SpaceX to the moon: mission profiles

[sevenperforce]

During the Apollo program, a variety of mission architectures were considered, including earth-orbit rendezvous, earth-orbit rendezvous with assembly, direct ascent, and finally LOR. There were other sub-parts, however; crasher stages, uncrasher stages, and so forth. A lot of these have already been discussed here or there on these forums.

Falcon 9 and Falcon Heavy aren't designed for prodigious BLEO performance, so they are automatically less than ideal for a lunar landing. Dragon V2 was designed as an LEO crew ferry with the possibility of Martian landings. SpaceX has no direct intentions for the moon; Elon has been pretty vocal about setting his sights on Mars. However, if SpaceX could support a manned lunar landing using the platforms they already have (or will have in the next year), they would have a substantial headstart on other options and be able to roundly demonstrate the legitimacy and flexibility of their platform. So I wanted to run some numbers and see what would be required for SpaceX to put men back on the moon.

A couple of things I eliminated right off were on-orbit assembly and on-orbit refueling. Neither have ever been used for a transfer vehicle, and I don't want to propose completely untested mission steps. Plus, those sorts of steps encourage an unrealistically large number of launches and aren't limiting at all. "Let's launch eight Falcon Heavys, use propellant transfer in orbit, then strap the full ones together! Wait, no, let's launch forty Falcon Heavys and take the whole ISS to the moon!" Not realistic.

I'm also eliminating ridiculously dangerous stuff like slapping landing legs on a Falcon 9 upper stage and setting it down on its tail. No matter how good SpaceX gets at suicide-burn Falcon 9 RTLS recovery, it's way too risky to consider for a manned landing on another world.

This makes lunar ascent a challenge, because you need a minimum of 2 km/s to get off the moon. No way around it.

The pressure-fed kerolox Kestrel engine used on the upper stage of Falcon 1 has a decent specific impulse. But trying to use it would require SpaceX to design a completely new platform for what they consider to be a dead-end mission profile, which won't really work. This means the only engines potentially available for ascent are the SuperDracos on the Dragon V2. Now, this isn't too far-fetched; Elon has spoken specifically about the use of the Dragon V2 platform for landing on a variety of worlds, including the moon, suggesting that the heat shield and parachutes could be exchanged for a larger fuel tank to increase dV.

Unfortunately, the SuperDracos on the Dragon V2 are extremely under-expanded, resulting in a really pathetic specific impulse of 240 seconds. Getting 2 km/s out of such low-impulse engines requires a propellant mass fraction of 57%, which means an empty Dragon V2 (with a dry mass of 4.2 tonnes) would need at least 5.6 tonnes of propellant in order to get off the surface of the moon, 370% of its current fuel capacity.

However, the SuperDracos run on MMH/NTO, which has an optimal vacuum ISP of 336 seconds. Theoretically, then, SpaceX should be able to design a SuperDraco Vacuum engine with an extended exhaust bell capable of operating in a vacuum at a much higher expansion ratio. Even though the engines are pressure-fed, they have a combustion chamber pressure of 1000 psi, which should allow maximum specific impulse. The thrusters are mounted at an angle of 15 degrees, but if the extended exhaust bells can angle that downward by half the angle, that's an effective specific impulse of 362 seconds and a propellant mass fraction of 43%.

Thus, retrofitting a Dragon V2 frame with larger tanks and extended-nozzle SuperDraco Vacuum engines should allow it to act as a Lunar Dragon descent or ascent vehicle. This means that a variety of mission profiles can be generated using only Falcon 9, Falcon Heavy, and the Dragon V2 platform.

So far, I've come up with the following:

1. Dual series launch to double LOR. Falcon Heavy with unmanned Lunar Dragon to LLO, followed by Falcon Heavy with stock manned Dragon V2 to LLO. Orbital rendezvous; crew transfers to Lunar Dragon and uses the first Falcon Heavy's upper stage as a crasher stage to the lunar surface and the Lunar Dragon hovers to a landing. Lunar Dragon then makes ascent, docks with the stock Dragon V2 for crew transfer, and the second Falcon Heavy upper stage returns the stock Dragon V2 to Earth.
2. ISS to EML-1; crasher-stage direct ascent. Single Falcon 9 launch takes crew and Dragon V2 to ISS; docks. Falcon Heavy lifts Lunar Dragon to the ISS; crew and consumables transfer; Falcon Heavy transfers to EML-1 and then burns crasher-stage to drop a Lunar Dragon with additional fuel on the lunar surface. Lunar Dragon makes ascent and transfer to ISS and crew returns to earth via docked Dragon V2.
3. Single launch to direct ascent. Standard Dragon V2 is retrofit with detachable nozzles and an internal auxiliary tank; launches with crew on a single Falcon Heavy to EML-1 and then is delivered via crasher stage to the lunar surface. Dragon V2 makes direct ascent to Earth aerobraking trajectory.

All are within dV limitations.

Any other possibilities?

[redliox]

SpaceX is probably considering some Moon plans, although I'm pretty sure they favor Mars more considerably.

Considering they'll have better experience in LEO, they could have something like a "traditional" D2 rendezvous with a Lunar Dragon to transfer crew (and maybe fuel) before essentially flying the Lunar Dragon for the remainder.  So my guess would be at least 3 launches: 1 apiece for crew, lunar vehicle, and fuel.  Anything cargo could be 2 launches sending a one-way vehicle.

SpaceX and the other commercial companies might wait until NASA makes a decision on if they want a new commercial vehicle, particularly for either Lunar or Martian landings, before investing further than LEO activity and crewless launchers.

[nadreck]

Orbital propellant transfer is on the critical path to Mars for SpaceX so I don't think it is fair to rule it out.

More than 20t could be delivered to the Lunar surface using an on orbit refueled Falcon upper stage in either crasher mode or with legs. I think the lowest risk lunar program with a reasonable cost using Falcon hardware, might involve lunar surface rendezvous with the return vehicle and most surface use equipment brought by 20t loads either in crasher stage mode or with landing legs and that the crew(s) initially be brought by one time dragon landers.

However, that is for a limited mission that someone other than SpaceX foots the ~$500M bill. And that is for the program up to the first crew.

It makes even more sense to wait for a raptor based architecture either with the MCT or the potential Falcon/Raptor upper stage.  With either of those a more substantial first mission for a similar price tag could be run.

I am all for 3 priorities for missions to the moon:

Polar ISRU, relatively low polar orbit station/depot/gateway along with high inclination communications constellation, EML-2 station/observatory and deep space communications node.

[IainMcClatchie]

If Falcon Heavy gets crossfeed, can a Lunar Dragon launched by FH land on the moon with a trunk and some useful payload in it?

[Rocket Science]

I toyed with this a while back for fun, have a look!

http://forum.nasaspaceflight.com/index.php?topic=30567.0

[launchwatcher]

1. Dual series launch to double LOR. Falcon Heavy with unmanned Lunar Dragon to LLO, followed by Falcon Heavy with stock manned Dragon V2 to LLO. Orbital rendezvous; crew transfers to Lunar Dragon and uses the first Falcon Heavy's upper stage as a crasher stage to the lunar surface and the Lunar Dragon hovers to a landing. Lunar Dragon then makes ascent, docks with the stock Dragon V2 for crew transfer, and the second Falcon Heavy upper stage returns the stock Dragon V2 to Earth.

open questions this inspires:

What's the on-orbit endurance of the Falcon upper stage?   How fast will its LOX boil off?   Will the mvac engine be able to restart after several days in vacuum?

Will the combined Dragon + upper stage have enough maneuverability to be able to dock with another Dragon?

[sevenperforce]

 

Considering they'll have better experience in LEO, they could have something like a "traditional" D2 rendezvous with a Lunar Dragon to transfer crew (and maybe fuel) before essentially flying the Lunar Dragon for the remainder.  So my guess would be at least 3 launches: 1 apiece for crew, lunar vehicle, and fuel.

SpaceX and the other commercial companies might wait until NASA makes a decision on if they want a new commercial vehicle, particularly for either Lunar or Martian landings, before investing further than LEO activity and crewless launchers.

I don't see anything more than two launches per mission, at least as far as essential components are concerned. A two-launch manned landing with a third launch for auxiliary/optional support payload is possible.

SpaceX has lunar contracts already. These are probably going to primarily be LLO missions, but some could be one-way unmanned surface missions using the Dragon V2 platform. So if SpaceX can generate a near a terms realize able mission profile for a manned return, I think they will.

Orbital propellant transfer is on the critical path to Mars for SpaceX so I don't think it is fair to rule it out.

Perhaps not rule it out entirely, but that would be something to test on a second manned mission with a secondary payload, rather than a first-time thing. That's another value of SpaceX servicing manned lunar landings: it gives them practice for what they will need to go to Mars.

If Falcon Heavy gets crossfeed, can a Lunar Dragon launched by FH land on the moon with a trunk and some useful payload in it?

By my calculations, FH full thrust with crossfeed can deliver 73 tonnes to LEO, 28 tonnes to EML-1, 20 tonnes to LLO, or 12 tonnes to the surface of the moon as a crasher stage.

