Starliner beyond LEO

[lrk]

In a hypothetical scenario where NASA ditches SLS/Orion and puts out a call for commercial crew transportation services to Gateway, derived from existing commercial crew vehicles -

Dragon + FH should be able to accomplish this with only relatively minor modifications, with the possible addition of a redesigned trunk/service module (or just use Starship if NASA agrees to crew-rate it...)

What would be required for Starliner to perform a similar mission, launching on a commercial HLV such as Vulcan Heavy?  Could currently planned variants of Vulcan inject Starliner on TLI or would a triple-core variant be needed?  What modifications would Starliner need?  Presumably at least a new heat shield. 

As I understand things Starliner already has a significant amount of dV since the launch abort propellant is also used for on-orbit maneuvering.  On ISS missions much of this fuel is intentionally consumed in the orbital insertion burn, but a more powerful booster could deliver Starliner to TLI with full propellant reserves.  Would the service module propellant tanks need to be further expanded to enter/leave a lunar NRHO, and if so would that pose an issue for launch abort?  I suppose with more prop in the service module, the abort engines could simply be fired for longer...

I believe the life support capacity would need to be expanded as well.  How difficult would this be?

Anything else I am missing? 

[Steven Pietrobon]

Starliner masses about 13 t with the LAS. A service module (SM) could be attached below the LAS to provide the 1200 m/s delta-V that was provided by the ESM. Assuming that none of the abort propellant can be used (since the SM is in the way and don't want to add the extra complexity of propellant line separation in an abort), I estimate the mass of the SM to be about 20 t (Orion has a 10.4 t capsule mass and 15.5 t ESM mass, with 8.6 t of propellant), for a total mass of 33 t. That's going to be a problem getting to orbit and then getting to the Moon.

https://space.skyrocket.de/doc_sdat/starliner.htm

Another solution is to use the LAS tower and ESM from Orion, so that way the Europeans can still be involved. I estimate the Starliner capsule mass to be about 8.6 t (using the formula 0.5+0.4*Dē, where D is the diameter in m and 0.5 t is the mass of the crew). The lower mass means that about 1.2 t less propellant needs to carried by the ESM, so that overall mass reduces to about 23 t.

[TrevorMonty]

Starliner was never design for BLEO, this part of interview few years ago with head of project.

Service module couldn't be easily if at all upgraded for extra DV as it is also LAS.  Dragon is in same position This is downside of push LAS compared to Orion pull LA tower.

[GWH]

As is Starliner is only designed for 60 hours of free flight - but I don't know what specifically limits that.

[ThatOldJanxSpirit]

Starliner was never design for BLEO, this part of interview few years ago with head of project.

Service module couldn't be easily if at all upgraded for extra DV as it is also LAS.  Dragon is in same position This is downside of push LAS compared to Orion pull LA tower.

Dragon LAS is accommodated in the capsule, not the trunk.

[TrevorMonty]

Starliner was never design for BLEO, this part of interview few years ago with head of project.

Service module couldn't be easily if at all upgraded for extra DV as it is also LAS.  Dragon is in same position This is downside of push LAS compared to Orion pull LA tower.

Dragon LAS is accommodated in the capsule, not the trunk.

Still push LAS system even through Supradracos and fuel are in capsule.  NB trunk needs to stay attached during abort to keep Dragon stable which limits combined stack's mass.

With Orion there is no limits to service module mass as its left behind in an abort.

[AU1.52]

Starliner was never design for BLEO, this part of interview few years ago with head of project.

Service module couldn't be easily if at all upgraded for extra DV as it is also LAS.  Dragon is in same position This is downside of push LAS compared to Orion pull LA tower.

Dragon LAS is accommodated in the capsule, not the trunk.

Still push LAS system even through Supradracos and fuel are in capsule.  NB trunk needs to stay attached during abort to keep Dragon stable which limits combined stack's mass.

With Orion there is no limits to service module mass as its left behind in an abort.

But with Dragon you could swap the trunk for a powered service module.

[Lars-J]

With Orion there is no limits to service module mass as its left behind in an abort.

But with Dragon you could swap the trunk for a powered service module.

It is not that simple. Dragon needs the trunk for aerodynamic stability after abort (like a shuttlecock).

They could probably design a solution, but it is definitely not as simple as juts swapping out the trunk for a service module.

[Pueo]

Starliner masses about 13 t with the LAS. A service module (SM) could be attached below the LAS to provide the 1200 m/s delta-V that was provided by the ESM. Assuming that none of the abort propellant can be used (since the SM is in the way and don't want to add the extra complexity of propellant line separation in an abort), I estimate the mass of the SM to be about 20 t (Orion has a 10.4 t capsule mass and 15.5 t ESM mass, with 8.6 t of propellant), for a total mass of 33 t. That's going to be a problem getting to orbit and then getting to the Moon.

https://space.skyrocket.de/doc_sdat/starliner.htm

Another solution is to use the LAS tower and ESM from Orion, so that way the Europeans can still be involved. I estimate the Starliner capsule mass to be about 8.6 t (using the formula 0.5+0.4*Dē, where D is the diameter in m and 0.5 t is the mass of the crew). The lower mass means that about 1.2 t less propellant needs to carried by the ESM, so that overall mass reduces to about 23 t.

