Speculation thread: intermediate-lift Raptor-derived RLV

[AncientU]

Frankly, the reason I believe is economical. A smaller vehicle can place the Internet constellation into orbit cheaper than F9 or full scale ITS. Also an SLS sized rocket can launch from the Cape, I believe the full scale it's would need an offshore launch platform. Which would be much more expensive. Again all economic reasons.

Two pads at the Cape to be exact.  Maybe Boca Chica, too, in time.

The comparison with SLS stops there, though.  This will be a fully reusable rocket, capable of launching monthly, weekly, whatever Mars development (and Lunar, ConnX, DoD, etc.) demands.  Reuse plus refueling on orbit will allow this system to gain most of the cost advantages of the 2016 IAC version.

This is a buildable rocket now -- assuming Raptor is flight qualified in the next 1-2 years, even if they need to make the first boosters of Li-Al and use landing legs.  The workforce is assembled and qualified, assembly line engine production is proven, pad(s) available, reuse technology proven, ..., and NASA is currently all hot on going to Mars, but is launcher constrained.  When would timing be better?

I still believe that the first of these boosters could fly in 2020... New Glenn, Vulcan-Centaur, SLS EM-1 timeframe.

Ok, this is sounding intriguing. So what do you envisage, roughly? A single stack, two stage, SLS sized, Raptor based, fully reusable rocket that is refuellable in LEO? With more or less what diameter and what  fully reusable payload to LEO?

As stated up-thread (and several other times dating back to October 2016):

...

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

...

Fully reusable payload would 100-150t.

[M.E.T.]

Frankly, the reason I believe is economical. A smaller vehicle can place the Internet constellation into orbit cheaper than F9 or full scale ITS. Also an SLS sized rocket can launch from the Cape, I believe the full scale it's would need an offshore launch platform. Which would be much more expensive. Again all economic reasons.

Two pads at the Cape to be exact.  Maybe Boca Chica, too, in time.

The comparison with SLS stops there, though.  This will be a fully reusable rocket, capable of launching monthly, weekly, whatever Mars development (and Lunar, ConnX, DoD, etc.) demands.  Reuse plus refueling on orbit will allow this system to gain most of the cost advantages of the 2016 IAC version.

This is a buildable rocket now -- assuming Raptor is flight qualified in the next 1-2 years, even if they need to make the first boosters of Li-Al and use landing legs.  The workforce is assembled and qualified, assembly line engine production is proven, pad(s) available, reuse technology proven, ..., and NASA is currently all hot on going to Mars, but is launcher constrained.  When would timing be better?

I still believe that the first of these boosters could fly in 2020... New Glenn, Vulcan-Centaur, SLS EM-1 timeframe.

Ok, this is sounding intriguing. So what do you envisage, roughly? A single stack, two stage, SLS sized, Raptor based, fully reusable rocket that is refuellable in LEO? With more or less what diameter and what  fully reusable payload to LEO?

As stated up-thread (and several other times dating back to October 2016):

...

New intermediate-sized Raptor rocket should maximize capability of LC-39A and B.  Build a 12+Mlbf booster (19 engines in three ring -- 1-6-12 -- hex pattern  would be my choice) with both a conventional second stage and fairing, plus a follow-on mini-ITS spaceship second stage.  Core diameter would be around 9m (8-10).  Reusable booster mode payload would be around 200t.

...

Fully reusable payload would 100-150t.

Apologies for missing the earlier posts, and thanks for providing the summary above.

Overall, the concept sounds great. I just keep wondering what this solves that ITS does not solve better, other than being achievable maybe 5 years sooner. But at the price of delaying ITS itself perhaps for decades. Personally, I'd rather wait an extra 5 years to get the full ITS, than settle for this mini-version instead.

ITS could do anything this intermediate rocket could do, and much more.

[guckyfan]

Overall, the concept sounds great. I just keep wondering what this solves that ITS does not solve better, other than being achievable maybe 5 years sooner. But at the price of delaying ITS itself perhaps for decades. Personally, I'd rather wait an extra 5 years to get the full ITS, than settle for this mini-version instead.

ITS could do anything this intermediate rocket could do, and much more.

It gives Elon Musk that Mars base years earlier. With all the experience that can be gained and engineering of habitats, ISRU and power.