1. Dual series launch to double LOR. Falcon Heavy with unmanned Lunar Dragon to LLO, followed by Falcon Heavy with stock manned Dragon V2 to LLO. Orbital rendezvous; crew transfers to Lunar Dragon and uses the first Falcon Heavy's upper stage as a crasher stage to the lunar surface and the Lunar Dragon hovers to a landing. Lunar Dragon then makes ascent, docks with the stock Dragon V2 for crew transfer, and the second Falcon Heavy upper stage returns the stock Dragon V2 to Earth.

open questions this inspires:

What's the on-orbit endurance of the Falcon upper stage?   How fast will its LOX boil off?   Will the mvac engine be able to restart after several days in vacuum?

Will the combined Dragon + upper stage have enough maneuverability to be able to dock with another Dragon?

The LOX shouldn't boil off at all. And yeah, particularly with the SuperDracos, docking with a Falcon upper stage attached shouldn't be a problem.

[Alf Fass]

Could SpaceX's pressure fed Kestrel engine be adapted for use as a descent stage engine? Thrust and Isp are similar to the descent engine used on the Apollo LEM.

[sevenperforce]

Could SpaceX's pressure fed Kestrel engine be adapted for use as a descent stage engine? Thrust and Isp are similar to the descent engine used on the Apollo LEM.

The SuperDracos on the Dragon V2 already each have twice the thrust of the Kestrel, and that's without a nozzle extension on the SuperDracos.

I suppose that if SpaceX wanted to design a single-purpose lander then they could use a Kestrel or a cluster of them, since they already have the designs. But if they want to use the Dragon V2 platform like Elon has talked about, it makes more sense to develop extended vacuum nozzles for the existing SuperDracos.

Using a single manned Falcon Heavy launch to EML-1 with gravity capture, free fall, and a Falcon upper stage crasher to land a direct ascent vacuum-optimized Dragon V2 would be....awesome.

[Eagandale4114]

If Falcon Heavy gets crossfeed, can a Lunar Dragon launched by FH land on the moon with a trunk and some useful payload in it?

By my calculations, FH full thrust with crossfeed can deliver 73 tonnes to LEO, 28 tonnes to EML-1, 20 tonnes to LLO, or 12 tonnes to the surface of the moon as a crasher stage.

Are those numbers with the Raptor upper stage? If not, could you run numbers with what we know of one?

[Chris_Pi]

Since there's much more fuel needed anyways could it make sense to put those tanks in the trunk along with one Vacuum SuperDraco? Leave the ones on the capsule as-is and possibly make up for the extra motor weight with a better expansion ratio and no cosine losses? It would avoid having to deal with detachable nozzle extensions on the capsule or extra fuel plumbing to those motors. They wouldn't be needed until Earth landing.

[QuantumG]

I had this silly idea the other day.. if we were to offer to pay SpaceX to design a reference mission to send crew and cargo to the Moon, would they do it? I know they like money and they have engineers and stuff, but I can imagine they might not want to "waste their time" if you couldn't show you were serious. I wonder how much it'd cost if they did.

[IainMcClatchie]

The idea of two launches for a moon-orbit rendezvous sounds pretty impressive, in the sense that you could put a couple guys on the moon for ~$200m launch cost.

According to Wikipedia, the LEM was 15 tonnes when it detached from the CM for the ride down to the surface.  20 tonnes is a bit better than that!

How did you get an effective ISP for BigBell SuperDraco of 362 seconds when the optimal vacuum ISP is just 336 seconds?  If 1730 m/s takes 43% of start mass as fuel, then you used something like ISP=314 s, right?  The LEM's stages were 311 s, so that sounds reasonable.

[sevenperforce]

By my calculations, FH full thrust with crossfeed can deliver 73 tonnes to LEO, 28 tonnes to EML-1, 20 tonnes to LLO, or 12 tonnes to the surface of the moon as a crasher stage.

Are those numbers with the Raptor upper stage? If not, could you run numbers with what we know of one?

Those are the numbers for the Falcon Heavy Full Thrust, back-calculated from the updates to GTO payload. The quoted FH payload to LEO has not changed since FH was first announced, but the GTO payload has gone up significantly.

The only difference between FH FT and F9 FT in GTO performance is the amount of fuel the upper stage has in the LEO parking orbit, so I used the performance from the SES-9 mission to determine how much fuel the FH upper stage would need in LEO in order to meet the quoted GTO payload flying fully-expendable. That's what gave me the 73-tonnes-to-LEO figure. The Full Thrust update gives the upper stage Merlin 1D Vacuum a specific impulse of 348 seconds, so everything else was just basic Hohmann transfer calculations from that starting point. It's possible that a bi-elliptic transfer on an unmanned segment of the mission could increase the payload significantly; that might be useful for two sequential launches where the first unmanned launch places the lander and crasher stage in stable LLO before the manned FH is cleared for launch.

I don't know the Raptor upper stage performance.

My two preferred mission profiles are the two-sequential-launch with double LOR and the single manned launch to EML-1 with a crasher stage and a direct ascent to aerobraking at Earth. The first one is safer than Apollo and has a huge payload for only two launches without any on-orbit assembly or refueling; the second one has the beauty of being a single launch and of landing the same spacecraft on more than one world.

Since there's much more fuel needed anyways could it make sense to put those tanks in the trunk along with one Vacuum SuperDraco? Leave the ones on the capsule as-is and possibly make up for the extra motor weight with a better expansion ratio and no cosine losses? It would avoid having to deal with detachable nozzle extensions on the capsule or extra fuel plumbing to those motors. They wouldn't be needed until Earth landing.

It doesn't make sense mathematically to drag engines down to the surface that you aren't going to use for ascent. Leave those engines in LLO and descend in a purpose-built lander.

Having separate descent and ascent stages can work, though I would still stick with the same engine set. The "descent stage" could consist of the landing legs and a drop tank. The only reason Apollo used two separate engines for the LM descent and ascent stages was that they hadn't gotten the hang of deep throttling (the descent stage engine was throttled by literally killing specific impulse and keeping the same fuel flow) and they wanted a descent stage with separate plumbing because they were worried about trying to do a drop tank. We have come a long way since then.

I really prefer the crasher stage architecture, though; if you have that big beefy transfer engine and its nice roomy tanks, why not use them? Then your lander only needs enough for hover and ascent rather than needing separate budgets for descent and ascent. It's also good because you get the dV-saving advantages of a suicide burn without the risks (at least, without the splat-landing risks; you have to add a stage separation event but that is basically the same as a launch abort so you should be fine). It's also good practice; eventually, you can use on-orbit propellant transfer and that crasher stage will have enough dV to return to orbit on its own for reuse.

If a separate engine is used, then SpaceX should dust off the Kestrel and build a purpose-built lander around it. But they've expressed a specific desire to use the Dragon V2 platform for these kinds of landings so that's probably the route they'd prefer.

I had this silly idea the other day.. if we were to offer to pay SpaceX to design a reference mission to send crew and cargo to the Moon, would they do it? I know they like money and they have engineers and stuff, but I can imagine they might not want to "waste their time" if you couldn't show you were serious. I wonder how much it'd cost if they did.

Actually this whole idea/thread was my attempt to personally do exactly that. If I can openly publish a series of mission architectures within high enough tolerances that SpaceX engineers can refine them into actual mission proposals, then they have every incentive to do so. Also to hire me. Though that last bit is more conjecture.

The idea of two launches for a moon-orbit rendezvous sounds pretty impressive, in the sense that you could put a couple guys on the moon for ~$200m launch cost.

More impressive if we can put a couple of guys on the moon with a single launch, though the tolerances for that mission profile are really tight.

How did you get an effective ISP for BigBell SuperDraco of 362 seconds when the optimal vacuum ISP is just 336 seconds?  If 1730 m/s takes 43% of start mass as fuel, then you used something like ISP=314 s, right?  The LEM's stages were 311 s, so that sounds reasonable

Whoops, it was supposed to be 332 seconds, not 362 seconds. I think I must have mistyped.

[shooter6947]

1. Dual series launch to double LOR. Falcon Heavy with unmanned Lunar Dragon to LLO, followed by Falcon Heavy with stock manned Dragon V2 to LLO. Orbital rendezvous; crew transfers to Lunar Dragon and uses the first Falcon Heavy's upper stage as a crasher stage to the lunar surface and the Lunar Dragon hovers to a landing. Lunar Dragon then makes ascent, docks with the stock Dragon V2 for crew transfer, and the second Falcon Heavy upper stage returns the stock Dragon V2 to Earth.

Sounds like this one would need propellant refrigeration -- not the end of the world, but a tech to develop.

[sevenperforce]

1. Dual series launch to double LOR. Falcon Heavy with unmanned Lunar Dragon to LLO, followed by Falcon Heavy with stock manned Dragon V2 to LLO. Orbital rendezvous; crew transfers to Lunar Dragon and uses the first Falcon Heavy's upper stage as a crasher stage to the lunar surface and the Lunar Dragon hovers to a landing. Lunar Dragon then makes ascent, docks with the stock Dragon V2 for crew transfer, and the second Falcon Heavy upper stage returns the stock Dragon V2 to Earth.