I realize that rockets are not LEGOs, but could you stage the notional "kick" service module after depletion and then use the current LAS containing service module for the rest of the ∆v?  I couldn't find a source on how much the ∆v the current service module actually supplies to Starliner, so it could be that this wouldn't be worth eating the mass of the duplicated OMAC thrusters.  This doesn't solve the problem of expanded life support of course.

Alternatively, could you just vent the extra LAS fuel into space?  It would double as inflight "entertainment" for the astronauts if the two expanding clouds of hypergolic were to touch.

[lrk]

To me it seems by far the simplest solution is just to build a bigger service module.  Sure it would be heavier due to the extra fuel, but you would also have more propellant available for launch abort, so it would seem workable just by adding additional abort engines. 

[Zed_Noir]

To me it seems by far the simplest solution is just to build a bigger service module.  Sure it would be heavier due to the extra fuel, but you would also have more propellant available for launch abort, so it would seem workable just by adding additional abort engines.

But that brings up the issue of the dual RL-10 engines in the Atlas V upper stage might not have enough excess thrust to fly Starliner with more propellants. The dual engine Centaur stage for the Atlas V N22 have only 198.2 kN (44,600 lbf) of thrust.

[Jimmy_C]

To me it seems by far the simplest solution is just to build a bigger service module.  Sure it would be heavier due to the extra fuel, but you would also have more propellant available for launch abort, so it would seem workable just by adding additional abort engines.

The rocket equation makes things difficult, because delta-v is proportional to the logarithm of the wet:dry mass ratio. According to otlski, the starliner masses are:

SM dry mass = 10000 lbs.
SM wet mass = 15000 lbs
CM dry mass = 14000 lbs
CM wet mass = 18000 lbs

That means the wet mass is 16.5 tons and the dry mass (with the CM still 18000 lbs) is 14 tons for a ratio of 1.14. The CST-100 SM provides 1200 m/s delta-v. Orion's SM provides 1500 m/s, or 1.25x more delta-v. So your ratio needs to go up by 1.18. This is a minimum of about 1 ton more propellent (not including mass of stretched SM, which is significant). For a spacecraft with 2.5 tons of propellent, stretching the SM propellent tanks by 40% is nontrival.

[Sesquipedalian]

I think* a simpler solution than any of the ones mentioned so far is to go the "distributed launch" route.  A used Falcon 9 could launch a big, dumb, Earth Departure Stage quite cheaply.  Dock Starliner and head off to wherever.

*Armchair rocket scientist here.  Haven't done the delta-v calculations or the cost analysis.  However, I have a hunch that launching a separate EDS would be much cheaper and less engineering-intensive than redesigning the Starliner or changing its launch configuration.

[Steven Pietrobon]

*Armchair rocket scientist here.  Haven't done the delta-v calculations or the cost analysis.  However, I have a hunch that launching a separate EDS would be much cheaper and less engineering-intensive than redesigning the Starliner or changing its launch configuration.

This doesn't solve the problem of getting Starliner into and out of NRO.

[su27k]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

[Steven Pietrobon]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

Yes, but that Space Tug will mass about 20 t in order to carry the 13 t Starliner into and out of NRO.

[docmordrid]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

Imagine the optics of a Starship Chomper vomiting Starliner out of its massive maw. Now imagine Boeing execs running from the idea at Warp 9.9 with their hair on fire.

[gemmy0I]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

Imagine the optics of a Starship Chomper vomiting Starliner out of its massive maw. Now imagine Boeing expects running from the idea at Warp 9.9 with their hair on fire.

Although I realize your statement was likely made in jest, it wouldn't actually have to be as crazy as that. There was some speculation/analysis here a while back (around the initial HLS awards announcement) that, as a transitional architecture before Starship is fully rated to carry crew during ascent and reentry (but accepted for lunar landings in its drastically simplified Moonship variant, which cuts out most of Starship's crew safety risks from the critical path for a 2024 landing), the existing Crew Dragon, launched on a Falcon 9 to LEO, could be boosted to lunar orbit while docked to the nose docking port of a Moonship.

This jumped out as an "obvious" and wonderfully straightforward/low-technical-risk architecture based on the otherwise-unexpected choice to locate Moonship's docking port on its nose instead of radially as in the regular crew Starship. Namely, it allows a docked capsule to be located cleanly along the vehicle's thrust axis during boost maneuvers with the Raptors. (The crew could hang out in the Moonship during the burns to avoid "eyeballs-out" acceleration.) Upon arrival in NRHO, Moonship would drop off the Dragon (either in free flight or at Gateway if it exists yet), and Moonship would do its landing with the subset of the crew participating therein. Post-landing, Moonship would dock with Dragon/Gateway again and the crew could go home in Dragon (since its heat shield is plenty capable for lunar reentry, and the return burn from NRHO is well within Dragon's delta-v given it didn't have to spend any on the way there). The Moonship could make its own lunar departure burn and gradually aerobrake back down to LEO on a gentle multi-pass trajectory, readying it for refueling and reuse on the next mission.

