SpaceX Falcon Heavy Discussion (Thread 6)

[Chris611]

I know rockets aren't legos.  However, what if NASA wanted to put a Delta IV heavy upper stage on a FH instead of the existing stage?  What kind of payload would that be to LEO? to TLI?  Say a stretched Delta IV heavy upper stage with say two or four RL-10 engines.

Probably not very much. iCPS is really weak compared to the Falcon second stage. Falcon S2 has a propellant mass of 107500kg, while iCPS only 27220kg. 4 RL10's have a thrust of less than half of the single Merlin Vacuum.
If you want a high-energy uppers-stage on Falcon Heavy, a new Raptor Methalox upper stage or even the proposed Ares I upper stage with J2X (1.3kN thrust with 135100 kg prop load) might be more appropriate.

[envy887]

I know rockets aren't legos.  However, what if NASA wanted to put a Delta IV heavy upper stage on a FH instead of the existing stage?  What kind of payload would that be to LEO? to TLI?  Say a stretched Delta IV heavy upper stage with say two or four RL-10 engines.

Probably not very much. iCPS is really weak compared to the Falcon second stage. Falcon S2 has a propellant mass of 107500kg, while iCPS only 27220kg. 4 RL10's have a thrust of less than half of the single Merlin Vacuum.
If you want a high-energy uppers-stage on Falcon Heavy, a new Raptor Methalox upper stage or even the proposed Ares I upper stage with J2X (1.3kN thrust with 135100 kg prop load) might be more appropriate.

It actually gets about 25% more payload to TLI. This is significant, since it is the difference between being able to launch Orion direct to TLI, and not being able to do this.

[envy887]

That seems backward. For a given engine+payload, extending the fuel tank improves the mass ratio (adding a small amount of tank-perimiter material, and all the fuel that fits in the cross section added), improving DV. it only becomes an issue when you start cutting into the booster's lift capability, but FH is much better endowed there than F9.

That helps get more payload to the same trajectory. But getting it to a higher trajectory is harder, and adding dry mass starts eating back the gains.

[Chris611]

I know rockets aren't legos.  However, what if NASA wanted to put a Delta IV heavy upper stage on a FH instead of the existing stage?  What kind of payload would that be to LEO? to TLI?  Say a stretched Delta IV heavy upper stage with say two or four RL-10 engines.

Probably not very much. iCPS is really weak compared to the Falcon second stage. Falcon S2 has a propellant mass of 107500kg, while iCPS only 27220kg. 4 RL10's have a thrust of less than half of the single Merlin Vacuum.
If you want a high-energy uppers-stage on Falcon Heavy, a new Raptor Methalox upper stage or even the proposed Ares I upper stage with J2X (1.3kN thrust with 135100 kg prop load) might be more appropriate.

It actually gets about 25% more payload to TLI. This is significant, since it is the difference between being able to launch Orion direct to TLI, and not being able to do this.

I really think that's with iCPS on top of the Falcon Second stage, not instead of the Falcon Second stage.

1) iCPS with Orion (and the stage adapter) as a payload has a delta-V of about 2905m/s. That's about enough to go to TLI from LEO (if we somehow can get a fully fueled iCPS with Orion into LEO).
2) Falcon S2 with the same payload, Orion (and the stage adapter), has a delta-V of 5075m/s. That wildly outperforms the iCPS. Of course some of this will be offset by the core stages having to lift a lighter payload thus staging happening at a bit higher speed in case (1). But then, gravity losses are a lot less for the second stage due to higher thrust for case (2).
3) Falcon S2 with Orion + iCPS as a payload has a delta V of 3428m/s.
4) That gives us a total total DeltaV of 2905 + 3428 = 6333m/s Falcon S2+iCPS with Orion as the payload. There's probably your 25% extra performance to TLI compared to (2)

Assumptions:
FalconS2_DryMass = 4500.0 #kg
FalconS2_FuelCapacity = 107500 #kg
FalconS2_GrossMass = FalconS2_DryMass + FalconS2_FuelCapacity #112000.0kg
FalconS2_Thrust = 934.0 #kN
FalsonS2_SpecificImpulse = 348 #s

iCPS_DryMass = 3490.0 #kg
iCPS_FuelCapacity = 27220.0 #kg
iCPS_GrossMass = iCPS_FuelCapacity + iCPS_DryMass #30710.0kg
iCPS_StageAdapterMass = 0 #???
iCPS_Thrust = 110.1 #kN
iCPS_SpecificImpulse = 464.5 #s

Orion_GrossMass = 26520.19   #orion injected mass
Orion_StageAdapterMass = 510 #kg

[John Alan]

IMHO.... The current common tank volume S2 uses on F9 and FH are already at the about the right size... 

