Is FH really too big for comsats?

[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:

- 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.

[cleonard]

No one ever didn't buy a launch service because the vehicle had too much performance.   It all has to do with cost.  If the Falcon Heavy is the least expensive option it will be chosen regardless how much excess performance it may have.

 

[ey]

You could always launch two satellites on one rocket.

Does the 17t include fuel needed for RTLS for the booster cores? http://www.spacex.com/falcon-heavy quotes the payload as 21t to GTO. Having extra performance margin would certainly be useful down the road for second stage RTLS, which may need to be heavier to deal with high speed reentry.

[cuddihy]

DoD could fill lots of secondary payload space to GEO if it was cheap enough.

[Llian Rhydderch]

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.

---snip---

I like the idea and think it is a good one to chew on.  I'm glad you brought it up by starting this thread.

Just one comment on the dropping the apogee kick motor and using the FH second stage to circularize to a near-geosynchonous orbit.  If the second stage does that job, it leaves the entire mass of the second stage up in orbit as a derelict in high-Earth orbit indefinitely.   

Even if it could drop the commsat off and then get the rocket body to the "approved" graveyard orbit, I'm guessing it might violate the sort of launch licenses that are granted for US launches nowadays, which generally require engineering analysis projections that show orbital decay and rentry within 25 years.  A GTO orbit leaves the rocket body/second stage dropping down to LEO altitude once each orbit for the next 25 years, which generally is sufficient to decay the orbit and cause reentry during the allotted period.

But that's just a detail.  Overall, I think your suggestion that we discuss and bluesky on the question of "what might commsat designers do if they had a larger mass budget on a lower cost launch service?"  is a good one!

[Dave G]

Quote from  Gwynne Shotwelll back in April 2010.

The Falcon 9 Heavy ... that will be a very important vehicle for SpaceX.  That vehicle gets about 18 tons to GTO, so that dramatically changes the satellite communications business.  If you dual-manifest  two big satellites on a Falcon 9 Heavy, you’ve cut the launch costs of that mission by almost a factor of 2.  So that’s an important vehicle for us and for the industry.

http://www.thespaceshow.com/detail.asp?q=1348
(starting around 33:15 into the program).

[Roy_H]

Interesting discussion on using the excess capacity to deliver the satellite to GEO. How about a tether launch, where the second stage goes to GTO and uses a tether to swing the satellite into GEO. This would simultaneously lower the orbit of the upper stage so it would fall back to earth. I am sure they could figure out a tether length and timing so that it re-entered at the right angle and entry point to return to launch site.

With full re-useability, side boosters, main core, and upper stage, the cost should be very competitive.

[ChrisWilson68]

The tether is a bunch of new complexity that costs money to develop and build and something else that can go wrong.  The point is that FH has a lot of performance left, so we can just use the performance that's already there to circularize the orbit at GEO.  Making the stage survive a few more hours so it can do the circularization burn is going to be a lot simpler than designing and building a tether system that can transfer that much delta-v.

[dorkmo]

- 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.

i dont know much about space circuitry but what would be the mass difference? batteries?

fun discussion

[luinil]

IF the stage does the circularization, you'll want to have extra fuel to move the stage on a junk depot orbit (and have more space junk) or return to earth for reuse.

[butters]

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.

[go4mars]

Bells and whistles.  Add standard optical interferometry PR scopes for pursuing the Fermi paradox.
Redundantly test heavier/cheaper ideas.

[a_langwich]

I think SpaceX's pricing shows how they intend to compete:
->   $77M if the payload is less than 6.4 tons, which is what the non-heavy competition is lifting (ie, Proton at ~$100M?). 

->   $135M for greater than 6.4 tons, which would only otherwise be an Ariane 5 ECA single payload manifest ($220M), or Delta IV Heavy ($300M+). 

Note that $135M is greater than $100M for a Proton flight, so it's NOT cheaper to buy the full Falcon Heavy than it is to buy a Proton launch.  If you have a 6-ton satellite, and if SpaceX did not allow you to buy a partial FH launch, Falcon Heavy would be too much for you.  SpaceX has stepped in, like Ariane does with the Ariane 5, and allowed satellite makers to buy partial launches.

