Author Topic: 2nd Stage Moon Lander  (Read 3811 times)

Offline qraal

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2nd Stage Moon Lander
« on: 04/02/2017 04:32 AM »
When Elon Tweeted about bringing back the 2nd Stage on the Falcon Heavy test-flight, I Tweeted back that with the landing legs it'd be able to land itself on the Moon.

A respondent promptly jumped on me with the claim that LOX boil-off would nix the idea due to the ~3 days to the Moon. Does anyone here know what the LOX boil-off rate is like for the Falcon 2nd Stage?

The actual mechanics of landing an empty 2nd stage on the Moon don't seem overly onerous in my mind, since it's already equipped to land at 1 gee on Earth. The comms would need to be souped up, but the additional mass budget is likely to be tiny.

Online TrevorMonty

Re: 2nd Stage Moon Lander
« Reply #1 on: 04/02/2017 05:36 AM »
Extending stage life from hours to 3-4days isn't easy. You have to address boil off of LOX, freezing of RP1 and operational power (currently use batteries). Also need maneuvering thrusts and their fuel system, which will not likely to be LOX/ RP1.

Read up on ULA IVF system to see what is required. They are first to develop systems that will extend US life to days if not weeks and maybe months. I suspect SpaceX and Blue are also working on this problem. In case SpaceX will mostly be for Methane stage not RP1.

Offline faramund

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Re: 2nd Stage Moon Lander
« Reply #2 on: 04/02/2017 05:49 AM »
And Stage 2 recovery to Earth would at least somewhat use the atmosphere to slow down.

Offline QuantumG

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Re: 2nd Stage Moon Lander
« Reply #3 on: 04/02/2017 05:55 AM »
We don't have numbers for the Falcon 9, of course, but I guess if we eyeball it we might say the second stage has a mass of about 4.7 tons dry and 78.1 tons gross. If that's so it can throw 24 tons to TLI and land 7 tons on the Moon - ignoring boiloff. Seems like a fair starting point.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Kaputnik

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Re: 2nd Stage Moon Lander
« Reply #4 on: 04/02/2017 08:02 AM »
it's already equipped to land at 1 gee on Earth.

Oh no it isn't.
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Offline qraal

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Re: 2nd Stage Moon Lander
« Reply #5 on: 04/02/2017 10:40 AM »
I meant the reusable 2nd Stage *will be* thus landing on the Moon should be easy. Not that it can *now* unmodified.

it's already equipped to land at 1 gee on Earth.

Oh no it isn't.

Offline qraal

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Re: 2nd Stage Moon Lander
« Reply #6 on: 04/02/2017 10:56 AM »
Extending stage life from hours to 3-4days isn't easy. You have to address boil off of LOX, freezing of RP1 and operational power (currently use batteries).

Thus the question. From what I've read from orbital depot studies, LOX boil-off isn't quick. I just don't have any figures on SpaceX's tankage & insulation to try to figure it out. Operational power presumably means solar panels on the stage. Perhaps a modified Dragon Trunk?

Quote
Also need maneuvering thrusts and their fuel system, which will not likely to be LOX/ RP1.

The reusable 2nd Stage would need maneuvering jets above the atmosphere, to return from LEO, so that's presumably being worked on. Hypergolics powering Dracos and/or SuperDracos, like on the Dragon. Thus not a big development leap.

Quote
Read up on ULA IVF system to see what is required. They are first to develop systems that will extend US life to days if not weeks and maybe months. I suspect SpaceX and Blue are also working on this problem. In case SpaceX will mostly be for Methane stage not RP1.

StackExchange covers ULA's IVF here: What is the point of ULA's IVF? (Integrated Vehicle Fluids) ...thanks for the pointer :-)


Offline qraal

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Re: 2nd Stage Moon Lander
« Reply #7 on: 04/02/2017 11:05 AM »
Of course, if SpaceX decide to send a 2nd Stage or better yet a Dragon to the Moon's orbit or close to, then maybe they're hoping for a commitment for something like this...

NASA, ISS partners quietly completing design of possible Moon-orbiting space station

Of course, pushing the *whole* ISS to Low Lunar Orbit - or EML-2, which is more stable and easier to access than Low Lunar Orbit - is probably out of the question, I wonder if a sub-section could usefully be sent there? Using a couple of tricked out Falcon Heavy 2nd Stages as boosters.

Offline Kaputnik

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Re: 2nd Stage Moon Lander
« Reply #8 on: 04/02/2017 11:52 AM »
I'm not going to say it's impossible, but don't underestimate the challenges.
ISS proxops probably preclude a huge kerolox rocket stage operating in its vicinity.
The ISS modules are designed for the LEO environment- could they function somewhere else? Maybe, some of them, with some upgrades. The thermal environment is different.
Perhaps most importantly- the core modules are approaching or have exceeded their design lives.
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Offline qraal

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Re: 2nd Stage Moon Lander
« Reply #9 on: 04/02/2017 08:56 PM »
Oh well. I guess they'll have to deorbit the Station when it's 'retirement' time.

