3.8t (the mass of Mars Science Laboratory) to Mars and still recover all boosters.  Of course there are lots and lots of estimates, handwaving, and assumptions behind this conclusion.

Offline guckyfan

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Re: FH payload to Mars, when fully re-usable
« Reply #1 on: 02/11/2018 03:41 pm »
Elon Musk once mentioned they might be able to fly RedDragon fully reusable but was not sure about the central core. So 10t may be the limit or whatever mass a RedDragon with limited payload may have.

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #2 on: 02/11/2018 05:22 pm »
One estimate can be obtained from NASA's Launch Vehicle Performance Website. I'm attaching the performance curves for the Falcon Heavy in both expendable and recoverable modes, as well as Atlas V 551 and Delta IV Heavy for comparison.

The Roadster was launched with C3 = 12 kmē/sē. At that energy (a typical value for decent Mars launch windows), according to these figures the max Falcon Heavy payload in recoverable mode is around 4000 kg, while in expendable mode it's about 9500 kg. I'm not sure how reliable or updated these figures are, though.

An interesting thing to note in the figure is how at launch energies below C3 = 30 kmē/sē (for comparison, Jupiter transfer requires about 80 kmģ/sģ) the Falcon Heavy (expendable) is king, but for higher launch energies the Delta IV Heavy seems to have better performance. I'd guess it's because the DIVH has a more efficient hydrolox-based upper stage.
« Last Edit: 02/20/2018 10:49 pm by meithan »

Offline hkultala

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Re: FH payload to Mars, when fully re-usable
« Reply #3 on: 02/11/2018 08:52 pm »
The FH just put the roadster, estimated at 1250 kg, on an orbit with Mars apogee.   But the first launch left a lot on the table.   How much can a recoverable FH lift to Mars?

First, it appears the first flight used a very tame throttle profile, with the center core not even at full thrust for liftoff,

Where is this claim based on?

Quote
and only 30 seconds of single-core operation after separation. 

A more aggressive throttle up at liftoff, then further down during 3 booster flight,  could save more fuel for after booster sep, giving some of the benefit of cross-feed.  A crude guess indicates they could get perhaps 500 m/s more staging velocity with this.

Throttling down hurts isp.

And the gravity losses would be worse.

And if the center core would be flying at higher velocity during the staging, it would also need to spend more delta-v for braking burn (called boostback burn).

And your calculations are simply badly wrongly calculated. You calculating the delta-v gotten from "almost empty" tanks twice. If the booster separation happens earlier, you are getting the delta-v of some time of tanks semi-full, not more tanks-empty time.

And, because of more fuel needed for braking burn, in reality actually the tanks would have MORE propellant at the last 30 second of the burn, meaning LESS delta-v for it.

Quote
Second, SpaceX had the ASDS close to shore.   

No, it did not.

Quote
Putting it further out means no boostback burn.  Another crude guess indicates they could get 500 m/s from this.

The ship was NOT very close to the shore. There were rumours about it, but those rumours were incorrect. The ship was much further away than the staging point.

It did NOT boost BACK. the "boostback burn" was just practically braking most of the horizontal velocity, which had to be done anyway. If it was not done by the "boostback burn" it would have needed a much longer "entry burn".

There is very little savings available by doing a smaller "boostback burn".

Your "1000m/s" if total bogus. It's maybe about 150m/s in reality.
« Last Edit: 02/11/2018 08:55 pm by hkultala »

Offline Robotbeat

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Re: FH payload to Mars, when fully re-usable
« Reply #4 on: 02/12/2018 12:40 am »
One estimate can be obtained from NASA's Launch Vehicle Performance Website. ...
This is a very good website to use, but note that the performance figures are older and much lower than what are on SpaceX's website. For instance, to TMI (i.e. about c3= 7km^2/s^2, optimistically), Falcon Heavy gets >16t, but the KSC website just gives 10t. So at high energy, I'd bet the actual figures SpaceX thinks they can do are at least 60% higher than on the KSC website.
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Offline ulm_atms

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Re: FH payload to Mars, when fully re-usable
« Reply #5 on: 02/12/2018 01:14 am »
Where is this claim based on?

