SpaceX Falcon Heavy Discussion (Thread 6)

[TrueBlueWitt]

Is that how others envisage FH will be used, vis-a-vis GEO payloads? Or do you think we will start to see many direct GEO insertions? Or alternatively do you expect to see more and more of the dV difference between LEO and GEO being offloaded to the payload over time, as per recent launches, with FH simply delivering lots of fuel-laden payloads to LEO, for them to make their own way from there?

I have wondered about this also.  It seems satellite manufacturers have designed based on the capability/track record/cost of available launchers.  For whatever reasons, they are saying "thanks, but we will get from LEO to GEO ourselves".  Falcon Heavy changes the design parameters to allow the design of satellites which are more robust/redundant with more fuel for station keeping, and so have a longer service life.

If I am right, we should start seeing larger satellites with more fuel, but being launched by FH direct to GEO.  I am not sure the satellite operators gain anything from launch to supersynchronous orbit.  If the launch vehicle is capable and the risk/cost is similar, they would want the launcher to put the satellite exactly where it can start making money as soon as possible.  I think that is how FH will capture that market, getting a GEO satellite direct to its operating orbit immediately without the satellite expending time and fuel to get there itself.  And allowing the satellite manufacturers to build more robustly for a longer service life.

Supersynch does make S2 disposal a lot easier. Unless you want a lot of S2 in graveyard orbits past geo?

[ulm_atms]

I don't see there being a change to lots of direct GEO profiles.  Those profiles have 1 big problem in that each launch ends up leaving 2 objects in GEO instead of just the sat since in reusable mode, the FH doesn't have the dV to de-orbit the second stage unless the sat is very light.  To allow for a de-orbit of S2, they would have to expend the center core...which is the most expensive core...so I don't see that being offered.  There is also the added loiter time needed to get S2 far enough away from the sat before firing it's main engine to de-orbit (not sure how far away 'enough' is though)

My feeling is that we will see larger sats with much larger fuel supplies and being ~7.5T each.  That should allow supersync GTO with full reuse and a lot of fuel reserve for 20+ year designs with FH.  Or the same size and subsync on F9 with a shorter life (~15 years)

~7.5T seems (at least to me) to be the sweet spot for the next Gen launchers coming online in the next 5 years.

[FinalFrontier]

I'm assuming that's a typo.

FH is specified as 60 tons to LEO.
Nominal stage mass would be around 175 tons.
To get 100 tons to LEO would need a stage mass of around 300 tons, or a more or less doubling of S2s length.

Call it two and a half times.
This would give an initial acceleration of 3m/s^2, and a burn of six minutes or so.
I don't think this naively quite hits the atmosphere, but it will need the trajectory steepened so it won't.
Stretching S2 has been called 'the easiest thing' - but this is quite a stretch indeed.

That depends.

Keep in mind FH as tested early in the year was a block four vehicle, including the upper stage.

Block five FH has substantially stretched second stage and the MVAC engine fires at a higher setting providing more thrust.

I am not sure whether or not the tested FH used a block five upper stage but off the top of my head I would say that no it did not.

100 MT would still be a surprise and is probably a typo or mis-speech but it might not be impossible. I am not sure if anyone to date really knows where block 5 FH is supposed to come in for performance, particularly in fully expendable mode.

[envy887]

I'm assuming that's a typo.

FH is specified as 60 tons to LEO.
Nominal stage mass would be around 175 tons.
To get 100 tons to LEO would need a stage mass of around 300 tons, or a more or less doubling of S2s length.

Call it two and a half times.
This would give an initial acceleration of 3m/s^2, and a burn of six minutes or so.
I don't think this naively quite hits the atmosphere, but it will need the trajectory steepened so it won't.
Stretching S2 has been called 'the easiest thing' - but this is quite a stretch indeed.

That depends.

Keep in mind FH as tested early in the year was a block four vehicle, including the upper stage.

Block five FH has substantially stretched second stage and the MVAC engine fires at a higher setting providing more thrust.

I am not sure whether or not the tested FH used a block five upper stage but off the top of my head I would say that no it did not.

