SpaceX Mars/Moon rover

[raketa]

Bit off-topic, but I could see the military interested in the tri-motor variant for terrestrial applications. Pricing and range are very impressive (also very very fast).

Some of those features may make it attractive for space applications as well.

I don’t know much about EV/battery technology. Only that cold weather is a challenge. Can someone more knowledge speak to whether one of these could be delivered to the moon on a Starship and used as an unpressurized rover as-is? Would electronics require rad hardening to survive?

As far as competitors, I recall some recent press releases about JAXA and Toyota working on a rover.

Battery actually has no trouble with cold when not used.
When they start to be charged or discharged they have to be warm up to temperature around 24C. Tesla make this technology better with every new car.

This is not accurate. Tesla batteries are actually far better than that.

Tesla lithium-ion batteries are capable of discharging even when below freezing (yes the cold reduces range, but the car doesn't stop working). But lithium-ion batteries should not be charged below that temperature, or else it will damage the cell. At low temperatures the Tesla software will first limit regenerative braking power, and then it will disable regenerative braking altogether (the dreaded  "dashed line").

Tesla diagnostic screens from different cars show different temperature numbers, but the "heat to" temperature is between -10C and 8C, and the "cool to" temperature is roughly 50C (though it will begin passive cooling with the radiator at 30-40C).

Sorry but you are wrong. Tesla invention to make last battery for years is keeping them in very narrow temperature when in use charge or discharge. This is reason Leaf sucks no temperature management.


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[Earendil]

I think a heavily modified version for Mars it is much more probable than for the Moon. And heh did say "Mars".

1. EVA suits for Mars will be much more compact - if you pyt just 2 large seats in front you can actually use Dragon-like pressure suits with helmet off.. then you just attach o2 packs and helmets, depressure the cabin (colelct air in tanks) and go out..
2.  Temp/amplitude extreems and lower for Mars than for the Moon - hence less overall insulation for cabin and electronics needed.
3. Motors and batteries should be overall fine.
4. Extendable solar panels are great as well..

More mass will be added because of insulation and life-support, but then it is 3 timess less gravity, so it will have a decent range even though it might use a lot of energy for life suppport... Think about it. even if 2 times more mass, that's still less on Mars. Then with max speed at say 30 mph... you know  that every EV is rated at 60ish mph and might get up to 1.5 times more range travelling slow..


I think it is doable.

Is it pracical though? As others have pointed - there is no much point in this shape on Mars..  You do not need the aerodinamics, you need volume and capability.. So you make it more van like, but then it looses connection with the cybertrk..

I think Elon will make everything possible to get the vehicle as close as possible to the original. It is matter of pride and a great selling point as well.. you get basically to buy the vehicle goig to Mars!

[Star One]

Battery wise everyone really seems to be waiting for solid state batteries.

[Twark_Main]

Bit off-topic, but I could see the military interested in the tri-motor variant for terrestrial applications. Pricing and range are very impressive (also very very fast).

Some of those features may make it attractive for space applications as well.

I don’t know much about EV/battery technology. Only that cold weather is a challenge. Can someone more knowledge speak to whether one of these could be delivered to the moon on a Starship and used as an unpressurized rover as-is? Would electronics require rad hardening to survive?

As far as competitors, I recall some recent press releases about JAXA and Toyota working on a rover.

Battery actually has no trouble with cold when not used.
When they start to be charged or discharged they have to be warm up to temperature around 24C. Tesla make this technology better with every new car.

This is not accurate. Tesla batteries are actually far better than that.

Tesla lithium-ion batteries are capable of discharging even when below freezing (yes the cold reduces range, but the car doesn't stop working). But lithium-ion batteries should not be charged below that temperature, or else it will damage the cell. At low temperatures the Tesla software will first limit regenerative braking power, and then it will disable regenerative braking altogether (the dreaded  "dashed line").

Tesla diagnostic screens from different cars show different temperature numbers, but the "heat to" temperature is between -10C and 8C, and the "cool to" temperature is roughly 50C (though it will begin passive cooling with the radiator at 30-40C).

