Folks

One of the arguments used to demonstrate we went to the Moon is the amount of Moon rocks brought back. The standard HB response is that robot probes could've brought them back.

It suddenly struck me that designing such a spacecraft would be quite a trick, so I thought I'd throw it to the engineers among you to design a theoretical robot spacecraft whose task would be to travel to the Moon, collect samples and return to Earth. Of most interest to me is what weight the spacecraft would have, and how this compares to the CSM/LM combo.

Certain things occur to me the non-engineer:

- To collect a diverse range of rocks, the lander would have to have some mobility, either built in, or a carried vehicle, like Sojourner.

- The return vehicle would have to be able to carry up to 100 kilograms of rock samples; it would also have to be able to carry core samples up to (say) 3 metres long.

- The return vehicle must be able to contain the rocks in a hermetically sealed container, must be able to achieve lunar escape velocity by itself, and survive re-entry on return to Earth.

- The vehicle collecting the samples must be able to split rocks, pick up rocks, and drill core samples; it must then either hand them over to the return vehicle, or place itself on the return vehicle.

So there you go, engineers. Pull out your slide-rules and have a go at that one. Let's see whether a NASA which apparently couldn't run a manned mission could develop such a sophisticated automated probe...

What were the nature of the Russian lunar samples?

What were the nature of the Russian lunar samples?

Regolith: dust and very small rocks.

Slide rules? Hey, come on... we're not that old. Well, not all of us, anyway...

With my HB hat on, I think I'd go for a "faked moon rocks" theory rather than a robot lander / return mission. I'm sure we could have cooked up some fancy fakes in the labs at Area 51.

Maybe the Russians helped. They might have told us what their samples looked like, or even lent us some.

[/HB]

Donnie,


Don't you know the Russians are in on the scam too? [img]/phpBB/images/smiles/icon_wink.gif[/img]

Don't you know the Russians are in on the scam too?

Of course. The Russians are in on the scam to beat the Russians.

We bribed 'em with all that wheat.

Or was it quatritriticale? [img]/phpBB/images/smiles/icon_confused.gif[/img]

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

All right, doggone it... who put the Tribbles in the quadrotriticale?

Damn it Jim, I'm a doctor. Not a forensic botanist.

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

I'm sure we could have cooked up some fancy fakes in the labs at Area 51.

Yeah, sure. How do you explain the lack of organic molecules in the moon rocks? Even when living organisms die or have been around, organic molecules are always left.

The greys showed us how to get rid of them.

<font size=-1>[ This Message was edited by: ToSeek on 2002-01-22 14:37 ]</font>

Sort of a wild guess, but it seems to me that the robotics of the day were quite primitive. Instead of an AI electronics controller, the drilling and scooping would probably have been controlled by belts and cams.

Scooping is fairly easy... Sweeping is fairly easy...

Core samples? As long as the lander lands in a stable, upright position, it should be able to drill straight down and pull up a core...

I wouldn't want to make the thing mobile, at least not at first. Just land, scoop, sweep, drill, and return. The whole lander would be from 1/10 to 1/4 the size of the Apollo Lander. And no need to dock with the command/service module, either. There would be no CM, and the SM can be reduced to maybe a 20th of the Apollo's SM. (Human beings require a LOT of stuff for breathin' and eatin' and keepin' warm.)

Silas

Of course, the third possibility is that there are no moon rocks at all. The labs that supposedly examined them were part of the conspiracy. The ones on public display are just gray Earth rocks, selected to look like the ones seen by Surveyor... assuming those landings actually took place.

The labs that supposedly examined them were part of the conspiracy.

Even the ones outside the United States? The U.S. and Soviets exchanged lunar material in the 1970s. Don't you think they would have said something like, "Hey, this is just gravel!" The point is that the evidence can only be explained away by dramatically extending the alleged conspiracy further into conjecture.

