#91 December 1995
Section 22.214.171.124.091.of the Artemis Data Book
Who would want to [build new lunar rovers from the old Apollo era plans]??? By today's standards the electronics on that thing are a science fair project....
Replace the frame with composites from Scaled Composites. The electric motors will be a fraction of the size and weight because magnet materials have improved vastly since then. Storage technology has not improved by as great a degree but still, it has advanced. We'll have commercial micro-machine accelerometers on the market soon, so the navigation hardware will be built right onto the chip with the electronic interface. The comm gear has shrunk to nearly nothing. Compare a walkie talkie in a '60s' era Edmund Scientific catalog with what you can pick up down at your local Tandy Radio Shack. R/C toys have better radio equipment than some of those '60s' comm units....
And then, most importantly of all - we know the environment it is to work in and have those old rovers, their problems and performance as an initial data point. And that data point is basically that it is no big deal building one. They are a piece of kit that a hobbyist could successfully build. It doesn't take an aerospace company to build an electric dune buggy.
Just a bit of caution on vacuum, a bit of thought on rad hardening, a bit of care on temperature range... And you needn't bother about outgassing of your materials. They'll never be inside your breathing space so who cares? That makes it a lot easier.
Oh, and some care in packaging may be required to ensure it isn't damaged by the vibration. I remember ruining a tire on my DT400 by not tying the tire down when hauling it in a trailer behind my car. Tire spun from the vibration and wore the nobbies bald...
While walking home recently one night I remembered some thoughts I had on lunar rovers a number of years back. There will be a need for different sorts of vehicles, and undoubtedly large hauling vehicles, whenever they are required, will need a good power source. Whether that be fuel cell, battery, solar power, beamed power or some mix I won't go into here. But the type of vehicle needed for a small, relatively self-sufficient group should have a number of characteristics that few of the designs in the literature ever consider.
The motive source should be 100% field repairable preferably with only a few tools and simple spare parts.
Spare parts should be such that they can be manufactured locally from small amounts of raw materials.
The vehicle should have a fail safe criteria that it can bring the driver home under almost any circumstances in which the driver is still capable of driving.
It must use indigenous energy supplies.
Now if you look at these requirements through the old-fashioned NASA eyes, you will come up with a billion dollar project. If you look at it with the eyes of an engineer, you immediately come to the conclusion that a human powered vehicle is just the ticket.
Research backs this up. In a Scientific American issue on Human Powered Vehicles a number of years ago, an article on bicycles had an extra data point for the performance of a vehicle on the moon. A racing biker, with no air resistance and 1/6 g could break 1000km/h in sprints. A normal, healthy person could cruise at over 100km/h all day, and could easily pull a trailer load at the equivalent of typical Earth-bound auto driving speeds.
The form of the vehicle is the recumbent bicycle like that used by Stephen K. Roberts (Computing Across America). And in fact, he would probably be the best person to speak to on the design of a lunar rover. He crossed the USA from end to end several times on his recumbent, traveling up and down through the Rockies, keeping up reasonable highway speeds - and all the while with a trailer that included solar power gathering and a satellite uplink so he could type on the keyboard in front of him (while peddling) and submit articles to magazines that funded his journeys. He also had navigation and maps built into his console processor. I don't think there is anything that a lunar rover built for days of unsupported prospecting would need that he didn't do 5-6 years ago.
Now, that is not to say there aren't issues unique to the moon. There is the issue of traction and off-road travel, which will drive the gearing ratios, axle loading, weight and balance, and wheel design.
Braking will have to be dynamic, feeding the energy back into a dynamo. Normal friction brakes are a bad idea for two reasons - 1) The abrasiveness of the regolith. 2) Brake cooling is purely by radiation to the background and conduction through the frame. Radiators are a problem as has been suggested before; and since I expect the frame to be composites, conduction is not very good either.
Gears and chains and deraileurs will have to be very robust and spares will be required. A design that can be field welded would be a good idea. Better to trade off a bit of elegance and performance for field maintainability. These parts can be built very ruggedly (I'm not talking about racing bikes here!!) and would need to be able to withstand the rigours of large temperature swings and abrasive particles. One could seal them, but then it is more difficult to field strip. And not to mention which, without herculean efforts the lunar grit will get in anyway. If anyone out there was in Desert Storm...
Another area of concern is space suit cooling. The loads will not be excessive under normal cruising since the peddling is only enough to replace frictional losses.