Sorry but you are wrong. Tesla invention to make last battery for years is keeping them in very narrow temperature when in use charge or discharge.

Sorry, but I am right.   But lets please go beyond "he said/she said."

I have given sources showing that Tesla batteries can be discharged at temperatures below 24C. And sources showing that Tesla's "narrow" battery temperature maintenance range is much wider than you claim.

What is your source saying Tesla batteries completely shut down at battery temperatures below 24C (which, let's not forget, is equal to a balmy 75.2F!), requiring that the battery to be warmed up to that temperature before it starts working? Spoiler: there is no source, because it's simply not true.

This is reason Leaf sucks no temperature management.

The old Leaf had no way to air condition the batteries, it could only blow air across them. That's why their temperature management sucked (and not because they discharged the battery below 24C/75F).

[lamontagne]

Cybertruck vs Semi accessorized as a boom truck

[lamontagne]

Semi as movable base vs cybertruck

[Sensei]

I do not see a lot of purpose for a pressured Cybertruck: Then you have a pressured capsule (Suit) in a pressured capsule (CT). Without a Airlock?!

The only two good usecases I could see is:

1. A striped-down CT without a pressured chassy. That would be a Luna Rover on steroids
2. A shuttle-vehicle without airlock for a use without a suit:

You will have a lot of uses where you only want to shuttle some persons or small material between the pressured garage of one Starship to an other Starship garage or the pressured garage of a base. Here you can jump in an CT without a suit, drive out of the vehicle-airlock, down the elevator some kilometers to the the other Starship.

[Mandella]

I do not see a lot of purpose for a pressured Cybertruck: Then you have a pressured capsule (Suit) in a pressured capsule (CT). Without a Airlock?!

The only two good usecases I could see is:

1. A striped-down CT without a pressured chassy. That would be a Luna Rover on steroids
2. A shuttle-vehicle without airlock for a use without a suit:

You will have a lot of uses where you only want to shuttle some persons or small material between the pressured garage of one Starship to an other Starship garage or the pressured garage of a base. Here you can jump in an CT without a suit, drive out of the vehicle-airlock, down the elevator some kilometers to the the other Starship.

Airlocks are really the exception rather than the rule. The LEM had none, you had to depressurize the entire cabin. A Mars/Luna rated Cybertruck could do the same thing, although of course all interior gear would have to be vacuum rated too.

[lamontagne]

One interesting option might be to have an optionally pressurized cab.  For short distances you keep it under vacuum, for longer trips you pressurize it and you can remove the helmet.

With a separate truck, you can have a longer trailer that fits into the Starship.  Really, an airstream shaped trailer would be perfect :-)

With the semi, you could have the same thing, but have a double habitat.  You could probably also haul a drill and a solar rig as a second trailer, so a single truck train could carry a whole base.

[Eka]

Why use trailers? Give them their own drive systems, and have them play follow the leader. Push comes to shove you can cannibalize them to keep your rover going and get home. Keep all the parts as common as possible. That way a wheel set or battery from a trailer can be taken and used on a rover.

edit: Spelling

[Sensei]

Really bad design for an offroad Trailer.  Far to high and narrow. And bad placement of axles 

[lamontagne]

Why use trailers? Give them their own drive systems, and have them play follow the leader. Push comes to shove you can cannibalize them to keep your rover going and get home. Keep all the parts as common as possible. That way a wheel set or battery from a trailer can be taken and used on a rover.

edit: Spelling

A trailer with its own drive system become a truck itself, no?  The interesting thing about a trailer is that it serves as a base camp while needing only a single motor in the hauling vehicle.
I don't think there would be any really practical way to cannibalize a trailer towards a vehicle.  We're talking about batteries that are massed in tonnes, not 12V batteries.
Trailer wheels will only be used for a few hundred kilometers over the lifetime of the vehicle.  Truck wheels will cover orders of magnitude more distances.  It may make sense to optimise them, or it may not.  It depends a lot on how exploration is done, really.  And the actual ruggedness of martian terrain.