This is what the claim is based on:

https://twitter.com/johnkrausphotos/status/960985711825620993

The whole way up you can tell that the center core was not throttled up as high as the side boosters.

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #6 on: 02/12/2018 01:28 am »
One estimate can be obtained from NASA's Launch Vehicle Performance Website. ...
This is a very good website to use, but note that the performance figures are older and much lower than what are on SpaceX's website. For instance, to TMI (i.e. about c3= 7km^2/s^2, optimistically), Falcon Heavy gets >16t, but the KSC website just gives 10t. So at high energy, I'd bet the actual figures SpaceX thinks they can do are at least 60% higher than on the KSC website.

Ah, I suspected the figures might not be updated. You're right, they do seem lower than the current official figures.

Any idea where one can get an updated performance curve for FH like those shown there?

Offline Robotbeat

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Re: FH payload to Mars, when fully re-usable
« Reply #7 on: 02/12/2018 02:31 am »
One estimate can be obtained from NASA's Launch Vehicle Performance Website. ...
This is a very good website to use, but note that the performance figures are older and much lower than what are on SpaceX's website. For instance, to TMI (i.e. about c3= 7km^2/s^2, optimistically), Falcon Heavy gets >16t, but the KSC website just gives 10t. So at high energy, I'd bet the actual figures SpaceX thinks they can do are at least 60% higher than on the KSC website.

Ah, I suspected the figures might not be updated. You're right, they do seem lower than the current official figures.

Any idea where one can get an updated performance curve for FH like those shown there?
The KSC website is the best we got, combined with SpaceX's figures. People have also made their own models, but I prefer the KSC+SpaceX route.
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Offline deruch

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Re: FH payload to Mars, when fully re-usable
« Reply #8 on: 02/12/2018 11:13 am »
Quote
Second, SpaceX had the ASDS close to shore.   

No, it did not.

Quote
Putting it further out means no boostback burn.  Another crude guess indicates they could get 500 m/s from this.

The ship was NOT very close to the shore. There were rumours about it, but those rumours were incorrect. The ship was much further away than the staging point.

It did NOT boost BACK. the "boostback burn" was just practically braking most of the horizontal velocity, which had to be done anyway. If it was not done by the "boostback burn" it would have needed a much longer "entry burn".

There is very little savings available by doing a smaller "boostback burn".

Your "1000m/s" if total bogus. It's maybe about 150m/s in reality.

The ASDS position was known from SpaceX's FCC applications/grants for use of radio spectrum.  It was positioned ~340km downrange, which is certainly "close to shore" compared to flying the Falcon Heavy on a ballistic trajectory the way they do for GTO launches on F9.  That was the point.  This distance was also considerably closer inshore than SpaceX uses for those GTO launches.  He isn't claiming that FH center core actually reversed direction from the boostback burn. 
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Offline Demidrol

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Re: FH payload to Mars, when fully re-usable
« Reply #9 on: 02/12/2018 11:27 am »
The ASDS position was known from SpaceX's FCC applications/grants for use of radio spectrum.
Here's the real position of ASDS based on MarineTrafic data

Offline LouScheffer

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Re: FH payload to Mars, when fully re-usable
« Reply #10 on: 02/12/2018 01:26 pm »

Your "1000m/s" if total bogus. It's maybe about 150m/s in reality.

Here's another way of showing much higher MECO without the complication of performance loss from the long coast.

Consider BulgaraSat at 3.7 tonnes.   F9 recoverable put this into a 250x65000x24o GTO.  This takes 2800 m/s from LEO.