100 MT would still be a surprise and is probably a typo or mis-speech but it might not be impossible. I am not sure if anyone to date really knows where block 5 FH is supposed to come in for performance, particularly in fully expendable mode.

Block 5 performance specs have been published by SpaceX since 2016, and I have seen zero evidence that the Block 5 upper stage (for either F9 or FH) was stretched.

It is true that the Block 5 MVac runs at higher thrust.

[rcoppola]

IIRC an additional 2nd stage stretch was mentioned within the context of possible mods for 2nd stage reuse. But no, 2nd stage has not been stretched for Block 5.

[hkultala]

I'm assuming that's a typo.

FH is specified as 60 tons to LEO.
Nominal stage mass would be around 175 tons.
To get 100 tons to LEO would need a stage mass of around 300 tons, or a more or less doubling of S2s length.

Call it two and a half times.
This would give an initial acceleration of 3m/s^2, and a burn of six minutes or so.
I don't think this naively quite hits the atmosphere, but it will need the trajectory steepened so it won't.
Stretching S2 has been called 'the easiest thing' - but this is quite a stretch indeed.

That depends.

Keep in mind FH as tested early in the year was a block four vehicle, including the upper stage.

... but the published specifications are for block 5, not block 4.

The planned original "1.1" version of FH was supposed to have payload of 53 tonnes with cross-feed, and something like 40-45 tonnes without crossfeed.

Then they increased the thrust of the engines and cooled the propellants, getting to about 53 tonnes without crossfeed, and dropped crossfeed.

Then they increased the thrust again and made some other changes with block 5 and got to 60 tonnes.

Block five FH has substantially stretched second stage and the MVAC engine fires at a higher setting providing more thrust.

Wrong. The second stage is exactly the same size as earlier versions.

I am not sure whether or not the tested FH used a block five upper stage but off the top of my head I would say that no it did not.

It did not, but this does not matter. it did not lift 50 tonnes payload to LEO either.

The performance numbers are based on calculations/simulations, not on flown missions. And the only flown mission could have been used to verify the correctness of these simulations.

100 MT would still be a surprise and is probably a typo or mis-speech but it might not be impossible.

It's definetely a typo, megatesla(MT) is not a unit of mass. The real payload is 60 Mg (megagrams) , or 60 tonnes.

Getting to 100 tonnes would require considerably more propellant. Much larger Raptor upper stage and stage 1 stretch, OR 5 cores(which would mean new pads and integration equipment etc.). Not going to happen unless they end up having serious issues with BFR and a new market emerges for ~100 tonne capability.

I am not sure if anyone to date really knows where block 5 FH is supposed to come in for performance, particularly in fully expendable mode.

SpaceX knows it very well, and it reads in their web page, 60 tonnes.

[jpo234]

Updated performance numbers for Falcon Heavy from NASA's Launch Vehicle Performance Website

https://www.reddit.com/r/spacex/comments/99dsxl/elvperf_news_falcon_heavy_performance_updated

[envy887]

NASA LSP finally posted FH Block 5 data. Greater performance than DIVH out to C3=100. 15.4 tonnes to TLI, compared to DIVH at 10.4 tonnes.



https://elvperf.ksc.nasa.gov/Pages/Query.aspx

[abaddon]

From https://elvperf.ksc.nasa.gov/Pages/Vehicles.aspx:

SpaceX has offered two performance levels for the Falcon Heavy on NLS-II. The first level includes booster performance holdbacks to allow for first stage recovery. The second level provides higher performance by utilizing the full vehicle capability, foregoing recovery of the first stage. Both performance levels are included on this site for planning purposes

Any thought on whether "first stage" means the core or core and boosters?

If I were to guess, the first level has booster RTLS and core ASDS, the second has all three expended.

[EDIT] Could also be that the second has boosters landing downrange and expends only the core.  According to Elon that's a 10% performance penalty over fully expendable.  That would make for a more consistent definition of "first stage".

[EDIT2] Anyone know why the Performance Query doesn't provide F9 or FH for LEO or Elliptical orbits?

[Paul451]

Just for completion. FH-R.

[Re: Expended core, recovered boosters. If we assume the partially expendable sits between the other two, with the same curve (same US Isp), then it should roughly match the throw of DIVH out to 20kmē/sē and just slips down to near AV(551) somewhere around 60kmē/sē. For BEO, it may be the most cost and mass effective option.]