The proposition that the lunar samples were falsified is absurd enough on its face. The evidence which stands against it is that the samples have been examined by qualified, eminent experts from all over the world. The only way that pesky fact can be dealt with is to provide yet another absurd and unproven proposition: that all these respected laboratories and scientists have been "bought off" or intimidated into silence. Piling conjecture upon conjecture is no way to run a railroad.

This scenario has two unfortunate side effects. First, to protect the secret, it is revealed to more people (i.e., the geologists). You don't protect a secret by revealing it. The probability that a secret will be inadvertently or intentionally revealed is roughly proportional to the square of the number of people who know it.

Second, the scientists selected to first study claimed lunar samples will necessarily be the most eminent and accomplished geologists. It would be perceived as suspicious to give the right of first scholarship to relatively unknown scientists who just happen to be under the control of the conspirators. Sooner or later very accomplished scientists will study the lunar samples. These scientists have professional reputations to consider and may not consent to being bought off or intimidated into silence. Nor will they be attracted by having to write bogus scientific papers purporting to describe falsified samples. Most eminent scientists will run at high speed away from evidence known to be falsified.

Honestly, the contention that the rocks could have been faked is pretty insulting to geologists. It implies they wouldn't be able to tell the difference between earth rocks and moon rocks, or that they couldn't tell a real from a fake. The geologists I have consulted know a great deal more about rocks than I believed it was possible to know. You and I might not be able to tell Rock A from Rock B, but they can.

All the variations of this hypothesis are significantly implausible. In order for it to be true, certain people would have had to be very stupid, or have acted irrationally or contrary to prior patterns of behavior. Hypotheses that rely on highly implausible and unproven premises are correctly rejected as unparsimonious.

The only way the world scientific community could be universally and plausibly convinced of the provenance of lunar samples is to obtain actual lunar surface material.

Okay, so let's design a spacecraft.

We work backwards. What has to land on earth? A sample-return cannister. This is qualitative design, not quantitative. If you want numbers you'll have to write me a check. [img]/phpBB/images/smiles/icon_smile.gif[/img] So we're not going to say how much the sample is. But at the very least you've got to have a sealed sample container.

In order to land on earth you need to hit the ground or water. That means some kind of shock absorption and/or water resistant container. Or you could arrange to snag it out of the air with an airplane.

You have to hit the ground at a reasonable speed, so that means a parachute. You have to survive the trip through the atmosphere, so that means a heat shield -- probably of the ablative variety. And a bit of aerodynamics.

You have to get back from the moon. That means a guidance system. Luckily the whole mission is close enough for a lot of remote control. But you still need antennas and computers, and that means a power supply. And you need thrusters, so you need a fuel supply. All of that can be jettisoned prior to re-entry.

You need to have left the moon. That means an ascent propulsion system and its fuel. We don't need to do a lunar orbit rendezvous, and that would be hard to do by remote control anyway.

You need to have collected samples. That means automated core samplers, rakes, scoops, and other robot-style arms. That means a power supply and a remote control receiver.

You need to have sampled a variety of terrain, requiring locomotion. That means some kind of undercarriage and its associated power supply and control unit. Plus you need eyes, so that means a television camera and associated communications equipment.

This puts us in a quandry. We have a tradeoff to consider. We can simplify the design if we just use one big roving spacecraft. But this far from earth we're limited to S-band communications, and that means a precisely aimed dish. You can't precisely aim an S-band dish if you're galumphing across the surface like an Apollo lunar rover. The dish could only lock on when the craft was stationary.

So you might consider small rovers that deploy from the base unit and collect the samples and return them to the base unit. The base unit is stationary and retains contact with earth via an S-band antenna. It relays the commands to the rovers via VHF radio. But now you've introduced much more complexity into the mission. You have to execute a lunar surface rendezvous, as well as provide for several self-contained rovers with independent control units and power supplies.

(We're designing in terms of 1960s technology, keep in mind.)