Now FH recoverable can put this same payload to Mars, according to the NASA chart above (and maybe more).  That takes LEO+3600 (see, for example, Hohmann Transfer, section "Application to Interplanetary Travel".

Now the second stage is the same in both cases.  So the only place the extra delta-v can come from is increased velocity at MECO.  BulgariaSat staged at 2362 m/s.   So a FH recoverable flight needs to stage at a minimum 3162 m/s (actually slightly more since it can throw heavier things to Mars).  The FH flight staged at about 2640 m/s, so at the very least it's capable of 522 m/s more at MECO than it demonstrated on the first flight.

If this increase, compared to the test flight, does not come from a better throttle profile, or further downrange landings, where does it come from?


Offline John Alan

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Re: FH payload to Mars, when fully re-usable
« Reply #11 on: 02/12/2018 04:45 pm »
Musk just tweeted a 3rd ASDS is to be constructed specifically for east coast FH OP's...  8)

He says with core expend and both boosters ballistic to ASDS landings... only loose 10%... 
And he quoted $95m on twitter...  :o

Links and topic...
https://forum.nasaspaceflight.com/index.php?topic=39766.msg1787564#msg1787564
« Last Edit: 02/12/2018 04:52 pm by John Alan »

Offline Kansan52

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Re: FH payload to Mars, when fully re-usable
« Reply #12 on: 02/12/2018 04:49 pm »
OK, first glance, a larger drone ship with two boosters landing on Gravitas?

Offline John Alan

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Re: FH payload to Mars, when fully re-usable
« Reply #13 on: 02/12/2018 04:54 pm »
OK, first glance, a larger drone ship with two boosters landing on Gravitas?

On twitter he said two ships for two booster cores, center expended...  ;)
At only $5 million more... my guess is FH with 3 core recovery just went out the window...  ???
« Last Edit: 02/12/2018 04:56 pm by John Alan »

Offline acsawdey

Re: FH payload to Mars, when fully re-usable
« Reply #14 on: 02/12/2018 05:06 pm »
OK, first glance, a larger drone ship with two boosters landing on Gravitas?

On twitter he said two ships for two booster cores, center expended...  ;)
At only $5 million more... my guess is FH with 3 core recovery just went out the window...  ???

No, I don't think so:

Quote
Not enough ignition fluid to light the outer two engines after several three engine relights. Fix is pretty obvious.

https://twitter.com/elonmusk/status/963107229523038211

Landing boosters on two drone ships and expending the core gets you 90% of expending all 3.


Offline John Alan

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Re: FH payload to Mars, when fully re-usable
« Reply #15 on: 02/12/2018 05:16 pm »
OK, first glance, a larger drone ship with two boosters landing on Gravitas?

On twitter he said two ships for two booster cores, center expended...  ;)
At only $5 million more... my guess is FH with 3 core recovery just went out the window...  ???

No, I don't think so:

Quote
Not enough ignition fluid to light the outer two engines after several three engine relights. Fix is pretty obvious.

https://twitter.com/elonmusk/status/963107229523038211

Landing boosters on two drone ships and expending the core gets you 90% of expending all 3.

My thinking when I said that was GEO birds and direct to geo flights...
Hmmm... build a big heavy satellite with a geo-1800 rocket kickstage...
Or just go all electric and pay +5 mil for direct to geo service...  ;)

But yes... they will fix the goof with running out of starting juice and do 2-RTLS and 1-ASDS when it makes sense.
« Last Edit: 02/12/2018 05:18 pm by John Alan »

Offline LouScheffer

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Re: FH payload to Mars, when fully re-usable
« Reply #16 on: 02/12/2018 05:45 pm »
Where is this claim based on?

This is what the claim is based on:

https://twitter.com/johnkrausphotos/status/960985711825620993

The whole way up you can tell that the center core was not throttled up as high as the side boosters.
Furthermore, the center core was even throttled down at liftoff.  This is exactly the opposite of what you would do for performance, where the center should be full throttle at liftoff to minimize gravity losses.   Then throttle down later in the trajectory when saving fuel becomes more important.  This John Kraus photo (also on the cover of Av Week) shows the center was throttled down from the beginning.

