SpaceX to the moon: mission profiles

[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.