Author Topic: ITS for the Moon  (Read 30584 times)

Offline lamontagne

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Re: ITS for the Moon
« Reply #80 on: 11/19/2017 09:12 PM »
What I like about BFR is that it can land rovers with Tesla model S type batteries, than can probably roam thousands of km per week before returning to get charged.  If we could land a few strategically placed charging solar stations before the main vehicle, then we probably could explore the whole moon in very little time, compared to now.

Online speedevil

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Re: ITS for the Moon
« Reply #81 on: 02/28/2018 03:40 PM »
In this thread I note that if you believe BFS can do 10 tons to SSTO (based off the 2017 IAC claims of SSTO with BFS and an extra engine since then) that you can do BFS to the moon, for 'only' a little more than a hundred launches.
With somewhat more optimistic assumptions, including suborbital refuelling - 25 or so launches.

With no BFR.

BFR makes everything better, of course.

Online Zed_Noir

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Re: ITS for the Moon
« Reply #82 on: 02/28/2018 09:15 PM »
What I like about BFR is that it can land rovers with Tesla model S type batteries, than can probably roam thousands of km per week before returning to get charged.  If we could land a few strategically placed charging solar stations before the main vehicle, then we probably could explore the whole moon in very little time, compared to now.

You are a bit dated with the near obsolete 18650 batteries used in the Model S & model X. It should be more inline with the 2170 batteries used in the Model 3 & Tesla Semi. The BFS should be able to land a stripped down Tesla Semi chassis. Wonder what the 800 km range on Earth Semi can do on the Moon without hauling cargo.


Offline alexterrell

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Re: ITS for the Moon
« Reply #83 on: 03/03/2018 06:10 PM »
Looking though this thread, it strike me that it might be better to have a dedicated lunar lander shuttling between a Gateway Station (L1 or High Lunar Orbit) and the lunar base. This would be refuelled by ITS tankers.

Reasons for this:
1. A special tanker could be long and thin, so the payload can be driven off it or out of it. Think of an unpressurised  9m diameter cylinder, 20m long. The four propellant modules (fuel and engines) are at each corner. The cylinder lands near the surface.
2. The lander could use BFS components.
3. It would be optimised for lunar landing. No need for heat shields, but maybe extra protection against debris in the underside. Last second gimballing of the four engines away from the centre to reduce debris kick back. There is enough thrust that in the event of engine failure, two engines can land/escape.
4. A crew variant would simply land a crew module inside the cylinder. However, the crew module would also be propulsive, so it could abort to orbit or to surface, in the event of failure.
5. The landing mass can be optimised. Perhaps 150 tons (the BFR payload) one way, return empty. Later, when ISRU is established, it could take 150 tons of fuel (or LOx) to the space station.
6. If it works out economical, we could use electric propulsion to deliver the fuel from LEO to the Gateway station.
7. We could use LOx/LH2 instead of methane. The advantage of that would be that the propellant could be delivered as water, and electrolysed into fuel. LOx/LH2 may be more suitable for Lunar ISRU.

The next suggestion would be for NASA to scrap SLS and spend the money on this system.
« Last Edit: 03/03/2018 06:13 PM by alexterrell »

Online speedevil

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Re: ITS for the Moon
« Reply #84 on: 03/03/2018 06:37 PM »
The next suggestion would be for NASA to scrap SLS and spend the money on this system.
I'm not saying there is no benefit from a better design of lander, but if the implication is that NASA should spend money developing a deep space station, and lander, I note that they are pretty much doing that - at a very much lower capability and spending many billions on it for the station only.

If BFR/S perform as specified, and cost 'only' $15M/launch, lasting ten or twenty flights, you get around $1M/ton landed cost of payload on the moon, using BFS (and the architecture of LLO refuelling upthread).

Never mind the lander, NASA has almost no relevant experience making payloads at $1M/ton.

For your typical 'small' NASA program, of a billion dollars, you can end up with a lander that might or might not work, or you can end up with a thousand tons on the moon. (perhaps much, much more).

If BFS is in fact reusable lots of times, the cost of a BFS in lunar orbit may be close to ten million dollars a year.






Offline alexterrell

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Re: ITS for the Moon
« Reply #85 on: 03/04/2018 09:51 AM »
Fair point - If NASA design and build it will take a decade and cost billions, and then get cancelled at the last minute.

But generally, NASA needs to get out of the launch business and focus on "boldly going". SpaceX will not have a commercial reason to develop a lunar lander - so maybe NASA needs to do it? Best still, NASA commissions lunar landers. And SpaceX design and build it.