I'm not going to say it's impossible, but don't underestimate the challenges.
ISS proxops probably preclude a huge kerolox rocket stage operating in its vicinity.
The ISS modules are designed for the LEO environment- could they function somewhere else? Maybe, some of them, with some upgrades. The thermal environment is different.
Perhaps most importantly- the core modules are approaching or have exceeded their design lives.

Offline Kaputnik

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Re: 2nd Stage Moon Lander
« Reply #10 on: 04/02/2017 09:11 PM »
Oh well. I guess they'll have to deorbit the Station when it's 'retirement' time.

https://www.nasa.gov/pdf/578543main_asap_eol_plan_2010_101020.pdf
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Offline savuporo

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Re: 2nd Stage Moon Lander
« Reply #11 on: 04/02/2017 09:28 PM »
Orion - the first and only manned not-too-deep-space craft

Offline Ludus

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Re: 2nd Stage Moon Lander
« Reply #12 on: 04/03/2017 06:44 AM »
I don't think trying to recover the S2 means trying it the same way they succeeded with the Booster. There was very little propellant margin for S1 to do what it does. There's a lot less for S2. If recovery isn't by a propulsive landing then S2 isn't adapted for that, no legs, no engine throttling that low.

Offline Kaputnik

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Re: 2nd Stage Moon Lander
« Reply #13 on: 04/03/2017 07:03 AM »
I'm not going to say it's impossible, but don't underestimate the challenges...

http://forum.nasaspaceflight.com/index.php?topic=36418.msg1307266#msg1307266

What has the Blok D got to do with repurposing the ISS?
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Offline savuporo

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Re: 2nd Stage Moon Lander
« Reply #14 on: 04/03/2017 07:22 AM »
I'm not going to say it's impossible, but don't underestimate the challenges...

http://forum.nasaspaceflight.com/index.php?topic=36418.msg1307266#msg1307266

What has the Blok D got to do with repurposing the ISS?

I thought this was in reference to long duration LOX/Kerosense stages ( which Blok-D was intended to be), my bad.
Orion - the first and only manned not-too-deep-space craft

Offline sevenperforce

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Re: 2nd Stage Moon Lander
« Reply #15 on: 04/04/2017 04:30 PM »
Landing S2 on Earth is totally different from delivering something to the lunar surface. No aerobraking; that alone changes everything.

Falcon Heavy can throw 22 tonnes to GTO; getting from a 185 km parking orbit to GTO takes about 2.475 km/s. Assuming that the S2 can be modded to allow restart a couple of days later, then a lower-payloads S2 should be able to have significant residuals upon reaching cislunar space, permitting a capture burn, a deorbit burn, and a partial braking burn. Might be enough to make up for the absence of aerobraking.

But you'd want vacuum nozzle extensions for whatever actual hover-landing engines you were going to use.

Online KelvinZero

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Re: 2nd Stage Moon Lander
« Reply #16 on: 04/05/2017 12:26 PM »
I started a thread on a related a while back. Forget the details of the second stage. It is a totally new beast perhaps. Still cheaper than SLS plus Altair!

I was thinking about what you can do with just F9R. You launch this specialised 2nd stage. You connect a ring of modules around the base once in orbit, each module no heavier than what an F9R can deliver. This ring of modules is left behind when it relaunches from the moon.

You refuel it in LEO, then you refuel it in LLO, and refuel it again when it returns to LLO, perhaps having used SEP tugs to drag fuel there.

I forget the numbers but the performance is just absurd. You could land an entire base with that thing. Just an F9R and a whole lot of launches. It was too big.. and yet we need SLS. Sigh.

Offline sevenperforce

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Re: 2nd Stage Moon Lander
« Reply #17 on: 04/05/2017 12:43 PM »
I started a thread on a related a while back. Forget the details of the second stage. It is a totally new beast perhaps. Still cheaper than SLS plus Altair!

I was thinking about what you can do with just F9R. You launch this specialised 2nd stage. You connect a ring of modules around the base once in orbit, each module no heavier than what an F9R can deliver. This ring of modules is left behind when it relaunches from the moon.

You refuel it in LEO, then you refuel it in LLO, and refuel it again when it returns to LLO, perhaps having used SEP tugs to drag fuel there.

I forget the numbers but the performance is just absurd. You could land an entire base with that thing. Just an F9R and a whole lot of launches. It was too big.. and yet we need SLS. Sigh.
The Falcon 9 second stage would need extensive redesign to permit on-orbit refueling.

Offline Rocket Science

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Re: 2nd Stage Moon Lander
« Reply #18 on: 04/05/2017 01:20 PM »
This is from the other thread using a Falcon S2 based lunar lander...#139
https://forum.nasaspaceflight.com/index.php?topic=42363.120
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Online KelvinZero

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Re: 2nd Stage Moon Lander
« Reply #19 on: 04/05/2017 01:30 PM »
The Falcon 9 second stage would need extensive redesign to permit on-orbit refueling.
That is sort of covered by "Forget the details of the second stage. It is a totally new beast perhaps. Still cheaper than SLS plus Altair!" Sorry If I wasn't clear enough, but some readers object to use of the Marquee function.  8)

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