SpaceX Crewed Dragon Circumlunar Mission

[toruonu]

Btw, what is the actual limitation on the second stage that it cannot survive a three day trip. Batteries? Couldn't it go into some deep sleep for the duration and conserve power or one could make a feedback connector that Dragon could feed S2 some of its solar power that it's gathering assuming the V2 panel covers can be jettisoned before Dragon is released.

[Barrie]

,,,assuming the V2 panel covers can be jettisoned before Dragon is released.

I don't think there are any panel covers on Dragon v2

[macpacheco]

Btw, what is the actual limitation on the second stage that it cannot survive a three day trip. Batteries? Couldn't it go into some deep sleep for the duration and conserve power or one could make a feedback connector that Dragon could feed S2 some of its solar power that it's gathering assuming the V2 panel covers can be jettisoned before Dragon is released.

The root problem is LOX will boil off and RP1 freeze. It would take significant solar panels to generate enough electricity to heat the RP1 and keep the LOX cold enough so it doesn't boil. This eliminates much reason in giving the 2nd stage enough battery power to be able to operate for a long time, since its essentially without purpose if its engine can't operate.
It *probably* won't require much to keep the 2nd stage batteries alive using Dragon solar panel electrons, but what's the purpose ?

[LouScheffer]

Frankly on a serious note I think the Dragon engineers would be extremely worried by a tourist crew engaging in unauthorized activities or horseplay in the vehicle. They could spill something on the control panel or worse. I would not be surprised if the contract includes a list of specifically prohibited activities.

I, for one, look forward to the day when enough spaceship accidents are due to horseplay that we need rules about it.  Blood alcohol content must less than 0.08% for re-entry!   Console cover must be used during activities involving exchange of precious bodily fluids!  Prank calls sending fake INS coordinates are strictly prohibited!

In all seriousness, if you are sending humans, you've got to expect human behavior.  When spacecraft are as common and reliable as cars, where more than 90% of the accidents are caused by driver error, we will need rules like this.   But we have a long, long way to go until passenger behavior even approaches technical errors as a cause of accidents.

[Jim]

Btw, what is the actual limitation on the second stage that it cannot survive a three day trip. Batteries? Couldn't it go into some deep sleep for the duration and conserve power or one could make a feedback connector that Dragon could feed S2 some of its solar power that it's gathering assuming the V2 panel covers can be jettisoned before Dragon is released.

Its avionics are not designed for deep space nor is any of the systems designed to last more than 10 hours or so.  The avionics are autonomous and no capability for updates.  And it is not that simple just to add a connector with power

[BobHk]

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

[Ben the Space Brit]

I doubt it; the last I heard, SpaceX were barely at the point where they were building a test stand for Raptor, let alone thinking of converting Merlin VAC to a new fuel mixture!

[envy887]

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

A fly-by mission doesn't need a Raptor stage. And Raptor on Falcon is unlikely to happen at all, for many reasons.

[Kenp51d]

More to it than just an changing out a Merlin for a Raptor engine or even modifying a Merlin to methane. Methane is less dense than rp9. So you need a bigger tank for it. You can only stretch a stage so far till you run into other complications (cg change for starters). Also limitations on making the stage fatter.
Those concerns were brought up on another sites comments section.
I'd be rather certain the issues could be successfully dealt with by SpaceX, but difficult and lot's of $$$$$$.

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[toruonu]

I doubt it; the last I heard, SpaceX were barely at the point where they were building a test stand for Raptor, let alone thinking of converting Merlin VAC to a new fuel mixture!

Well I doubt there'd be a raptor upper stage, but with regard to their progress, did you miss the raptor firing info just before Elon unrolled the mars plans in September? So they have a test stand and a prototype engine that actually works. Wasn't there also a video of the firing that was way longer than just a simple start-stop, didn't it last ~ten seconds.

[Space Ghost 1962]

Btw, what is the actual limitation on the second stage that it cannot survive a three day trip. Batteries? Couldn't it go into some deep sleep for the duration and conserve power or one could make a feedback connector that Dragon could feed S2 some of its solar power that it's gathering assuming the V2 panel covers can be jettisoned before Dragon is released.

Its avionics are not designed for deep space nor is any of the systems designed to last more than 10 hours or so.  The avionics are autonomous and no capability for updates.  And it is not that simple just to add a connector with power

FWIW, all this *by design*. US is a specialized mass/delta-V obsessively performance designed robot that takes payload(s) from near space to target orbit(s) and properly dispenses them.

If you build an in-space propulsion tug out of a US, its an all new vehicle, and the flight history/operations/economics/assembly line/logistics chain/missions/"business case" starts.

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

Add 4-5 years for that to happen, quadruple the costing (full absorption of cost for mission), and 1/10 the safety/reliability.

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

A fly-by mission doesn't need a Raptor stage. And Raptor on Falcon is unlikely to happen at all, for many reasons.