I doubt going for heavier materials would halve the cost of a satellite; if that were true, Ariane 5 ECA would get a lot more solo payloads of heavy-but-cheaper satellites.  It can launch 1 satellite at 10mT, but instead it has launched almost entirely pairs to GTO, 2 5mTs or 6+4mT etc.  So, if Ariane 5 ECA is $220M whole, $110M half, we can reason that satellite operators are not willing to spend an extra $110M to go from 5mT to 10mT.  In the Thuraya example, they could not save $110M or greater by adding the extra weight, apparently.

The question is how will SpaceX use Falcon Heavy for the {6.4 ton, $77M} GTO flights:  will they launch them mostly empty, and accept less money for the launch?  Or will they try to dual-manifest, and struggle as Ariane has to fill both slots?  Ariane has fairly often filled one of its slots with a satellite associated with its member nations, ie from the pool of guaranteed customers it has.  SpaceX has no such pool, so they would have to rely on their fabulous prices.  I suppose it's conceivable they could even triple-manifest, although those opportunities probably won't be often, unless new markets open up, or people are willing to wait extremely long times at that price point.

I could see SpaceX using Falcon Heavy extra payload space to launch test articles of their ideas for in-space innovation, in the same way they've packed post-separation reusability studies in Falcon 9 flights with spare performance.  No doubt they will also be working on reusability, too, where it makes sense.  I'm not sure it makes sense on a second stage headed to GTO, but maybe they've got ideas.

[ChrisWilson68]

Yes, the fact that satellite makers haven't built larger birds for Ariane 5 is a good point against the idea that costs can be reduced by making bigger satellites.  However, in the past Ariane 5 has been the only option for such large satellites.  Satellite owners always seem to want the option of more than one launch provider, and until now a 10 t satellite would lock them into Ariane 5.  With Falcon Heavy coming on line, now there will be two options for 10 t payloads to GEO.  So we might see more interest in 10 t comms satellites.

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.

Of course, all of this applies only to commercial satellites for which Ariane 5 is an option.  For U.S. government payloads, it's possible they would be made much bigger to bring the costs down if Falcon Heavy were available.  It's also possible U.S. government payloads would get much bigger to make use of Falcon Heavy not to reduce costs but to pack more functionality in -- DoD seems to have more fun packing in more features and making things more expensive rather than making them less so.

[CuddlyRocket]

No one ever didn't buy a launch service because the vehicle had too much performance.   It all has to do with cost.  If the Falcon Heavy is the least expensive option it will be chosen regardless how much excess performance it may have.

Exactly. The question should not be whether FH is really too big for comsats but whether it is really too expensive for comsats!

[MP99]

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

[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:

- 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.

---snip---

Just one comment on the dropping the apogee kick motor and using the FH second stage to circularize to a near-geosynchonous orbit.  If the second stage does that job, it leaves the entire mass of the second stage up in orbit as a derelict in high-Earth orbit indefinitely.   

Even if it could drop the commsat off and then get the rocket body to the "approved" graveyard orbit, I'm guessing it might violate the sort of launch licenses that are granted for US launches nowadays, which generally require engineering analysis projections that show orbital decay and rentry within 25 years.  A GTO orbit leaves the rocket body/second stage dropping down to LEO altitude once each orbit for the next 25 years, which generally is sufficient to decay the orbit and cause reentry during the allotted period.

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.

[Dave G]

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.

[LouScheffer]

[...]

I doubt going for heavier materials would halve the cost of a satellite; if that were true, Ariane 5 ECA would get a lot more solo payloads of heavy-but-cheaper satellites.  It can launch 1 satellite at 10mT, but instead it has launched almost entirely pairs to GTO, 2 5mTs or 6+4mT etc.  So, if Ariane 5 ECA is $220M whole, $110M half, we can reason that satellite operators are not willing to spend an extra $110M to go from 5mT to 10mT.  In the Thuraya example, they could not save $110M or greater by adding the extra weight, apparently.

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.

For the lower cost satellite market to develop, it would be good if both SpaceX and Ariane could develop this option (5t dropped off in GEO).  Otherwise you are single-sourced, and that's always risky and puts you in a very bad negotiating position.

[edkyle99]

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. 

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

[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

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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

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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.

