New Moon Direct

louis · 2008-04-06 14:12:30

Here's a new thread Terraformer...

OK - my first question:

Can we use an SSTO retrorocket lander to take 10 tonnes to the moon and bring it back to earth - and then be available for re-use.

I don't see why not especially as the gravity well for the Moon is not so deep.

Second question: do the lunar night and day present any serious problems for ISRU. My answer: no. We can have energy abundance to allow energy storage and see us through the lunar night. But I understand in any case there are South Pole locations which actually enjoy almost continuous light.

Third question are you happy with solar power as the sole power source?

Fourth - where do we get water from?

JoshNH4H · 2008-04-06 15:03:20

I don't know if this thread is addressed to me, but I will put my 2 cents in. If you don't want me to answer, just ignore it.

1.

Can we use an SSTO retrorocket lander to take 10 tonnes to the moon and bring it back to earth - and then be available for re-use.

SSTO from earth? As it hasn't yet been demonstrated, I will say no for the moment. Using nuclear tech, maybe. Going to the moon and back, assuming that you use the same vehicle you launch with is possible, but not feasible, it makes more sense to drop the empty fuel tanks. Retrorockets are a necessity on the moon, as there is no atmosphere.

2.

do the lunar night and day present any serious problems for ISRU

No, absolutely not. Especially if you can wait for 2 weeks, ISRU can be done during the day. If you are using Nuclear, Day/night is no problem.

3.

are you happy with solar power as the sole power source?

Absolutely not. your thin film solar cells are too fragile, too large, and too expensive to meet the energy requirements of even an outpost. Also, power storage is a real kicker. However, due to the abundance of lunar silicon, some solar cells would be a good way to get additional energy.

4.

where do we get water from?

This is a real problem. There is some located near the poles, but not very much. Mostly it can be imported from earth.

JoshNH4H · 2008-04-06 15:14:54

Oh, seeing the long durations thread, now I understand the purpose. Actually, I would suggest a two stage, ammonia decomposition/ LOX first stage, and a LANTR (Lox Augmented NTR) using U-233 pebble bed reactor to orbit, then refuel with NH3 in orbit, then go to the moon in Nerva mode. On the moon, you can bake O2 out of the large majority of SiO2 and other oxides in the soil, and use that in your NTR to go home.

How long do you think the stay should be?
How many people ?
ETC.

The Isp of an Ammonia fueled NTR is appx. 5/8 of Hydrogen.

JoshNH4H · 2008-04-06 15:22:42

Oh, btw, NH3 decomp and lox can be found in my thread NEW FUEL.

louis · 2008-04-06 15:58:30

Jumpboy -

Is there any reason we can't manufacture water on the moon if there is hydrogen and oxygen there, bound up in rocks.

Regarding retrorockets, I am afraid I don't get. Can't we be specific?

How much rocket mass is required to lift a 10 tonne payload to GEO, travel to the moon, get into moon orbit, lower the craft on to the moon, launch off the moon, return to earth and land safely, using retrorockets?

JoshNH4H · 2008-04-06 16:16:40

there is next to no Hydrogen.

JoshNH4H · 2008-04-06 16:29:23

well, As I understand it, retrorockets are a requisite for the moon, because there is no other way to stop.

Delta V to orbit is between 10-12 km/s. LEO to the moon's surface is 6 km/s.

6 Km/s bact to LEO, then aerobake to remove 8 km/s.

So use a rocket equation calculator to see the feasability.

Terraformer · 2008-04-07 03:59:42

There is Hydrogen on the moon, bound up in frozen water near the poles, which means we can also get 29/28 sunlight. Plus there's silicon on there to use. I wonder if blasting Silicon Oxide ith hydrogen will produce Silane and O2?

I think louis was referring to a lunar SSTO.

If we can mine silicon we could probably make solar cells on the moon. If we can churn them out fast enough it doesn't matter about meteorites (which I assume you were referring to when you said PV cells were to fragile.)

