Is FH really too big for comsats?

[LouScheffer]

On the other hand, that is also an argument that there won't be much demand for the excess capacity of Falcon Heavy above 10 t.

2 x 7t = 14t, + some overhead to dual manifest.

As I've said before, speculation is great, but when the president of SpaceX goes on record saying they intend to dual-manifest Falcon Heavy, we should stop speculating.

Dual manifesting is great, and is an obvious use of the capacity.  SpaceX would be silly not to offer it, and it will be at least one use of the larger throw weight.

But on the other hand, if a customer had an idea for a heavy satellite (cheap or not), and wanted to buy a full FH,  I can't imagine SpaceX would refuse to sell a rocket to  them on the grounds that they offer a dual-launch capability for smaller satellites.

[Llian Rhydderch]

There are existing Centaur missions that do exactly this.  They must have some (approved) disposal strategy, so presumably you can copy that.

I believe the rule is you either need to put it in a disposal orbit that won't intersect any useful orbit for hundreds of years, OR make it re-enter in 25 years.  A circular orbit above GEO is very cheap in delta-V, and I believe is the preferred disposal solution.

Thanks, Lou.  That is good information.

I wonder what the disposal/graveyard orbit is for the second stage rocket bodies that do that?  Is it the same as the standard commsat parking orbit, or something different?

So extending your point just a bit:  if the Falcon second stage not only put the commsat in GTO as it does today, but also has the operational duration to circularize the orbit to GEO after about 6 hours, it seems to me that it would then also need the (somewhat additional) capability to put itself into a graveyard orbit after some additional time following separation and time to allow for a safe reboost, before ultimately passivating its batteries and propellants.

[john smith 19]

This is a good point, but some of the major cost saving ideas are not available to Ariane customers, since the upper stage cannot restart.  In particular, you cannot delete the apogee motor nor the hydrazine propellant.

I don't know about the cryogenic version but the storable version is capable of 4 re-starts, and has been used on several occasions.

Ideas of trading satellite weight and life expectancy for satellite cost go back to the idea of Shuttle servicing. 

The 3 biggest things operators want are a)More station keeping fuel b) More transponders. c) Failure to meet the interface requirements for the LV. IE Failing the coupled loads analysis.

Higher payload means you can improve the first two and if the structure is not stiff enough then stiffeners can be added more easily that requiring more detailed re-design and complex reanalysis. You could also trade materials and subsystems costs. So Aluminium plates substituted for aluminium or carbon fibre honeycomb structure. Lower tech (cheaper) batteries. I'll note that historically satellite costs have bee 3x that of the launch and operations have been 3x the cost of the satellite.

So if you cut the launch cost logically you need to cut the rest as well.

Time will tell if this is viable. 

[Avron]

On the other hand, that is also an argument that there won't be much demand for the excess capacity of Falcon Heavy above 10 t.

2 x 7t = 14t, + some overhead to dual manifest.

As I've said before, speculation is great, but when the president of SpaceX goes on record saying they intend to dual-manifest Falcon Heavy, we should stop speculating.

I guess we still need to see that FH and the capacity to manufacture at a rate to supply demand, as there will be demand if the current price and reliability numbers are upheld. If the build it, it will be used with that assumption, who knows how big com-stats will then become

[Roy_H]

In the long-run, the role of FH in the SpaceX product line depends on whether they can recover the center core. If they can, then SpaceX could market FH for the GEO comsat market, perhaps using dual-manifests. If they can't. then they will most likely position it as a high-end solution for NRO, NASA, and Bigelow.

I believe that center core recoverability is much easier if launched at Brownsville, Texas, and is in fact the primary driver why SpaceX is so interested in that site. The core stage can come down to an island in the Florida Keys, it does not have to have the huge amount of fuel it would require to go all the way back to the launch site.

In fact I'll stick my neck out even farther and suggest that the Brownsville site would be a poor choice if you do NOT want to recover the center core. That core will come down somewhere and even though that area is mostly ocean there is a chance that an uncontrolled vehicle would crash down on an island and even on someone's private property. Not publicity SpaceX or anyone else would want to get.

[Herb Schaltegger]

I believe that center core recoverability is much easier if launched at Brownsville, Texas, and is in fact the primary driver why SpaceX is so interested in that site. The core stage can come down to an island in the Florida Keys, it does not have to have the huge amount of fuel it would require to go all the way back to the launch site.