[go4mars]

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

2nd stage reuse from GTO will be incredibly expensive to payload mass.  If FHR is 7 tonnes with no upper stage reuse, I believe the thread title can be answered "no", and one could argue it's part of the rationale for the new 10 meter core.  Full reusability that is.

 But this was chatted through years ago during "reusable powered clamshell" discussions.  I don't remember which threads that was spread out on. 

[Dave G]

F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

Also note: SpaceX has said FH-Booster R should be relatively straightforward,
but FH-R will be much more difficult.

In other words, FH-R will take a lot longer, if it ever happens at all.

[Roy_H]

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

2nd stage reuse from GTO will be incredibly expensive to payload mass.  If FHR is 7 tonnes with no upper stage reuse, I believe the thread title can be answered "no", and one could argue it's part of the rationale for the new 10 meter core.  Full reusability that is.

 But this was chatted through years ago during "reusable powered clamshell" discussions.  I don't remember which threads that was spread out on.

I disagree with your statement about expense of recovery of upper stage. Yes it will be very difficult because of the requirement for thermal shielding etc, but not high in fuel costs. Payload hit will be minimal. The upper stage will remain in orbit (most likely 1 full day) until it is in the right position to return to launch site when re-entering earth atmosphere. It does not have to have a long boost back trajectory like the first stage.

[Coastal Ron]

F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

Also note: SpaceX has said FH-Booster R should be relatively straightforward,
but FH-R will be much more difficult.

In other words, FH-R will take a lot longer, if it ever happens at all.

Haven't heard any mention of cross-feed recently, but that was supposed to be required for the 53mt version.  Since the cross-feed system would likely add more complexity and weight, I wonder how that would affect reusability?  And where does that come into play with the capacities to GTO?

For instance, I would imagine that the FH-Expendable could be cross-fed, but FH-R would not (or maybe even "could not")?

Lot's of combinations of factors at play here.  But if there are lots of combinations of capabilities, then that would mean that Falcon Heavy could cover the entire range of comsat needs, and still be less expensive than competitors like Ariane 5 and Atlas/Delta.

Or SpaceX may self-limit their configurations to cut down on managing too many variations.

[guckyfan]

Also note: SpaceX has said FH-Booster R should be relatively straightforward,
but FH-R will be much more difficult.

I don't think it is more difficult. It just takes a huge amount of fuel so causes a big payload hit. But if you have a comsat within that weight range you can still do it.

[Roy_H]

Haven't heard any mention of cross-feed recently, but that was supposed to be required for the 53mt version.  Since the cross-feed system would likely add more complexity and weight, I wonder how that would affect reusability?  And where does that come into play with the capacities to GTO?

For instance, I would imagine that the FH-Expendable could be cross-fed, but FH-R would not (or maybe even "could not")?

Cross-feed and re-useability are separate issues and not dependent on each other. The 53mT capacity is ultimate, that is using both cross-feed and expendable. No reason why a cross-feed core stage cannot be landed, and I think it is only practical from the Brownsville, Texas launch site where the center core would land in the Florida Keys.

[Dave G]

Cross-feed and re-useability are separate issues and not dependent on each other. The 53mT capacity is ultimate, that is using both cross-feed and expendable.

53mT is for low earth orbit, and not relevant for comsats, so its off-topic for this thread.

For the previous numbers:

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

I believe these are all cross-fed.  For a cross-fed FH, returning the center core back to the pad (fully and rapidly reusable) is hard.   The center core is almost like a second stage.

[LouScheffer]

Cross-feed and re-useability are separate issues and not dependent on each other. The 53mT capacity is ultimate, that is using both cross-feed and expendable.

53mT is for low earth orbit, and not relevant for comsats, so its off-topic for this thread.

For the previous numbers:

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

I believe these are all cross-fed.  For a cross-fed FH, returning the center core back to the pad (fully and rapidly reusable) is hard.   The center core is almost like a second stage.

My calculations indicate they don't need crossfeed, or even center throttling, to get 7mt to GTO.  Just burn all three in parallel, so recovering the middle booster is no harder than the others (though they are all harder than the F9, since they burn out further downrange and going faster than the single core case).

Throttling down the center core until booster sep (as Delta-IV does) and ultimately cross-feed, will increase payload but make the center booster harder to recover, as many have pointed out.  I suspect only SpaceX can figure accurate numbers for these cases, and even then only after they recover a few stages and have a good idea of the fuel needed.