You should do okay with the monolithic lander/rover. You simply command it to go in a certain direction for a certain distance, then stop and reacquire contact with earth.

You don't need the collectors or wheels once you leave the moon, so they stay there. The undercarriage is the launch platform for the ascent stage containing the sample cannister.

You had to have soft-landed on the moon, and that means a descent stage. We could probably incorporate that into the undercarriage. But it would need to have enough fuel to execute a powered descent and landing. And its engine would need to be throttled.

You need an orbital maneuvering system. You have to execute a capture into lunar orbit, and that requires an engine. Whether you used the same engine and fuel as the descent stage is another design tradeoff. Engines are not infinitely relightable, and you don't know how many times it may have been fired before. So you could either design the descent system to also serve as an orbital manuevering system, or provide a separate propulsion module that would be discarded after arrival in lunar orbit.

Because of the speeds involved, you don't want to attempt to land directly on the lunar surface. You will want to slow down and be captured into lunar orbit. It also lets you execute the descent orbit from a known state -- a stable lunar orbit. You arrive there, collect your wits, and compute the parameters for the descent orbit based on your lunar parking orbit.

You have to get to the moon, or at least into the moon's sphere of dominant influence. That means a big, hefty burn out of low earth orbit, and that means a big engine with lots of fuel. You don't want to go right off the earth's surface into a translunar trajectory (a direct ascent). First, it's too complicated a maneuver to get out of the atmosphere and then go to the moon. Second, you'll benefit from a rev or two around the earth to check things out and stretch your wings. You can deploy and test some of your spacecraft systems before committing to the mission.

The translunar trajectory insertion is a precision burn, and it's best accomplished -- as above -- from a known stable state: a low earth orbit.

If you can break up a mission into phases, in between which are opportunities for "resting", you have scored points. So you have a boost phase into LEO, at which you can let the spacecraft do as many revs as it takes to satisfy you that it's ready (and you're ready). You have a TLI followed by a coast phase including possible mid-course corrections, followed by a lunar orbit insertion phase. You can stay in lunar orbit for as long as it takes to convince yourself that everything and everyone is ready. Then you have the descent and landing phase, followed by the deployment and operation phase, which can last as long as it needs to, and then the ascent and return phase.

So let's talk propulsion. You can't keep cryogenic fuel in large quantities forever on a translunar mission. It boils off. So you can only use it for the first part of the mission -- say, boost and TLI. That means the rest of your propulsion has to use more stable propellants which, unfortunately, have a lower specific impulse and therefore are not as weight-efficient.

The boost phase could use a two-stage booster with cryogenic propellants, with a third stage to execute TLI.

The cruise and LOI phase could use a service module with hypergolic fuels. This stage is jettisoned just prior to descent orbit insertion. DOI happens with the descent engine (hypergolic). The ascent engine (hypergolic) is tuned for a direct ascent, or it could be retuned for an ascent to lunar orbit followed by a transearth injection in a separate burn -- the partitioning principle.

The problem is that most of these burns have to be done on the farside, out of radio contact. That means the spacecraft has to have substantial ability for pre-programming and autonomous execution of these engine manuevers.

You need comm and brains throughout the entire mission, so the major guidance and control system would have to be on the core spacecraft containing the sample-return cannister, as would the S-band antenna.

Silas is right in that the majority of the weight on manned missions (aside from fuel) is the equipment necessary to sustain the life of the astronauts. Those are generally non-negotiable consumables. You can't just ask astronauts to breath shallow. Manned space flight also requires considerably more exacting thermal control.

Without the benefit of doing any computations, I'd guesstimate that a spacecraft of the design I've worked out here would, if specified to return 50-100 pounds of lunar surface material, have a wet launch weight on the order of 10,000 to 15,000 pounds.

So, if three people know it, it's 9 times more likely to be spilled?

JayUtah, I'm wondering...using technology and materials from the early 60's, would it be possible to build what you described above?