Sounds like this one would need propellant refrigeration -- not the end of the world, but a tech to develop.

If I recall correctly, LOX won't need refrigeration for a couple of weeks, particularly when the tank isn't very full and has room to self-pressurize a bit.

[nadreck]

Orbital propellant transfer is on the critical path to Mars for SpaceX so I don't think it is fair to rule it out.

Perhaps not rule it out entirely, but that would be something to test on a second manned mission with a secondary payload, rather than a first-time thing. That's another value of SpaceX servicing manned lunar landings: it gives them practice for what they will need to go to Mars.

The only values for SpaceX by their stated goals for servicing any lunar missions are for revenue first, then mission and craft development and refinement.

So if we go with my thesis of a lunar surface rendezvous, we send the return craft and support material/supplies via a refueled S2 launched on an FHR refeuled by three FHR launches. Once it has successfully landed the manned craft launches via FHE and lands beside the return craft. Total 4 FHR flights at total $320M one FHE $125M + 2 dragons and development to modify them adequately probably in the order of $200M.


Oh and I think freezing RP-1 will be the issue to worry about with propellant instead of losing all the LOX.

[sevenperforce]

So if we go with my thesis of a lunar surface rendezvous, we send the return craft and support material/supplies via a refueled S2 launched on an FHR refeuled by three FHR launches. Once it has successfully landed the manned craft launches via FHE and lands beside the return craft. Total 4 FHR flights at total $320M one FHE $125M + 2 dragons and development to modify them adequately probably in the order of $200M.

For a first mission, I think they would fly FH expendable all the way (except, of course, for the F9R if they staged at the ISS). Save FHR and on-orbit refueling for a second or third mission with non-mission-critical elements. If you look at SpaceX's track record, they always take a conservative approach and then attempt testing after all other mission elements have been satisfied...like the way they tested a second restart on the upper stage with the Jason mission in order to get ready for SES-9.

But a lunar surface rendezvous off a double FHE is an interesting possibility that I hadn't considered. It should allow for even more payload than a double LOR. It just lacks any sort of landing abort provisions and requires EVA to the ascent vehicle, which seems really risky.

[CuddlyRocket]

I don't think SpaceX will be going to the Moon until after the BFR/MCT has been developed. A system capable of getting to Mars and back will in all likelihood be capable of going to the Moon and back (perhaps with some modifications). I expect SpaceX would be willing to utilise the system on lunar missions - they would be useful test flights - and especially if someone else is paying!

[sevenperforce]

I don't think SpaceX will be going to the Moon until after the BFR/MCT has been developed. A system capable of getting to Mars and back will in all likelihood be capable of going to the Moon and back (perhaps with some modifications). I expect SpaceX would be willing to utilise the system on lunar missions - they would be useful test flights - and especially if someone else is paying!

I would imagine that if SpaceX can go to the moon now, with existing platforms, they would jump at the opportunity to test the tech and operations needed for Mars. The moon is a lot closer than Mars, and if they can use non-mission-critical legs of lunar missions to test technology like orbital propellant transfer, repeat rendezvous, uncrasher stages, hoverslam landings, and so forth, they can get to Mars that much earlier.

And as far as the bill is concerned...if SpaceX can offer a return to the moon 5-8 years earlier than the closest competitors, I am sure someone high-ranking at NASA would at least consider it.

[MikeAtkinson]

Getting 2 km/s out of such low-impulse engines requires a propellant mass fraction of 57%, which means an empty Dragon V2 (with a dry mass of 4.2 tonnes) would need at least 5.6 tonnes of propellant in order to get off the surface of the moon, 370% of its current fuel capacity.

That 4.2 tonnes is probably just the mass of the capsule, to that you need to add astronauts, moon suits, ECLSS consumables + margin, tools and equipment, mass for the extra tankage and bigger SuperDracos and propellant margin and residuals, and the trunk. So probably more like 8 tonnes which will need over 10 tonnes of propellant.

Dragon V2 is not designed for extended use without the trunk, which provides both power and cooling. Both of these might be might be problematic on the Lunar surface, due to Sun angle and reflected heat.

I think the best solution is to turn the trunk into a true service module, landing and ascent stage, but that is likely to mass even more.

Then EOR + propellant transfer. Second stage does TLI and then acts as a crasher stage. Landing by service module engine, ascent by service module engine to LLO, where it meets up with another second stage with propellant as its payload, propellant transfer to the service module then TEI and powered landing on Earth.

Significant enhancements to the second stage would be required and a completely new service module, but no major modifications to Dragon V2 (no outer mold line changes like would be needed for a larger nozzle SuperDraco).

I think however SpaceX will wait until MCT, the BFS should be able to do a moon mission with plenty of margin.

[IainMcClatchie]

Consider the following:

Elon Musk proposes the following to Hillary or Donald (I don't want to touch which one in this forum):
* Boots on the moon with NASA badges on the shoulders and no Russian vehicles or speakers during the 2020 re-election campaign, for $5 billion.  This is way cheaper than even a small military foray.
* Major, sustained distraction from foreign policy nightmares by a team that has demonstrated ongoing ability to capture and keep the American public's attention.
* Executed by a NewSpace company (free enterprise and all that).
* Clears away all the old government SLS crap, appears decisive, and yet provides plenty of jobs in CA, TX, and FL.  Also can be seen to validate the Commercial Crew initiative if under a Democratic administration.
* Will be visibly different than Apollo:
   * high-def landing and relaunch video via preplaced unmanned lander
   * landing video of and from the lunar crasher stage.  People love watching stuff go boom.
   * Lots of downlink bandwidth via three lunar orbiting relays
   * GoPros on practically everything, dedicated production staff similar to an NFL game, lots of earnest engineers explaining how it works (SpaceX has to get better at this).
   * bigger and better looking hardware that looks like an Apple product
   * more people on the surface at one time.  Three will do.
   * obviously practice with the hardware for Mars landing, so there is a future.  This means inflating stuff and driving around.

[wannamoonbase]

Consider the following:

Elon Musk proposes the following to Hillary or Donald (I don't want to touch which one in this forum):
* Boots on the moon with NASA badges on the shoulders and no Russian vehicles or speakers during the 2020 re-election campaign, for $5 billion.  This is way cheaper than even a small military foray.
* Major, sustained distraction from foreign policy nightmares by a team that has demonstrated ongoing ability to capture and keep the American public's attention.
* Executed by a NewSpace company (free enterprise and all that).
* Clears away all the old government SLS crap, appears decisive, and yet provides plenty of jobs in CA, TX, and FL.  Also can be seen to validate the Commercial Crew initiative if under a Democratic administration.
* Will be visibly different than Apollo:
   * high-def landing and relaunch video via preplaced unmanned lander
   * landing video of and from the lunar crasher stage.  People love watching stuff go boom.
   * Lots of downlink bandwidth via three lunar orbiting relays
   * GoPros on practically everything, dedicated production staff similar to an NFL game, lots of earnest engineers explaining how it works (SpaceX has to get better at this).
   * bigger and better looking hardware that looks like an Apple product
   * more people on the surface at one time.  Three will do.
   * obviously practice with the hardware for Mars landing, so there is a future.  This means inflating stuff and driving around.

Nice ideas, but lets see if whomever the POTUS is and congress can agree on anything at all first.

I'm hopeful the next POTUS dumps the flat and lame asteroide mission thing and aims straight to the moon.  Orion, SLS, commercial capabilities. 

But again they branches of government need to work at a primitive level first.

[JamesH65]

Consider the following:

Elon Musk proposes the following to Hillary or Donald (I don't want to touch which one in this forum):
* Boots on the moon with NASA badges on the shoulders and no Russian vehicles or speakers during the 2020 re-election campaign, for $5 billion.  This is way cheaper than even a small military foray.
* Major, sustained distraction from foreign policy nightmares by a team that has demonstrated ongoing ability to capture and keep the American public's attention.
* Executed by a NewSpace company (free enterprise and all that).
* Clears away all the old government SLS crap, appears decisive, and yet provides plenty of jobs in CA, TX, and FL.  Also can be seen to validate the Commercial Crew initiative if under a Democratic administration.
* Will be visibly different than Apollo:
   * high-def landing and relaunch video via preplaced unmanned lander
   * landing video of and from the lunar crasher stage.  People love watching stuff go boom.
   * Lots of downlink bandwidth via three lunar orbiting relays
   * GoPros on practically everything, dedicated production staff similar to an NFL game, lots of earnest engineers explaining how it works (SpaceX has to get better at this).
   * bigger and better looking hardware that looks like an Apple product
   * more people on the surface at one time.  Three will do.
   * obviously practice with the hardware for Mars landing, so there is a future.  This means inflating stuff and driving around.

Nice ideas, but lets see if whomever the POTUS is and congress can agree on anything at all first.

