Author Topic: SpaceX to the moon: mission profiles  (Read 26230 times)

Offline cuddihy

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Re: SpaceX to the moon: mission profiles
« Reply #40 on: 03/24/2016 12:56 am »
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?
« Last Edit: 03/24/2016 12:57 am by cuddihy »

Offline stoker5432

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Re: SpaceX to the moon: mission profiles
« Reply #41 on: 03/24/2016 02:26 am »
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.

Offline Owlon

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Re: SpaceX to the moon: mission profiles
« Reply #42 on: 03/24/2016 05:17 am »
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.

Offline AncientU

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Offline MattMason

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Re: SpaceX to the moon: mission profiles
« Reply #44 on: 03/24/2016 02:42 pm »
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.
"Why is the logo on the side of a rocket so important?"
"So you can find the pieces." -Jim, the Steely Eyed

Offline RanulfC

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Re: SpaceX to the moon: mission profiles
« Reply #45 on: 03/24/2016 03:33 pm »
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
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline nadreck

Re: SpaceX to the moon: mission profiles
« Reply #46 on: 03/24/2016 04:11 pm »
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.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline sevenperforce

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Re: SpaceX to the moon: mission profiles
« Reply #47 on: 03/24/2016 05:53 pm »
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.

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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.

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Quote
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.

Offline nadreck

Re: SpaceX to the moon: mission profiles
« Reply #48 on: 03/24/2016 07:01 pm »
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.
« Last Edit: 03/24/2016 07:05 pm by nadreck »
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline sevenperforce

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Re: SpaceX to the moon: mission profiles
« Reply #49 on: 03/24/2016 07:34 pm »
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.

Offline nadreck

Re: SpaceX to the moon: mission profiles
« Reply #50 on: 03/24/2016 08:06 pm »
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).
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline su27k

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Re: SpaceX to the moon: mission profiles
« Reply #51 on: 03/25/2016 02:42 am »
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.

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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.

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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.

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

Government money....

Offline Eric Hedman

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Re: SpaceX to the moon: mission profiles
« Reply #52 on: 03/27/2016 02:49 pm »
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

Offline the_other_Doug

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Re: SpaceX to the moon: mission profiles
« Reply #53 on: 03/27/2016 03:10 pm »
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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"...
-Doug  (With my shield, not yet upon it)

Offline stoker5432

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Re: SpaceX to the moon: mission profiles
« Reply #54 on: 03/27/2016 04:39 pm »
Quote
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.

Offline docmordrid

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Re: SpaceX to the moon: mission profiles
« Reply #55 on: 03/27/2016 05:35 pm »
Quote
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
DM

Online FutureSpaceTourist

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Re: SpaceX to the moon: mission profiles
« Reply #56 on: 03/28/2016 07:11 am »
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.

Offline Hauerg

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Re: SpaceX to the moon: mission profiles
« Reply #57 on: 03/28/2016 08:50 am »
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

Offline hopalong

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Re: SpaceX to the moon: mission profiles
« Reply #58 on: 03/28/2016 09:00 am »
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.
« Last Edit: 03/28/2016 09:02 am by hopalong »

Offline Hauerg

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Re: SpaceX to the moon: mission profiles
« Reply #59 on: 03/28/2016 09:06 am »
Danke.