[sdsds]

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

Yes. In particular the propellant needed for non-destructive re-entry propulsion could consume much of the "excess" mass budget.

Consider the case of payload delivery to an 80000x295 km transfer orbit. A destructive re-entry from there could be accomplished with a 14 m/s retrograde burn at apogee. That puts the perigee at 50 km, where the velocity would be 10,743 m/s. In contrast consider a two-burn re-entry profile, first reducing the apogee to a 2000x295 km orbit and then reducing perigee to 50 km. For that approach the velocity at the 50 km perigee would be a somewhat more survivable 8,377 m/s, but the delta-v to perform the maneuvers is something like 2,440 m/s.

Translating that 2,440 m/s of delta-v into propellant mass would require making assumptions about the dry mass of the stage. But it's fairly clear that maneuvers of that size would require lots of propellant!

(WARNING: My orbital mechanics spreadsheet could be wrong!)

[Dave G]

My calculations indicate they don't need crossfeed, or even center throttling, to get 7mt to GTO.

OK, so that leaves:

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

that use cross-feed.

In other words, with cross-feed, the center core is always expendable.

[Lars_J]

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F9-R 3.5mT GTO

FH-R 7mT GTO

FH-Booster R 14mT GTO

FH-Expendable 21mT GTO

Does anyone know how these options translate to LEO payload capacity?

[Dave G]

Does anyone know how these options translate to LEO payload capacity?

Off topic for this thread.  For LEO, F9 is more than adequate for any comsat.

[MP99]

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

2nd stage reuse from GTO will be incredibly expensive to payload mass.  If FHR is 7 tonnes with no upper stage reuse, I believe the thread title can be answered "no"...

Agreed.

Cheers, Martin

[Lobo]

Also note: SpaceX has said FH-Booster R should be relatively straightforward,
but FH-R will be much more difficult.

I don't think it is more difficult. It just takes a huge amount of fuel so causes a big payload hit. But if you have a comsat within that weight range you can still do it.

This is why I think (my speculation) that one of the "markets" for a SpaceX fully reusable, HLV with 10m core, is these heavier payloads to GTO, GSO and escape.  (Or two payloads like Ariane 5)   It will have a lot of margin so that big reusable upper stage can get to those orbits, deploy the payload, and then do the burns necessary to get back to Earth and land propulsively.  A bit like how STS was a HLV to take EELV-heavy payloads to LEO.  A HLV that could take EELV-heavy payloads BLEO (being more powerful and lighter than the Shuttle, obviously)
If it can be processed and reflown affordably, then that and your fuel are your major launch costs, not the hardware itself. It could replace FH for those types of payloads, while acting as a test bed and money generator for their eventual MCT and Mars abitions.

[CuddlyRocket]

If [a SpaceX fully reusable, HLV] can be processed and reflown affordably, then that and your fuel are your major launch costs, not the hardware itself. It could replace FH for those types of payloads, while acting as a test bed and money generator for their eventual MCT and Mars ambitions.

The cost of construction still has to be amortised over the expected number of flights and I'd expect that to exceed at least the fuel costs. But I think the construction costs may well be less than those of an FH, so I think there's a good chance it will replace the FH for all types of payloads.

[Burninate]

There is an intermediate option where 2 cores are recovered at significant payload cost in proximity to the launch site, and the third burns up in a hypersonic reentry.  This might allow for launching (as a blind guess) maybe a 13 ton (EELV class) payload to GTO, at a very similar cost to a Falcon 9 launch.

The complexity of hypersonic reentry, and of the organizational & liability overhead of recovering something a thousand kilometers downrange, is likely to push the third-core reusability back a ways.

edit: If the boosters separated while still in the lower atmosphere, *very* early, effectively generating two vertical Grasshopper tests plus a normal F9 launch from 10km height, would that account for the payload cost structure seen now, without multiple payload piggybacking?

[Adaptation]

This is how I understand the situation, sorry if its a little basic. 

So comsats like GEO so ground stations don't have to track.  From an RF point of view you want separation between you and anyone else using a similar frequency.  With a few degrees of separation and decent gain antennas (directional) you can reuse all the same frequencies as another satellite without any interference issues.  But GEO lies on the equator and there are only a few slots over a range of latitudes with enough separation. 