I looked at this some time back and ran numbers six ways from Sunday, and decided let it sit and revisit in a year...
I read all the above and other postings saying, do this, and do that, and I still think today... NOPE, leave it be... 

Bottom line...
FH as flown twice now and back figured by many here, can likely put the spec'd "up to 63+ metric tonnes" of payload into a low low LEO... 
I also looks like FH can darn near put S2 w/no payload into LEO with almost all it's prop intact and ready to go on somewhere else...
It's the perfect "dial a rocket" as flying and certified in this price range ($62M F9 recovered to $165M FH fully expended it's said)
With F9 covering the bottom and FH covering the top... This system is now likely the envy of every other global orbital spaceflight group... period.
And I bet GS (and the whole team) is just overjoyed at the profit margin this thing has, now that R&D is winding down on F9/FH...

SO... how do users adapt to what F9/FH system offers...
THAT IS WHAT YOU NEED TO ASK YOURSELF... 
SSL showed starting with Telestar 19 one way... And I think the best way... IMHO
<key talking point>
Integrate a "larger 3rd stage" into the payload itself and build it to fit a price point offered in the F9/FH system...
/<key talking point>
SSL designed Telstar 19 and 18 by designing the main payload first, THEN adding enough Delta-V so it FIT on ASDS recovered F9 block 5 (the cheapest ride to space for the payloads size)
By in effect ignoring the industry standard GEO-1800 and building to a mutually agreed contracted number in the 2200-2300 range... SSL showed that THIS is how the payload industry needs to adapt to lower the overall cost to put payloads into orbit.

Putting payloads BEO needs to follow the same idea...
Stop trying to change F9/FH... Change the BEO payloads and probes to be able to go from an agreed on release orbit (preferably IMHO with just enough S2 prop left to reenter/dispose of S2) and take itself off toward it's destination.
Think of it, as combining your maneuvering system on you payload with enough prop tankage volume to also serve as a stand in "3rd stage" as used on old school rockets to put the payload all the way where it needs to go...

I think SpaceX would be eager to book a 60 metric tonne payload on FH so it can finish and demo it's HD payload adaptor and S2 mods needed to make that work...
And if you can't design a payload with integrated kick/maneuver system using up to a 60 tonne budget... to get from LEO to anywhere in the Solar System... 
Then please find another line of work... 

[ZachS09]

Even though SpaceX only wants to reuse the side boosters for STP-2, given that the center core had a slim chance of landing safely, why would they not reuse the center core once it comes back to port?

[lonestriker]

Even though SpaceX only wants to reuse the side boosters for STP-2, given that the center core had a slim chance of landing safely, why would they not reuse the center core once it comes back to port?

I don't think SpaceX has ever said they would not reuse the ArabSat center core.  They just can't contractually use it on STP-2, as they are only allowed to reuse the side boosters through a contract change.

I fully expect they'll reuse the center core for some other mission unless the stress was beyond limits.

[su27k]

So has anyone calculated how much performance improvement FH expendable can get by adding a shortened S2 as 3rd stage, as woods170 suggested in the other thread?

I gave it a try on http://silverbirdastronautics.com/LVperform.html, by using a 3rd stage half as big as 2nd stage (the numbers actually doesn't seem sensitive to the exact size), the increase is not that big, TLI payload only increased by 3 tons or so.

Not surprising as you're carrying two Mvac worth of mass and tank domes/bulkheads uphill instead of one..
Also adds way more $$$ throwing away 2 Mvac instead of 1.. Just don't see how that case ever closes.

Betting much better bang for buck stretching S2, as adding a meter or two to the tank walls takes very little cost/added mass. 

But silverbirdastronautics calculator is not showing this, it shows stretching S2 produces very little performance improvement, as envy887 mentioned in the post above

Using the assumptions below, and adding 500 kg dry mass and 30,000 kg prop to the upper stage, it shows 3% more payload to LEO, 2.2% more to TLI, and 1.6% more to TMI for the stretched stage compared to the standard stage. The returns of stretching the stage are small for a full expendable, and they get smaller as the final energy increases.

