Automatic or Manual Transmission - Moon/Mars Rovers

Tom Kalbfus · 2006-09-27 22:11:46

So what works best for Lunar and Martian conditions. a Rover with a stick shift or an automatic transmission?

C M Edwards · 2006-09-28 07:09:41

I would include direct drive with "automatic" in this case. Without that, I would have to change my vote: standard transmissions tend to be lighter, are simpler to build, have larger working tolerances, and are easier to repair than an equivalent automatic transmission. If you plan to ship one to Mars, fix it when it gets there, or make one from scratch, then choose a standard.

Neither standard nor automatic automobile transmissions can beat direct drive in any of those categories, though. Direct drive, golf cart style, is what we should use.

Tom Kalbfus · 2006-09-28 07:30:25

Direct drive is what? I haven't seen that option in many showrooms.

C M Edwards · 2006-09-28 11:08:33

Direct drive is what? I haven't seen that option in many showrooms.

Probably because you haven't seen electric and/or hybrid electric without coupled driveshafts in many showrooms. Basically, you put a wheel on one end of a variable speed electric motor and a power source with a rheostat on the other end.

Tom Kalbfus · 2006-09-28 12:55:35

Ok, so it mechanical motion to generator to electricity to electric motor to mechanical motion. Isn't this somewhat inefficient. The engine produces both heat and motion the motion drives the generator and in the process the friction in the generator loses some more heat due to moving parts in contact with each other, then an electric current is generated travels down wires that are not perfect conductors so their is heat generated due to electrical resistance, and then the electricity powers the electric motor which turns the wheel and their is electrical resistance and friction in that as well. I suppose on Mars this waste heat is put to good use.

C M Edwards · 2006-09-28 15:03:48

Ok, so it mechanical motion to generator to electricity to electric motor to mechanical motion. Isn't this somewhat inefficient.

Any power source can be employed. A fuel-fired generator is just one of many possibilities. I am essentially referring to a transmissionless electric car - whether it's an electric hybrid is incidental.

A vehicle with a direct drive can be just as efficient as one with a transmission - it's just a matter of where the power goes. Here on Earth, vehicles of this type are usually used where torque is needed more than speed. Examples range from golf carts (cargo capacity < 500kg) to freight trains (cargo capacity >50000000 kg). A gear box is sometimes employed for these applications, but not a variable speed transmission.

I suppose on Mars this waste heat is put to good use.

I wouldn't know, having never been. But I sure hope so!

Tom Kalbfus · 2006-09-28 15:46:53

I suppose a Mars car is umlikely to be traveling at 75 miles per hour without an established road. What would a Martian road be made out of anyway. I'm not sure if asphalt would be the best thing. How would one come by asphalt anyway, requires a source of petroleum, most likely synthesized from the air. Perhaps concrete would be better.

cjchandler · 2006-09-28 19:26:00

Electric motors right in the wheel, no transmission or gears to get dusty, so I guess that's automatic.

Austin Stanley · 2006-09-28 20:18:45

Another vote for electic motors, but not necessarily based in the wheels. I'm not opposed to axels, whichever solution is the most reliable and masses the least should be used. Their are certianly pros and cons to both solutions.

The mars rover's engine is going to need lots of torque but will not likely be driven at high speeds. So even if we were going to use an ICE engine (or even a nuclear turbine or something else) a heavy transmission typical of automobiles probably would not be needed. The engine needs lots of toqure and little else, so one gear or maybe two is all that would be needed. The rover is more like an overgrown tractor than a car realy.

Tom Kalbfus · 2006-09-29 08:49:16

Would you want a rover that couldn't go any faster than an astronaut could walk?
I guess its not expected that astronauts would ever be in any hurry for whatever reason, but lets think about it for a second. Lets say the astronauts have a base and a rover. Probablythe only place the rover can refuel is at the base.