I'll post the composition of the lunar regolith when I can find a site showing me it.

louis · 2008-04-07 06:11:08

My interest first is in just whether it is possible to have a craft that is integral and undertakes the whole journey there and back.

Although it may be large, I think there will be advantages from reuse and simplification of processes. It may not have been attempted before in the past because we have been looking to put up much larger payloads rather than making use of ISRU, recycling of life support materials etc.

Even if a craft cannot get all the way to the moon and back with a retro landing on both moon and earth, we should be able to set up a refuelling facility on both the Moon (and possibly in LEO) which will probably mean the size of the craft can be reduced by 40% or more.

SpaceNut · 2008-04-07 08:56:05

The problem still remains that who ever funds the program must be willing to do so based on the descision or science/exploration versus survival/settlement.
Going to the moon in cooperation only spreads the bill to go amoung more parties and does nothing to speed the process up or to change the mode from science to one of survival.
Yes we can make solar cells from the moon regolith and we can make all the oxygen we need to breath.
Can we use an SSTO vehicle not possible at this time IMO, can we design the complete vehicle or pieces to be reuseable sure but at what cost.

RedStreak · 2008-04-07 14:10:40

I don't think a single stage vehicle for the moon will be possible for a good century.

What would be possible should be a vehicle that could go from LEO to the Lunar Surface.

I can picture something like a supped-up Altair/LEM with a J-2X that'd do the major maneuvering. Could a large reuseable lander work provided there's ISRU on the moon?

Gregori · 2008-04-07 17:41:23

We can't do SSTO on Earth quite yet.

I've got a slightly different Idea though.

An SSTO vehicle from the Lunar surface could be possible. If so, we could produce LOX fuel from the Lunar surface using a machine. An SSTO craft on the Moon could refuel ships in orbit periodically, to help the journey to Mars (or elsewhere)

If this process can be highly automated, that will probably be alot better.

The trouble is, no one has designed such a machine. The sooner, the better.

I believe that Solar power on the Lunar surface will be a fine power source for the time being esp near the pole. The moon has a large free open space to deploy massive solar cells. These don't need too much maintenance. If worst comes to worst, a batteries can store back up power.

louis · 2008-04-07 18:28:34

Everybody tells me an SSTO is impossible. But no one ever gives any figures.

Here's one estimate of an SSTO configuration:

"So how bad is this? Well, it's not good. Even with hydrogen, an SSTO launcher which weighs (say) 800,000 lbs at launch has to be 7/8ths fuel. We've got 100,000 lbs for tanks to hold 700,000 lbs of fuel, engines to lift an 800,000 lb vehicle, a heatshield to protect the whole thing on return, structure to hold it all together at high acceleration...and some payload to make it all worthwhile. Most of the dry weight has to go for the vehicle itself; only a small part of it can be payload. (That is, the "payload fraction" is quite small.) To get any payload at all, we need to work hard at making the vehicle ("dry") very lightweight."

So that's a 50 tonnes for tanks to hold 350 tonnes of fuel, engines, and the rest, including the payload.

But how much payload?

Saturn V was I think about 3000 tonnes in total mass.

Does that give us some leeway.

What if we had a 3000 tonne SSTO. Could that carry a 10 tonne payload.

RedStreak · 2008-04-07 19:49:03

Everybody tells me an SSTO is impossible. But no one ever gives any figures.

Saturn V was I think about 3000 tonnes in total mass.
Does that give us some leeway.
What if we had a 3000 tonne SSTO. Could that carry a 10 tonne payload.

Saturn V was 3000 tonne of multiple rocket stages that jettisoned - all that fuel spent ulimately sent up just the Apollo and LEM at the very tip of the whole structure! Both combined weighed considerably LESS than 3000 tonne! If you're talking a solid vehicle you may as well be talking about something like Star Trek Enterprises.