It would establish SpaceX as interplanetary player. They could no longer be ignored. Side effect Jeff Bezos would not have bragging rights over Elon Musk for New Glenn for years if at all which would annoy Elon Musk.

[raketa]

I just find out , that 1 stage of ITS will be very similar to Falcon 9 1 stage, almost nothing to be developed.If they keep aluminum body, it will be just a bigger body, with 42 different engine. A major effort will be build spaceship and there is now compromises. It has to go to Mars and come back.

[guckyfan]

A side thougt just occured to me. If any of this happens, the recently rejuvenated reusable upper stage for Falcon would be redundant and likely not happen.

[Confusador]

A side thougt just occured to me. If any of this happens, the recently rejuvenated reusable upper stage for Falcon would be redundant and likely not happen.

If this turns out to be what's announced, I'm convinced it will be because they went back over the reuse numbers for FH upper stage and still just couldn't make it work... and then said "well, what if we just used Raptor?"  But using Raptor on just the upper stage is operationally inefficient, so here we are.

I think Musk is frustrated at not being able to get full reuse working, and that's enough for him to pursue this.  The "economic case" being that full reuse increases profit margins, and the sooner they can do that the more they can devote to Mars.

[M.E.T.]

A side thougt just occured to me. If any of this happens, the recently rejuvenated reusable upper stage for Falcon would be redundant and likely not happen.

And Falcon Heavy will have a very short operational life.

[Semmel]

I don't think there will be a traditional second stage and fairing. Why develop such a system when a small ITS ship needs to be developed and would obsolete the second stage plus fairing design? Sounds like a distraction. And I am not convinced that developing a second stage plus fairing is simpler/easier than a small ITS with cargo doors and a satellite dispenser.

[AncientU]

I don't think there will be a traditional second stage and fairing. Why develop such a system when a small ITS ship needs to be developed and would obsolete the second stage plus fairing design? Sounds like a distraction. And I am not convinced that developing a second stage plus fairing is simpler/easier than a small ITS with cargo doors and a satellite dispenser.

Depends upon who is buying rides.  If SpaceX only, then I agree -- not much use for big payloads that have no lander.  But if someone needs a 'fluffy' 100t payload put into LEO, a large (8.4m) monolithic mirror telescope for instance -- MSFC ATLAST 8, or a space hotel, then a throw-away second stage with recoverable 10m fairings would be useful.  Or someone might want to throw a big lander to a Jovian moon...

[M.E.T.]

I don't think there will be a traditional second stage and fairing. Why develop such a system when a small ITS ship needs to be developed and would obsolete the second stage plus fairing design? Sounds like a distraction. And I am not convinced that developing a second stage plus fairing is simpler/easier than a small ITS with cargo doors and a satellite dispenser.

Depends upon who is buying rides.  If SpaceX only, then I agree -- not much use for big payloads that have no lander.  But if someone needs a 'fluffy' 100t payload put into LEO, a large (8.4m monolithic mirror telescope for instance -- MSFC ATLAST 8m), or a space hotel, then a throw-away second stage with recoverable 10m fairings would be useful.  Or someone might want to throw a big lander to a Jovian moon...

Why a throwaway 2nd stage? Why not a reusable one?

[AncientU]

If the mass margin is there, sure, why not.

[punder]

Fully reusable payload would 100-150t.

Count on extreme political pushback. You are describing an SLS Killer after all.   

Edit for Robotbeat: An SLS Killer is a great idea, didn't mean to imply otherwise. Just that there will be a dumb, short-sighted pushback campaign to protect local economies from temporary disruption, no matter the obvious longer-term benefits to those economies. It happened with F9 entry into USAF, commercial cargo, and commercial crew, and it will happen on a much larger scale with ITS Lite. As in those instances it will fail, but there will certainly be a fight.

I am one of those who see ITS as a bridge too far, and ITS Lite as much more doable and, incidentally, competitive with BO, which could take a lot of market from SpaceX if Musk left F9/FH to fend for themselves against NG during full ITS development.

[Robotbeat]

Fully reusable payload would 100-150t.

Count on extreme political pushback. You are describing an SLS Killer after all.   

Extreme? No. Everything SpaceX wants to do is going to run into political opposition, and the best defense against that is to be wildly successful and have politicians knocking on /your/ door.

In this way, instead of begging NASA & Congress for financial help, SpaceX will be able to develop the initial ITS with their own (and constellation investors') money. You'll have politicians begging to have SpaceX facilities built in their district.