__________________
"You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep seated need to believe." [Carl Sagan]

"Piling conjecture upon conjecture is no way to run a railroad."

It is in Britain, you should see the state of our railways!

__________________
Up the Imps!

So, if three people know it, it's 9 times more likely to be spilled?

That's the rule of thumb used by people in the security business.

JayUtah, I'm wondering...using technology and materials from the early 60's, would it be possible to build what you described above?

Debatable. The technology of the 1960s advanced quite a bit due to the massive influx of Apollo dollars. But the degree of automation required for this spacecraft is much greater than that required for Apollo. Automation means small, light, powerful computers. The AGC weighed something like 80 pounds, and was the state of the art. This spacecraft would require something even more sophisticated and reliable.

And take, for example, the guidance platform. The Apollo guidance platform maintained its alignment over a 2-week period because it had human astronauts to execute a fine alignment procedure every few days or when necessary. It would be much more difficult to design a self-aligning guidance platform for an unmanned spacecraft.

I described the sample collection mechanism as a set of scoops, samplers, and corers. I was hoping someone would press me for details on those, because the kind of stuff you'd need wasn't really available in the 1960s. The movie Silent Running has a few good examples of actual cutting-edge robot arms available in 1970. They're bulky, massive, and not very dextrous.

I think such a spacecraft could possibly have been built in the 1960s, but it would have been considerably more difficult to design, build, and operate successfully than a manned spacecraft, a la Apollo. Wernher von Braun firmly believed that a human pilot was the best "computer" you could put on board a spacecraft. He went on to say they had the advantage of being mass producible with relatively unskilled labor.

Keep in mind that this has already been done. The soviet probe Luna 16 landed on the moon in 1970, dug up some dirt, and shot it back to Earth. True, it was about 100 grams, but that shows that they had the technology at the time to do a sample-return mission. Getting more dirt and rocks would mostly be an issue of scale, not implementation.

And with a robot probe you probably don't need such an exact landing location as you would want in a manned mission, which gives you some leeway both in fuel and computing power.

http://www.solarviews.com/eng/luna16.htm

Keep in mind that this has already been done.

Quite true, although neither Luna 16 nor my hypothetical spacecraft satisfies the stipulations of the original post. Something to do that would have been impossible in 1969, and I believe is still largely impossible today.

The Soviets obtained a convenience sample. They were glad to get their 100 grams and didn't much care where on the moon it came from or whether it was especially representative. (As it turns out, the Soviet samples are from a part of the moon Apollo didn't sample. That's why everyone was so keen on sharing information. We wanted a scoop of the Soviet sample, and we didn't have any political problem whatsoever giving them a baggie of Apollo material in return.)

that shows that they had the technology at the time to do a sample-return mission.

If you pay attention to how Luna 16 was designed, how I specified my hypothetical spacecraft, and how Grumman build the Apollo LM, you start to see a pattern. The technology for landing on the moon and returning safely to earth is largely unchanged regardless of the payload.

Getting more dirt and rocks would mostly be an issue of scale, not implementation.

Well, half true. Scale means mass, and mass is everything in spacecraft design. I keep having to mentally revise my estimates upward for the s/c weight and downward for the sample capacity. I'm thinking more like 20,000 pounds for the s/c and 20-50 pounds for the sample. Luna 16's launch weight was on the order of 12,000 pounds. It return 101 grams of material.

I'm sure you've encountered the scale problem in spacecraft design. If you want to put 10 pounds into earth orbit, that translates to a certain amount of propellant. Let's say your payload expands to 11 pounds. That means you need 10% more propellant, right? Wrong. You need that much more propellant, plus more propellant to lift that propellant, plus more tanking to hold that propellant, plus more propellant to lift that tanking, and bigger tanking to hold that propellant, and so forth.
In sample-return terms, let's say you want to bring back a kilogram of material instead of 100 g. That means your heat shield has to be beefier, since a heavier spacecraft will take longer to slow down in the atmosphere. That ripples back through the design: more TEI fuel, more ascent fuel, more LOI fuel, more TLI fuel, and more boost fuel, all of which can easily exceed the capacity of your original launch vehicle.