Use of a small motor like that in a minibike could solve a number of problems (if they don't add too much complexity on their own). The motor could be the means by which braking returns energy to storage. Energy can be recovered on downhill stretches and used to ease uphill travel. It also can reduce the heat loading on the space suit during acceleration from a standing start, or indeed any acceleration under load. The motor would, of course, need to be built such that it can be disconnected from the system entirely if it fails. The overall system would have to be able to get the lunan back home regardless. So think of it only as a luxury item on the bike.
The suit would be a live-in suit, so that puts some extra design load on it. You might have to do better than a diaper if you're going to be out for a week.... But this is a problem that needs to be solved anyway. The Stars Wars rovers that some NASA scenarios show us are not going to be feasible on any realistic budget, and in any case you'd only be able to afford one of them for the same price as giving every lunan their own personal lunabike.
It seems wholly superior to any rover concept I've yet to see. Just about anyone out there could have run circles around the Lunar Rover and been out 20 km and back before it was barely out of sight of the LEM...
Ah, you say, bikes are good on highways, but off-road you're going to want a trike! The lunar surface has huge areas that are much like beaches and dunes. Covered with hardpacked fine regolith that follows the contours of the land in a very smooth and gentlly rolling fashion. This is not to say that crater rims and such are quite the same - but large tracts of the moon should be easily negotiable.
As to bike vs. trike, there is no inference above, of a two wheel design - in fact I believe the recumbents are usually trikes. At least the Robertson one that I saw in 1989 was... DA
Sounds delightfully low-tech, doesn't it? Tired and stressed out after a long day's work in your lunar office, mine, or factory? Just don your out-vac trike suit and head for the airlock and get some heal-all unwinding exercise! Reminds me of an Arthur C. Clarke story where the hero does a kangaroo-lope to safety 600 km across Mare Imbrium in just a spacesuit.
The question arises: without an open air heat sink, where does all the body heat generated by such exertion go? An out-vac triking suit needs not only to be self-contained (in RV-camper-trailer talk that means "with toilet"), but able to handle/shed internally-generated heat, and perspiration as well. That also means being able to keep the wearer from getting a chill soaked in his/her own sweat once the exertion is over. Perhaps the suit's insulation material could be an eutectic salt in a quilt of pocket cells, melting to absorb internally-generated heat, solidifying to release it - automatically, on demand. PK
Having tried both [an EVA suit and a diver's dry suit], let me tell you that a pressurized conventional spacesuit is much more restricting than a drysuit.
Spacesuit design has been hampered by thinking of it only as a garment. It is also a small space vehicle. A conventional suit is no place to be for more than a few hours. For longer durations, you need to be able to pull your arms in so that you can scratch, or eat, or sleep, or void. This suggests that the lunabike should be integrated with the suit -- in other words, the suit would be a light-weight pressurized canister with wheels (4, for stability), with a shirt-sleeve internal environment for pedaling and living. The canister would be equipped with pressurized gloves, waldoes or other attached tools for manipulating the external environment.
It might be necessary to carry a conventional suit, donnable inside the canister, so that you could get out and get under if something broke, or go climb that cliff over there (where, as Arthur Clarke has told us, The Sentinel is waiting), or, in extremis, walk home. For routine use, (such as getting from one pressurized dome to another) the mobile canister alone might be sufficient. The real safety reason for carrying a conventional suit is to avoid potentially fatal single-point failure modes, an objective that might be met by careful design of the canister/bike alone. PC
Response from Dale Amon to Chapman's suggestion
[What I have in mind is an outvac cycle that fits every lunan's budget. So] the bike must be mostly buildable from local materials with simple tools and basic stock materials; all systems required for it to function as transport must be field repairable. Simplicity. Something a back yard mechanic can build and repair - exclusive of the electronics, of course - but there should be no electronics that are absolutely required for the bike to operate. Electronics must be something that is bolted on and if necessary unbolted and tossed into a crater to lighten the load.
The minute part of the design requires a special tool or material, my design criteria demands that that element be discarded from consideration. Simple. Indigenous. Independent.
One of the more ambitious goals outlined in the plan for ISDC '98 - Milwaukee is to present a number of low budget ($100-$5,000) technology demonstrations of tidbits of technology that will be needed, or useful on the space frontier, and which should not take that much money to demonstrate.
A human-powered Moon Trike is such a possibility. Because gravity is only 1/6th Earth-normal, but momentum remains full Earth-normal, to prevent tipping, the vehicle should have a very wide track, wheels that lean into turns, and a low center of gravity (hence a recumbent rider position seems ideal). Any interested group should attempt to find its own industrial and corporate sponsors, advisors, project managers, etc. and register their effort with
ISDC '98 - Milwaukee,which will attempt to provide advice and assistance.
P.O. Box 2102,
Milwaukee WI 53201
Contents of this issue of Moon Miners' Manifesto