And now the question.

How much 'station keeping' would it require to maintain an artificial 'stationary' orbit that would naturally be inclined 4° but is purposely kept 4° north +-0.5°.  Would a large solar array and electric thrusters be feasible to maintain this position? 

Alternatively (and even more futuristically) could a long tether with a counterweight be used to keep a satellite in such a position.

[douglas100]

The plane of the orbit you describe does not pass through the centre of the Earth. Continuous thrusting is needed to maintain such an orbit.

Your question really belongs in Advanced Topics.

[Proponent]

How much 'station keeping' would it require to maintain an artificial 'stationary' orbit that would naturally be inclined 4° but is purposely kept 4° north +-0.5°.  Would a large solar array and electric thrusters be feasible to maintain this position?

Absolutely not.  The acceleration of gravity at GEO is about 0.3 m/s².  Since 4^o is equivalent to 0.07 rad, the required acceleration would be about (0.07)(0.3 m/s²) = 0.02 m/s².  That doesn't sound like much, but over a day (86,400 s), it's a delta-V of 1800 m/s.

An appropriately-angled solar sail might offer some hope, but it's going to be a little complicated, especially if occasional passages through the earth's shadow need be factored in.  I think Robert Forward or Colin McInnes may have written something about this.
 

Alternatively (and even more futuristically) could a long tether with a counterweight be used to keep a satellite in such a position.

That would be an interesting dynamics problem.  The tether will be a few thousand kilometers long and will itself present a substantial cross-section and possible collision hazard.

EDIT: "dynamics problems" -> "dynamics problem";
           "1800 km/s" -> "1800 m/s", per MP99 (thanks!)

[LouScheffer]

This is how I understand the situation, sorry if its a little basic. 

How much 'station keeping' would it require to maintain an artificial 'stationary' orbit that would naturally be inclined 4° but is purposely kept 4° north +-0.5°.  Would a large solar array and electric thrusters be feasible to maintain this position? 

Alternatively (and even more futuristically) could a long tether with a counterweight be used to keep a satellite in such a position.

It would take far too much fuel to 'hold' a satellite there, even with electric propulsion.  And a tether does not help, since the forces are towards the equator and would put the tether in compression, not tension. 

However, a satellite in such a position will naturally oscillate back and forth from north to south.  If instead of one satellite in the slot, you put (for example) 8, and space them out and let them all oscillate, then there would always be one north of the equator, one near the equator, and one south of the equator, though which one is in which position will switch.  This might be a sensible way to trade off satellite cost for increased capability.

[john smith 19]

Judging by the expected huge payload hit stage reuse is taking I'd say "no."

This is a vehicle that's expected to have an expendable  payload to LEO of 53 tonnes.

Yet once you start factoring payload hits due to reuse you're down to what? 6 tonnes?

Staggering.

That said putting a 53 tonne tug up which stayed in orbit and handled the GTO process might make a lot of sense. the question would then be who would own (and develop) such a vehicle?

[Elmar Moelzer]

Yet once you start factoring payload hits due to reuse you're down to what? 6 tonnes?

6 tonnes to GTO

[Excession]

An appropriately-angled solar sail might offer some hope, but it's going to be a little complicated, especially if occasional passages through the earth's shadow need be factored in.  I think Robert Forward or Colin McInnes may have written something about this.

Using solar sails to create displaced orbits has been proposed and the dynamics worked out. It's very viable if you have a light enough solar sail.

[Llian Rhydderch]

Yet once you start factoring payload hits due to reuse you're down to what? 6 tonnes?

6 tonnes to GTO

So that seems to provide at least one answer to the original poster:

If SpaceX were to get the reusable parts of FH working, Falcon Heavy is not too big for commsats!

YMMV, and you can make different assumptions, in which case different answers might fall out.

[Adaptation]

It would take far too much fuel to 'hold' a satellite there, even with electric propulsion.  And a tether does not help, since the forces are towards the equator and would put the tether in compression, not tension. 

Using solar sails to create displaced orbits has been proposed and the dynamics worked out. It's very viable if you have a light enough solar sail.

Thanks I guess its sifi for now. 

