Discussion Falcon Heavy might match first version of SLS.

[RGClark]

SpaceX has said the improvement of the performance with the Falcon 9 v1.2 would be about 30%. With the upgraded engines and densified propellants applied to the Falcon Heavy, the max payload of the FH to LEO could then also be increased from 53 metric tons to 70 mT.

If so, then the FH, at a ca. $100 million cost, could match the capability of the initial Block I version of the gigadollar SLS at 70 metric tons to LEO.

First Falcon Heavy Launch Scheduled for Spring.
by Jeff Foust — September 2, 2015
http://spacenews.com/first-falcon-heavy-launch-scheduled-for-spring/

Actually, I'm dubious of the cited payload of the Block I SLS as 70 mT. I think it's likely to be closer to 90 mT:

SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 5: A 90+ metric ton first launch of the SLS.
http://exoscientist.blogspot.com/2013/09/sls-for-return-to-moon-by-50th.html


Bob Clark

 

[Kyle]

I believe FH's payload capability include the v1.2 upgrade, so it would be 53 metric tons to LEO (and I believe that's with crossfeed, which SpaceX might not be actively working on, so the payload capability may be less, about on pair with DIVH), so I do not believe FH will be on pair with SLS.

 

[Cosmic Penguin]

(I'm sure this topic has been lingering around for many years already)

 

[Pipcard]

Even if it had a higher lift capacity, the 5.2 m fairing would still be too small for super-heavy payloads, unless you were using it to directly launch small probes to the outer planets.

(meanwhile, the "Heavy" variant of Hatsunia's [fictional] next-generation M-3 launcher is planned to have around the same capacity as SLS Block I, but with larger core and fairing diameters compared to Falcon 9/Heavy)

 

[francisdrake]

I am wondering, if the Falcon Heavy could substitue the SLS in case the SLS financing is cancelled, or development drags along forever. From a reliability point of view, using the often-flown Falcon cores may be better than the rare launches of an SLS. And the lower price tag would allow to compose a mission based on two Falcon launches instead of one SLS.

But what seems significant is the lower capacity of the Falcon beyond LEO. Especially later versions of the SLS show very high payload figures here. I think this mainly due to the cryogenic upper stage providing more dV. I am wondering how the Falcon would perform using a Centaur upper stage (although Boeing will probably never allow that )

 

[ISProgram]

The initial SLS version was mandated BY LAW to have a capacity of 70mT to LEO, but that was with 4-segmented SRBs. Last I heard it was ~86 mT to LEO.

Gotta find the source though, last saw it months ago...

 

[K_Jameson]

Even if it had a higher lift capacity, the 5.2 m fairing would still be too small for super-heavy payloads, unless you were using it to directly launch small probes to the outer planets.

I agree; in fact, baseline SLS could work with fairing up to 10 or even 12 meters, that are simply impossible to fly with the current FH configuration. Very profitable interplanetary missions will be possible with FH, anyway.

I think that SpaceX should make its crossfeed system functional, at first. And then speak of payload capabilities.

I'm also convinced that the 70 tons capability for the baseline SLS is a pretty cautious statement (in fact, the 70 mT is only the Congress requirement). STS, with three SSME instead of four, old SRB and no cryogenic upper stage, had at least 105 tons of payload, if we take in account the orbiter itself...

(Returning to old times, even the 118 mT figure that is generally accepted for the Saturn V is pretty underestimated. In fact the design limit was higher - maybe over 130/135 mT.)

 

[Andy44]

Yes, the STS stack put quite a huge mass into LEO. That system had legs in it that were never fully developed. Shuttle-C and other variants would've been true heavy lifters.

 

[Dantassii]

I think that SpaceX should make its crossfeed system functional, at first. And then speak of payload capabilities.

The Falcon Heavy as designed already has crossfeed built in the system so that when the 2 side boosters are released the center line booster has a full fuel load. In fact, my understanding is that event is what determines when the 2 side boosters are released, when all the fuel is in the center line booster and the side boosters are empty.

I suspect that the reason the Falcon Heavy doesn't have the throw weight of a Saturn V or a SLS beyond LEO is because it's effectively a 2 stage vehicle with all stages being LOX-RP1. Comparing the Falcon Heavy to the 2 stage Saturn V that boosted Skylab into LEO is an apples to apples comparison. If the 2nd stage of the Falcon Heavy was replaced with 2 stages, both LOX-H2, then it would probably have a more comparable throw weight beyond LEO. Then you'd still have to deal with the payload fairing issue. Sadly, using LOX-H2 in any stage of the Falcon would increase the cost of the vehicle well outside it's current price range, which is 1 of the main selling points of the Falcon rocket family.