Some parts of the Keys are fairly heavily populated and the rest is fairly- to heavily-traveled by residents and tourists. Further, large swathes of it is a protected marine sanctuary.

[Jim]

Everyone thinks FH is too big for comsats.  It can loft maybe 17t to GTO, and the biggest comsats are about 6-7t, so this seems to make sense.  Even Gwen Shotwell said "I'll talk very briefly about Falcon Heavy. So from a commercial perspective Falcon Heavy, it's an over-sized vehicle. It's got more capacity than folks in this room need".

But it seems to me only that the rocket is too big for comsats as they exist today.  If I was a comsat designer, and my boss came to me and told me they bought a FH, and is there anything I could do to make the satellite cheaper/more reliable/more capable with extra mass, I'd have lots of ideas.  Consider that a comsat now is about 6.5t with 4t of empty mass and 3.5t of fuel.  Some ideas might be:

- Drop the apogee motor entirely.   If the FH can put 17t into GTO, it can surely put 7t or so into GEO, assuming it can keep working for the 6 hours or so to reach apogee.  Then use Xenon for station keeping.  This gets rid of  tons of poisonous, sloshing liquid. making handling and testing easier and cheaper.  You can use the extra mass to make things cheaper and more reliable.

- Get rid of all the composites, beryllium, and other expensive materials.  Build it of aluminum.  Up the structural margins so you can eliminate a lot of painstaking design (to keep weight down) and inspection (if the margins are bigger, you can afford to miss small flaws).

- Double up on the solar panels, giving it twice what it needs.  Array deployment failures and solar cell degradation are two of the major failure modes.  This protects against both.

- Similarly, double up on reaction wheels, thrusters, or anything else that is remotely suspicious.

- Where possible, replace space-rated electronics with additional copies of merely mil-spec electronics.

And I'm sure there are many more ways to trade mass for cost or reliability.

Noting that two HS-702 satellites cost Thuraya a billion dollars ( http://space.skyrocket.de/doc_sat/hs-702.htm ), if you could make them for half the cost by letting them be twice as heavy, it would be well worthwhile to get an FH to launch them.

So from a systems life cycle cost viewpoint, it might well be that a FH is a better size, compared to a just-barely big enough rocket lofting a excruciatingly designed and tested satellite made of the finest unobtainium.

Nope.  Major flaw in this line of thinking. Commercial comsats are not going to be designed to be compatible with only one launch vehicle.

[LouScheffer]

But it seems to me only that the rocket is too big for comsats as they exist today.  If I was a comsat designer, and my boss came to me and told me they bought a FH, and is there anything I could do to make the satellite cheaper/more reliable/more capable with extra mass, I'd have lots of ideas.  Consider that a comsat now is about 6.5t with 4t of empty mass and 3.5t of fuel. 

I believe that the Falcon Heavy that will initially fly will lift much less than advertised.  SpaceX seems intent on using up much of the advertised capability to recover the boosters.  A recoverable version seems set to lift only 6.4 tonnes to GTO, for example, based on the prices listed by SpaceX.  In addition, an initial version reusable Falcon Heavy might not lift as much as a Delta 4 Heavy to LEO.  Expendable versions will lift more, but I think it will still be far from advertised at first. 

- Ed Kyle

The higher payloads require crossfeed, and make the core harder to RTLS.

The payload hit increases if they recover boosters, more for the core, more again for the second stage from LEO and yet more recovering second stage from GTO.

I wonder just how much margin a fully recoverable FH would have on the big commsats? And margin is nice to have if you're also getting a good price due to recovering the hardware.

cheers, Martin

I think the GTO for FH will be about 10t, assuming no second stage recovery, but recovery of all first stages.  Here's why I think that.  We know the regular, expendable Falcon 9 can loft 5.3t to GTO (this was just announced, up from 4.85t).  We know the second stage holds 90t of fuel (this was a call-out on the launch audio). Assuming an empty stage of 5t, and a load of 5.3t, ISP=340, the delta-V of the second stage is roughly 7580 m/s.  Increasing the load to 10t decreases the second stage delta-V by 1100 m/s.  So we need this much more from the first stage.

For the expendable first stage, we know it had 386t of fuel (again call-out on the launch audio).  Assuming the (no leg) first stage masses 20t, and no margin for boost back, this gives a delta-V of 4380 m/s.  Assuming the simplest, lowest-performance option - a triple core with 3x the fuel, no crossfeed, all three burn out at the same time, we can still get the extra delta V with 125t of mass at burnout.  That's 20t each for three cores, 2t each for legs, and just under 20t of fuel left for boost-back per core.   This super-simple configuration gives about 26t to LEO, a little less than the Delta-IV as Ed stated, but with booster recovery.

