SpaceX and cis-lunar Space Tourism

[meekGee]

and with that very good summary, we can move past the moon-mars debate because there is no "Mars" in the title or the thread.

[Owlon]

Is it feasible to use a single FH to launch a Dragon V2 on a lunar free return trajectory with a small BEAM or Cygnus sort of hab module in the trunk that could then be ejected and docked with? This would have 3-5 crew/passengers. Ideally it would involve as close to zero modification and new development as possible.

Other than improved communications hardware and maybe power upgrades, what modifications might be needed for such a Dragon mission? A new navigation system? It sounds like the planned ECLSS could support this sort of mission.

The cost with a fully expendable FH at $135 million, a $20 million hab module, and a roughly $20 million per mission cost of a reusable modified Dragon flying five crew comes out to $35 million per person ($175 million total). That could come down a lot if:
a) FH has the performance to reuse the side boosters on a launch like this
b) the extra hab module is cheaper (NASA is paying ~$18 million for BEAM)
c) Dragon has a lower effective per-mission cost due to more reuses, or
d) some combination of the above.

Am I overlooking anything major?

[MP99]

The moon is closer from a travel time, and communication perspective but it's not that much closer from a deltaV perspective, as upthread analysis shows.

As a Moon-firster, this suggests to me that SpaceX's architecture for Mars could be relatively efficient at delivering payloads to the Moon. (With Gucky's caveat re Lunar ISRU).

As I see it, SpaceX won't do the Moon themselves just because they want to concentrate their resources on Mars.

But, once they start to build their Mars architecture, I believe that companies like Golden Spike will take the opportunity to buy services based on that hardware for Moon missions.

They'll just have to accept that they won't be able to buy a launch during Mars conjunction or opposition. But, it will provide a paying customer for the infrastructure between Mars missions.

With SpaceX providing the infrastructure, business will see an opportunity to go to the Moon with lower risk than Mars, and the chance for a more rapid return on investment. Tourism will be a part of this, encouraged by the fact that risks are lower when they're just one user of the architecture, since that architecture will mature as it sees more and more use.

Cheers, Martin

[Burninate]

Is it feasible to use a single FH to launch a Dragon V2 on a lunar free return trajectory with a small BEAM or Cygnus sort of hab module in the trunk that could then be ejected and docked with? This would have 3-5 crew/passengers. Ideally it would involve as close to zero modification and new development as possible.

Other than improved communications hardware and maybe power upgrades, what modifications might be needed for such a Dragon mission? A new navigation system? It sounds like the planned ECLSS could support this sort of mission.

The cost with a fully expendable FH at $135 million, a $20 million hab module, and a roughly $20 million per mission cost of a reusable modified Dragon flying five crew comes out to $35 million per person ($175 million total). That could come down a lot if:
a) FH has the performance to reuse the side boosters on a launch like this
b) the extra hab module is cheaper (NASA is paying ~$18 million for BEAM)
c) Dragon has a lower effective per-mission cost due to more reuses, or
d) some combination of the above.

Am I overlooking anything major?

No, I don't think you are overlooking anything serious, though BEAM is rather small to make an especially comfortable habitat, and the next step up Bigelow has made concepts of is the too-heavy BA-330.  Myself, I wonder what people might pay for a single brief Lunar flyby versus several very low passes.  There's also a question about whether you might want to actually berth/dock a hab module from launch rather than doing an Apollo-style spin-around docking with something from the trunk once in orbit.

{Free return} is much easier than {low orbit & return} is much easier than {landing & return}.

I can foresee financial difficulties, even if SpaceX manages to make everything reusable,  burning up a comfortable-sized hab on every mission.  Perhaps with magnetoshell aerobraking, after detaching you could perch it back in LEO (and indeed, build a space station out of these slightly-used modules), but so long as they're expendable, there's incentive to get as much value out of them as possible.

What do you think of this compromise?

I will present another tourist mission concept for you though:

The Lunar Cruise
After burning initially on a free return trajectory, a crew capsule + inflatable hab transfer into a highly elliptical Lunar orbit on the order of 24 hours orbital period (compare to minimum LLO period: ~2 hours).  Every morning, the tourists wake up to begin another very close Lunar approach, and get a very good look at the terminator.  The cruise lasts ~4 weeks, the passengers get to see the Lunar surface from all sides, and by the end, the orbit is aligned such that a low-dV transfer back to Earth is possible.

12 cruise windows per year, each several days long (the constraint being full daylight during the closest approach).  The inflatable hab burns up in the atmosphere.  The Dragon comes down to a spaceport pad.

Semimajor axis for 24hr orbit calculated at 9750km.
Periapsis: However close ops dares, plausibly even closer than a LLO, which has to deal with masscons.
Apoapsis: 16000km above the surface, a vew of the night side of the Moon.

Does anyone have the tools to calculate how much additional dV this would require on top of the free return trajectory?  I'm hoping something on the order of hundreds, rather than thousands, of meters per second?