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #17 on: 02/13/2018 01:33 am »
What a coincidence, Musk tweeted just today about the NASA KSC Performance figures being outdated, and said that the "SpaceX GNC team is submitting updated numbers". Awesome!

Many interesting comments regarding performance in the Twitter thread.

Offline envy887

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Re: FH payload to Mars, when fully re-usable
« Reply #18 on: 02/13/2018 03:50 pm »
OK, first glance, a larger drone ship with two boosters landing on Gravitas?

On twitter he said two ships for two booster cores, center expended...  ;)
At only $5 million more... my guess is FH with 3 core recovery just went out the window...  ???

No, nobody really needs 90% of expendable FH performance right now. All existing commercial payloads can launch with full recovery. Even large DoD direct to GSO missions are likely within reach of FH with full recovery.

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #19 on: 02/20/2018 06:09 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Offline Coastal Ron

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Re: FH payload to Mars, when fully re-usable
« Reply #20 on: 02/20/2018 06:42 pm »
Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

I'm not sure we can start estimating prices for an expendable Falcon 9/H yet, since a Block 5 has a lot of residual value after it's built, so the price of expending one may depend on how many flights it has made, or conversely, how many it can fly before requiring some amount of significant additional investment (i.e. refurbishment).

For instance, if you wanted to expend the center core of a Falcon Heavy, the price may be prohibitive if a brand new core is all that is available. But if there is a center core that has already flown 9 times, and after the tenth flight it would require extensive refurbishment, then the price may be far less than an un-flown core.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #21 on: 02/20/2018 07:08 pm »
Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

I'm not sure we can start estimating prices for an expendable Falcon 9/H yet, since a Block 5 has a lot of residual value after it's built, so the price of expending one may depend on how many flights it has made, or conversely, how many it can fly before requiring some amount of significant additional investment (i.e. refurbishment).

For instance, if you wanted to expend the center core of a Falcon Heavy, the price may be prohibitive if a brand new core is all that is available. But if there is a center core that has already flown 9 times, and after the tenth flight it would require extensive refurbishment, then the price may be far less than an un-flown core.
Elon quoted a core-expendable Falcon Heavy at $95M: https://twitter.com/elonmusk/status/963094533830426624

From what we've seen so far, SpaceX has been offering discounts to customers who are willing to fly on reused rockets. I anticipate a shift as SpaceX begins making reuse standard and charges a premium for customers who demand a brand-new booster.

Offline whitelancer64

Re: FH payload to Mars, when fully re-usable
« Reply #22 on: 02/20/2018 07:31 pm »
This thread should probably be merged with this one

"Comprehensive Falcon Family Performance"
https://forum.nasaspaceflight.com/index.php?topic=45033.0
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Offline Lar

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Re: FH payload to Mars, when fully re-usable
« Reply #23 on: 02/20/2018 08:48 pm »
From what we've seen so far, SpaceX has been offering discounts to customers who are willing to fly on reused rockets. I anticipate a shift as SpaceX begins making reuse standard and charges a premium for customers who demand a brand-new booster.
Mathematically, those are the same thing. But there is a vast perception/marketing difference.
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"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #24 on: 02/20/2018 09:14 pm »
From what we've seen so far, SpaceX has been offering discounts to customers who are willing to fly on reused rockets. I anticipate a shift as SpaceX begins making reuse standard and charges a premium for customers who demand a brand-new booster.
Mathematically, those are the same thing. But there is a vast perception/marketing difference.
Well, mathematically they are only the same if they are currently starting high and marking down but in the future will start low and mark up. If they have been starting at $62M and marking down for reuse, but will soon begin starting at $62M but marking up for a new booster, that's very different.