[rakaydos]

I dont reconize the Km^2/sec^2 unit type.

What is it's relationship to DV (m/s) and Acceleration? (m/s^2)

[Semmel]

I dont reconize the Km^2/sec^2 unit type.

What is it's relationship to DV (m/s) and Acceleration? (m/s^2)

C3 is called characteristic energy and is a convenience number to describe the energy of an orbit escaping object. The units are energy divided by mass, or J/Kg.

[CorvusCorax]

I dont reconize the Km^2/sec^2 unit type.

What is it's relationship to DV (m/s) and Acceleration? (m/s^2)

See
https://en.m.wikipedia.org/wiki/Characteristic_energy

C3 is positive for escape trajectories and negative for captured orbits. For escape trajectories, C3 is Vinf squared ( where Vinf is the velocity the escaping craft still has after completely escaping the orbital body.) On this page the numbers are relative to earth.


Edit: OK, now that we have the performance curve, who can calculate the exact  Falcon9/FH Upper stage dry mass from these numbers?

[speedevil]

Just for completion. FH-R.

[Re: Expended core, recovered boosters. If we assume the partially expendable sits between the other two, with the same curve (same US Isp), then it should roughly match the throw of DIVH out to 20kmē/sē and just slips down to near AV(551) somewhere around 60kmē/sē. For BEO, it may be the most cost and mass effective option.]

On twitter - of reusability and payload Elon said

Side boosters landing on droneships & center expended is only ~10% performance penalty vs fully expended. Cost is only slightly higher than an expended F9, so around $95M.

[LouScheffer]

Just for completion. FH-R.

From these curves, FH could have launched New Horizons and/or the Parker Solar Probe, but would have required the expended configurations to do either one.  (PSP had a mass of about 2700 kg at separation at a C3 of 60 km^2/sec^2.  New Horizons had a somewhat lower C3 and mass.)

[Paul451]

On twitter - of reusability and payload Elon said

Side boosters landing on droneships & center expended is only ~10% performance penalty vs fully expended. Cost is only slightly higher than an expended F9, so around $95M.

I assume that is meant to be "higher than a fully reusable".

[Edit: I read that expended F9 as expended FH. Hence my confusion.]

But yeah, as I said, I suspect the expended-core variant is the most mass/cost effective for big-throw missions.

[envy887]

Just for completion. FH-R.

From these curves, FH could have launched New Horizons and/or the Parker Solar Probe, but would have required the expended configurations to do either one.  (PSP had a mass of about 2700 kg at separation at a C3 of 60 km^2/sec^2.  New Horizons had a somewhat lower C3 and mass.)

Expended core, but likely recovered side boosters. At least for New Horizons.

[niwax]

On twitter - of reusability and payload Elon said

Side boosters landing on droneships & center expended is only ~10% performance penalty vs fully expended. Cost is only slightly higher than an expended F9, so around $95M.

I assume that is meant to be "higher than a fully reusable".

No, higher than expended F9. As in, the side boosters don't cost a lot, expending the core drives cost both times.

[docmordrid]

Just for completion. FH-R.

From these curves, FH could have launched New Horizons and/or the Parker Solar Probe, but would have required the expended configurations to do either one.  (PSP had a mass of about 2700 kg at separation at a C3 of 60 km^2/sec^2.  New Horizons had a somewhat lower C3 and mass.)

Expended core, but likely recovered side boosters. At least for New Horizons.

And PSP wasn't an off the shelf D4H - it used the Star-48BV kick stage.

[LouScheffer]

Just for completion. FH-R.

From these curves, FH could have launched New Horizons and/or the Parker Solar Probe, but would have required the expended configurations to do either one.  (PSP had a mass of about 2700 kg at separation at a C3 of 60 km^2/sec^2.  New Horizons had a somewhat lower C3 and mass.)

Expended core, but likely recovered side boosters. At least for New Horizons.

And PSP wasn't an off the shelf D4H - it used the Star-48BV kick stage.

Falcon Heavy would need to do the same.  I was counting the kick stage as part of the payload.