I'm hopeful the next POTUS dumps the flat and lame asteroide mission thing and aims straight to the moon.  Orion, SLS, commercial capabilities. 

But again they branches of government need to work at a primitive level first.

Asteroid mission is scientifically more interesting I suspect.

[stoker5432]

2. ISS to EML-1; crasher-stage direct ascent. Single Falcon 9 launch takes crew and Dragon V2 to ISS; docks. Falcon Heavy lifts Lunar Dragon to the ISS; crew and consumables transfer; Falcon Heavy transfers to EML-1 and then burns crasher-stage to drop a Lunar Dragon with additional fuel on the lunar surface. Lunar Dragon makes ascent and transfer to ISS and crew returns to earth via docked Dragon V2.

This mission profile looks like a winner to me for the manned part of the mission. Here's why:

1. Cheapest combination of launch vehicles: Falcon 9R and Falcon Heavy Expendable
2. Unused seats on Commercial Crew spacecraft (possible subsidizing)
3. Possible replacement of crasher stage and refueling of lunar dragon for future missions. ISS robotic arms courtd also prove useful in this operation. (possibly moving to Falcon Heavy reusable)
4. Various present and future docking options: ISS, spacecraft to spacecraft, Bigelow
5. Other options for earth to LEO crew delivery that can be substituted for both the spacecraft and launch vehicle.

[sevenperforce]

2. ISS to EML-1; crasher-stage direct ascent. Single Falcon 9 launch takes crew and Dragon V2 to ISS; docks. Falcon Heavy lifts Lunar Dragon to the ISS; crew and consumables transfer; Falcon Heavy transfers to EML-1 and then burns crasher-stage to drop a Lunar Dragon with additional fuel on the lunar surface. Lunar Dragon makes ascent and transfer to ISS and crew returns to earth via docked Dragon V2.

This mission profile looks like a winner to me for the manned part of the mission. Here's why:

1. Cheapest combination of launch vehicles: Falcon 9R and Falcon Heavy Expendable
2. Unused seats on Commercial Crew spacecraft (possible subsidizing)
3. Possible replacement of crasher stage and refueling of lunar dragon for future missions. ISS robotic arms courtd also prove useful in this operation. (possibly moving to Falcon Heavy reusable)
4. Various present and future docking options: ISS, spacecraft to spacecraft, Bigelow
5. Other options for earth to LEO crew delivery that can be substituted for both the spacecraft and launch vehicle.

Yeah, it's nice. The biggest drawback here is that it requires the largest dV for the lander. Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

[stoker5432]

Yeah, it's nice. The biggest drawback here is that it requires the largest dV for the lander. Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

Yes if your only talking about dV and not cost, but I'm assuming the profile you gave was still plausible for a useful manned mission. Was I incorrect in this assumption?

[the_other_Doug]

Yeah, it's nice. The biggest drawback here is that it requires the largest dV for the lander. Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

Yes if your only talking about dV and not cost, but I'm assuming the profile you gave was still plausible for a useful manned mission. Was I incorrect in this assumption?

Oh, it's plausible.  It's something of a flags-and-footprints mission, in that it requires more launches, and more equipment, than the two launches proposed to do more than what Apollo managed to accomplish.

Not that this is a bad idea.  If it can be done for a tenth of Apollo's cost, and provide an architecture with enough re-usable elements to also reduce ongoing equipment costs, then we have a transport capability that, depending on what you want to do with it, could be considered semi-affordable.

I think, though, that it makes more sense to wait a few years, let NASA set up an Orion-serviced way station in high lunar orbit, and use that for your reusable lander resupply shop.  The delta-V requirements to get to the lunar surface from HLO and back are much lower than those quoted for LLO, aerocapture and LEO, right?

So, you could start out with needing three or four FH launches to set things up, and after that you would launch two FH's for every expedition.  But both would be used to refurbish a reusable lander that just shuttled from HLO to the lunar surface, and to provide a return vehicle from HLO back to Earth.

It's not a bad idea to test out some of those systems with a more limited flags-and-footprints set of missions, but you want to make certain you're not throwing a ton of money into dead-end technology that won't be useful once you get the cislunar way station set up -- much less into technology that doesn't serve to support the main goal of putting a colony on Mars.

To my knowledge, SpaceX has not yet seen a business case for attempting crewed lunar landings.  This could change, of course -- this is SpaceX, after all.

I'd love to see it, but I guess I'm not holding my breath.

[sevenperforce]

Yeah, it's nice. The biggest drawback here is that it requires the largest dV for the lander. Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

Yes if your only talking about dV and not cost, but I'm assuming the profile you gave was still plausible for a useful manned mission. Was I incorrect in this assumption?

No, it's plausible; it just greatly limits payload since so much of your landing vehicle has to be fuel. And FHE might have trouble getting enough mass to the lunar surface with any remaining payload.

If I get a chance I'll put together a comprehensive diagram of the exact dV and FHE payload numbers to and from each Earth-Lunar node. There are some helpful tricks along the way...for example, if you take a highly-eccentric Hohmann transfer just past EML-1, you can "fall through" into the lunar gravity well without needing to circularize, saving you about 500 m/s of dV. But you can't efficiently enter lunar orbit from this node; it's only useful if you are willing to drop straight to the surface and suicide burn away the 2.24 km/s impact speed. Also, Hohmann transfer from a 100 km parking orbit to any lunar node saves you noteworthy dV over transfer from the ISS thanks to old Oberth.

The only Earth Orbit Assembly I could see being feasible would be mating a crew capsule to a Falcon upper stage at the ISS using Canadarm, because it's something they could conceivably test as a nonessential part of a routine mission. Dock the capsule with the Falcon 9 upper stage still attached, then use Canadarm to remove it and replace it a couple of times. If that's simple enough, then it would be reasonable to launch the unmanned, loaded Lunar Dragon and the manned Dragon V2 to the ISS on a couple of F9Rs and then launch an empty FHE to the ISS to be mated to the Lunar Dragon as a transfer vehicle.

[stoker5432]

I like option 3 too of course, but I have to wonder how much work has to be done on that Dragon to make it dual purpose verses a Dragon derived lunar lander.

[sevenperforce]

I think, though, that it makes more sense to wait a few years, let NASA set up an Orion-serviced way station in high lunar orbit, and use that for your reusable lander resupply shop.  The delta-V requirements to get to the lunar surface from HLO and back are much lower than those quoted for LLO, aerocapture and LEO, right?

Getting from LLO to an Earth aerocapture trajectory is actually really, really cheap. You can do a highly eccentric Hohmann transfer to EML-1, slide through, and essentially free fall to the high-velocity re-entry at an angle of your choosing with just a couple of RCS puffs. There is a good bit of dV spent circularizing that you can avoid if you do this sort of maneuver.

Regardless, SpaceX's major advantage disappears if you wait for a cislunar station. The Falcon family has very poor BLEO performance. The advantage exists if and only if SpaceX can boast lunar capability now, despite the low performance of their platforms.

[sevenperforce]

I like option 3 too of course, but I have to wonder how much work has to be done on that Dragon to make it dual purpose verses a Dragon derived lunar lander.

It would take a lot of work, but not necessarily any more work than it would take to build a single-function Dragon-derived lunar lander. The major issue would be installing an auxiliary fuel tank inside the cabin without introducing significant risk. You end up with a significantly smaller payload, but the advantage of only needing a single vehicle for both the Moon and Earth cannot be overstated.

[stoker5432]

You need the trunk. Why don't you put the extra propellant there?

[sevenperforce]

You need the trunk. Why don't you put the extra propellant there?

You can use batteries; that's what the LM did. Landing on the trunk requires a second set of landing legs and an extended egress system, and is riskier due to the high center of mass.

[MikeAtkinson]

I like option 3 too of course, but I have to wonder how much work has to be done on that Dragon to make it dual purpose verses a Dragon derived lunar lander.

It would take a lot of work, but not necessarily any more work than it would take to build a single-function Dragon-derived lunar lander. The major issue would be installing an auxiliary fuel tank inside the cabin without introducing significant risk. You end up with a significantly smaller payload, but the advantage of only needing a single vehicle for both the Moon and Earth cannot be overstated.

Won't work.

The final mass of the Dragon 2 after ascent will be about 8 tonnes, needing about 10 tonnes of propellant. This extra propellant will take up essentially the whole of the cabin.

This 8 tonnes includes the trunk as Dragon can only survive a short time without the power and cooling provided by the trunk. Also fuel margin and residuals, extra tank(s) and predestination system. Also crew, ECLSS supplies, etc.

[IainMcClatchie]

Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

So with your Lunar Dragon + Return Dragon mission, we can compare the delta-V needed for both Dragons after they've both achieved LLO.
* Lunar Dragon needs 1.9 km/s down and 1.9 km/s back up.  That's 3.8 km/s.
* Return Dragon needs something like 0.9 km/s to get from LLO to aerobraking return.  That's a lot less.