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station.  Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

[guckyfan]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism. How much does the LIDS need? Could a sufficiently heavy station be put in place with a Falcon Heavy?

I would not be too concerned with the cost of a BEAM. A Falcon Heavy sending a Dragon to the moon would lose the central core and the second stage at least, at much higher cost than a BEAM. If the BEAM allows 4 or 5 passengers instead of 2 it is well worth it.
I do remember Gwynne Shotwell said at some occasion they have considered mounting an inflatable volume on top of Dragon to provide more space. So not even docking would be required. Just the ability to drop it before reentry. They have not given it much thought though.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

[LouScheffer]

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism

The ascent stage of the lander (the lightest part) docked with the CSM just fine in lunar orbit.

[Burninate]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Very low lunar orbit for completely passive spacecraft is perturbed by an unevenly spherical distribution of mass - 'Mass concentrations' or 'masscons' sprinkled over the surface, which only certain specific inclinations are safely balanced between.  Deviations in the terrain closest to an orbiter during periapsis can affect the altitude of apoapsis significantly.  In this case, though, the orbiter spends very little time in close proximity to the terrain, and the apoapsis has an inordinately high amount of 'give' before it starts crashing into mountains.  I suspect you wouldn't have to worry about masscons at all - to the extent that you could fly lower than people actually in LLO dare to go, since they have to integrate the orbital deviations caused by the terrain perturbations over 360 degrees times large numbers of orbits.  Any slight deviation can be corrected for using tractable amounts of ion thrusters for station keeping - like our GSO commsats have to do to deal with lunar perturbations.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

Never going to LLO saves a lot of delta V.  Getting to the Moon, inserting in a small burn, then sticking to a high elliptical orbit that lasts about four weeks, then transferring back to Earth in a small burn at just the right orbital phase (as you're going at close to escape velocity at periapsis, in the direction you would want to go to transfer, already), is what makes it delta V efficient.  BEAM itself is a pretty small/light hab - only 1.5 tons for 16 m^3 is what Bigelow is claiming.  Add another ton for a 4-way docking nexus and a small ion thruster or two for stationkeeping, , and you're up to 2.5 tons on top of the Dragon.  That's not a lot, compared to the mass of the Earth descent module (Dragon) and service module (trunk), because the Lunar periapsis burn to transfer back to Earth is in theory a small one.  What it would buy you if you left the hab in high lunar orbit is, if you run this mission again a year later, you can insert into the same trajectory, rendezvous, and get to use the same hab again, as part of a 2-BEAM station, and the next year, a 3-BEAM station.  If BEAM's mass is manageable but the volume is unfortunately low, using a bunch of them should quickly allow for a fairly comfortable station, relative to the alternative;  It doesn't require advanced aerocapture tech to be developed, it doesn't require a larger more comfortable, expensive inflatable to burn up every cruise, and it doesn't limit the cruise to a level of privacy and claustrophobia that most billionaires won't tolerate.

Concept, I dub thee 'Earthrise Lunar Cruise' and 'Earthrise Lunar Station'.

[Sean Lynch]

I can imagine a future when spindly propulsion modules are printed, assembled and fueled in LEO, joined to inflatable taxi habs that fly to stations in eccentric orbits that have the delta v's required...each leg of the journey having it's own mission specific requirements which won't require the mass of a heat shield and structural rigidity of a reentry pressure vessel.

[AncientU]

Alternately, maybe detach the hab in a highly elliptical Lunar orbit, which would allow you to build up a station there.     A BEAM + berthing nexus + minimal ion propulsion for the hab would allow your Lunar passengers to spend a few days getting to Lunar orbit in cramped conditions, then rendezvous with the hab for an eventually luxurious number of cubic meters, then climb back in the Dragon to return, leaving the hab behind to build up the station. 

This raises some questions with me.

Would such an orbit be sufficiently stable so you can leave a station there?

Very low lunar orbit for completely passive spacecraft is perturbed by an unevenly spherical distribution of mass - 'Mass concentrations' or 'masscons' sprinkled over the surface, which only certain specific inclinations are safely balanced between.  Deviations in the terrain closest to an orbiter during periapsis can affect the altitude of apoapsis significantly.  In this case, though, the orbiter spends very little time in close proximity to the terrain, and the apoapsis has an inordinately high amount of 'give' before it starts crashing into mountains.  I suspect you wouldn't have to worry about masscons at all - to the extent that you could fly lower than people actually in LLO dare to go, since they have to integrate the orbital deviations caused by the terrain perturbations over 360 degrees times large numbers of orbits.  Any slight deviation can be corrected for using tractable amounts of ion thrusters for station keeping - like our GSO commsats have to do to deal with lunar perturbations.

Bonus: Detaching the hab in high-elliptical lunar orbit saves you a little dV.