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

[TrueBlueWitt]

So has anyone calculated how much performance improvement FH expendable can get by adding a shortened S2 as 3rd stage, as woods170 suggested in the other thread?

I gave it a try on http://silverbirdastronautics.com/LVperform.html, by using a 3rd stage half as big as 2nd stage (the numbers actually doesn't seem sensitive to the exact size), the increase is not that big, TLI payload only increased by 3 tons or so.

Not surprising as you're carrying two Mvac worth of mass and tank domes/bulkheads uphill instead of one..
Also adds way more $$$ throwing away 2 Mvac instead of 1.. Just don't see how that case ever closes.

Betting much better bang for buck stretching S2, as adding a meter or two to the tank walls takes very little cost/added mass. 

But silverbirdastronautics calculator is not showing this, it shows stretching S2 produces very little performance improvement, as envy887 mentioned in the post above

Using the assumptions below, and adding 500 kg dry mass and 30,000 kg prop to the upper stage, it shows 3% more payload to LEO, 2.2% more to TLI, and 1.6% more to TMI for the stretched stage compared to the standard stage. The returns of stretching the stage are small for a full expendable, and they get smaller as the final energy increases.

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

I can't mentally make the case close and think there's something wrong with their calculations.

Even when I use the same mass for S2 at 3000kg(instead of 4000kg)  as I would for an additional S3(~3000kg) + existing S2 then use same amount of prop in stretched 3000kg S2 as I would in the combined S2+S3 case, somehow I get quite a bit lower performance to TMI for the stretched 2 stage version..   

For this case I put 40,000kg of prop in S3.

Payload to TMI(C3=8.1)
S2(4000kg + 111,000kg fuel) = 3688 kg (Baseline)
S2(3000kg + 151,000kg fuel) = 5099 kg
S2(4000kg + 111,000kg fuel)+S3(3000kg + 40,000kg fuel) = 7408 kg

Doesn't pass the "sniff" test.


Note:
This was for F9 not FH.. but doesn't matter here.. Could do same for FH.. But calculation at site needs to be fixed first.  Is there another calculator to try this? There are others on here that have their own tools who can verify this.

[envy887]

So has anyone calculated how much performance improvement FH expendable can get by adding a shortened S2 as 3rd stage, as woods170 suggested in the other thread?

I gave it a try on http://silverbirdastronautics.com/LVperform.html, by using a 3rd stage half as big as 2nd stage (the numbers actually doesn't seem sensitive to the exact size), the increase is not that big, TLI payload only increased by 3 tons or so.

Not surprising as you're carrying two Mvac worth of mass and tank domes/bulkheads uphill instead of one..
Also adds way more $$$ throwing away 2 Mvac instead of 1.. Just don't see how that case ever closes.

Betting much better bang for buck stretching S2, as adding a meter or two to the tank walls takes very little cost/added mass. 

But silverbirdastronautics calculator is not showing this, it shows stretching S2 produces very little performance improvement, as envy887 mentioned in the post above

Using the assumptions below, and adding 500 kg dry mass and 30,000 kg prop to the upper stage, it shows 3% more payload to LEO, 2.2% more to TLI, and 1.6% more to TMI for the stretched stage compared to the standard stage. The returns of stretching the stage are small for a full expendable, and they get smaller as the final energy increases.

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

I can't mentally make the case close and think there's something wrong with their calculations.

Even when I use the same mass for S2 at 3000kg(instead of 4000kg)  as I would for an additional S3(~3000kg) + existing S2 then use same amount of prop in stretched 3000kg S2 as I would in the combined S2+S3 case, somehow I get quite a bit lower performance to TMI for the stretched 2 stage version..   

For this case I put 40,000kg of prop in S3.

Payload to TMI(C3=8.1)
S2(4000kg + 111,000kg fuel) = 3688 kg (Baseline)
S2(3000kg + 151,000kg fuel) = 5099 kg
S2(4000kg + 111,000kg fuel)+S3(3000kg + 40,000kg fuel) = 7408 kg

Doesn't pass the "sniff" test.


Note:
This was for F9 not FH.. but doesn't matter here.. Could do same for FH.. But calculation at site needs to be fixed first.  Is there another calculator to try this? There are others on here that have their own tools who can verify this.