Falcon Heavy is already roughly in SLS class. Full ITS is fully capable of launching SLS payloads.

Unless you don't want SpaceX to build ITS, they have to do this sooner or later.

[docmordrid]

I don't think there will be a traditional second stage and fairing. Why develop such a system when a small ITS ship needs to be developed and would obsolete the second stage plus fairing design? Sounds like a distraction. And I am not convinced that developing a second stage plus fairing is simpler/easier than a small ITS with cargo doors and a satellite dispenser.

Depends upon who is buying rides.  If SpaceX only, then I agree -- not much use for big payloads that have no lander.  But if someone needs a 'fluffy' 100t payload put into LEO, a large (8.4m monolithic mirror telescope for instance -- MSFC ATLAST 8m), or a space hotel, then a throw-away second stage with recoverable 10m fairings would be useful.  Or someone might want to throw a big lander to a Jovian moon...

Why a throwaway 2nd stage? Why not a reusable one?

Why not an upper sage with the Spaceships form factor & EDL with a clamshell front for deployment? Or a side door & arm? Side door and ejection deployment cells for CommX? Or...

[guckyfan]

For large probes to the outer planets the upper stage will be expended, no matter what. But compared to presently planned very heavy lifters, what are even $200 million expended for the upper stage for a huge payload to high energy trajectories? That's the given cost for a ITS  ship. Lots of things the ship has, will not be needed so less than that. Probably more than the $130 million for a tanker.

Edit: A third stage could be developed. The second stage throws it to earth escape, then turns back. The third stage continues. But is it worth it for a few missions? I guess not.

[M.E.T.]

For large probes to the outer planets the upper stage will be expended, no matter what. But compared to presently planned very heavy lifters, what are even $200 million expended for the upper stage for a huge payload to high energy trajectories? That's the given cost for a ITS  ship. Lots of things the ship has, will not be needed so less than that. Probably more than the $130 million for a tanker.

Edit: A third stage could be developed. The second stage throws it to earth escape, then turns back. The third stage continues. But is it worth it for a few missions? I guess not.

In Elon's ITS presentation, the ITS Spaceship could travel to the outer Solar System using fuel depots at various points along the way.  Since this constituted a manned voyage, I presume it allowed for the return trip to Earth, and therefore, by implication, reusability.

But I get that you are referring to the mini-ITS, and I guess even the full ITS, in the years before fuel depots are set up across the Solar System.

[guckyfan]

I was using given cost for the full ITS. But the same would be true for the mini-ITS. I doubt that depots would be worth it for a single upper stage. That would be done for manned missions. With very high cost for placing the depots.

[Robotbeat]

For large probes to the outer planets the upper stage will be expended, no matter what. But compared to presently planned very heavy lifters, what are even $200 million expended for the upper stage for a huge payload to high energy trajectories? That's the given cost for a ITS  ship. Lots of things the ship has, will not be needed so less than that. Probably more than the $130 million for a tanker.

Edit: A third stage could be developed. The second stage throws it to earth escape, then turns back. The third stage continues. But is it worth it for a few missions? I guess not.

Not "no matter what." If you refuel a BFS at near escape, then you have enough delta-V even after the departure burn and releasing the payload to flip around and do a burn to stay in Earth vicinity.

[guckyfan]

Not "no matter what." If you refuel a BFS at near escape, then you have enough delta-V even after the departure burn and releasing the payload to flip around and do a burn to stay in Earth vicinity.

Probably doable. But at speeds for deep space, outer planet probes it will be a lot of propellant needed and that means a number of tankers going out there, all refuelled in orbit. Is it worth it?

[Robotbeat]

Not "no matter what." If you refuel a BFS at near escape, then you have enough delta-V even after the departure burn and releasing the payload to flip around and do a burn to stay in Earth vicinity.

Probably doable. But at speeds for deep space, outer planet probes it will be a lot of propellant needed and that means a number of tankers going out there, all refuelled in orbit. Is it worth it?

Yeah. ITS tankers are like $3.6 million per launch and $130 million to build. So it'd take 35 tanker launches to equal the cost of expending one of them (less since an expendable tanker would cost less to make, but still). Scaled for this smaller ITS, of course. So even if it takes like a dozen tanker flights, it's still worth it.