And with a robot probe you probably don't need such an exact landing location as you would want in a manned mission, which gives you some leeway both in fuel and computing power.

Well, yes and no. Automated landings require more automation than piloted landings, no matter where the target is. Apollo made precision landings because they could, not so much because their mission would have been fruitless otherwise.

An unmanned spacecraft can't necessarily see the boulder field that marked Apollo 11's designated landing site. Had Apollo 11 been an unmanned spacecraft, it would have crashed. Let's not forget Luna 15. You can't presume a flat, obstacle-free landing site.

It's true you may not care as much where you land, but pinpoint landing is not the problem in automated landing. The sticky wicket is avoiding obstacles.

So, in essence, it would have just made more sense, weight and monetary-wise, to send up three humans. Let's say they each weigh about 250 pounds on the heavy side. That's 750 lbs. of man you gotta send up, along with food, a breathable atmosphere, environmental suits, etc. I'd say a total of no more than 1,000 pounds you gotta send up and bring most of it back. Compare that with just a 100 pounds of moon rocks, the rocks are nearly negligible.

Now, the only thing we gotta do is convince a HB of this logic... Anybody got a free decade or two? [img]/phpBB/images/smiles/icon_wink.gif[/img]

__________________
"You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep seated need to believe." [Carl Sagan]

Assuming that the reason for sending a robot craft to the Moon is in order to hoax a manned landing, then the order of the day is "quick and dirty". That being the the case then such expences as reliability could be discarded. For such things as a rover you could use a 2 pound, radio controlled, toy bulldozer, made in Japan for $2.95. Modifications by NASA for $2,500,000. Of course the Japaneese subcontractor wouldn't even need to know. You'd probably be able to stick the whole thing on a Titan rocket.

SAMU

Folks

Thanks for the answers, particularly JayUtah. That's what I was after. Would you mind me quoting some of this information at some time in the future? It would make a great supplementary chapter on HBs.

In particular, one thing I hadn't realised was that some actions would have to be performed on the far side of the Moon, which would complicate things a little.

For those with comments tangential to my original post, remember, this was an exercise to design a robot probe to go to the Moon in place of Apollo, and what the design of the spacecraft would involve.

As I had originally guessed (and remember, I'm no engineer!) the spacecraft would've been large - what, about 7 or 8 tons all up, and can still only return about 50 kilograms of samples. Remember, we have over 300 kilograms of Moon rocks. And if we assume that the first robot missions didn't gather that sort of weight, then you'd be looking at 7 or 8 successful missions, let alone all the failures. (How many times before Ranger worked perfectly?)

As for faking the rocks, I have it from a geologist that some of the crystals in Moon rocks grow at the rate of a millimetre every thousand years, or slower. Yet these crystals are several millimetres long. Either the rocks came from the Moon, or NASA has a time machine -

Aaaah! I know how they did it! [img]/phpBB/images/smiles/icon_smile.gif[/img]

Either the rocks came from the Moon, or NASA has a time machine -

Right. They would also needed a time machine to make the rocks' exposure of cosmic rays to four billion years. [img]/phpBB/images/smiles/icon_smile.gif[/img]

<font size=-1>[ This Message was edited by: AstroMike on 2002-01-24 14:06 ]</font>

<font size=-1>[ This Message was edited by: AstroMike on 2002-01-24 14:07 ]</font>

So, in essence, it would have just made more sense, weight and monetary-wise, to send up three humans.

Not necessarily. An unmanned spacecraft doesn't have to be as reliable as a manned spacecraft. If an unmanned spacecraft goes wonky, you're only out a little money. If a manned spacecraft goes wonky, people's lives are in danger. So it takes quite a bit of money to build a manned spacecraft because you have to make it redudant and provide greater safety margins.