Your question really belongs in Advanced Topics.

Sorry, the main subquestion of the tread was what could you do as a comsat with a bunch of extra mass, that was my idea on how to utilize it.

If instead of one satellite in the slot, you put (for example) 8, and space them out and let them all oscillate, then there would always be one north of the equator, one near the equator, and one south of the equator, though which one is in which position will switch.  This might be a sensible way to trade off satellite cost for increased capability.

Perhaps an elliptical constellation similar to what Sirius XM does could get by with fewer.  For terrestrial receivers a simple low cost parabolic based dish can be designed to receive a broad beam width in azimuth and a narrow one in elevation.  Would it be amicable to co launch a constellation like this on a FH or would the need for different insertion point consume too much delta-v?

[Lar]

Solar sails and "orbits" that don't go through the center of mass of the orbital system are off topic for this thread.  If someone can point me to a good topic area in Advanced concepts via PM I will move the posts prior to this note there. Posts after this note will be trimmed.

I love to go off topic but that's really FAR afield.

Edit: Trimmed one after this line I drew. I sent the text back to the author...   this time... Next time? maybe I will, maybe I won't. Why chance it! Find the right place so your nuggets of wisdom don't get lost for all eternity in the howling aether...

[john smith 19]

So that seems to provide at least one answer to the original poster:

If SpaceX were to get the reusable parts of FH working, Falcon Heavy is not too big for commsats!

YMMV, and you can make different assumptions, in which case different answers might fall out.

Yes.

Although I suspect the answer is highly counter intuitive to most people (well it was for me.    ).

[Ludus]

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.

I think part of the OP's point goes way beyond the technical details of FH and FHR. It's that a large part of the enormous costs associated with comsats or indeed space hardware in general come from very limited payloads and enormous costs imposed by current launch vehicle technology. If reusability drives launch costs down by an order of magnitude or two, and SpaceX continues it's plans to build much larger launch vehicles that are also rapidly reusable, there are hundreds of ways to use that vastly larger mass budget to lower costs.

[AncientU]

At a recent Astro technology conference, I was discussing the display piece of an extremely light-weighted mirror (1.25m I believe).  The light weighting was 95%!  I asked how much would it cost if it was only light weighted 90% -- answer was 'half as much.'  This illustrates some of the potential when we back off of the bleeding edge of light-weighting.

[john smith 19]

I think part of the OP's point goes way beyond the technical details of FH and FHR. It's that a large part of the enormous costs associated with comsats or indeed space hardware in general come from very limited payloads and enormous costs imposed by current launch vehicle technology. If reusability drives launch costs down by an order of magnitude or two, and SpaceX continues it's plans to build much larger launch vehicles that are also rapidly reusable, there are hundreds of ways to use that vastly larger mass budget to lower costs.

I think you should add "recoverability" to that list.

Big life limiting failure modes for comm sats are a)Running out of station keeping fuel b)Loosing pointing accuracy.

Being able to therefor a)Refuel and b) Replace on orbit certain components would reduce satellite replacement costs quite substantially, but only if the sats can be brought back to LEO or serviced in GEO (and restored there). 

[Adaptation]

I think you should add "recoverability" to that list.

Big life limiting failure modes for comm sats are a)Running out of station keeping fuel b)Loosing pointing accuracy.

Being able to therefor a)Refuel and b) Replace on orbit certain components would reduce satellite replacement costs quite substantially, but only if the sats can be brought back to LEO or serviced in GEO (and restored there). 

The delta-v required by a service vehicle is non trivial.  Electric pulsive service unit could help.  I would think designs would have to be highly standardised and modular for this kind of repair to be practical, and it would be best with nearly universal adoption.  Given the state of ITAR restrictions I don't see this as something that could be american led effort.

[john smith 19]

The delta-v required by a service vehicle is non trivial.  Electric pulsive service unit could help.  I would think designs would have to be highly standardised and modular for this kind of repair to be practical, and it would be best with nearly universal adoption.  Given the state of ITAR restrictions I don't see this as something that could be american led effort.

Actually not as much as you might think.

NASA Goddard has been very active in the mechanical and electrical engineering needed to design "Orbital Replaceable Units" since the 1970's. Their biggest success was with Hubble where it's on orbit servicing missions have substantially extended its life. There are several conference proceedings on the subject.