Now what if the rover crawls as fast as an astronaut can walk? Remember the Astronauts are going to stay here for two years. During the early part of the mission, the astronauts might concentrate on the area around the base, but later on they might want to go further and further out. If the rover crawls, its going to slowly pass through terrotory that the astronauts have already explored, before getting to those sites that are of interest.

SpaceNut · 2006-09-29 13:51:29

You just indicated the issues surounding any manned eploration of the planets in that the rover must be dependable, repairable and quite possibly equipped with a secondary means to make it move should the crew become stranded by the primary method of making the rover go.

Even if the rover has an enclosed cabin with life support it still is only a stop gap for crew survival.

Would you want a rover that couldn't go any faster than an astronaut could walk?
Now what if the rover crawls as fast as an astronaut can walk?

The ability to walk back to base camp if nothing or anything else must be also a main consideration of the rovers design.

C M Edwards · 2006-09-29 14:01:28

I just got this mental image of Alvin Straight in a space suit...

Nevermind. Anyway, electric drive isn't necessarily slow, especially if you're willing to include a simple gearbox to step up the speed. True, fifteen to thirty miles per hour might be the best you can do over rough terrain, but that's not too much worse than you could do offroad with a gas powered Jeep. It's still 100 miles or more per day. And nobody except Superman ever outran a diesel-powered electric train in a full out footrace.

Electric motors can do the job, as long as we're willing to give up moving the Baha 500 to Mars.

Tom Kalbfus · 2006-09-30 00:44:44

A few other options to consider:

Would you want an open top Rover and require the astronauts to sit in their spacesuits uncomfortably unable to even scratch their nose? You can't get you hand inside your face plate to scratch you nose. What if an astronaut sneezes while doing work in his space suit and its splattered all over the inside of the glass obstructing his vision? An enclosed rover allows the astronaut some creature conforts, he can have plush leather seating, a DVD player, his seat can fully recline so he can sleep in it etc.

What else can you include on a Mars Rover? How about windshield wipers. No doubt dust can accumulate on the windshield and make it harder to see out off. Perhaps the wipers will be more like brushes. If you squirt cleaning fluid on the outside of the windshield, it will boil away, but can it remove dirt before it entirely does so?

I think a rover could use headlights and a GPS system. How about airbags? Maybe a spare tire. I think a sun roof would be a nice feature. The windows of course would not roll down.

Austin Stanley · 2006-09-30 01:47:35

Would you want a rover that couldn't go any faster than an astronaut could walk?
I guess its not expected that astronauts would ever be in any hurry for whatever reason, but lets think about it for a second. Lets say the astronauts have a base and a rover. Probablythe only place the rover can refuel is at the base.

No, not really. The two key aspects to the rover are reliability/safey and range/fuel efficency. These needs are best served by keeping the speed down, 30mph, tops, generaly much slower. Rember, ALL of mars is unimproved terrain. There are no roads or highways anywhere on the planet. Attempting high speed travel over rough, unexplored, completely virgin territory, millions of miles from a repair shop is foolhardy. In these conditions high speed travel is far more dangerous than delay in arrival could cause. The rover has to be no-fail or fail-safe anyways. If somethink breaks when the crew is 300km out, they are boned, end of story.

Now what if the rover crawls as fast as an astronaut can walk? Remember the Astronauts are going to stay here for two years. During the early part of the mission, the astronauts might concentrate on the area around the base, but later on they might want to go further and further out. If the rover crawls, its going to slowly pass through terrotory that the astronauts have already explored, before getting to those sites that are of interest.

High speed does not equal more exploration range, in fact it means quite the opposite. The rover will be constrained primarily by it's fuel supply (not it's crew consumables), which is best preserved by going slow and steady. Furthermore, a rover driven at walking speed is still going to cover a lot of ground during it's 2 years on Mars, and since all of it is virgin territory to us, it is all of intrest.

----

Again I repeate, the Rover is more like a heavy-duty recreational vehicle/tractor then some sort of off-road dunebuggy or whatever.