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #25 on: 02/20/2018 10:48 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Actual source for those figures (you don't link any source in your linked post, so that's not a source)? Importantly, at what C3? The launch energy for Mars Hohmann transfers can vary quite a bit (as Mars' orbit is elliptic).

The NASA performance website I quoted in the previous page shows around 4.0 tonnes with full recovery (sides RTLS, core ASDS) at C3 = 12 kmē/sē (which is a conservative "typical" estimate; some windows, like this year's, require as little as 7 kmē/sē).

However Musk recently tweeted that those figures are based on the Block 1 F9 performance, and that current figures should be higher. So 3.17 tonnes to Mars with full recovery is probably a substantial underestimation.

Offline Lar

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Re: FH payload to Mars, when fully re-usable
« Reply #26 on: 02/21/2018 12:29 am »
See also this thread

"Comprehensive Falcon Family Performance"
https://forum.nasaspaceflight.com/index.php?topic=45033.0

A merger suggestion was made but I think they are different, and should stay standalone.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #27 on: 02/21/2018 01:32 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Actual source for those figures (you don't link any source in your linked post, so that's not a source)? Importantly, at what C3? The launch energy for Mars Hohmann transfers can vary quite a bit (as Mars' orbit is elliptic).

The NASA performance website I quoted in the previous page shows around 4.0 tonnes with full recovery (sides RTLS, core ASDS) at C3 = 12 kmē/sē (which is a conservative "typical" estimate; some windows, like this year's, require as little as 7 kmē/sē).

However Musk recently tweeted that those figures are based on the Block 1 F9 performance, and that current figures should be higher. So 3.17 tonnes to Mars with full recovery is probably a substantial underestimation.
That was using a trans-Martian injection dV of 4.3 km/s from LEO. Don't know what C3 that corresponds to.

See also this thread

"Comprehensive Falcon Family Performance"
https://forum.nasaspaceflight.com/index.php?topic=45033.0

A merger suggestion was made but I think they are different, and should stay standalone.
In theory, you could subsume this thread into that one, but since this thread came first, it would probably be rude.

Offline AncientU

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Re: FH payload to Mars, when fully re-usable
« Reply #28 on: 02/21/2018 06:10 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Actual source for those figures (you don't link any source in your linked post, so that's not a source)? Importantly, at what C3? The launch energy for Mars Hohmann transfers can vary quite a bit (as Mars' orbit is elliptic).

The NASA performance website I quoted in the previous page shows around 4.0 tonnes with full recovery (sides RTLS, core ASDS) at C3 = 12 kmē/sē (which is a conservative "typical" estimate; some windows, like this year's, require as little as 7 kmē/sē).

However Musk recently tweeted that those figures are based on the Block 1 F9 performance, and that current figures should be higher. So 3.17 tonnes to Mars with full recovery is probably a substantial underestimation.

And also note that the FH just flown is a test vehicle.  The Block 5 version up next should be substantially beefier.  Adding any number of enhancements (Raptor second stage, cross feed, kick engine, down range booster landings, etc.) could significantly increase the Mars injection numbers if this becomes a significant need.  Think of the difference between Block 1 SLS and the eventual Blocks 1B/2.
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Offline speedevil

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Re: FH payload to Mars, when fully re-usable
« Reply #29 on: 02/21/2018 06:53 pm »
Adding any number of enhancements (Raptor second stage, cross feed, kick engine,

By kick engine, do you mean a small kick stage under the actual payload, to drop the mass of the second stage?

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #30 on: 02/21/2018 07:02 pm »
And also note that the FH just flown is a test vehicle.  The Block 5 version up next should be substantially beefier.  Adding any number of enhancements (Raptor second stage, cross feed, kick engine, down range booster landings, etc.) could significantly increase the Mars injection numbers if this becomes a significant need.  Think of the difference between Block 1 SLS and the eventual Blocks 1B/2.
Raptor upper stage won't happen, and neither will crossfeed. Kick engine could be part of a payload, but then it's part of the payload, so...yeah. Downrange booster landings with a recoverable core is very unlikely; the side boosters need to RTLS for the core to be able to stop at all.