Whatever form a SSTO or to Moon, Mars, ect. space vehicle takes, I bet it will have one of two things:

1) In Situ Propellant Production - if it relies on chemical propulsion still it could get around weight problem by only carrying enough fuel for part of the trip.

2) Non-propellant drive - I'm talking something like solar sails or the vaguely related magnetic sail - heck even the Star Trek Warp Drive counts. A means of propulsion that might require power but not fuel.

To fully implement either will require more technology than we have now, but of the two the first option is closer to implementing that the second (attemps to launch solar sails have been made, but sadly none have yet to actually delpoy and prove concept ).

Gregori · 2008-04-07 20:15:58

Everybody tells me an SSTO is impossible. But no one ever gives any figures.
Here's one estimate of an SSTO configuration:
"So how bad is this? Well, it's not good. Even with hydrogen, an SSTO launcher which weighs (say) 800,000 lbs at launch has to be 7/8ths fuel. We've got 100,000 lbs for tanks to hold 700,000 lbs of fuel, engines to lift an 800,000 lb vehicle, a heatshield to protect the whole thing on return, structure to hold it all together at high acceleration...and some payload to make it all worthwhile. Most of the dry weight has to go for the vehicle itself; only a small part of it can be payload. (That is, the "payload fraction" is quite small.) To get any payload at all, we need to work hard at making the vehicle ("dry") very lightweight."
So that's a 50 tonnes for tanks to hold 350 tonnes of fuel, engines, and the rest, including the payload.
But how much payload?
Saturn V was I think about 3000 tonnes in total mass.
Does that give us some leeway.
What if we had a 3000 tonne SSTO. Could that carry a 10 tonne payload.

Its not impossible. Its just not practical or easy to do atm. Multiple stage rocket are way easier to do. Even Scaled Composites White Knight had to use a two stage process to get into a sub orbital space.

If it were easy to do, it would have been done by now!!

Such a vehicle could be operated from the Lunar surface because of its weak gravity. Ships destined for Mars and beyond could be refueled in orbit by such a ship using LOX derived from the lunar surface.

In fact, ships could be potentially constructed from materials on the Moon.

Commodore · 2008-04-07 22:17:20

Were not going to be able to build a single craft to go from Earth to the Moon for a good long time. ISRU will require bulk amounts very special elemental materials to augment what is found on the moon. Life support and agricultural needs, hydrogen(I'm assuming what is there is saved for life support), propellant, ect. By themselves its probably better to consider smaller 20ton shipments, and save the big industrial and hab launches for the bigger rockets.

Instead, what we really need is individual systems for the different environments.

1)Earth to LEO: Near term we have started on the Ares I. I think as a follow up we'll eventually have a Venturestar like spaceplane once the air force gets around to declassifying it. Short of a full fledged elevator, I think we can develop a vacuum tube to extract atmospheric gases to orbit.

2) LEO to Lunar Space: Pretty straightforward. Cargo ships fueled on either end, OX on the lunar end, H2 on the Earth end.

3) Lunar space to Surface: After the Altair, I think we'll end up with something like the Delta Chipper, extracting the bulk of its fuel by weight (ox) from the surface. Later, I think we can reduce liquid fuel use by adding solid boosters produced on the lunar surface. Later, those will be replaced by mass drivers, again only using liquid fuel for docking maneuvers.

RobertDyck · 2008-04-07 22:24:29

The amount of water at the lunar poles is hotly debated. The neutron spectrometer suite on Lunar Prospector was designed to measure hydrogen in the top metre of lunar soil. One announcement is they found one cup of water over an area the size of a football field. That's at the bottom of craters at the poles where sunlight never touches them. Others point out the total quantity of water found and claim there must be a lot, ignoring the fact that water is spread over hundreds of square miles. The neutron spectrometer was able to detect separately any large chunks of ice, but didn't find any. That is, any large chunks or even snowball size pieces would absorb high speed neutrons, but the instrument saw no reduction of reflected high speed neutrons. What it did see was reduction of epithermal neutrons, which means there is some hydrogen there. That doesn't say what form the hydrogen is in; it could be hydrated minerals such as clay or gypsum, or it could be small ice crystals the size of a grain of salt. If the source of hydrogen was a carbonaceous chondrite asteroid impact, then it could be hydrated minerals. But the low concentration makes it not useful as rocket propellant.