Tom Kalbfus · 2006-09-30 11:41:11

One possibility is that the Rover could come equipped with rocket engines to fly over impassible terrain.

Jack Chandley · 2006-10-13 09:57:18

So what works best for Lunar and Martian conditions. a Rover with a stick shift or an automatic transmission?

What? No CVT?

Commodore · 2006-10-14 20:32:51

What would independant electric motors for each wheel fall under?

GCNRevenger · 2006-10-22 12:16:19

Neither, electric motors in the wheels wouldn't need a transmission, which is one reason why I like them. With adjustable power in each wheel independantly, it also means such a rover would be less likely to get stuck than a centrally powerd one.

Modern cargo trains and super-heavy dump trucks use large diesel generators coupled to electric motors to avoid the need for a transmission and increase reliability. Same thing with USN's newest submarines, where the nuclear reactor is used to spin a generator, and electric motors used to spin the propellar in turn, so the drive shaft doesn't have to be nearly as long. A rover with electric motors in each wheel wouldn't need one at all.

MarsDog · 2006-11-21 05:58:06

Mitsubishi In-wheel motor Electric Vehicle;

The in-wheel motor makes it possible to regulate drive torque and braking force independently at each wheel without the need for any transmission, drive shaft or other complex mechanical components.

http://media.mitsubishi-motors.com/pres … l1269.html

Complex electronics, simple mechanics.

dreammaker · 2007-01-09 09:00:57

even before you decide what the car should look like or handle... you need to figure out what its power source will be. nuclear power? chemical? batteries? each one has its pros and cons, and each one has a different weight, space, and load limits that have to be taken into consideration. if we need a mini nuclear reactor onboard, the vehicle will need to be pretty big, more than likely like a mac truck.

SpaceNut · 2007-01-09 09:34:10

Welcome Dreammaker,

Not only is that a problem in size but it is also a problem for landing it on the surface when it is "mac truck" in size as well weight.

dreammaker · 2007-01-09 09:42:34

good to be here...

size is a problem.. so is power, and even the wheel .. there is still some debate over wire mesh or solid stock for a wheel.
while landing it is another story... one nice thing about a manned mission would be this.. you could have something the size of a mac truck landed in seperate crates and then assembled, where as you'd have to drop it whole if it were unmanned.

SpaceNut · 2007-01-09 10:03:02

You can also throw into the mix internal engine, compressed gas and others as to how to make it move.

dreammaker · 2007-01-09 10:17:48

then you have to factor in where are you going to get your fuel and what is your max range.

more than likely batteries will win out only due to the fact that they are more or less in the middle, and when coupled with PV pannels you get some of your fuel back when your out there working.

SpaceNut · 2007-01-09 10:55:16

While panels on the rover will give some energy a plan for more may be what will be needed if you can make it back to base. It might need to have a concentrator added to make it give extra for the just in case rather than hoping nothing goes wrong.

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#1 2006-09-27 22:11:46

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#2 2006-09-28 07:09:41

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#3 2006-09-28 07:30:25

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#4 2006-09-28 11:08:33

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#5 2006-09-28 12:55:35

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#6 2006-09-28 15:03:48

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#7 2006-09-28 15:46:53

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#8 2006-09-28 19:26:00

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#9 2006-09-28 20:18:45

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#10 2006-09-29 08:49:16

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#11 2006-09-29 13:51:29

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#12 2006-09-29 14:01:28

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#13 2006-09-30 00:44:44

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#14 2006-09-30 01:47:35

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#15 2006-09-30 11:41:11

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#16 2006-10-13 09:57:18

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#17 2006-10-14 20:32:51

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#18 2006-10-22 12:16:19

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#19 2006-11-21 05:58:06

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#20 2007-01-09 09:00:57

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#21 2007-01-09 09:34:10

Re: Automatic or Manual Transmission - Moon/Mars Rovers

#22 2007-01-09 09:42:34

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#23 2007-01-09 10:03:02

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#24 2007-01-09 10:17:48

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