I can't replicate your results in the silverbird calculator. The 3000 kg 2nd stage gives more payload than a 4000 kg and 3000 kg 2nd and 3rd stage with the same fuel mass. Can you post a screenshot with the numbers you put in and the results?

[Robotbeat]

The Silverbird calculator may not be making good assumptions about gravity losses and number of burns.

[TrueBlueWitt]

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

I can't mentally make the case close and think there's something wrong with their calculations.

Even when I use the same mass for S2 at 3000kg(instead of 4000kg)  as I would for an additional S3(~3000kg) + existing S2 then use same amount of prop in stretched 3000kg S2 as I would in the combined S2+S3 case, somehow I get quite a bit lower performance to TMI for the stretched 2 stage version..   

For this case I put 40,000kg of prop in S3.

Payload to TMI(C3=8.1)
S2(4000kg + 111,000kg fuel) = 3688 kg (Baseline)
S2(3000kg + 151,000kg fuel) = 5099 kg
S2(4000kg + 111,000kg fuel)+S3(3000kg + 40,000kg fuel) = 7408 kg

Doesn't pass the "sniff" test.


Note:
This was for F9 not FH.. but doesn't matter here.. Could do same for FH.. But calculation at site needs to be fixed first.  Is there another calculator to try this? There are others on here that have their own tools who can verify this.

I can't replicate your results in the silverbird calculator. The 3000 kg 2nd stage gives more payload than a 4000 kg and 3000 kg 2nd and 3rd stage with the same fuel mass. Can you post a screenshot with the numbers you put in and the results?

Here's what I ran.. Feel free to try, or show me what I did wrong here.


Edit Actual 2 stage(3000kg/151,000kg prop) is even lower ~5100kg payload when I put 1st stage ISP back to an avg of 300


I've written to John Schilling to see what he can make of it, if he chooses to look into it.

[envy887]

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

I can't mentally make the case close and think there's something wrong with their calculations.

Even when I use the same mass for S2 at 3000kg(instead of 4000kg)  as I would for an additional S3(~3000kg) + existing S2 then use same amount of prop in stretched 3000kg S2 as I would in the combined S2+S3 case, somehow I get quite a bit lower performance to TMI for the stretched 2 stage version..   

For this case I put 40,000kg of prop in S3.

Payload to TMI(C3=8.1)
S2(4000kg + 111,000kg fuel) = 3688 kg (Baseline)
S2(3000kg + 151,000kg fuel) = 5099 kg
S2(4000kg + 111,000kg fuel)+S3(3000kg + 40,000kg fuel) = 7408 kg

Doesn't pass the "sniff" test.


Note:
This was for F9 not FH.. but doesn't matter here.. Could do same for FH.. But calculation at site needs to be fixed first.  Is there another calculator to try this? There are others on here that have their own tools who can verify this.

I can't replicate your results in the silverbird calculator. The 3000 kg 2nd stage gives more payload than a 4000 kg and 3000 kg 2nd and 3rd stage with the same fuel mass. Can you post a screenshot with the numbers you put in and the results?

Here's what I ran.. Feel free to try, or show me what I did wrong here.


Edit Actual 2 stage(3000kg/151,000kg prop) is even lower ~5100kg payload when I put 1st stage ISP back to an avg of 300


I've written to John Schilling to see what he can make of it, if he chooses to look into it.

Shouldn't an MVac based 3rd stage have an ISP of 348, not 384?

[TrueBlueWitt]

At least according to silverbirdastronautics calculator, a 3rd stage is definitely a better option performance wise. Of course there's the chance that silverbirdastronautics is not accurate, that's why I'm wondering if anybody else has done similar calculation.

The 3rd stage option is interesting since this is supposed to be a real proposal from SpaceX for launching Orion, as mentioned by woods170 here.

I can't mentally make the case close and think there's something wrong with their calculations.

Even when I use the same mass for S2 at 3000kg(instead of 4000kg)  as I would for an additional S3(~3000kg) + existing S2 then use same amount of prop in stretched 3000kg S2 as I would in the combined S2+S3 case, somehow I get quite a bit lower performance to TMI for the stretched 2 stage version..   

For this case I put 40,000kg of prop in S3.

Payload to TMI(C3=8.1)
S2(4000kg + 111,000kg fuel) = 3688 kg (Baseline)
S2(3000kg + 151,000kg fuel) = 5099 kg
S2(4000kg + 111,000kg fuel)+S3(3000kg + 40,000kg fuel) = 7408 kg

Doesn't pass the "sniff" test.