Thinking about it more - it's a simple vehicle. I've gone off the cylinder, but a 20m long, 7m wide, 4.5m high container, open-able at each end, unpressurised (That would fit in the BFS - though I'm not sure how it would get out). At each corner, an engine pod has a Raptor engine (low thrust variant?) and fuel stores. Each pod needs about 30 tons of propellant, is mounted several metres to the side and above the cargo container, and can angle to the side.

Unlike BFS, this is designed to land on the moon and deliver a cargo. So no need to carry thermal protection, and no need for three sea-level Raptors. No need for cranes to unload cargo. No risk of damaging the BFS on the moon. And a crew version can be provided with an escape to orbit solution.

Attached is a very rough graphic. This does not look like any rocket in existence! The four rocket pods can fit into the container for launch on the BFR.
« Last Edit: 03/04/2018 10:37 AM by alexterrell »

Offline IRobot

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Re: ITS for the Moon
« Reply #86 on: 03/04/2018 10:13 AM »
But generally, NASA needs to get out of the launch business and focus on "boldly going". SpaceX will not have a commercial reason to develop a lunar lander - so maybe NASA needs to do it? Best still, NASA commissions lunar landers. And SpaceX design and build it.
This is the mentality we need to change. NASA has to start commissioning cargo and passenger capacity and service to the Moon. Commissioning a vehicle gets us back to the old situation.

Offline alexterrell

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Re: ITS for the Moon
« Reply #87 on: 03/04/2018 10:47 AM »
But generally, NASA needs to get out of the launch business and focus on "boldly going". SpaceX will not have a commercial reason to develop a lunar lander - so maybe NASA needs to do it? Best still, NASA commissions lunar landers. And SpaceX design and build it.
This is the mentality we need to change. NASA has to start commissioning cargo and passenger capacity and service to the Moon. Commissioning a vehicle gets us back to the old situation.
For anything which has been done before - like launching mass from Earth to orbit - absolutely.

Whether you can extend this to new stuff is a questionable. Let's say we want a capacity to land on Europa, penetrate the ice to the water below, and send back data. Can NASA commission that capability? Or does it need to commission the vehicle?

A lunar lander is a bit in between. Maybe it's "Private sector: can you land this 20m x 7m x 4.5m container?", or is "can you provide us with a reusable lander that will land this container"?

Online MATTBLAK

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Re: ITS for the Moon
« Reply #88 on: 03/04/2018 10:54 AM »
I've waited most of my life to see a real version of these Bonestell scenes... BFS on the Moon represents a huge step towards that. But bigger and better!! :)
« Last Edit: 03/05/2018 12:40 AM by MATTBLAK »
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Offline IRobot

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Re: ITS for the Moon
« Reply #89 on: 03/04/2018 02:14 PM »
But generally, NASA needs to get out of the launch business and focus on "boldly going". SpaceX will not have a commercial reason to develop a lunar lander - so maybe NASA needs to do it? Best still, NASA commissions lunar landers. And SpaceX design and build it.
This is the mentality we need to change. NASA has to start commissioning cargo and passenger capacity and service to the Moon. Commissioning a vehicle gets us back to the old situation.
For anything which has been done before - like launching mass from Earth to orbit - absolutely.

Whether you can extend this to new stuff is a questionable. Let's say we want a capacity to land on Europa, penetrate the ice to the water below, and send back data. Can NASA commission that capability? Or does it need to commission the vehicle?

Not really, there was a NASA plan to evaluate the possibility to use a Dragon for Mars drilling (1 meter, AFAIK) for sample analysis.
So in that case I guess NASA would do the drilling and scientific platform and Dragon would make sure it landed and would have some sort of mechanism to put it out of the spacecraft, perhaps through the existing hatch.

It's time to stop thinking of single purpose spacecrafts, which are optimized for mass to orbit and not for price.

Online speedevil

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Re: ITS for the Moon
« Reply #90 on: 03/04/2018 04:00 PM »
It's time to stop thinking of single purpose spacecrafts, which are optimized for mass to orbit and not for price.

I wonder what a Europa orbiter looks like, for a vehicle where you're entirely OK with the fact that the sensitive equipment is inside a four meter cube of water, and you don't really care if it takes fifty tons of propellant to make orbit.

And - well - if you look at it right, if your probe needs a kilowatt, and you need fifty tons of shielding anyway, then a valid alternative might just be fifty tons of batteries, which enables a years active life.