If you reduce the payload to 6.4t, the FH can do this with 50t of fuel *per core* left over.  So there is definitely performance to spare at 6.4t, and if boost-back goes as most think, somewhere about 10t for GTO.  And even without crossfeed you can do better by throttling the center booster until the side boosters run out.  This makes recovering the side boosters easier, but the center one harder, and definitely a more complex analysis.   Without running the numbers, I'd suspect it would not help enough to enable dual launch, but would let FH catch up to Delta IV for LEO.

Of course all these numbers are wild guesses, and should be taken with a lump of salt, until there are real numbers for boost-back and recovery.

[GalacticIntruder]

No, because the FH will use most of the extra performance for first stage/booster RTLS.

“Where I basically see this netting out is Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages,” he said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO “if, for example, we went expendable on the center core.”

  -----Elon Musk per AW

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:41fcfd6c-a6f2-42d5-b20b-52e31a103011


F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

[LouScheffer]

Everyone thinks FH is too big for comsats.  It can loft maybe 17t to GTO, and the biggest comsats are about 6-7t, so this seems to make sense.  Even Gwen Shotwell said "I'll talk very briefly about Falcon Heavy. So from a commercial perspective Falcon Heavy, it's an over-sized vehicle. It's got more capacity than folks in this room need".

But it seems to me only that the rocket is too big for comsats as they exist today.  If I was a comsat designer, and my boss came to me and told me they bought a FH, and is there anything I could do to make the satellite cheaper/more reliable/more capable with extra mass, I'd have lots of ideas.  Consider that a comsat now is about 6.5t with 4t of empty mass and 3.5t of fuel.  Some ideas might be:

[...]
So from a systems life cycle cost viewpoint, it might well be that a FH is a better size, compared to a just-barely big enough rocket lofting a excruciatingly designed and tested satellite made of the finest unobtainium.

Nope.  Major flaw in this line of thinking. Commercial comsats are not going to be designed to be compatible with only one launch vehicle.

Absolutely true.  But Ariane can already loft more than 10t to GTO.  Maybe that's why no one has done it yet, since it up to now it would only allow one launch vehicle.  But if/when FH comes on line there will be two vehicles that can do this, and perhaps then it will be worth trying.

[Jim]

  But Ariane can already loft more than 10t to GTO. 

It is going away

[LouScheffer]

“Where I basically see this netting out is Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages,” he said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO “if, for example, we went expendable on the center core.”

  -----Elon Musk per AW

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:41fcfd6c-a6f2-42d5-b20b-52e31a103011

OK, in this article Musk makes it very clear he is quoting not just any GTO, but a 1500 m/s deficit GTO comparable to that of Ariane (which requires a much smaller plane change).  This is the type of orbit used by SES-8.  But previously he said that SES-8 reserved the whole capacity of the rocket, and now he says they can do recoverable with the same payload.

So I'm guessing that SES-8 ended up with a lot of fuel left over in the second stage, enough that they could have cut off the first stage earlier (to allow for recovery) and still would have had enough delta-V for the final orbit.  It also implies they could have dropped SES-8 into a much better orbit, using the margins that could have been used for recovery to instead reduce the inclination.  After all, if a 3.5t recoverable can get to a 1500 m/s deficit GTO, then a 3.5t expendable should get to a better orbit yet.  But perhaps they were just trying to keep things simple and aim for a good enough orbit on the first try.

Anyway, taking Elon's numbers as gospel and using a 1500 m/s deficit, and assuming 20t of fuel for boost-back in the F9 case, I get 34 t/core in the FH case for the same total delta-V (assuming a simple three-booster in parallel burn).  This seems roughly plausible since the FH boosters stage faster and further down-range.

So if all this is the case, the only remaining contradiction is Ms. Shotwell's comment that the FH is too big.  7t to GTO to with a 1500 m/s  deficit, using the cheapest configuration, seems just about right.    Yes, a more-costly, too-big, less recoverable configuration exists, and maybe it's even cheaper if you can schedule a dual launch of big satellites, but a mostly recoverable launch with one 7t satellite would seem to hit the sweet spot.

[Zed_Noir]

  But Ariane can already loft more than 10t to GTO. 