The numbers I gave above were based on the Block 5 Falcon Heavy with triple recovery. However, the other thread did point out that the 8 tonnes to GTO currently advertised by SpaceX are Block 3 numbers. Block 5 FH will likely be able to do about 4 tonnes to TMI and almost 10 tonnes to GTO.

Offline wannamoonbase

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Re: FH payload to Mars, when fully re-usable
« Reply #31 on: 02/21/2018 07:20 pm »
And also note that the FH just flown is a test vehicle.  The Block 5 version up next should be substantially beefier.  Adding any number of enhancements (Raptor second stage, cross feed, kick engine, down range booster landings, etc.) could significantly increase the Mars injection numbers if this becomes a significant need.  Think of the difference between Block 1 SLS and the eventual Blocks 1B/2.
Raptor upper stage won't happen, and neither will crossfeed. Kick engine could be part of a payload, but then it's part of the payload, so...yeah. Downrange booster landings with a recoverable core is very unlikely; the side boosters need to RTLS for the core to be able to stop at all.

The numbers I gave above were based on the Block 5 Falcon Heavy with triple recovery. However, the other thread did point out that the 8 tonnes to GTO currently advertised by SpaceX are Block 3 numbers. Block 5 FH will likely be able to do about 4 tonnes to TMI and almost 10 tonnes to GTO.

FH numbers for down range boosters and expendable core should be very impressive.

They’ll have two easy coast ASDS.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #32 on: 02/21/2018 07:32 pm »
And also note that the FH just flown is a test vehicle.  The Block 5 version up next should be substantially beefier.  Adding any number of enhancements (Raptor second stage, cross feed, kick engine, down range booster landings, etc.) could significantly increase the Mars injection numbers if this becomes a significant need.  Think of the difference between Block 1 SLS and the eventual Blocks 1B/2.
Raptor upper stage won't happen, and neither will crossfeed. Kick engine could be part of a payload, but then it's part of the payload, so...yeah. Downrange booster landings with a recoverable core is very unlikely; the side boosters need to RTLS for the core to be able to stop at all.

The numbers I gave above were based on the Block 5 Falcon Heavy with triple recovery. However, the other thread did point out that the 8 tonnes to GTO currently advertised by SpaceX are Block 3 numbers. Block 5 FH will likely be able to do about 4 tonnes to TMI and almost 10 tonnes to GTO.

FH numbers for down range boosters and expendable core should be very impressive.

They’ll have two easy coast ASDS.
10% payload penalty compared to fully-expendable, according to Elon. So ~57 tonnes to LEO, ~24 tonnes to GTO, 23 tonnes to TLI, or 15 tonnes to TMI, all for just $5M more than a fully-recoverable Falcon Heavy.

Offline AncientU

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Re: FH payload to Mars, when fully re-usable
« Reply #33 on: 02/21/2018 08:21 pm »
And also note that the FH just flown is a test vehicle.  The Block 5 version up next should be substantially beefier.  Adding any number of enhancements (Raptor second stage, cross feed, kick engine, down range booster landings, etc.) could significantly increase the Mars injection numbers if this becomes a significant need.  Think of the difference between Block 1 SLS and the eventual Blocks 1B/2.
Raptor upper stage won't happen, and neither will crossfeed. Kick engine could be part of a payload, but then it's part of the payload, so...yeah. Downrange booster landings with a recoverable core is very unlikely; the side boosters need to RTLS for the core to be able to stop at all.

The numbers I gave above were based on the Block 5 Falcon Heavy with triple recovery. However, the other thread did point out that the 8 tonnes to GTO currently advertised by SpaceX are Block 3 numbers. Block 5 FH will likely be able to do about 4 tonnes to TMI and almost 10 tonnes to GTO.