This architecture would work just as well with Starliner, or with Orion (or even Dream Chaser) for that matter. What's great is that it completely decouples the lander/earth-departure-stage component of the mission from the crew-launch/return component. Any crew return vehicle capable of doing an ISS mission can launch to LEO as usual and dock with Moonship there using the same interface as at ISS. The only additional requirements beyond an ISS mission is that the heat shield be capable of lunar reentry (already OK for Dragon, Orion, and possibly Starliner as well since it uses a modern ablative formulation competitive with, although different from, PICA), and that its electronics be capable of handling beyond-LEO radiation. Life support would be augmented by Moonship and Gateway for enough of the mission that the capsule's own supplies shouldn't need to be extended beyond existing Commercial Crew standards.

I completely agree that Boeing would want absolutely nothing to do with this architecture if they have anything to say about it, as it entirely undermines their case for SLS. But if Boeing were willing to set aside their pride for a moment, it would actually be a great way for their existing Starliner vehicles to contribute materially to Artemis with very little additional R&D needed on their part. In fact, if NASA were to embrace this architecture (which isn't really up to Boeing since Dragon would be the reference design), the case for SLS already evaporates, leaving this as perhaps Boeing's only path to save face and have any part whatsoever in Artemis. NASA, for its part, would surely love the idea of having not one but three (or even four) crew launch vehicles providing dissimilar redundancy in Artemis. Besides Dragon, Starliner, and Dream Chaser, Orion-to-LEO has several good launch vehicle options (Falcon Heavy, Delta IV Heavy/Vulcan Heavy, and New Glenn); New Glenn in particular is a likely candidate as Blue's existing partnership with Lockheed through the National Team makes it an attractive way to get Blue into the crew launch business.

The beautiful thing about this is that, as su27k implied, it isn't just limited to Starship. All of the HLS lander designs could be adapted (with varying degrees of work) to this sort of architecture where some component of the lander is responsible for boosting a crew capsule from LEO to NRHO. It fits most naturally with Starship because I suspect SpaceX designed Moonship with this expressly in mind as a "plan B" if/when SLS is delayed further, but the National Team's three-stage design is also a good fit, as its hydrolox in-space Transfer Stage could be adapted as a tug with very little diversion from the current development plan.

[gemmy0I]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

Yes, but that Space Tug will mass about 20 t in order to carry the 13 t Starliner into and out of NRO.

The National Team's hydrolox in-space Transfer Stage module of their three-stage lander could be a good fit for this if they can stretch its tanks at all (which shouldn't be too hard, and would be silly for them not to consider given the enormous potential such a product would have both for Artemis and the commercial market). Any of the heavy launchers being considered for launching their (IIRC) ~13 t Transfer Stage to TLI would be capable of putting a ~20 t variant into LEO.

As I noted at the end of my previous post, such a tug would work not just for Starliner but also other options like Dragon, Orion, and Dream Chaser, providing a lot of dissimilar redundancy and competitive options.

[TrevorMonty]

Need a space tug instead of EDS, I think the HLS landers (or component of a lander) can be used for this role, with some slight modifications.

Yes, but that Space Tug will mass about 20 t in order to carry the 13 t Starliner into and out of NRO.

The National Team's hydrolox in-space Transfer Stage module of their three-stage lander could be a good fit for this if they can stretch its tanks at all (which shouldn't be too hard, and would be silly for them not to consider given the enormous potential such a product would have both for Artemis and the commercial market). Any of the heavy launchers being considered for launching their (IIRC) ~13 t Transfer Stage to TLI would be capable of putting a ~20 t variant into LEO.

As I noted at the end of my previous post, such a tug would work not just for Starliner but also other options like Dragon, Orion, and Dream Chaser, providing a lot of dissimilar redundancy and competitive options.

Why take capsule out to moon and back  when OTV with habitat could do round trip. Uses less fuel on way out as habitat mass is lower than capsules. Extra fuel for propulsive return to LEO isn't that big a deal,  just an additional launch. Eventually source return fuel from moon.

With two OTVs at LEO and one at Gateway, there is always a rescue OTV ready to cover both legs of trip.

A crew vehicle only supports reduced crew for BLEO missions compared to LEO taxi mission. OTV habitat can be built to support what ever number is viable, most likely 6-7 ie full LEO taxi, the additional passengers help pay for return fuel tanker.
In end seat price may work out cheaper.
A single OTV can support multiple missions a year compared BLEO crew vehicle which takes months to refurbish. Still need refurbish LEO taxi but there are more of them.