F9H-Centaur hybrid

[Skipper]

Would it be possible to replace SLS with extended Centaur stage launched on top of Falcon Heavy?

My rough calculations says "almost" but I'm not an expert in that sort of math. Besides in such scenario we are replacing 2 stage rocket with 3 stage one so maybe some extra optimizations in flight profile are possible?..

Note: I'm not talking about replacing F9H second stage, I'm talking about launching fully-fueled Centaur as either PAYLOAD of Falcon Heavy or as a third stage (so in such scenario "payload" - Centaur - separation happens earlier than if it was a normal payload).

Also, can we expect Lockheed-Martin to make an extended Centaur (just stretched fuel tanks) in reasonable time and at reasonable cost?
Musk said that extending fuel tanks is a trivial task but he was talking about SpaceX and their hardware obviously.

PS. Not sure if this topic should be in SpaceX, ULA, or General Commercial section. I hope moderator will move it if I choose wrong.

[MATTBLAK]

Do you mean Centaur V? It would need to be a lot bigger than Centaur V, which will have about half the propellant load and less than half the thrust of the standard FH upper stage, albeit with a lot higher specific impulse. The best upper stage upgrade an FH could have would be one powered by a single Raptor vacuum engine and switching the stage to LOX/CH4 propellants for that engine. This revised stage could keep the same length, but widening it to 5.2 meters to match the payload fairing would be worthwhile and would usefully increase the propellant load.

Such a modification to Falcon was seriously considered at one point, but after Starship became the path forward; Elon lost interest. Such an upgrade to Falcon Heavy would have made a useful alternative to SLS. A reusable version with the Raptor upgrade should have placed about 50 metric tons into L.E.O. and more than 70 tons in fully expendable mode.

[Jim]

Would it be possible to replace SLS with extended Centaur stage launched on top of Falcon Heavy?

My rough calculations says "almost" but I'm not an expert in that sort of math. Besides in such scenario we are replacing 2 stage rocket with 3 stage one so maybe some extra optimizations in flight profile are possible?..

Note: I'm not talking about replacing F9H second stage, I'm talking about launching fully-fueled Centaur as either PAYLOAD of Falcon Heavy or as a third stage (so in such scenario "payload" - Centaur - separation happens earlier than if it was a normal payload).

Also, can we expect Lockheed-Martin to make an extended Centaur (just stretched fuel tanks) in reasonable time and at reasonable cost?
Musk said that extending fuel tanks is a trivial task but he was talking about SpaceX and their hardware obviously.

PS. Not sure if this topic should be in SpaceX, ULA, or General Commercial section. I hope moderator will move it if I choose wrong.

Also, can we expect Lockheed-Martin to make an extended Centaur (just stretched fuel tanks) in reasonable time and at reasonable cost?
Musk said that extending fuel tanks is a trivial task but he was talking about SpaceX and their hardware obviously.

PS. Not sure if this topic should be in SpaceX, ULA, or General Commercial section. I hope moderator will move it if I choose wrong.

No, Centaur can not do horizontal integration
and Lockheed Martin does not manufacture the Centaur

[Skipper]

Not an upgrade - completely separate third stage.

So we would have regular Falcon Heavy with its boosters, core and second stage PLUS Centaur riding on top of second stage.

Centaur V is still too small though but I assumed that increasing its propellant tanks size should not be a big problem (say 30 tones of propellant instead of 21).

Replacing F9H second stage with Raptor-powered one makes even more sense, but it would require a lot more development, and the point of my idea is to use existing hardware to save money (and having extra bonus political points for using ULA hardware and not just shipping contract to SpaceX completely, sigh).

[Skipper]

No, Centaur can not do horizontal integration
and Lockheed Martin does not manufacture the Centaur

Doesn't SpaceX have vertical integration facility for F9H payloads? I thought they did but that could be false memories

Also I thought that it was LM rather than Boeing manufacturing Centaurs... This is sad. Dumping the Boing is entire point

[rpapo]

Doesn't SpaceX have vertical integration facility for F9H payloads? I thought they did but that could be false memories

Not yet.  A vertical integration tower is or was being built at 39A for Defense payloads.

[tbellman]

Also I thought that it was LM rather than Boeing manufacturing Centaurs... This is sad. Dumping the Boing is entire point

Neither of Lockheed Martin and Boeing are making Centaur.  It is United Launch Alliance (ULA) that manufactures Centaur.  (Centaur does come from the LM side of ULA; originally from General Dynamics, but GD sold their space division to LM in 1994, and the parts of LM that made Centaur was then later transfered to ULA.)