Dantassii
HUMONGOUS IMS shipbuilder

 

[francisdrake]

The Falcon Heavy as designed already has crossfeed built in the system

On the crossfeed capability I read that it will be kind of simplified: The side boosters will supply their own 9 engines + 3 neighbouring core engines. The central 3 core engines are supplied by the core stage. After staging the core stage continues on these 3 engines only. While this does not provide a fully fueled core stage after separation, it tremendously simplifies plumbing. Looking forward to see the Heavy in action!

 

[Dantassii]

On the crossfeed capability I read that it will be kind of simplified: The side boosters will supply their own 9 engines + 3 neighbouring core engines. The central 3 core engines are supplied by the core stage. After staging the core stage continues on these 3 engines only. While this does not provide a fully fueled core stage after separation, it tremendously simplifies plumbing. Looking forward to see the Heavy in action!

That's the first time I've heard anything about exactly how the crossfeed capability in the Falcon Heavy is being implemented. Bottom line is, all 3 of the 1st stage cores are identical in terms of propulsion (9 engines) and tank sizes. The only way that the center core would be able to burn longer than the 2 side cores if if there was some sort of crossfeed going on during the 1st stage burn.

I do think that if Falcon is ever going to be a viable "beyond GTO" vehicle that some sort of high energy (read LOX-H2) upper stage(s) are going to have to be built. While this will increase the cost per vehicle by quite a bit, it is the only way that this vehicle will be able to compete with the Atlas and Delta vehicles in throw weight beyond GTO, let alone compete with the SLS.

This all assumes that you are still working in the land of "1 vehicle to do everything" mode. If you build a vehicle specifically to take people and cargo from LEO to beyond GTO, then all the Falcon (of 1 flavor or another) has to do is get this vehicle into LEO, something the Falcon family is VERY good at doing it seems, at least for a reasonable price.

Dantassii
HUMONGOUS IMS shipbuilder.

 

[Urwumpe]

That's the first time I've heard anything about exactly how the crossfeed capability in the Falcon Heavy is being implemented. Bottom line is, all 3 of the 1st stage cores are identical in terms of propulsion (9 engines) and tank sizes. The only way that the center core would be able to burn longer than the 2 side cores if if there was some sort of crossfeed going on during the 1st stage burn.

Or the core engines throttled down, if there is no or just little cross-feed.

 

[Andy44]

Launch vehicle families are largely modular, so there could be a new Falcon model with a high energy upper stage if there is a market for it, while keeping Falcon 9 all kerosene if they want. The key would be to make sure Falcon 9 can keep cost down by not subsidizing the high energy project.

 

[dman]

SpaceX has said the improvement of the performance with the Falcon 9 v1.2 would be about 30%. With the upgraded engines and densified propellants applied to the Falcon Heavy, the max payload of the FH to LEO could then also be increased from 53 metric tons to 70 mT.

Thats assuming they dont blow it up...........

 

[Urwumpe]

Launch vehicle families are largely modular, so there could be a new Falcon model with a high energy upper stage if there is a market for it, while keeping Falcon 9 all kerosene if they want. The key would be to make sure Falcon 9 can keep cost down by not subsidizing the high energy project.

Yes, there would have to be a proper unit cost analysis first to check how much a launch with a high energy upper stage would change the profits of the whole company... but that's standard business administration.

 

[ISProgram]

SpaceX has said the improvement of the performance with the Falcon 9 v1.2 would be about 30%.

Let me just point out that LEO performance and GTO performance do not scale up linearly, and SpaceX only said that the performance improvement would be 30%.

They've never said WHICH performance was increased by 30%, and it's possible that "performance" is not referring to "mass put in orbit" at all.

 

[N_Molson]

And they still have to develop a reliable Falcon 9. This thread is a flame-bait :dry:

 

[Hlynkacg]

And they still have to develop a reliable Falcon 9. This thread is a flame-bait :dry:

Define "reliable", SpaceX is batting 15 for 16 at the moment.

 

[Andy44]

Define "reliable", SpaceX is batting 15 for 16 at the moment.

Exactly. Falcon 9 reliability is in the same ballpark as most modern launchers so far.

 

[Urwumpe]

Define "reliable", SpaceX is batting 15 for 16 at the moment.

Except that most of the 16 launches had been done by a different configuration and alone the known anomalies during flight, that had to be documented during USAF and NASA launches, suggest a much lower quality than the PR-friendly statistic tells.

Also, remember that the Saturn V also had a much better statistic in its few launches - despite only plain luck preventing it from killing its crew multiple times. Successful missions alone are no indication of quality (The Space Shuttle had 24/24 successes before STS-51L)