If I understand correctly, you are thinking that Lunar Dragon gets the extra delta-V by not having a heat shield and having better Isp from bigger engine bells... and then just much bigger tanks.  Since both are postulated to lift off with the same Falcon Heavy launcher, the return Dragon is going to have a bunch of extra payload capacity compared to the Lunar Dragon.

It seems to me you are going to want to put a few tonnes of stuff on the return Dragon and then transfer that stuff to the Lunar Dragon in LLO before descent.  Would it make sense for the return Dragon to carry the Lunar Dragon's extra-big fuel tanks, and plonk them ON TOP of the Lunar Dragon?  They'll be mostly empty once it lands, so the center-of-mass problem isn't so bad.

Having a nice diagram which makes it easy to understand how to allocate delta-V would be great.  Something like this, which I'm sure you've seen:

[Andy Smith]

Assuming one reusable tanker was built (enlarged second stage tanks with Pica, launched by FHR), then refuelling a depot at LEO is achievable, multiple fuelling runs just cost fuel. Later on, refuelling the tanker itself from the depot, means the now fully loaded tanker could travel to EML-2 and refuel a second depot before returning to Earth.

Second stages for lunar missions could be refuelled twice (LEO and EML-2) and carry at least 25 tons to the lunar surface - not quite so much of a hover slam when carrying that payload.

The depot could be an F9 first stage, modified for refuelling capability. A first stage is just about ssto capable with no payload, then following fuelling it could be used as a depot, or take itself to EML-2. For decommissioning, or maintenance, the "depot" would have enough delta v to slow down and land without needing heat shielding (ssto in reverse).

Almost fully reusable infrastructure could make the costs of achieving lunar missions very very low

[nadreck]

Regardless, SpaceX's major advantage disappears if you wait for a cislunar station. The Falcon family has very poor BLEO performance. The advantage exists if and only if SpaceX can boast lunar capability now, despite the low performance of their platforms.

The FH is projected to have better TLI performance than any current vehicle. But there is no advantage to SpaceX to building any sort of lunar capacity with the current Falcon Upper stage. Without being commissioned for a mission like this that requires it, they have no reason to keeping RP-1 from freezing for more than 12 hours, they have no reason to transfer RP-1, they have no reason to make a dragon with that much ΔV, no reason to work towards long term ECLSS before the MCT, and they have no reason to make an ascent vehicle before the MCT.

So if someone commissions them in the very short term, it would be that organizations imperative (and therefore funds) that drove it.  However, if SpaceX wants to test elements of its eventual Mars capability and if they actually go through with developing at Raptor based FH upper stage then, maybe, I can see them working with a partner with lunar ambitions towards a manned excursion/base.  In that circumstance some SpaceX ambition might drive giving the partner some cost advantages as SpaceX proves capability. In all other circumstances, except using the Dragon as a lander without ascent capability, I expect the only driver for SpaceX would be that it was a contract that furthers their business aims, but not one that tests anything useful to be incorporated on future Mars expeditions. In the meantime SpaceX can and will work on unmanned lunar projects, possibly even a communications constellation.

[CuddlyRocket]

I don't think SpaceX will be going to the Moon until after the BFR/MCT has been developed. A system capable of getting to Mars and back will in all likelihood be capable of going to the Moon and back (perhaps with some modifications). I expect SpaceX would be willing to utilise the system on lunar missions - they would be useful test flights - and especially if someone else is paying!

I would imagine that if SpaceX can go to the moon now, with existing platforms, they would jump at the opportunity to test the tech and operations needed for Mars.

But SpaceX can't go to the Moon with existing platforms - Falcon/Dragon - or at least not without extensive modifications, the development of which will take both financial and engineering resources away from developing BFR/MCT, delaying the latter. Plus there's little overlap between the tech proposed to be used for, and the operations of, Falcon/Dragon lunar and BFR/MCT Mars missions.

The moon is a lot closer than Mars, and if they can use non-mission-critical legs of lunar missions to test technology like orbital propellant transfer, repeat rendezvous, uncrasher stages, hoverslam landings, and so forth, they can get to Mars that much earlier.

You don't need to use lunar missions for most (all?) of this; it can be done in LEO. But more importantly, you're not testing the BFR/MCT; you're testing similar equipment on other spacecraft. As an analogy, testing and flying the Airbus A-320, A-340 etc didn't reduce the testing required for the A-380.

And as far as the bill is concerned...if SpaceX can offer a return to the moon 5-8 years earlier than the closest competitors, I am sure someone high-ranking at NASA would at least consider it.

Probably. But possibly they might consider it better to wait for the BFR/MCT. After all, they don't need to beat the closest competitors by 5-8 years. One year would suffice for bragging rights.

[Zed_Noir]

I like option 3 too of course, but I have to wonder how much work has to be done on that Dragon to make it dual purpose verses a Dragon derived lunar lander.

It would take a lot of work, but not necessarily any more work than it would take to build a single-function Dragon-derived lunar lander. The major issue would be installing an auxiliary fuel tank inside the cabin without introducing significant risk. You end up with a significantly smaller payload, but the advantage of only needing a single vehicle for both the Moon and Earth cannot be overstated.

Won't work.

The final mass of the Dragon 2 after ascent will be about 8 tonnes, needing about 10 tonnes of propellant. This extra propellant will take up essentially the whole of the cabin.

This 8 tonnes includes the trunk as Dragon can only survive a short time without the power and cooling provided by the trunk. Also fuel margin and residuals, extra tank(s) and predestination system. Also crew, ECLSS supplies, etc.

How about having an external prop module with the trunk functions mounted on the Dragon's nose. Along with an austere trunk discarded prior to landing on the Moon. Presuming you can land the Dragon with a module on top. To land this LEGO stack on the Moon will need to stacked another prop module as a pop off crasher stage.

Again presuming you can land the Dragon with a module on top. The modifications on the Dragon will be external prop lines and trunk function interfaces with the prop module through the docking hatch.

[cuddihy]

What does an "austere tank" look like exactly. I've always puzzled over this one when drop tanks are discussed for a lander--where does it physically fit in a stack for launching and how does it detach kinematically?

[stoker5432]

Oh and I think freezing RP-1 will be the issue to worry about with propellant instead of losing all the LOX.

So basically all these mission profiles dead in the water if this problem can't solved. Knew it was to good to be true.

[Owlon]

Oh and I think freezing RP-1 will be the issue to worry about with propellant instead of losing all the LOX.

So basically all these mission profiles dead in the water if this problem can't solved. Knew it was to good to be true.

Yes, any proposal using a Falcon 2nd stage in the vicinity of the moon involves some significant changes to the stage. For all we know some of that work might already be underway for one reason or another, but the 2nd stage as-is can't do it.

[AncientU]

woah...
http://clapway.com/2016/03/24/nasa-spacex-colonize-moon/

[MattMason]

Consider the following:

Elon Musk proposes the following to Hillary or Donald (I don't want to touch which one in this forum):
* Boots on the moon with NASA badges on the shoulders and no Russian vehicles or speakers during the 2020 re-election campaign, for $5 billion.  This is way cheaper than even a small military foray.
* Major, sustained distraction from foreign policy nightmares by a team that has demonstrated ongoing ability to capture and keep the American public's attention.
* Executed by a NewSpace company (free enterprise and all that).
* Clears away all the old government SLS crap, appears decisive, and yet provides plenty of jobs in CA, TX, and FL.  Also can be seen to validate the Commercial Crew initiative if under a Democratic administration.
* Will be visibly different than Apollo:
   * high-def landing and relaunch video via preplaced unmanned lander
   * landing video of and from the lunar crasher stage.  People love watching stuff go boom.
   * Lots of downlink bandwidth via three lunar orbiting relays
   * GoPros on practically everything, dedicated production staff similar to an NFL game, lots of earnest engineers explaining how it works (SpaceX has to get better at this).
   * bigger and better looking hardware that looks like an Apple product
   * more people on the surface at one time.  Three will do.
   * obviously practice with the hardware for Mars landing, so there is a future.  This means inflating stuff and driving around.

I'm going to echo Jim's typical comments that I often see from him about the government and the Moon:

 Why? There's no project whatsoever that justifies a government-sponsored or financed Moon mission at this time.

Such a mission would undermine any Mars development funding. Such funding would also be shooting somebody in their political foot with all the activism of "keeping money at home" in social programs with protests that have never stopped in intent since the Apollo era.

The last POTUS killed NASA's Constellation program intent on returning to the Moon, anyway--which was proposed by his predecessor.

Any return to the Moon, in my opinion, will be of commercial interests only. And that reason may come only when some billionaire(s) convince other billionaires that a lunar hotel and city or mining interest would be a very cool and lucrative idea. And that can't happen until the companies who are finalizing private LEO vehicles are flying regularly, and then only once LEO commercial public applications (hotels or commercial use) are in place to convince the public that going to space is safe, much less straight to the moon.

I agree that there's not a technical reason why SpaceX can't return to the moon. The question is, what would drive them to go there? Hint: It's not Elon Musk. Some other high interests must contract his company to go there.