Mass wise, Falcon Heavy can definitely throw a fully fuelled Centaur to orbit.  But Centaur is too long to fit within the standard fairing; it would need to use the long fairing that SpaceX is developing (but hasn't flown yet), and even that would not leave much space for an actual payload on top.

There are other practical considerations as well.  E.g, Centaur needs to be fuelled with liquid hydrogen and liquid oxygen a couple of hours before launch (and, I think, then be continously topped off until launch occurs); this capability would need to be added to SpaceX's transporter-erector, or to the launch tower.

Also, ULA doesn't sell Centaur to third parties, just launch services, so a potential customer would probably need to buy the launch from ULA, who would in turn contract SpaceX to put Centaur+spacecraft into orbit.  That doesn't sound very likely to happen.

Then there is the question of why you would do this, and who would want it.  It would be a pretty expensive launch, due to the modifications of the launch pad and one-off analyzis/testing needed to put this together, and the only thing it would be useful for is throwing a small and dense payload on a high energy trajectory.  The payload customer would almost certainly be better off buying one or two normal kick stages (e.g. the STAR series) and attach to their spacecraft.

[freddo411]

Would it be possible to replace SLS with extended Centaur stage launched on top of Falcon Heavy?

My rough calculations says "almost" but I'm not an expert in that sort of math. Besides in such scenario we are replacing 2 stage rocket with 3 stage one so maybe some extra optimizations in flight profile are possible?..

Note: I'm not talking about replacing F9H second stage, I'm talking about launching fully-fueled Centaur as either PAYLOAD of Falcon Heavy or as a third stage (so in such scenario "payload" - Centaur - separation happens earlier than if it was a normal payload).

Also, can we expect Lockheed-Martin to make an extended Centaur (just stretched fuel tanks) in reasonable time and at reasonable cost?
Musk said that extending fuel tanks is a trivial task but he was talking about SpaceX and their hardware obviously.

PS. Not sure if this topic should be in SpaceX, ULA, or General Commercial section. I hope moderator will move it if I choose wrong.

This concept was discussed at length and in detail here on NSF.   search for “Orion on Falcon heavy”. Thread was active about 2017 or 18

TLDR:  not practical in a “rockets are legos” sense, but perhaps technically feasible in a “it is possible if you throw huge amounts of money at it” sense.

[Jim]

Also I thought that it was LM rather than Boeing manufacturing Centaurs... This is sad. Dumping the Boing is entire point

Neither does.  ULA manufactures Centaurs
Anyways, why is there a need to dump Boeing?

[Firehawk153]

This sounds like a Titan IIIE for the 21st Century.

[spacenut]

I think, if Starship hadn't come along, SpaceX could have made a 5.5m diameter upper stage using a 200,000 lb. thrust downsided Raptor.  The length could have been the same as the existing upper stage, thus making minor mods to the erector and adding methane handling at the pad.   This new wider metholox powered upper stage could have done about 70-75 tons to LEO if I remember correctly, and could have thrown Orion to trans lunar injection.  This would have been much cheaper than SLS.  One cost reduction is use of existing rockets and tooling.  Another is not using solids.  Another is the way SpaceX manufactures.  The FH could have done a complete lunar program using distributed launches.  Probably 5 launches of FH would cost about the same as one SLS and deliver 350 tons to orbit vs 95 with SLS. 

Five launches would be Orion, a large lander that could be assembled using two launches or so.  Then the Artemis components for an Artemis station.  If NASA could have spent the money they used on SLS, these components could have already been built and launched using FH.  We would already be back at the moon. 

The hybrid you are talking about would have to be a NASA project as a replacement to SLS.  Neither ULA or SpaceX needs this.  Starship being developed is the elephant in the room.     

[Skipper]

Then there is the question of why you would do this, and who would want it.  It would be a pretty expensive launch, due to the modifications of the launch pad and one-off analyzis/testing needed to put this together, and the only thing it would be useful for is throwing a small and dense payload on a high energy trajectory.  The payload customer would almost certainly be better off buying one or two normal kick stages (e.g. the STAR series) and attach to their spacecraft.

To have much cheaper alternative to SLS that doesn't need additional hardware development and employs traditional NASA contractors.

At the current SLS launch prices and schedule Artemis would have the same fate as Apollo. At best we would see dozen more moonwalkers and that's it.

I don't find such results satisfactory.