Won't happen... does that put these potential mods on par with SLS Block 2 which everyone seems to assume is a done deal?
« Last Edit: 02/21/2018 11:02 pm by AncientU »
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Offline wannamoonbase

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Re: FH payload to Mars, when fully re-usable
« Reply #34 on: 02/21/2018 08:40 pm »
Sevenperforce, those are crazy performance numbers!

It’d be fun to see that required someday. 
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #35 on: 02/21/2018 10:20 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Actual source for those figures (you don't link any source in your linked post, so that's not a source)? Importantly, at what C3? The launch energy for Mars Hohmann transfers can vary quite a bit (as Mars' orbit is elliptic).

The NASA performance website I quoted in the previous page shows around 4.0 tonnes with full recovery (sides RTLS, core ASDS) at C3 = 12 kmē/sē (which is a conservative "typical" estimate; some windows, like this year's, require as little as 7 kmē/sē).

However Musk recently tweeted that those figures are based on the Block 1 F9 performance, and that current figures should be higher. So 3.17 tonnes to Mars with full recovery is probably a substantial underestimation.
That was using a trans-Martian injection dV of 4.3 km/s from LEO. Don't know what C3 that corresponds to.

From a 200 km circular Earth orbit, a Δv of 4.3 km/s gives C3 ~ 25 kmē/sē; that's a bit higher than the typical Mars launch (for reference, MAVEN was launched with C3 = 12.2 kmē/s^2, ExoMars with C3 = 7.4 kmē/sē). C3 = 12 kmē/sē would require Δv = 3.8 km/s from that orbit. On the other hand, the FH did the TMI burn at perigee on a 142 x 6862 km orbit; for C3 = 12 kmē/sē that was a Δv of 2.5 km/s.

Considering that large launch energy your 3.17 tonnes figure now makes sense. For one, it's substantially higher than the outdated value reported in the NASA performance website (2395 kg at C3 = 25 kmē/sē for recoverable FH). Where are you getting the figures from (I did not catch a source in the other thread)? I hope that SpaceX provides updated figures to the NASA folks in charge of that website (assuming there's still some one in charge).

Offline speedevil

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Re: FH payload to Mars, when fully re-usable
« Reply #36 on: 02/21/2018 10:23 pm »
I hope that SpaceX provides updated figures to the NASA folks in charge of that website (assuming there's still some one in charge).

I idly wonder if FOIAing the SpaceX communication might not get the data faster.

Offline sevenperforce

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Re: FH payload to Mars, when fully re-usable
« Reply #37 on: 02/21/2018 10:42 pm »
Falcon Heavy can send 3.17 tonnes on a Hohmann transfer to Mars with full recovery of all three boosters (side boosters RTLS, core on ASDS). Note that Falcon 9, on the other hand, can send up to 4.04 tonnes to Mars when flying expendable.

Expend the core and land each side booster on an ASDS, and you can send over 15 tonnes on TMI, for only $3M more than an expendable Falcon 9.

Source.

Actual source for those figures (you don't link any source in your linked post, so that's not a source)? Importantly, at what C3? The launch energy for Mars Hohmann transfers can vary quite a bit (as Mars' orbit is elliptic).

The NASA performance website I quoted in the previous page shows around 4.0 tonnes with full recovery (sides RTLS, core ASDS) at C3 = 12 kmē/sē (which is a conservative "typical" estimate; some windows, like this year's, require as little as 7 kmē/sē).

However Musk recently tweeted that those figures are based on the Block 1 F9 performance, and that current figures should be higher. So 3.17 tonnes to Mars with full recovery is probably a substantial underestimation.
That was using a trans-Martian injection dV of 4.3 km/s from LEO. Don't know what C3 that corresponds to.