Key features are a)Retainable fastners (so bolts don't float away) b)Restraining modules so they reliably interlock (that includes insuring electrical connectors are rigidly mounted (like computer boards going into a PC motherboard) rather than just a plug on the end of a bundle of wires, like a monitor cable.

Agreement is helpful but it's more a state of mind and the willingness to (possibly) add a bit of weight.

The simplest upgrade would be to allow in flight refueling (of either hypergols or Xenon) to extend lives.

Given the toxicity of hypergols I think current fittings are 2 part sealable IE when the join separates both ends seal off from the atmosphere. The trick is to put those connections on the outside of the sat, with some kind of docking markers.

I'd admit getting a comm sat with hypergol station keeping back to LEO is likely easier than ion thrusters as it can deliver a higher thrust kick, but I think it's possible with ion thrusters as well.

[Jim]

The delta-v required by a service vehicle is non trivial.  Electric pulsive service unit could help.  I would think designs would have to be highly standardised and modular for this kind of repair to be practical, and it would be best with nearly universal adoption.  Given the state of ITAR restrictions I don't see this as something that could be american led effort.

Actually not as much as you might think.

NASA Goddard has been very active in the mechanical and electrical engineering needed to design "Orbital Replaceable Units" since the 1970's. Their biggest success was with Hubble where it's on orbit servicing missions have substantially extended its life. There are several conference proceedings on the subject.

Key features are a)Retainable fastners (so bolts don't float away) b)Restraining modules so they reliably interlock (that includes insuring electrical connectors are rigidly mounted (like computer boards going into a PC motherboard) rather than just a plug on the end of a bundle of wires, like a monitor cable.

Agreement is helpful but it's more a state of mind and the willingness to (possibly) add a bit of weight.

It is a lot of weight since the spacecraft would have to be designed for orbital access vs weight and ease of terrestrial assembly.

Standardization is doable within a specific spacecraft manufacturer but not worldwide.  There isn't going to be a "universal" system. Just as car, planes and trains aren't. ITAR isn't the issue, it is corporate "secrets" and propriety information.  Refueling would be easier to do. 
Satellite are like computers, they have common subsystems (chips and boards) but not common enclosures and mounting methods.

[john smith 19]

It is a lot of weight since the spacecraft would have to be designed for orbital access vs weight and ease of terrestrial assembly.

I think that depends on how much of the satellite is designed for on orbit repair/upgrade. My instinct would be propellant, torque wheels and batteries. Provided the sat passes on orbit checkout torque wheels seem to be the big item.

Standardization is doable within a specific spacecraft manufacturer but not worldwide.  There isn't going to be a "universal" system. Just as car, planes and trains aren't. ITAR isn't the issue, it is corporate "secrets" and propriety information.  Refueling would be easier to do. 
Satellite are like computers, they have common subsystems (chips and boards) but not common enclosures and mounting methods.

I'd say a sizable part of the sections most likely to fail are on the bus side of most satellites so are likely to be quite standardized to begin with.
Actually given the high cost of space qualifying new parts I'd guess the range of parts used is quite small.

The real issue AFAIK is that satellites seem to be assembled with lots of wiring looms and plug/sockets which are no problem for humans but a royal PITA for robotic assembly/disassembly.

[Jim]

torque wheels

And they are usually buried in the spacecraft.

[Jim]

I'd say a sizable part of the sections most likely to fail are on the bus side of most satellites so are likely to be quite standardized to begin with.
Actually given the high cost of space qualifying new parts I'd guess the range of parts used is quite small.

The real issue AFAIK is that satellites seem to be assembled with lots of wiring looms and plug/sockets which are no problem for humans but a royal PITA for robotic assembly/disassembly.

No, like I said, they are contractor specific.   The buses are unique to each contractor.  And there are more than ten contractors/organizations in just the US   Most systems are installed on the basic structure of the vehicle or on inside of the exterior panels (using the outside as radiator).  And there are a lot of parts to chose from.

[LouScheffer]

torque wheels

And they are usually buried in the spacecraft.

On Kepler, at least, they were mounted on the outside of the structural panels, though probably covered with MLI.

http://spaceref.com/exoplanets/kepler-mission-manager-update-pointing-test.html