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