[RanulfC]

woah...
http://clapway.com/2016/03/24/nasa-spacex-colonize-moon/

Agreed, that's one terribly unclear, misleading and un-informative article! And it's precursor's are worse!
(And Mars was musically referenced by Elton John, not David Bowie )

Considering the author cites a previous article he wrote about Russia going to the Moon, (in which it specifically states that the Russian's are significantly cutting their program funding, yet notes it is still "seriously" considering a Lunar COLONY by 2039) and then cites "research" having NASA buy Falcon Heavy launches to supply a colony on the Moon, I'm wondering if the author hasn't seen the Lunar Station thread here on NSF and inferred far to much into the concept.

Randy

[nadreck]

woah...
http://clapway.com/2016/03/24/nasa-spacex-colonize-moon/

Agreed, that's one terribly unclear, misleading and un-informative article! And it's precursor's are worse!
(And Mars was musically referenced by Elton John, not David Bowie )

Considering the author cites a previous article he wrote about Russia going to the Moon, (in which it specifically states that the Russian's are significantly cutting their program funding, yet notes it is still "seriously" considering a Lunar COLONY by 2039) and then cites "research" having NASA buy Falcon Heavy launches to supply a colony on the Moon, I'm wondering if the author hasn't seen the Lunar Station thread here on NSF and inferred far to much into the concept.

Randy

"Life on Mars" is a song by David Bowie from the Album Hunky Dorie then the Ziggy Stardust Album had at least one song that referenced Mars "5 Years"

However the article is incredibly weak and the headlined timeline is in no way supported by any item in the article. So it just counts as click bait to me.

[sevenperforce]

I like option 3 too of course, but I have to wonder how much work has to be done on that Dragon to make it dual purpose verses a Dragon derived lunar lander.

It would take a lot of work, but not necessarily any more work than it would take to build a single-function Dragon-derived lunar lander. The major issue would be installing an auxiliary fuel tank inside the cabin without introducing significant risk. You end up with a significantly smaller payload, but the advantage of only needing a single vehicle for both the Moon and Earth cannot be overstated.

Won't work.

The final mass of the Dragon 2 after ascent will be about 8 tonnes, needing about 10 tonnes of propellant. This extra propellant will take up essentially the whole of the cabin.

This 8 tonnes includes the trunk as Dragon can only survive a short time without the power and cooling provided by the trunk. Also fuel margin and residuals, extra tank(s) and predestination system. Also crew, ECLSS supplies, etc.

I came up with slightly different numbers.

The Dragon V2 has a dry mass of 4.2 tonnes and a quoted payload capacity of 3.3 tonnes with an internal pressurized volume of 10 cubic meters. You have to assume that the fully-crewed version will mass lower than 3.3 tonnes; people and their living space aren't very dense. So it's conservative to set the mass of a crew of two plus consumables at 1.1 tonnes.

The Dragon V2's 10 cubic meters of space allocates 1.43 m³ per crew member...slightly less than the 2.07 m³ allocated by the Apollo CM or the 3.35 m² allocated by the LM. Let's strike a balance and give each of our two crew members 50% more space than the Dragon V2 would typically give them: 2.14 m² each. That more than the CM, though less than the LM.

This means we have freed up 7.86 cubic meters of internal volume. If we can pack regular-solid tanks with 95% efficiency, and the tank volume is 4% of the fuel volume (allowing for a pressurization tank), then we have 7.17 cubic meters of fuel capacity to work with. MMH/NTO masses 1200 kg per cubic meter so that's 8.6 tonnes of fuel.

Add the 1,388 kg of fuel already in the stock internal tank and you have 9,990 kg of fuel.

I'm not sure what mass cost would be incurred by adding extended protruding nozzles to the SuperDracos, but I'll just throw out 100 kg as a round number. Let's allow 200 kg for the mass of the auxiliary tanks and associated systems, bringing the loaded mass of the Dragon V2 (without the trunk) to 15.59 tonnes.

With the previously-noted target impulse of 332 seconds (accounting for the angle offset), this gives you 3,331 m/s of dV. That's not enough for descent and ascent, but it's more than enough to launch to LLO and burn the transfer to LEO intercept and aerobrake. So if your FHE can deliver this plus the trunk in a crasher stage configuration to just above the lunar surface, you're golden.

Note: setting crew and consumables at 1100 kg means everything. Assume the crew eats up 200 kg, leaving 900 kg for food, oxygen, batteries, repressurization air, waste disposal, spacesuits, and a flag (total for lunar stay and return trip; additional consumables used in cislunar transfer will be consumed or dumped before ascent). That may or may not be realistic. The Dragon V2 can supposedly survive depressurized re-entry, so its control systems must be solid-state, so you'll want to weigh the mass cost of repeated cabin repressurization against the mass cost of adding an inflatable airlock a la Volga.

This is for a single-capsule landing on a single FHE. For the somewhat safer double-series FHE with separate Lunar Dragon, the Lunar Dragon can lose its parachute and heat shield and hold significantly more fuel volume while also allowing for a larger crew. If you want to stage from the ISS, then the Lunar Dragon will have to have at least 3.8 km/s of dV so that it can make descent and ascent on its own and use the Falcon upper stage for the 4 km/s transfer back to the ISS.

Getting from the lunar surface to LLO requires 1.9 km/s; getting from the lunar surface to Earth aerobraking trajectory requires 2.8 km/s; getting from the lunar surface to LEO requires a whopping 5.9 km/s. Direct ascent to Earth aerobraking is so much cheaper than direct ascent to LEO.

So with your Lunar Dragon + Return Dragon mission, we can compare the delta-V needed for both Dragons after they've both achieved LLO.
* Lunar Dragon needs 1.9 km/s down and 1.9 km/s back up.  That's 3.8 km/s.
* Return Dragon needs something like 0.9 km/s to get from LLO to aerobraking return.  That's a lot less.

If I understand correctly, you are thinking that Lunar Dragon gets the extra delta-V by not having a heat shield and having better Isp from bigger engine bells... and then just much bigger tanks.  Since both are postulated to lift off with the same Falcon Heavy launcher, the return Dragon is going to have a bunch of extra payload capacity compared to the Lunar Dragon.

It seems to me you are going to want to put a few tonnes of stuff on the return Dragon and then transfer that stuff to the Lunar Dragon in LLO before descent.  Would it make sense for the return Dragon to carry the Lunar Dragon's extra-big fuel tanks, and plonk them ON TOP of the Lunar Dragon?  They'll be mostly empty once it lands, so the center-of-mass problem isn't so bad.

Having a nice diagram which makes it easy to understand how to allocate delta-V would be great.  Something like this, which I'm sure you've seen: (snip)

Yeah, I've seen that, but it's not quite as detailed as I am thinking.

I can't imagine that putting tanks on top of the lander is a good idea. You have to deal with fuel lines running from outside the vehicle to inside...and, if you are carrying them somewhere else, then you have de facto on-orbit assembly of hypergolic tanks. Yikes.

I don't think SpaceX will be going to the Moon until after the BFR/MCT has been developed. A system capable of getting to Mars and back will in all likelihood be capable of going to the Moon and back (perhaps with some modifications). I expect SpaceX would be willing to utilise the system on lunar missions - they would be useful test flights - and especially if someone else is paying!

I would imagine that if SpaceX can go to the moon now, with existing platforms, they would jump at the opportunity to test the tech and operations needed for Mars.

But SpaceX can't go to the Moon with existing platforms - Falcon/Dragon - or at least not without extensive modifications, the development of which will take both financial and engineering resources away from developing BFR/MCT, delaying the latter. Plus there's little overlap between the tech proposed to be used for, and the operations of, Falcon/Dragon lunar and BFR/MCT Mars missions.

The moon is a lot closer than Mars, and if they can use non-mission-critical legs of lunar missions to test technology like orbital propellant transfer, repeat rendezvous, uncrasher stages, hoverslam landings, and so forth, they can get to Mars that much earlier.

You don't need to use lunar missions for most (all?) of this; it can be done in LEO. But more importantly, you're not testing the BFR/MCT; you're testing similar equipment on other spacecraft. As an analogy, testing and flying the Airbus A-320, A-340 etc didn't reduce the testing required for the A-380.

Elon has talked very clearly about using the Dragon V2 to deliver payload to the moon and other bodies. So that's definitely something they are developing. And as far as testing is concerned, sure, it's not directly applicable, but we are less in the Airbus A-320 era and more in the Wright Brothers era when it comes to interplanetary manned travel.

And as far as the bill is concerned...if SpaceX can offer a return to the moon 5-8 years earlier than the closest competitors, I am sure someone high-ranking at NASA would at least consider it.

Probably. But possibly they might consider it better to wait for the BFR/MCT. After all, they don't need to beat the closest competitors by 5-8 years. One year would suffice for bragging rights.

They better get an early start, considering their record on delays....

Oh and I think freezing RP-1 will be the issue to worry about with propellant instead of losing all the LOX.

So basically all these mission profiles dead in the water if this problem can't solved. Knew it was to good to be true.