Ok, so what fuel is available on the Moon? In the late 1980s John Wickman developed something called Lunar Soil Propellant. He noticed solid rockets use finely ground aluminum as fuel, and some solid that breaks down to produce oxygen such as sodium nitrate. Most lunar minerals are oxides, and there's plenty of silicon and aluminum. He found powdered aluminum suspended in liquid oxygen as a monopropellant does work. Since this is a monopropellant, one concern was exploding the tank. His tests showed the rocket engine does not flash back into the fuel tank. However, he found an alternative: dry aluminum powder blown into the rocket chamber with compressed nitrogen gas, and liquid oxygen fed in separately. The problem is the moon doesn't have nitrogen either. You can also do this with magnesium powder and liquid oxygen, but as a monopropellant it is shock sensitive. That means magnesium/LOX will explode if you give it a good knock, but aluminum/LOX won't. The magnesium fuel mixture proved useful for Mars because there is nitrogen on Mars, and magnesium will burn in a CO2 atmosphere. So a jet engine that uses magnesium powder with pressurized nitrogen to blow it into the jet, will work in Mars atmosphere. But on the Moon you're back to monopropellant.

One aerospace engineer literally laughed at me when I mentioned this idea, calling it suicide. John Wickman did extensive tests to prove the aluminum/LOX monopropellant isn't shock sensitive, and his rocket will not let combustion flash back into the tank. But it's still a question whether you want to trust that for human space travel. If not, you have to deliver hydrogen fuel from Earth or an asteroid. Lunar poles just don't have enough in sufficient concentration to be practical for fuel.

Commodore · 2008-04-07 22:38:20

You can also do this with magnesium powder and liquid oxygen, but as a monopropellant it is shock sensitive. That means magnesium/LOX will explode if you give it a good knock, but aluminum/LOX won't.

I've heard stories about folks from the ATK plant in Utah bringing home little bits of the SRB fuel and letting the kids smack them with hammers. You got to be careful get a good grip on the hammer or it will keep going when it flies back of the way it came.

RobertDyck · 2008-04-08 00:15:07

SSTO from Earth surface to LEO is possible, it just takes work. SSTO from lunar surface to trans-Earth trajectory is easy. So the question is what do you want?

VentureStar was an attempt to develop an SSTO space shuttle to replace the current shuttle. It was a pure lifting body that would launch vertically, land horizontally. Specifications:
total launch mass including fuel: 991,000kg
payload to 185km orbit at 28° inclination: 26,800kg
crew size: 1

Unfortunately they had a few development problems. NASA included a clause in the contract that stated any set-backs would be cost shared with the contractor. Lockheed-Martin signed the contract, but when the first set-back occured they refused to pay.

They made a last minute design change to replace the solid wall composite fuel tank with a hollow wall honeycomb structure. Tests with liquid nitrogen showed the hollow wall design caused microfractures in the thin wall that let liquid nitrogen in, then when the tank was drained the liquid didn't get out of cells in the wall. When the tank was warmed the microfractures sealed shut due to thermal expansion. When the nitrogen boiled to gas it caused pressure which burst the cells; the tank literally disintegrated. Ok, so that means you can't use a hollow wall tank with cryogenic propellant.

The obvious solution is to go back to the original design of a solid wall composite tank. But after years of lawyers arguing over who would pay for it, they went back to an aluminum tank like every rocket since the Redstone. That aluminum tank added so much weight that the design became difficult to work as an SSTO. Then there was a presidential election, George W. Bush saw the project as an icon of the previous administration so he cancelled it.