Yes. But isn't everything bolt-on legos that self test/integrate/operate/universal function? Its so easy, right ?? Not.

I doubt it; the last I heard, SpaceX were barely at the point where they were building a test stand for Raptor, let alone thinking of converting Merlin VAC to a new fuel mixture!

Well I doubt there'd be a raptor upper stage, but with regard to their progress, did you miss the raptor firing info just before Elon unrolled the mars plans in September? So they have a test stand and a prototype engine that actually works. Wasn't there also a video of the firing that was way longer than just a simple start-stop, didn't it last ~ten seconds.

Raptor is irrelevant to this thread.  They are also having enough fun with existing GSE and vehicle. Soon to be "vehicles".

[gospacex]

This is a stepping stone to lunar tourism.
Think about it.
While flying in a can for a few days with no actual destination except the landing back on Earth is not really that exciting after a few first flights, a tourist trip to the Moon surface is way more interesting for potential tourist-type customers.

[envy887]

....  They are also having enough fun with existing GSE and vehicle. Soon to be "vehicles".

Aren't they retiring Dragon when Dragon 2 is qualified? Or is this a reference to another launch vehicle?

[Jim]

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

There is no such thing.

[ugordan]

So who wants to bet the moon mission will use a second stage with a methane fed raptor engine?

There is no such thing.

Maybe not in the real world, but in the armchair rocket scientist universe it is very much a reality.

[DAZ]

The real beauty of this mission is that it is basically using the same things that SpaceX is planning to do in the near future so SpaceX is designing and building them right now. About the only exception to this would be the deep space communications system on the Dragon 2 capsule. Even this is along the same line, as it will need to build something like this for the Red Dragon mission.

But thinking along the lines of what SpaceX still needs to do for its stated objectives has given me a head scratching moment. SpaceX has announced and shown that it is working on the new Raptor engine. There is also information available that they are working on how to build the new composite propellant tanks for the ITS. It was also announced that the ITS would use gaseous methane/oxygen engines for attitude control. These attitude control thrusters would probably need to be bigger than the present Draco engines but probably smaller (but not necessarily) than the Super Draco engines. So the part that has my head itching has anybody heard anything related to the development of these new engines?

Now for the speculation part related to this thread. If just about everything that SpaceX works on is related on how to get to Mars this would lean against SpaceX using any resources toward developing a Raptor S2 for the Falcon 9. It would also lean against SpaceX developing a breakaway kit using a super Draco engine to fit in the trunk of the Dragon system to be used as a service module. All of which would be within the ability of SpaceX to produce but as they have no missions/customers that need it would be most likely a waste of resources. Now developing the above mentioned new gaseous methane/oxygen engines for attitude control is definitely on their list of things to do but is probably on their due later as opposed to do earlier list. If on the other hand, they were to move this to the do earlier list could they also possibly be willing to expend the extra resources for a breakaway service module kit?

This would allow them to accomplish something else on there to do list earlier and at the same time possibly get more experience with it. For a relatively low cost this would put another tool in their toolkit that others could conceivably use (and obviously be willing to pay SpaceX) for possible BLEO missions.

[Kenp51d]

This mission could get other companies (or even NASA) develop the needed hardware for a return to the moon.  Would likely require 2 or more launches to put both the Dragon and moon hardware in Leo.
Would likely need real big money and several years.

Ken

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[woods170]

Maybe not in the real world, but in the armchair rocket scientist universe it is very much a fantasy reality.

There, fixed that for ya.

[rakaydos]

Now for the speculation part related to this thread. If just about everything that SpaceX works on is related on how to get to Mars this would lean against SpaceX using any resources toward developing a Raptor S2 for the Falcon 9. It would also lean against SpaceX developing a breakaway kit using a super Draco engine to fit in the trunk of the Dragon system to be used as a service module. All of which would be within the ability of SpaceX to produce but as they have no missions/customers that need it would be most likely a waste of resources. Now developing the above mentioned new gaseous methane/oxygen engines for attitude control is definitely on their list of things to do but is probably on their due later as opposed to do earlier list. If on the other hand, they were to move this to the do earlier list could they also possibly be willing to expend the extra resources for a breakaway service module kit?

This idea intrigues me. It's not a NESSISARY vehical for their mars plans, but as a Technical readiiness demonstrator for the Methane/GOx mini-engine, the usefullness of a high Loiter, high energy propellant satelite-deployment 3rd stage is not to be underestimated for GEO missions. Sizing the demostrater to fit in Dragon's trunk opens up BEO options, White Dragonlab, and possibly even more payload to mars under Red Dragon.

[Jim]

the usefullness of a high Loiter, high energy propellant satelite-deployment 3rd stage is not to be underestimated for GEO missions.

There is no need for such a stage, there is no additional benefit.  The second stage is all that is necessary for GEO deployments.