It is going away

Maybe not if the comsat operators start introducing 7+ mT birds to gain more capability per GSO orbital slot.

[mmeijeri]

Nope.  Major flaw in this line of thinking. Commercial comsats are not going to be designed to be compatible with only one launch vehicle.

Case in point: Europe's flagship Alphabus is being advertised as compatible with the 5m Ariane, but also the 4m Proton.

[MP99]

No, because the FH will use most of the extra performance for first stage/booster RTLS.

“Where I basically see this netting out is Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages,” he said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO “if, for example, we went expendable on the center core.”

  -----Elon Musk per AW

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:41fcfd6c-a6f2-42d5-b20b-52e31a103011


F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

I wonder how low that FH payload would go if they tried to recover the upper stage, too??

Cheers, Martin

[edkyle99]

I think the GTO for FH will be about 10t, assuming no second stage recovery, but recovery of all first stages.  Here's why I think that.  We know the regular, expendable Falcon 9 can loft 5.3t to GTO (this was just announced, up from 4.85t). 

My understanding was that this 5.3 tonne payload (SES-10) was going to be inserted into a sub-synchronous transfer orbit, which is why the mass exceeds the announced GTO capability.

 - Ed Kyle

[Llian Rhydderch]

I wonder how low that FH payload would go if they tried to recover the upper stage, too??

Cheers, Martin

I have always thought that the FH would not be the launch vehicle on which the reusable second stage is added as a flight-ready commercial offering.

Elon has said that while he hoped to have first stage reusability working by 2015, the reusable second stage would be developed as "part of a future design architecture."  Since the FH design was nearly complete at the time he said that, I always took it to mean that we not not see second stage commercial reusability on FH or F9, but on whatever new second stage comes next.  (MCT?  BFR?  or whatever.)

Now if the FH is "too big" for commsats, as is the thesis of the discussion that kicked off this thread, and if there is significant excess payload mass left over, perhaps an early prototype technology development effort on the reusable technology might be started on a modified FH second stage. 

Call it Skyhopper. 

Analagous to the Grasshopper prototype technology development vehicle that was built on an old F9 v1.0 first stage, Skyhopper could be a limited run set of FH second stages with some technology additions to assist SpaceX in testing out some of their reusable second stage design ideas:  TPS, GNC, improved RCS, landing thruster, longer design duration in orbit, etc.

The fact that these prototype technologies would all eat into the mass budget--as well as the fuel required for limited crosstrack, final divert maneuver, and landing--might just be an economic way for SpaceX to take advantage of the "excessive" payload capability that FH for the commsat market that is asserted by some in this thread.

[MP99]

No, because the FH will use most of the extra performance for first stage/booster RTLS.

“Where I basically see this netting out is Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages,” he said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO “if, for example, we went expendable on the center core.”

  -----Elon Musk per AW

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:41fcfd6c-a6f2-42d5-b20b-52e31a103011


F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

Hmm, I wonder if that 7mT figure is for RTLS, or perhaps a "FTLS" launched from Texas and recovered in a Landing site in Florida?

If it's for RTLS, I wonder where the crossfeed + FTLS recovery would sit in that 7-14mT range? If not, what's the hit for RTLS / "rapid reuse".



Also, SpaceX have said that they will have capacity for a large number of cores per year. Elon makes it sound like they'll mostly be making upper stages rather than cores.

Cheers, Martin

[Avron]

F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

Looking at those numbers, simply stated, just shows the capabilities so clearly. 33% for FH-R wow .. Thanks

[LouScheffer]

I think the GTO for FH will be about 10t, assuming no second stage recovery, but recovery of all first stages.  Here's why I think that.  We know the regular, expendable Falcon 9 can loft 5.3t to GTO (this was just announced, up from 4.85t). 

My understanding was that this 5.3 tonne payload (SES-10) was going to be inserted into a sub-synchronous transfer orbit, which is why the mass exceeds the announced GTO capability.

 - Ed Kyle

@pbdes said this about SES-10:  "SpaceX: Falcon 9 can lift 5,300kg to GTO. Published 4,850kg max included 450kg we reserved for ourselves. So 5,300kg SES-10 fits on F9."

I'm sure this a minimal (1800 m/s deficit) GTO, but it's not sub-synchronous.    Likewise, the 10t I estimated above is to this type of orbit.  If you want a GTO compatible with Ariane (1500 m/s) then the FH drops to 7t or so, per Elon's statement.