From a 200 km circular Earth orbit, a Δv of 4.3 km/s gives C3 ~ 25 kmē/sē; that's a bit higher than the typical Mars launch (for reference, MAVEN was launched with C3 = 12.2 kmē/s^2, ExoMars with C3 = 7.4 kmē/sē). C3 = 12 kmē/sē would require Δv = 3.8 km/s from that orbit. On the other hand, the FH did the TMI burn at perigee on a 142 x 6862 km orbit; for C3 = 12 kmē/sē that was a Δv of 2.5 km/s.

Considering that large launch energy your 3.17 tonnes figure now makes sense. For one, it's substantially higher than the outdated value reported in the NASA performance website (2395 kg at C3 = 25 kmē/sē for recoverable FH). Where are you getting the figures from (I did not catch a source in the other thread)? I hope that SpaceX provides updated figures to the NASA folks in charge of that website (assuming there's still some one in charge).
ULA's Zegler gave values for a "typical" Mars burn from LEO at 4.3 km/s (page 4). Wikipedia's "delta v budget" page gives minimal TMI cost at 3.6 km/s, which would change quite a few of my values but would probably still keep everything pretty close.

Also, note that the other thread has as discussion suggesting that the "8 metric tonne" limit on FHR is Block 3, and that 10 tonnes is closer to correct.

Plus, if they can successfully bring back the booster after Hispasat on Sunday, that'll be a HUGE datapoint for ASDS landings.

Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #38 on: 02/21/2018 11:48 pm »
ULA's Zegler gave values for a "typical" Mars burn from LEO at 4.3 km/s (page 4). Wikipedia's "delta v budget" page gives minimal TMI cost at 3.6 km/s, which would change quite a few of my values but would probably still keep everything pretty close.

Also, note that the other thread has as discussion suggesting that the "8 metric tonne" limit on FHR is Block 3, and that 10 tonnes is closer to correct.

Plus, if they can successfully bring back the booster after Hispasat on Sunday, that'll be a HUGE datapoint for ASDS landings.

I don't know where Zegler gets that number. But take a look at the NASA Ames Trajectory Browser. That link goes directly to a query for Mars trajectories. You can see that the "Injection Δv" minima for each launch window (the colorful vertical clusters ~26 months apart) are typically below 4 km/s. And the C3 values I quoted above for MAVEN and ExoMars definitely support that (ExoMars launched with 7.4 kmē/sē, which requires Δv = 3.6 km/s from a 200 km LEO).

I think that 4.3 km/s (C3 = 25 kmē/sē from 200 km LEO) might be too high as a nominal value for the "typical" Mars launch.
« Last Edit: 02/22/2018 12:08 am by meithan »

Offline speedevil

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Re: FH payload to Mars, when fully re-usable
« Reply #39 on: 02/21/2018 11:51 pm »
ULA's Zegler gave values for a "typical" Mars burn from LEO at 4.3 km/s (page 4). Wikipedia's "delta v budget" page gives minimal TMI cost at 3.6 km/s, which would change quite a few of my values but would probably still keep everything pretty close.
It varies a little with time.
This page shows you the results of previous simulations to various bodies.

Starting out at 3.53 ((Dec 4, 208 days) or so, going up to about 4 for 100 day transits, and 5 for 80 days. (minimum approx speeds for each time).

This is all departure from a 200km circular LEO.



Offline meithan

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Re: FH payload to Mars, when fully re-usable
« Reply #40 on: 02/22/2018 12:07 am »
speedevil, was that telepathy? ;)

Offline speedevil

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Re: FH payload to Mars, when fully re-usable
« Reply #41 on: 02/22/2018 02:09 am »
speedevil, was that telepathy? ;)

It's a handy page, and has been posted a fair bit.
I keep meaning to find/ install something better, but it's so easy!
Are there any other low-barrier-to-entry tools people are aware of?
http://gmatcentral.org/display/GW/GMAT+Wiki+Home is awesome - but it's not exactly easy.

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