Note:
This was for F9 not FH.. but doesn't matter here.. Could do same for FH.. But calculation at site needs to be fixed first.  Is there another calculator to try this? There are others on here that have their own tools who can verify this.

I can't replicate your results in the silverbird calculator. The 3000 kg 2nd stage gives more payload than a 4000 kg and 3000 kg 2nd and 3rd stage with the same fuel mass. Can you post a screenshot with the numbers you put in and the results?

Here's what I ran.. Feel free to try, or show me what I did wrong here.


Edit Actual 2 stage(3000kg/151,000kg prop) is even lower ~5100kg payload when I put 1st stage ISP back to an avg of 300


I've written to John Schilling to see what he can make of it, if he chooses to look into it.

Shouldn't an MVac based 3rd stage have an ISP of 348, not 384?

I must have been dyslexic typing last night: 

You're correct, Now S2+S3 is back down..
Although still slightly higher than than just the lightweight S2.
Still not sure how that works as you're carrying another 4000kg of dry mass through most of it.

Mission Performance:
Launch Vehicle:     User-Defined Launch Vehicle
Launch Site:     Cape Canaveral / KSC
Escape Trajectory:     C3 = 8 km2/s2, 0 deg
Estimated Payload:     5478 kg
95% Confidence Interval:     4110 - 7113 kg

[snotis]

SpaceX has put an exclusive page on their website just for this mission with descriptions of the payloads and a launch animation

www.spacex.com/stp-2

On that page - I saw this:

Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars.

Maybe they are changing their mind on certifying Falcon Heavy to carry humans?

[CuddlyRocket]

Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars.

Maybe they are changing their mind on certifying Falcon Heavy to carry humans?

Certified by whom? They only need NASA certification if they're carrying out a NASA mission or (perhaps) NASA astronauts. Not to say that isn't what they're thinking of; for the Lunar Gateway perhaps?

[woods170]

Falcon Heavy was designed from the outset to carry humans into space and restores the possibility of flying missions with crew to the Moon or Mars.

Maybe they are changing their mind on certifying Falcon Heavy to carry humans?

Certified by whom? They only need NASA certification if they're carrying out a NASA mission or (perhaps) NASA astronauts. Not to say that isn't what they're thinking of; for the Lunar Gateway perhaps?

Correct. Initially FH would launch a non-NASA manned circumlunar mission. No certification for carrying humans required.

Human-rating comes into play when NASA is involved.

[Herb Schaltegger]

General FAA commercial spaceflight regulations do come into play, however, including those directed toward human crew and passengers. Those regulations are rather ambiguous and subject to a great degree of further interpretation and development as befits an industry segment that’s not yet well established.

But the point is that the FAA would still have to issue a launch license, and for a mission carrying human beings, the process will be a somewhat more than simple paperwork.

[rakaydos]

General FAA commercial spaceflight regulations do come into play, however, including those directed toward human crew and passengers. Those regulations are rather ambiguous and subject to a great degree of further interpretation and development as befits an industry segment that’s not yet well established.

But the point is that the FAA would still have to issue a launch license, and for a mission carrying human beings, the process will be a somewhat more than simple paperwork.

Wouldn't it be an FAA form notifying the arstronauts that FH is not approved for human spaceflight by NASA, that the nasa employees have to sign before peforming human spaceflight?

[envy887]

General FAA commercial spaceflight regulations do come into play, however, including those directed toward human crew and passengers. Those regulations are rather ambiguous and subject to a great degree of further interpretation and development as befits an industry segment that’s not yet well established.

But the point is that the FAA would still have to issue a launch license, and for a mission carrying human beings, the process will be a somewhat more than simple paperwork.

Wouldn't it be an FAA form notifying the arstronauts that FH is not approved for human spaceflight by NASA, that the nasa employees have to sign before peforming human spaceflight?

The FAA requires informed consent of "commercial spaceflight participants". The "informed" part includes telling them that the vehicle is not certified for flight-worthiness by any federal agency, and also telling them how many times it has flown and how many times it has crashed.

However, as I recall, federal employees flying on the government dime do not count as "commercial spaceflight participants". NASA would probably either have to rate the vehicle or waive their rating requirements in order to send astronauts on it.