(Centaur does come from the LM side of ULA; originally from General Dynamics, but GD sold their space division to LM in 1994, and the parts of LM that made Centaur was then later transfered to ULA.)

Ah, so this is where I got the memory that LM manufactures Centaur!

Anyways, why is there a need to dump Boeing?

Because Boeing is over budget, behind schedule and plagued by technical failings in all of their recent projects.
Boeing of today is not the company it once was. If it was, SLS would've been done 10-15 years ago.

I think, if Starship hadn't come along, SpaceX could have made a 5.5m diameter upper stage using a 200,000 lb. thrust downsided Raptor.  The length could have been the same as the existing upper stage, thus making minor mods to the erector and adding methane handling at the pad.   This new wider metholox powered upper stage could have done about 70-75 tons to LEO if I remember correctly, and could have thrown Orion to trans lunar injection.  This would have been much cheaper than SLS.  One cost reduction is use of existing rockets and tooling.  Another is not using solids.  Another is the way SpaceX manufactures.  The FH could have done a complete lunar program using distributed launches.  Probably 5 launches of FH would cost about the same as one SLS and deliver 350 tons to orbit vs 95 with SLS. 

Five launches would be Orion, a large lander that could be assembled using two launches or so.  Then the Artemis components for an Artemis station.  If NASA could have spent the money they used on SLS, these components could have already been built and launched using FH.  We would already be back at the moon. 

The hybrid you are talking about would have to be a NASA project as a replacement to SLS.  Neither ULA or SpaceX needs this.  Starship being developed is the elephant in the room.     

Neither Starship nor Raptor exist in practical sense.

Even before recent Musk revelations about SpaceX troubles with Raptor I was skeptical about that we will see Starship flying in 5 years, at least in its reusable form.

Fully-expendable Starship is probably another good alternative to SLS - and maybe a good way for SpaceX to fund its further development - but it will require significant second stage rework because as far I understand as of now its structurally not strong enough have payload mated on top of Starship (and then we have issue of changed center of gravity, inertia momentum, aerodynamics, etc.).
Metholox Raptor F9H second stage is also good concept but it needs a lot of development to be done, and we have Raptor that have some unsolved technical issues and too high thrust on top of that.

But the main problem with these two solutions is IMHO political: as far as I understand the main reason of SLS existence is Congress forcing NASA to employ traditional aerospace contractors. So my thought was that "Titan IIIE for the 21st Century" (I really like this comparison!) could be a good enough political compromise.

[spacenut]

I think the problem with Raptor is speed of manufacturing and cost of manufacturing.  Seems they are running well.  Also, Musk wants to increase their thrust.  He said he needs 1000+ per year manufactured.  It is currently about 150 per year being produced.  Current thrust is a little over 400,000 lbs, but he wants 500,000 lbs thrust.  In my opinion it is fine as is, but to get the goal of 150 tons to LEO, it needs more thrust, simplify construction, and speed up construction, to be able to have 1,000's of Starships for Mars colonization. 

Starship will work even if they can't land the booster, or the Starship upper stage.  It would still be cheaper than SLS.  I don't think they will have a problem with landing the booster, Starship re-entry and landing will be what they have to master. 

As far as this thread goes, unless NASA wants to put a Centaur upper stage on a FH for some deep space work, it is not going to happen. 

[Jim]

g is over budget, behind schedule and plagued by technical failings in all of their recent projects.
Boeing of today is not the company it once was. If it was, SLS would've been done 10-15 years ago.

That is so wrong on many levels,

[envy887]

g is over budget, behind schedule and plagued by technical failings in all of their recent projects.
Boeing of today is not the company it once was. If it was, SLS would've been done 10-15 years ago.

That is so wrong on many levels,

Haven't you heard? SLS should have been finished at least 4 years before it started. If not more... make that 20 years ago!

[1]

In Hawthorne CA, just south of the intersection of Hawthorn and El Segundo Blvds, there exists a mock-up of a Falcon Heavy. The artist did pretty decent job with the main rocket body. It's been there for years; before the FH or the block 5 F9 ever flew.

The payload fairing, however, resembles an Atlas-V fairing more than a Falcon fairing. I've jokingly referred to this as Falcon-Centaur whenever I run across SpaceX employees (usually at LA Ale Works). It's a cool, if slightly inaccurate, model. There are red light bulbs in the engines on all three boosters that light up at night.

But, it's also the closest thing we're ever going get to a Falcon-Centaur stack.