Yes, any proposal using a Falcon 2nd stage in the vicinity of the moon involves some significant changes to the stage. For all we know some of that work might already be underway for one reason or another, but the 2nd stage as-is can't do it.

That's a critical issue, one I hadn't thought about. How long does it take for RP-1 to freeze in space?

This also completely prevents any consideration of putting a fuel depot in space because even if RP-1 can last long enough for a lunar mission it's not going to just sit around up there.

[nadreck]

Oh and I think freezing RP-1 will be the issue to worry about with propellant instead of losing all the LOX.

So basically all these mission profiles dead in the water if this problem can't solved. Knew it was to good to be true.

Yes, any proposal using a Falcon 2nd stage in the vicinity of the moon involves some significant changes to the stage. For all we know some of that work might already be underway for one reason or another, but the 2nd stage as-is can't do it.

That's a critical issue, one I hadn't thought about. How long does it take for RP-1 to freeze in space?

This also completely prevents any consideration of putting a fuel depot in space because even if RP-1 can last long enough for a lunar mission it's not going to just sit around up there.

It can't really be pumped below -50C and the issue isn't how quickly it cools off in space, but how quickly does it cool off in contact with the common bulkhead with the Lox tank?  You could come up with a system to add heat to the RP-1 but then you are heating the LOX. Theoretically if you used active cooling on the Lox you could dump the waste heat from the active cooling into the RP-1, however it makes far more sense for a long life cryo stage to use two liquids that have close to compatible temps like Lox and Methane.

[sevenperforce]

How long does it take for RP-1 to freeze in space?

This also completely prevents any consideration of putting a fuel depot in space because even if RP-1 can last long enough for a lunar mission it's not going to just sit around up there.

It can't really be pumped below -50C and the issue isn't how quickly it cools off in space, but how quickly does it cool off in contact with the common bulkhead with the Lox tank?  You could come up with a system to add heat to the RP-1 but then you are heating the LOX. Theoretically if you used active cooling on the Lox you could dump the waste heat from the active cooling into the RP-1, however it makes far more sense for a long life cryo stage to use two liquids that have close to compatible temps like Lox and Methane.

All you would need, I suppose, is a pressurized bulkhead that can be voided in space. No temperature exchange that way.

[nadreck]

How long does it take for RP-1 to freeze in space?

This also completely prevents any consideration of putting a fuel depot in space because even if RP-1 can last long enough for a lunar mission it's not going to just sit around up there.

It can't really be pumped below -50C and the issue isn't how quickly it cools off in space, but how quickly does it cool off in contact with the common bulkhead with the Lox tank?  You could come up with a system to add heat to the RP-1 but then you are heating the LOX. Theoretically if you used active cooling on the Lox you could dump the waste heat from the active cooling into the RP-1, however it makes far more sense for a long life cryo stage to use two liquids that have close to compatible temps like Lox and Methane.

All you would need, I suppose, is a pressurized bulkhead that can be voided in space. No temperature exchange that way.

But that is no longer the Falcon upper stage then, this adds mass, changes the structure and tooling, and won't be done unless their is a compelling reason. While it is only my WAG, this change would not be important enough to them to bother with if they were working on a Methalox US for the Falcon family even if it turned out to be needed for GSO missions (ie if they couldn't get 8 hours out of the existing US).

[su27k]

Why? There's no project whatsoever that justifies a government-sponsored or financed Moon mission at this time.

At the risk of going off-topic:
* It would give BLEO part of NASA something worthwhile to do
* It's a goal near enough that should be achievable within 2 presidential terms
* It's something both old space and new space can participate, a compromise that should get it sufficient support in congress.

Such a mission would undermine any Mars development funding.

The problem with Mars is it's a binary choice, either you go with SLS/Orion or you go with SpaceX BFR/MCT, there's no choice in between, and I doubt Elon Musk has enough lobbying power to dislodge the SLS/Orion cult in congress.

Such funding would also be shooting somebody in their political foot with all the activism of "keeping money at home" in social programs with protests that have never stopped in intent since the Apollo era.

I think the idea here is that the project will just use the existing NASA exploration budget, no funding increase required. Obviously you'll have to cancel SLS for this.

The question is, what would drive them to go there?

Government money....

[Eric Hedman]

Here is the first article I've seen on SpaceX's plans for a Moon base by 2026:

http://www.thesundaytimes.co.uk/sto/news/article1682341.ece

[the_other_Doug]

The question is, what would drive them to go there?

Government money....

That's like asking "What would drive a man to the mall with a truckload full of guns, ready to shoot everyone he sees?" and getting the answer "A Ford F-150"...

[stoker5432]

The question is, what would drive them to go there?

Government money....

That's like asking "What would drive a man to the mall with a truckload full of guns, ready to shoot everyone he sees?" and getting the answer "A Ford F-150"...

Same rational as when people say SpaceX will land BFS on the moon.

[docmordrid]

The question is, what would drive them to go there?

Government money....

That's like asking "What would drive a man to the mall with a truckload full of guns, ready to shoot everyone he sees?" and getting the answer "A Ford F-150"...

Same rational as when people say SpaceX will land BFS on the moon.

"I don't think the Moon is a necessary step, but I think if you've got a rocket and spacecraft capable of going to Mars, you might as well go to the Moon as well - it's along the way. "
~~ Elon Musk

http://shitelonsays.com/transcript/elon-musk-at-mits-aeroastro-centennial-part-2-of-6-2014-10-24

[FutureSpaceTourist]

Here is the first article I've seen on SpaceX's plans for a Moon base by 2026:

http://www.thesundaytimes.co.uk/sto/news/article1682341.ece

Thanks for this. Hopefully the fact that Steve Jurvetson is pushing this means there's some real SpaceX interest? (although Steve has been a lunar base proponent for years)

Of course SpaceX used to market lunar payload services (see attached), although I've not seen anything since 2008. My guess is that they were opportunistically targeting GLXP entrants.

[Hauerg]

Here is the first article I've seen on SpaceX's plans for a Moon base by 2026:

http://www.thesundaytimes.co.uk/sto/news/article1682341.ece

Is there any newish info in there? (Is behind a paywall).
Thanks

[hopalong]

Here is the first article I've seen on SpaceX's plans for a Moon base by 2026:

http://www.thesundaytimes.co.uk/sto/news/article1682341.ece

Is there any newish info in there? (Is behind a paywall).
Thanks

It is virtually information free. All it says is that the plan is being pushed by Steve Jurvetson, a private space sector investor, along with Elon Musk’s SpaceX and Planet Labs, a satellite firm at a cost of $6.5B. The target is Peary Crater near the north pole.

It is more 'click bate' than an article.

[Hauerg]

Danke.

[Jimmy Murdok]

Here is the first article I've seen on SpaceX's plans for a Moon base by 2026:

http://www.thesundaytimes.co.uk/sto/news/article1682341.ece

Linked to this presentation by 16'40"?  http://www.bloomberg.com/news/videos/b/afa4e9f6-16a0-40e6-ad19-9bfe7e51fe53

[stoker5432]

From all the numbers being presented I'm getting the impression that a two person crew on a dragon derived lander with enough propellant and supplies to get to the surface of the moon and back to LEO could be launched by a Falcon Heavy. The waiting crew could be launched on an F9r, dock with the lander, and then proceed to the moon. Yeah it involves an additional f9r flight but no additional in cabin fuel tanks or batteries and possibly more payload capability. The LEO dragon should be able to wait in LEO for the returning crew. Two flights of two different LV's in a short time span when staging seems more realistic than 3, 4 or even 2 Falcon Heavy launches so close together.

[sevenperforce]

From all the numbers being presented I'm getting the impression that a two person crew on a dragon derived lander with enough propellant and supplies to get to the surface of the moon and back to LEO could be launched by a Falcon Heavy. The waiting crew could be launched on an F9r, dock with the lander, and then proceed to the moon. Yeah it involves an additional f9r flight but no additional in cabin fuel tanks or batteries and possibly more payload capability. The LEO dragon should be able to wait in LEO for the returning crew. Two flights of two different LV's in a short time span when staging seems more realistic than 3, 4 or even 2 Falcon Heavy launches so close together.

The problem with any sort of Earth Orbit Rendezvous on return is the LEO circularization burn. It is basically a transfer injection burn in reverse. Circularizing in LEO costs roughly 3 km/s more than simply diving straight into the atmosphere with a heat shield. That's why it is pretty much absolutely necessary to put the re-entry vehicle in lunar orbit (or at least at EML-1).

[stoker5432]

So you just invalidated your option 2.

[stoker5432]

Circularizing in LEO costs roughly 3 km/s more than simply diving straight into the atmosphere with a heat shield. That's why it is pretty much absolutely necessary to put the re-entry vehicle in lunar orbit (or at least at EML-1).

Or you take the fuel and tankage with you for the extra 3 km/s and save a Falcon heavy expendable launch. Can the 73 tons to LEO do this or not?

[Space Ghost 1962]

Or you launch your F9R+FH Dragon's for a high eccentric orbit that requires much less dV to return from lunar, then do a minimal cost, low energy TLI/TEI.