Somewhat related to this thread as precisely the same things that make NASA problematic apply, in the face of the cheap launch that makes ITS (well, BFR) to the moon plausible.


Offline BeamRider

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Re: ITS for the Moon
« Reply #91 on: 03/04/2018 04:55 PM »
I watched the Spacex video of a BFS moon landing. Just like in the moon landing in “2001 A Space Odyssey” the dust kicked up by the landing burn billowed as if it was in an atmosphere. No biggie, but it got me wondering about what was hidden, and that was the landing gear! The narrow-stance legs shown in the Mars ITS videos are obviously only useful for a prepared landing site, and given the base width compared to the overall height, maybe even dicey for that. Remember, on landing with a payload, the tanks are going to be nearly empty, so a lot of the overall mass is going to be up near the nose/top! Doesn’t feel right, and certainly unsafe for unprepared landing sites like will be encountered in exploratory flights.

The BFR tanker is apparently intended to land on some kind of landing / launch ring structure, back at its launch site, to get refilled and launched again. I wonder if there will be a need for an “LL Ring” that can be used by either of the ITS rockets to land on unimproved sites on the Moon, or Mars? Such a ring would have wide-stance landing legs, perhaps permanently deployed for simplicity. It could be used to land (say) at a new outpost location on the Moon, and left behind on departure to allow the next ship to land on a ring in safety, and with no weight penalty. It might evolve that most ships used for surface work from orbit would dispense with any landing legs of their own, and use pre-positioned rings. Such a ring could have the ability to hydraulically level itself to give its using ships an exactly vertical resting orientation, which I suspect will be required for all sorts of reasons.

In the spirit of some of the discussion above, perhaps these rings could eventually be free-flying and able to position themselves without hitching a ride on a BFR/S. That certainly seems doable for ballistic hops from one site to another, with no requirement to enter orbit. Think the Curiosity sky-crane on steroids. 

Thoughts?

Online speedevil

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Re: ITS for the Moon
« Reply #92 on: 03/04/2018 06:02 PM »
I watched the Spacex video of a BFS moon landing. Just like in the moon landing in “2001 A Space Odyssey” the dust kicked up by the landing burn billowed as if it was in an atmosphere. No biggie, but it got me wondering about what was hidden, and that was the landing gear! The narrow-stance legs shown in the Mars ITS videos are obviously only useful for a prepared landing site, and given the base width compared to the overall height, maybe even dicey for that. Remember, on landing with a payload, the tanks are going to be nearly empty, so a lot of the overall mass is going to be up near the nose/top! Doesn’t feel right, and certainly unsafe for unprepared landing sites like will be encountered in exploratory flights.

The absence of an atmosphere will tend to mean that the flow is much less turbulent, and pretty much all in a constant direction away from the BFS.

The nominal BFS '20 ton' direct from LEO approach has about 200m/s or so of margin if you use all of that payload as margin.

So, one approach you might consider is to have a first vehicle hover in a spiral 50m over the proposed landing point for a couple of minutes, and burst the engines to full power a few times and see what happens, getting progressively lower until almost touching.

At some point, it's reasonable to conclude that if it'll take a thousand ton pulse from 15m up, without major surface changes (after some excavation), it's safe for landing on around 50 tons on one engine, gently.
Of course, if you're at a hundred meters altitude, you may as well load a few teeny rovers into t-shirt cannons to explore the area.

Offline Patchouli

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Re: ITS for the Moon
« Reply #93 on: 03/04/2018 11:57 PM »
If you could keep a depot at L1 or L2 the landed mass becomes the full 150 tons by refilling tanks partly.
This is where a SEP tug could be a very useful addition.
Later on the O2 can be made from lunar regolith so only methane would need to be shipped to the depot.

Since the payload is so large I'd bring a couple of SEVs in rover configuration.
« Last Edit: 03/05/2018 12:03 AM by Patchouli »

Online speedevil

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Re: ITS for the Moon
« Reply #94 on: 03/05/2018 12:08 AM »
For lunar missions BFS could really benefit from depots and SEP tugs.

If you could keep a depot at L1 or L2 the landed mass becomes the full 150 tons.

It really doesn't.
You put a second BFS in LLO, and transfer TLI fuel to it before landing, and back after.
This gets you a hundred tons or so on the moon every eight launches.

It is questionable if you can even use Xenon with a free, massless SEP tug to move fuel cheaper than BFS. (Xenon is expensive).