A couple other problems: one set of tanks was left outside the aircraft hanger where they were made. The cleaning crew thought they were garbage so removed them with the garbage.

One of the tanks was made by students under supervision of an experienced engineer. One of the students used tape to hold down a piece of carbon fibre while applying epoxy. The tape acted as a foreign object, so created a weak spot. When the tank started to fall apart it broke at that spot, blowing apart in a small explosion. However, the tank fell apart primarily due to liquid nitrogen getting to the cells of the hollow wall, so it would have come apart anyway. The tape created a weak spot, but the whole design doesn't work with cryogenic propellants anyway.

Could VentureStar have flown if they stuck with solid wall composite tanks, and didn't use tape in the fabrication of the tanks? Frankly, yes.

Oh, I should mention these tests were done with a 1/4 scale model that was supposed to fly a suborbital trajectory. The small scale thing was called X-33, it wasn't expected to achieve orbit. X-33 itself cost millions to build, a cost that would be hard to justify if everything worked perfectly. The idea was to test technology on a 1/4 scale demonstrator so if something went wrong they could fix it for less money. So investment in X-33 would only pay off if something went wrong. Well it did, the hollow wall composite tank didn't pass the first cryogenic test. Ok, that should have proved the X-33 was a sound investment, fix the problem and move on. But they didn't because Lockmart tried to scam NASA for money. I can't use any other word than "scam" considering they never had any intention of honouring the contract clause that said they had to share the cost of a set-back.

There are nay-sayers who like to criticize every failure, but truth is every development has bumps in the road. The reason X-33 and VentureStar failed had nothing to do with engineering, everything to do with project management and contract relations.

louis · 2008-04-08 02:13:29

Very interesting Robert.

Well it seems to me that what is holding people back here is really the investment costs and the challenge of developing all the necessary new knowledge - not any physical limits. It's probably similar to what happened with jet aircraft. The delta concept coudl have been developed with the cabin built into the wings. Many engineers think that could be a more efficient design. But to design a plane like that now means you would have to go back to basics in a lot of areas - and that is expensive and difficult to predict in terms of outcome i.e. there might be a serious problem we haven't anticipated.

I can see why a company like Space X will not want to go back to basics - far too expensive. Why not just go with the basic multi stage approach with which engineers are familiar and which delivers immediate upfront benefits.

However, I am quite encouraged by what you say. Seems to me a ten tonne payload to the Moon and back again with full retro rocket landing at both ends (but maybe with refuelling on the moon) is certainly doable. The great advantage would be turn round times, convenience, lack of heat damage, reusability greater reliability - which, once the initial investment is discounted must translate into reduced costs.

RobertDyck · 2008-04-08 06:11:38

Are you talking about a single stage that goes from the surface of Earth to the surface of the Moon? And them back again with "sit on its tail" landing on the Earth? That's entirely different. There are physics limits that prevent that.

A space shuttle that goes from the surface of Earth to Low Earth Orbit will barely get out of the atmosphere. Notice the altitude, you can lift a substantial weight to 185km. The Earth is 12,750km diameter, geostationary orbit is roughly 36,000km above the surface of the Earth. One astronaut said if the Earth were a peach the shuttle would be skimming the peach fuzz. SSTO is possible with chemical engines via used of modern composites. You can use the same black heat shield tiles as the current space shuttle one the external tank is eliminated; no foam to come off. Those tiles are about one inch thick of silica foam, with the weight of styrofoam. The black glaze is about as thick as a coat of paint. Every weight saving technique is already incorporated.

A space shuttle requires wings, heat shield, wheels, aerodynamic control surfaces, a lot of stuff that are completely useless in space. But they mean you don't need propellant to land on Earth; once you enter the atmosphere it's all aerodynamic, no fuel. So such a design can never be efficient for in-space travel. Don't expect a shuttle will ever be able to travel to the Moon much less land on it. You want it to take off from the Moon, travel back to Earth, and land on the Earth as well? Forget it. Won't happen.