This is operationally complicated by the difficulty in matching exactly such insertions due to a plethora of issues/factors (some of which can be compensated for), and likely increases radiation exposure of the crew in the Van Allen belts.

The weakness of these kind of approaches is that too much needs to go perfectly, and there is little margin for error and/or capability to recover the mission if it has a bad day. The only was to "fix" that is to preposition long-lived assets in lunar proximity that can be called upon. Its where you come up short.

Which brings you back to some kind of facility you have to maintain, thus a persistent cost and additional risk.

For a "one shot", perhaps you can have a long lived SC+props as a crutch to make this work, but that becomes your weakest link fairly fast.

LOR with a hypothetical reusable, refuelable (we don't have this)  Dragon in "frozen" LLO makes for a better approach IMHO. Operationally sound, but limited in access to lunar surface.

[stoker5432]

Or you launch your F9R+FH Dragon's for a high eccentric orbit that requires much less dV to return from lunar, then do a minimal cost, low energy TLI/TEI.

This is operationally complicated by the difficulty in matching exactly such insertions due to a plethora of issues/factors (some of which can be compensated for), and likely increases radiation exposure of the crew in the Van Allen belts.

Is this really necessary or are we trying to squeeze out more payload capacity?

[Space Ghost 1962]

Or you launch your F9R+FH Dragon's for a high eccentric orbit that requires much less dV to return from lunar, then do a minimal cost, low energy TLI/TEI.

This is operationally complicated by the difficulty in matching exactly such insertions due to a plethora of issues/factors (some of which can be compensated for), and likely increases radiation exposure of the crew in the Van Allen belts.

Is this really necessary or are we trying to squeeze out more payload capacity?

No additional payload capacity. Just safety margins and proven abort scenarios given operational considerations for ground support/rescue(LON) of BEO missions. Bad days have to be planned for.

[stoker5432]

So the way I suggested is possible if you can live with the risk. That's all I really wanted to know. Thanks.

[TrevorMonty]

Most future lunar missions, human especially will be focused on the poles. These are not as easy to access as equatorial locations. Whatever architecture SpaceX were to design would need to allow for this.

See link.

http://www.nap.edu/read/11220/chapter/6

[Space Ghost 1962]

Irrelevant.

Access to the surface of Moon/Mars/others will happen on an economics driven basis first, as speculative efforts establishing a basis for missions through immediate results.

There is no need/desire for an overarching system. What was being posited in the prior posts was an interim means to afford a high risk "reach to the surface" of the Moon. The closest (and only chance!) to a proposal that might be heard.

[sevenperforce]

Incidentally, a mission to one of the poles may be made easier by passing through EML-1. Inclination changes there are awfully cheap.

But yeah, this is more about a cheap moon shot than establishing anything permanent.

Some time tomorrow I should have an exhaustive deltaV map showing the exact requirements for virtually every conceivable route to and from the moon. There are a LOT of ways to do a moon shot.

[AncientU]

Incidentally, a mission to one of the poles may be made easier by passing through EML-1. Inclination changes there are awfully cheap.

But yeah, this is more about a cheap moon shot than establishing anything permanent.

Some time tomorrow I should have an exhaustive deltaV map showing the exact requirements for virtually every conceivable route to and from the moon. There are a LOT of ways to do a moon shot.

Seems that rendezvous at EML-1/2 (2 is optimum delta-v wise) is the profile with the largest leverage on future progress, and either provide for full Lunar coverage.  Ultimately, this is where propellant and exploration outpost should be delivered/positioned.

[Space Ghost 1962]

Seems that rendezvous at EML-1/2 (2 is optimum delta-v wise) is the profile with the largest leverage on future progress, and either provide for full Lunar coverage.  Ultimately, this is where propellant and exploration outpost should be delivered/positioned.

Yes if you a)can afford the consumables/props to "come and go" to the surface, and b)you wish to afford the option of standing down your "gateway station" for 4 months to years because you can't afford the follow on missions until later.

No if you have a steady stream of missions accessible from the "frozen" LLO a few times a year. It also takes much less consumables "there and back again". Like in the case of, say, a commercial means to let billionaires play Neil Armstrong

[sevenperforce]

Haven't worked out all the numbers yet but I'm not sure that EML-2 is optimum...why do you say that?

[AncientU]

Haven't worked out all the numbers yet but I'm not sure that EML-2 is optimum...why do you say that?

Lowest delta-v to get to cis-Lunar rendezvous point and maximal access to surface, launch and return profile flexibility, future jump-off point for newly-refueled, inter-planetary spacecraft (heading for Europa, for instance)...

Here I am assuming that the Moon is not the final destination (I.e., not flags and footprints), but a step in the direction(s) beyond.

[inventodoc]

How about a custom Dragon trunk that is a lunar lander descent stage with legs?    It could have a descent engine of its own or it could use Dragon engines.  Lots of room for fuel there.   The dragon then launches off of the trunk when it needs to ascent and has a full load of fuel. (and needs only enough fuel to ascent and return to earth for aerocapture).

Secondly, it would be much more mass efficient to have a dedicated lander upper stage (ala LEM) instead of a Dragon 2.    You could build a space only craft with a much lighter frame than even a lightened lunar dragon would have.   I imagine a lightweight metal frame or even plastic/composite or inflatable hab space.    Obviously a space only craft would require rendezvous with a lunar space station or waiting Dragon 2.   

[sevenperforce]

How about a custom Dragon trunk that is a lunar lander descent stage with legs?    It could have a descent engine of its own or it could use Dragon engines.  Lots of room for fuel there.   The dragon then launches off of the trunk when it needs to ascent and has a full load of fuel. (and needs only enough fuel to ascent and return to earth for aerocapture).

Secondly, it would be much more mass efficient to have a dedicated lander upper stage (ala LEM) instead of a Dragon 2.    You could build a space only craft with a much lighter frame than even a lightened lunar dragon would have.   I imagine a lightweight metal frame or even plastic/composite or inflatable hab space.    Obviously a space only craft would require rendezvous with a lunar space station or waiting Dragon 2.   

Egress from a Dragon V2 on top of a long trunk would be unpleasant, to say the least. Plus, the descent stage really isn't the problem; it's the ascent that you need more fuel for. You can use a crasher stage for descent.

It would certainly be cheaper in mass terms to use a purpose-built LEM. But the point of my proposal was to see whether there would be a way to go to the moon with the basic platform that SpaceX is currently getting ready to field.

[stoker5432]

Egress from a Dragon V2 on top of a long trunk would be unpleasant, to say the least.

Probably wouldn't be any worse than Altair.

[Space Ghost 1962]

How about a custom Dragon trunk that is a lunar lander descent stage with legs?    It could have a descent engine of its own or it could use Dragon engines.  Lots of room for fuel there.   The dragon then launches off of the trunk when it needs to ascent and has a full load of fuel. (and needs only enough fuel to ascent and return to earth for aerocapture).

The advantages to using Dragon is volume of production. Depart from that but a little and you quickly go from configuration issues to full cost + development + certification out of your own pocket. As a rule, small additions / deletions from the "base vehicle" aren't a big deal. You'd be surprised how little it takes to break this rule and "own your own billion dollar nightmare" and its debt service

Secondly, it would be much more mass efficient to have a dedicated lander upper stage (ala LEM) instead of a Dragon 2.    You could build a space only craft with a much lighter frame than even a lightened lunar dragon would have.   I imagine a lightweight metal frame or even plastic/composite or inflatable hab space.    Obviously a space only craft would require rendezvous with a lunar space station or waiting Dragon 2.   

No, it wouldn't. Here's your best mod to enable lunar access (landings and  - extend the hypers tankage to cover the lower half of Dragon 2. There - your props are now adequate for a two man crew.

The SuperDraco's come in pairs. So you have a redundant set for descent/ascent already. If you want another few tweaks, you change with the 3D printer the throat geometries and do some qualification tests. Now you'd have vacuum optimized SD's, even though you still have the cosine losses. But you'd gain significant advantages for an in space lander. This is what I mean by small changes.

Your other changes likely will be long range comm's, likely on a deployable boom (something like what the MER's have but about 30% bigger. And significant ECLSS additions.

[sevenperforce]

Haven't worked out all the numbers yet but I'm not sure that EML-2 is optimum...why do you say that?

Lowest delta-v to get to cis-Lunar rendezvous point and maximal access to surface, launch and return profile flexibility, future jump-off point for newly-refueled, inter-planetary spacecraft (heading for Europa, for instance)...

Here I am assuming that the Moon is not the final destination (I.e., not flags and footprints), but a step in the direction(s) beyond.

I created an exhaustive dV map for planning lunar missions; it's available in this thread.

[stoker5432]

That 4.2 tonnes is probably just the mass of the capsule,

Is this really correct? I've seen information stating the maximum mass of the Dragon is 12,000 kg. The maximum payload is 6,000 kg. I've also seen information stating the trunk weighs around 1,000 kg so that would only leave 800 kg for propellant.