Actually it saves a lot ov delta-V compared to LLO. Maybe enough to do it with a stock Dragon?

Never going to LLO saves a lot of delta V.  Getting to the Moon, inserting in a small burn, then sticking to a high elliptical orbit that lasts about four weeks, then transferring back to Earth in a small burn at just the right orbital phase (as you're going at close to escape velocity at periapsis, in the direction you would want to go to transfer, already), is what makes it delta V efficient.  BEAM itself is a pretty small/light hab - only 1.5 tons for 16 m^3 is what Bigelow is claiming.  Add another ton for a 4-way docking nexus and a small ion thruster or two for stationkeeping, , and you're up to 2.5 tons on top of the Dragon.  That's not a lot, compared to the mass of the Earth descent module (Dragon) and service module (trunk), because the Lunar periapsis burn to transfer back to Earth is in theory a small one.  What it would buy you if you left the hab in high lunar orbit is, if you run this mission again a year later, you can insert into the same trajectory, rendezvous, and get to use the same hab again, as part of a 2-BEAM station, and the next year, a 3-BEAM station.  If BEAM's mass is manageable but the volume is unfortunately low, using a bunch of them should quickly allow for a fairly comfortable station, relative to the alternative;  It doesn't require advanced aerocapture tech to be developed, it doesn't require a larger more comfortable, expensive inflatable to burn up every cruise, and it doesn't limit the cruise to a level of privacy and claustrophobia that most billionaires won't tolerate.

Concept, I dub thee 'Earthrise Lunar Cruise' and 'Earthrise Lunar Station'.

A BA-330 or two (a.k.a., a commercial station) at EML-1 or 2 would be long-term stable, advance the NASA BEO agenda, and allow for access to any return path desired without awaiting phasing of a high elliptical orbit.  EML-1 is located on the way to the Moon and EML-2 only adds 15% to the journey length.  Each require less delta-v than LLO.

[Burninate]

EML2 or EML1 would be a more convenient place to put a station in terms of ops, but at 60,000km from the Moon, the Moon is 3 degrees across instead of 140 degrees across, as it is from 100km.  If the mission is to put tourists in close proximity to the Moon, the Lagrange points don't work.

What I don't quite get is what EML points offer operationally over LEO, for any mission except perhaps efficient SEP unmanned bulk transport, and as short-term maneuver keyholes for interplanetary missions.

[guckyfan]

Docking needs a minimum weight of the two vehicles so they can dock. For Apollo to dock with the lunar lander it needed the lander still attached to the stage to generate enough resistance for the docking mechanism

The ascent stage of the lander (the lightest part) docked with the CSM just fine in lunar orbit.

You are right.

[meekGee]

Thinking as a tourist, most of the value is in going around the moon, even once.   Doing it 5 times, meh.  Flying real low - now that's something.

Comfort is nice, (e.g. toilet), but not much more.  These are "adventurer tourists". Hardship is part of the trip. (as is risk). 

[Mader Levap]

Post moved here, per meekGee suggestion.

[meekGee]

Part of me wants to delete Moon/Mars posts after my previous warning.
Part of me wants to argue back.
Another part says, meh, just ask them again to drop that argument.
Part of me is busy today.

The first part won.


Mader - copy your post for posterity, and start a Moon-vs-Mars thread with it.  We can argue there.
I'll be back in an hour to trim.

Cheers

[TrevorMonty]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

[A_M_Swallow]

Somewhere along the line it becomes financially viable to make a chemical tug to push the Dragon around.  The tug would basically be a lunar lander with big fuel tanks and a docking port.

[Owlon]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

Having an inflatable module pre-docked would likely be a better option in the long run, but a BEAM derivative in the trunk might need much less development; it could potentially just be essentially BEAM with a docking port instead of berthing port.

[ChrisWilson68]

The biggest issue I had with habitat module for flyby was having to dock with it once in space. Guckyfan stated that SpaceX had considered launching Dragon with deflated Beam module already docked. This leaves trunk free for extra fuel and oxygen. The only problem I see with this would be Dragon's max abort weigh.

Having an inflatable module pre-docked would likely be a better option in the long run, but a BEAM derivative in the trunk might need much less development; it could potentially just be essentially BEAM with a docking port instead of berthing port.

Why the fear of docking in space?  It seems like a pretty mature technology by now.

[TrevorMonty]

For beam to dock it would need a propulsion system, also how do extract it from trunk without a robotic arm.

[ChrisWilson68]

For beam to dock it would need a propulsion system, also how do extract it from trunk without a robotic arm.

Just basic attitude stabilization.  No need for a robotic arm, just release it and have Dragon move itself and the trunk off of it.

Adding a few cold gas thrusters to the inflatable habitat module seems a much smaller change than having the Falcon 9/Dragon stack have to lift off with a big new something screwed onto the nose.  The pad abort and max-Q abort tests, at a minimum would have to be redone with the habitat attached.