The most efficient design would be a shuttle from Earth surface to LEO and back. A separate craft from LEO to the lunar surface, refuel on the Moon, then travel back to Earth and aerocapture into orbit. Aerocapture would result in an elliptical orbit, separate aerobraking would be required to drop into a low circular orbit.

louis · 2008-04-08 12:03:07

Robert -

Yes, ultimately that would be the goal I think. But certainly as a half way house, let's assume a full refuel on the Moon. So really it's SSTO, journey to moon and moon landing I'm thinking about.

On the question of weight, doesn't a retrorocket descent preclude the need for a specialist heat resisting skin? Surely some weight saving there - although you say the materials used are v. light.

Is there anyway of describing a rule of thumb for the physics limits? I've read 100 to 1 for mass to payload to get into orbit. Not sure if that's LEO, or GSO but I guess that's on the assumption of multi-stage rockets. .

Saturn V was nearly 3,000 tonnes and that got a 30 tonne command and service module to the moon and back. So I am assuming it is GSO.

Of course there sometimes appear to be ambiguity about what constitutes payload and what is dry mass.

I suppose I'm wondering what a 3,000 tonne monster with today's materials and fuels but SSTO could do in terms of a 10 tonne payload.

Thanks for the peach image - that's one to keep in mind.

Terraformer · 2008-04-08 14:19:07

So the oxygen could be produced on the Moon? And the fuel could be possible if we were willing to use Aluminum?

JoshNH4H · 2008-04-08 14:40:33

SSTO is very difficult. I believe that The LANTR Concept (Lox Augmented NTR) would be good for a SSTO (I know I've mentioned it before, but I feel that it is not very well known.) Specifically, LANTR using Ammonia as a fuel. The isp, (assuming that a NTR using just ammonia would be 625 (That assumes that with Hydrogen, it would be 1000. 5/8 is a reasonable assumption, shown herehttp://www.projectrho.com/rocket/rocket3c2.html). But anyway, the total Isp would be 540ish, and it would be able to lift off.

Gregori · 2008-04-08 16:54:06

It seems that SSTO is very very difficult and and a few decades away from becoming reality. Hopefully it can be achieved eventually, but maybe we should deal with developing the technology we have now.

The less stuff we have to lift from Earth, the better. Robotics and automation have shown a lot of success in recent years with the Jules Verne ATV, the Twin Martian Rovers etc etc

I feel we should develop the Moon and the Asteroids as much as possible for exploring Mars and further. SSTO can easily be achieved from these low gravity bodies. The Moon could serve as an important assembly and refueling point for Mars bound spacecraft/cargo.

Many asteroids could contain a lot of water ice and useful minerals that would be easier and less expensive to aquire and bring to the Moon than bringing them from Earth. The Moon is rich in minerals that could be used to manufacture spacecraft hulls, Habitat shells, Solar Panels, LOX, Glass, White Paint... They're going to need an Electric arc Furnace and some computerised Metal Cutting machines on the Moon.

I reckon we should try to push the manufacturing base for space travel as much into space and the Moon as possible. That will require a very heavy inital investment in Space manufacturing facilities and technology (and loads of Heavy Lifting Rockets) but this will bear incredible fruits later on.

If this network of resources can be made as efficient as possible, the only things being carried by expensive rockets from Earth's surface into space should be mostly humans.

The distances in space are considerable and can take months and years for craft to travel to their destination. To overcome this delay, a constant stream of craft could make transport and supplies steady. Titan and Ceres have resources that would be incredibly invaluable to human colonies and space manufacturing. Ceres may have volatiles necessary to support life and grow food. Titan is full of hydrocarbons that could be used for plastics ...

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