[lamontagne]

Really bad design for an offroad Trailer.  Far to high and narrow. And bad placement of axles 

Well, I'm not a professional off road trailer designer     but I'm always willing to learn 

The main constraint of the trailer design is likely to be how to fit it into Starship, not so much how it is operated.  It would be nice to be able to stand up in it as well.  This particular design is build around a rectangular vertical air lock, so that does give it a vertical aspect ratio.
Is this better?

[lamontagne]

I do not see a lot of purpose for a pressured Cybertruck: Then you have a pressured capsule (Suit) in a pressured capsule (CT). Without a Airlock?!

The only two good usecases I could see is:

1. A striped-down CT without a pressured chassy. That would be a Luna Rover on steroids
2. A shuttle-vehicle without airlock for a use without a suit:

You will have a lot of uses where you only want to shuttle some persons or small material between the pressured garage of one Starship to an other Starship garage or the pressured garage of a base. Here you can jump in an CT without a suit, drive out of the vehicle-airlock, down the elevator some kilometers to the the other Starship.

Airlocks are really the exception rather than the rule. The LEM had none, you had to depressurize the entire cabin. A Mars/Luna rated Cybertruck could do the same thing, although of course all interior gear would have to be vacuum rated too.

The LEM was a highly optimised vehicle without an extra kilogram.  Martian exploration material is the SpaceX fuel rich design environment can be much less mass effective, as long as it is quick and rapid to produce.  In that sense whatever is simpler to design would probably be the best.

Elon Musk has hinted that the Cybertruck has some of the characteristics of the James Bond mini submarine.  The main one would be that is is leak proof, but on Mars the pressure direction would be inverted, so perhaps it's not that.
It's pretty clear that Spaceship Mk1 was fitted with Tesla battery packs.  So adapting them to Mars may be a simple exercise.  It's also unlikely that martian rovers will require the full peak power of the packs, so the cooling requirements may be lowered by optimising for long use and lower power levels.

[Steve G]

The Cybertruck is already the ugliest pick-up truck on Earth, and will no doubt be the ugliest truck on any celestial body unfortunate to have its surface desecrated by it.

[AC in NC]

In that sense whatever is simpler to design would probably be the best.

Wouldn't it be the case that "simpler to design" (while I agree vs. weight-optimized) would take a back seat utility, interoperability, and maintainability?

Except perhaps at just the very beginning, I would be surprised to see anything other than very modular (Lego-like) systems of drive elements, power module decks, and chassis.  Maybe I'm jumping too far ahead of the initial missions.

[Eka]

Why use trailers? Give them their own drive systems, and have them play follow the leader. Push comes to shove you can cannibalize them to keep your rover going and get home. Keep all the parts as common as possible. That way a wheel set or battery from a trailer can be taken and used on a rover.

edit: Spelling

A trailer with its own drive system become a truck itself, no?  The interesting thing about a trailer is that it serves as a base camp while needing only a single motor in the hauling vehicle.
I don't think there would be any really practical way to cannibalize a trailer towards a vehicle.  We're talking about batteries that are massed in tonnes, not 12V batteries.
Trailer wheels will only be used for a few hundred kilometers over the lifetime of the vehicle.  Truck wheels will cover orders of magnitude more distances.  It may make sense to optimise them, or it may not.  It depends a lot on how exploration is done, really.  And the actual ruggedness of martian terrain.

So what happens when that single motor dies? Battery pack? Control computer? There is no AAA on Mars. You are most likely on your own. Either you rescue yourself, wait for non experienced rescuers, or die.

I made a comment earlier about gravity and wheel slippage. Lower gravity = less traction = more wheel slippage. Try towing a trailer up a loose regolith slope...

Look up the voltage of a Tesla main drive battery. They are the ones I'm talking about swapping. Go look at the drive units that Tesla puts into their cars. Easily swapped out in their current design.