However, the unmanned spacecraft will have to employ a lot more complicated technology than a manned spacecraft because you have to provide automation that substitutes for a human crew. It's a matter of innovating instead of just doubling up on stuff.

Man-rating isn't rocket science. There are well-established low-tech methods for making something reliable. They're just expensive because they're so exhaustive.

Creating a fully automated capsule to accomplish a complicated task is rocket science. It's a matter of building much better computers with much more sophisticated software, it's a matter of making an un-tip-overable undercarriage. It's a matter of making sure you don't lose radio contact. It's a matter of miniaturizing and augmenting robot technology.

So it's not really valid to say manned space flight is cheaper. In fact, it's considerably more expensive, on average, than unmanned space flight. But it's valid to say that it's easier to accomplish, because you can count on a human crew to act intelligently, creatively, and across a wide variety of fields of expertise.

It is the "easier" stipulation which affects the hoax theory. And here hoax theorists diverge.

Those who contend that NASA lacked the technical know-how to carry out a manned flight to the moon cannot answer the moon rock question by saying that they were retrieved by unmanned spacecraft; that would require more technical know-how.

Those who contend that it was impossible for NASA to send astronauts to the moon because of radiation or some such obstacle can argue that the moon rocks were obtained by unmanned spacecraft no matter what the technical requirements. However the discussion shifts to why it was supposedly impossible to send human astronauts.

Would you mind me quoting some of this information at some time in the future?

Sure, of course. Just keep in mind that it's a thought experiment to convey certain concepts, not a working spacecraft design.

In particular, one thing I hadn't realised was that some actions would have to be performed on the far side of the Moon, which would complicate things a little.

LOI-1 must occur on the farside. LOI-2 is a circularization manuever, and theoretically could occur either at apocynthion (near side) or pericynthion (far side). The problem with an "apocynthion kick" style of circularization manuever is that it would raise the pericynthion, when what you really want to do is lower the apocynthion. Hence the correct LOI-2 burn must be on the farside.

If you want your landing point to be on the nearside, then DOI must occur on the farside.

TEI must occur on the farside.

Nearly all the critical manuevers must occur on the farside.

For those with comments tangential to my original post, remember, this was an exercise to design a robot probe to go to the Moon in place of Apollo...

Right, specifically for documented sample return on the order of dozens or hundreds of pounds. I don't think my design would necessarily satisfy your original problem.

The main problem is fuel. Whatever fuel is required to accelerate 50 kg of specimens plus the surrounding spacecraft into lunar escape velocity has to be sent to the moon in the first place.

To emphasize what AstroMike said:
There is no way to fake either cosmic ray effects or pitting from micrometeorites.

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

I was reluctant to post this because I don't want to give the HB'rs more ammo, but to play devil's advocate, it seems to me that the perfect vehicle and opportunity existed to launch a robotic vehicle to the moon--the Apollo missions themselves.

Just think about it. First, you have a very large lifting vehicle in the Saturn V, more than enough for one big lander or several smaller ones to go at the same time. And you can launch them in full view of everybody just by saying they are manned flights and doing some theatrics beforehand. There would be ships waiting at the splashdown point to pick up the return canisters. Nobody will think twice about the flurry of activity involved so you don't have to hide anything. Just tell them it's something else. [img]/phpBB/images/smiles/icon_smile.gif[/img]

As a bonus, you could use the robotic probes to transmit "live" data at the same time and make it look like there are real people up there, thus countering the arguments that people could track the missions all the way to the moon.

If I were planning a moon hoax and needed actual samples of moon rock, that's how I'd do it. Assuming I had the necessary tech, I would combine my "manned" mission hoax with the actual sample collection. Two birds with one stone.

__________________
...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

So, what do you do if your robot lander crashes while trying to land? Do you secretly execure the "astronauts" who were supposed to have been flying your moon ship? After all, them being around and alive after their lander just crashed would be hard to explain.