SEP tugs have very questionable value in a scenario where fuel is cheap until you get to several times the total exhaust velocity delta-v over which the fuel must be transported over.
And even then, if your alternative can aerobrake some of the velocity off, that can be a massive advantage for it.



Offline BeamRider

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Re: ITS for the Moon
« Reply #95 on: 03/05/2018 12:23 AM »
The landing ring addresss the “coffin corner” situation, where there is not a level enough or firm enough spot for the narrow and highly-loaded landing gear I have seen envisioned. Yes you can hover for a while, but it doesn’t matter - if you can’t land you don’t have the option to abort to orbit like Neil Armstrong had - you must land someplace! A ring clamped to the tail with very long horizontal legs and low weight loading could land on anything, even a moderate slope! I think something like this is a must if you are doing no-abort landings into unknown / unprepared terrain.

Offline BeamRider

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Re: ITS for the Moon
« Reply #96 on: 03/05/2018 12:23 AM »
The landing ring addresss the “coffin corner” situation, where there is not a level enough or firm enough spot for the narrow and highly-loaded landing gear I have seen envisioned. Yes you can hover for a while, but it doesn’t matter - if you can’t land you don’t have the option to abort to orbit like Neil Armstrong had - you must land someplace! A ring clamped to the tail with very long horizontal legs and low weight loading could land on anything, even a moderate slope! I think something like this is a must if you are doing no-abort landings into unknown / unprepared terrain.

Online speedevil

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Re: ITS for the Moon
« Reply #97 on: 03/05/2018 12:56 AM »
The landing ring addresss the “coffin corner” situation, where there is not a level enough or firm enough spot for the narrow and highly-loaded landing gear I have seen envisioned. Yes you can hover for a while, but it doesn’t matter - if you can’t land you don’t have the option to abort to orbit like Neil Armstrong had - you must land someplace!

You missed the point of my comment on hovering, it was not to find somewhere to land, but to test the landing site.
If you can pulse the engines at 1100 tons thrust, 10m off the surface, and nothing much moves, then landing with them 3m off the surface on a thrust of 50 tons is a very much smaller risk.
In principle, you can add leg extensions which are only good for lunar gravity.

Your 200m/s extra propellant from not having any payload on a first vehicle can allow you to abort back to earth (or even be planned that way) after 'brushing' the candidate landing site.
And, unless you insist on maximum payload to the surface on the first vehicle - abort without unloading cargo all the way back to earth is quite possible.

I'm not saying that it may not be desirable to improve the surface, but that incremental testing can be done to see if it's in fact required.

Offline Patchouli

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Re: ITS for the Moon
« Reply #98 on: 03/05/2018 12:59 AM »
For lunar missions BFS could really benefit from depots and SEP tugs.

If you could keep a depot at L1 or L2 the landed mass becomes the full 150 tons.

It really doesn't.
You put a second BFS in LLO, and transfer TLI fuel to it before landing, and back after.
This gets you a hundred tons or so on the moon every eight launches.

It is questionable if you can even use Xenon with a free, massless SEP tug to move fuel cheaper than BFS. (Xenon is expensive).

SEP tugs have very questionable value in a scenario where fuel is cheap until you get to several times the total exhaust velocity delta-v over which the fuel must be transported over.
And even then, if your alternative can aerobrake some of the velocity off, that can be a massive advantage for it.




Keep in mind aerobreaking on BFS is not free in that it costs nothing as the TPS is an ablator which is consumed.
Replacing all the TPS means a lot of labor which can get expensive so to keep costs down you'll want to limit the number of high speed returns on the tankers.
A SEP tug can do a less intense form of aerobreaking due to it's high surface area to mass ratio.
Though you don't have to use Xenon gas either Argon can also be used esp with VASIMR engines.
It may even be possible to use some of the methane as a propellant at least you can in an arcjet or solar thermal engine though these may not be high enough ISP to fully justify the added complexity and cost.
« Last Edit: 03/05/2018 01:04 AM by Patchouli »

Offline BeamRider

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Re: ITS for the Moon
« Reply #99 on: 03/05/2018 03:35 AM »
Yes, I agree that a landing abort is made possible by limiting cargo on the first landing at a new site. But as a matter of standard operating procedure, I would recommend that all sites be “improved” anyway. To me the best way to improve them is by providing a landing/launching ring. The use of a ring would probably have been mastered and standardized on Earth long before, and adopting the practice would allow your whole lunar fleet to dispense with landing gear altogether. Seems like a good safety practice that will also improve overall efficiency, no?

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