In that sense whatever is simpler to design would probably be the best.

Wouldn't it be the case that "simpler to design" (while I agree vs. weight-optimized) would take a back seat utility, interoperability, and maintainability?

Except perhaps at just the very beginning, I would be surprised to see anything other than very modular (Lego-like) systems of drive elements, power module decks, and chassis.  Maybe I'm jumping too far ahead of the initial missions.

Ding! Ding! Ding! You got it. Redundancy in everything. BTW modular is KISS too and allows field repairs.

[josephcouvillion]

Electric power allows stuff that was hard to do with ICE.

Would powered wheels in a trailer improve the towing physics enough to be worth the complication? They could be controlled from the truck automatically for optimal improvement of traction and breaking. Any thoughts?

[lamontagne]

Let's try to be a bit systematic.

First, the specs of the cybertruck, (with some comments in brackets):
1 to 3 independent electric motors. (likely the same as model 3, so up to 280+ hp per motor)
2 controllers (from the Tesla autonomous driving presentation)
Batteries for 250 miles (350 km)range (perhaps 80-90 kWh?, 350 to 400V) 
1500 pound (700 kg) payload, 7500 lbs towing (+3000 kg towing)
Official Tesla Mars truck  (from Elon Musk's Twitter feed)
Weight, unknown, should be the same as Ford F150 (1 846 à 2 236 kg, so about 2 tonnes)

For the Tesla Semi:

4 electric motors. (likely the same as model 3, so up to 280+ hp per motor)
2 controllers (from the Tesla autonomous driving presentation)
Batteries for 500 miles range (800 km, likely 4x 100+ kWh independant battery packs)  Megacharger sets have plugs with four sets of contacts, so probably 4 independant power trains)  That's safe.
Haulage : Overall vehicle weight 80 000 lb max us, so perhaps 40 000 pounds + (20 000)
Weight, unknown, class 8 trucks start at 33 000 pounds ( 15 000 kg) including the trailer, so might be about 12000 kg on its own.

So the semi is a whole different class of vehicle, up to six times heavier, but hauling up to six times more mass.  So you could bring six Cybertrucks to Mars for the mass of a single semi.  I think that is the most interesting point, it's a fairly small vehicle, compared to the 100+tonnes payload of the Starship, so can bring quite a few.  This pretty much solves the redundancy question:  You have entirely redundant vehicles, and you do not go more than 150 km away from Starship, unless you install solar chargers and battery packs along the way.

There is absolutely no need for a self moving base if you can fit all you need into a 3 tonne trailer.  Just take two Cybertrucks, if you are worried about failures.  Take two 3 tonne trailers while you're at it, and assemble them at destination.  If one truck fails, they fit six people :-)

Lower gravity = less traction but also = less load, a 3 tonne mass trailer will weigh less, so the result is about the same.  It'll be a pain to corner though, and dangerous at high speed.  I think the angle of repose on Mars is about the same as on Earth.  Going up a sandy hill is a pain anywhere in the solar system.  How loose is martian regolith?  Depends a lot on where you are, doesn't it?  I expect they will be building roads as fast as they can figure out the best way to do so.

Tesla battery packs are not easily swapped out. They require a substantial piece of equipment to do so.  https://electrek.co/2017/09/15/tesla-new-battery-swap-technology-to-deploy-trailer/

So my opinion is that the Cybertruck is relatively small and light, so you can bring more than one and have safety and flexibility in numbers.  They will be ok for the earlier part of the colony, but when serious work will need to be done, they will bring in Mars capable semis and Cybertrucks will have the same support roles they have on Earth.

[Star One]

The Cybertruck is already the ugliest pick-up truck on Earth, and will no doubt be the ugliest truck on any celestial body unfortunate to have its surface desecrated by it.

More fool those who can’t see beyond its external appearance.

As it says in this video its design and build materials significantly decrease production cost, hence the lower asking price. Something I’d argue is way more important than the trivialities of its appearance. It also outlines other positives such as performance and flexibility.