A car in the moon...

[AlexGTV]

...would reach vastly greater final speeds than on earth due to no air drag?.

A Veyron say would reach the 300 m/h landmark? Or would the engine explode working without counter at redline?

 

[Northstar]

It wouldn't even start.

Or are we taking the whole "engines need air to work" thing out of the equation?

 

[AlexGTV]

It wouldn't even start.

Or are we taking the whole "engines need air to work" thing out of the equation?

Either that or the engine would be loaded in a closed system with "earth air" liquidified in a tank.

Oh I forgot, also suppose many parts of the car would be iron along with balasts to bring the car to have it earthly weight counterpart on the moon.

 

[aLLeKs]

made my day.... how big should the container be which carries the "earth air"?
have you ever thought how much air an engine consumes....

let me quote the wikipedia article about the veyron "Jeremy Clarkson, driving a Veyron from Italy to London, noted that at top speed the engine consumes 10,000 imperial gallons (45,000 L) of air per minute (as much as a human breathes in four days"

 

[Jim Prower]

There's a couple cars on the moon. They're electric, and their batteries have long run out...and they have no suspension...

 

[Troux]

So you're asking if air plays a factor in "air drag?" Short answer, yes. Long answer, obviously.

 

[niky]

Let's see:

First we'll need to build a road on the moon. No bumps, please... unless we want our downforce-deficient cars to go flying off into space. At 2 tons, the Veyron should have at least 300 kilograms of weight to hold it down on a flat road... but we need the road to be perfectly flat. Should take a few decades to get it all up there...

But then the Veyron will need oxygen. A whole lot of it. Stored in onboard tanks. We can probably big flexible bladders to hold it... pressurized. Each bladder would detach when it was out of air. Just have to make them strong enough to resist the acceleration and reinforce them to keep them from sagging to the ground.

Would be an interesting exercise.

 

[porkchop87]

Let's pretend there was air and oxygen on the moon... said Veyron would maybe surpass the Earth's landmark because it would weigh a lot less on the moon (less gravity on the moon...) or at least accelerate a lot quicker... but in theory the Veyron is only built to withstand the top speed it reaches on Earth... so who knows how well the tires, chassis, engine etc would hold on the moon under intense speed...

 

[Troux]

^You need to think about the difference between weight and mass, and which one the engine has to move.

 

[r2nyGT5]

The road would have to be completely flat. I single pebble could send a car flying off into space or barrel roll for mins before it lands again.

 

[Jim Prower]

The road would have to be completely flat. I single pebble could send a car flying off into space or barrel roll for mins before it lands again.

Aileron roll.

Ever since learning Peppy used the term incorrectly it's bugged me.

Actually, the moon's gravity is significant enough to keep the vehicle on the ground. Sure, we hop a good bit, but it still took a fair rocket burn to get the Apollo landers' crew module off the ground and into orbit.

a road could likely be built, following the curve of the moon, that would hold a car geared for a few hundred mi/h. That being said, only rolling friction and friction of the drivetrain would determine top speed. Handling would likely suffer, but the lost downforce would be negated to some point by the loss of lift on the car. There is a possibility that the car could eventually reach orbital speed, in which case the torque would force the front tires off the road in something resembling a top fuel blowover...without the crash back down, depending on how much scrapes the road.

Oxygen could easily be supplied in pure form (as in the Apollo landers) or in the form of Nitrous oxide: pure O2 would be better, as less would be used per mile than N2O, as it's purer. Fill the passenger seat with a giant oxygen bottle, with the stuff in compressed liquid form...may be an issue.

There are other engineering issues: temperature extremes, special tires that won't leak all their air or blow up due to the vacuum, The fact that the driver will need a fully sealed space suit due to the weatherstripping not keeping atmosphere in the car, (with with MCP suits, may not be as much of a problem) the fact that radiators won't work due to there being nothing to cool them...and it goes on, and on, and on....

Unless you drive a Tesla.

Perhaps someone more knowledgeable can find the Lunar Orbital speed of the Command Module during the Apollo missions. Top speed of the car would be somewhere higher than that, if geared correctly.

 

[Danoff]

My guess is that you'd have major... major.... major thermal problems. Can your radiator even hold in a vacuum? Will the engine oil boil? Will it freeze? The gasoline almost certainly won't be liquid. All of the lubricants and coolants in the car are suspect. Not to mention the fact that you will definitely be attempting to drive in a space suit since the air and temperature in the car will be incompatible with living.

Tires will explode, gas will spew out of the tank (as a gas, ironically, probably leaving some frozen portion behind), suspension lubricants will boil or freeze, the engine won't turn because the oil will be solid, the water pump will explode, the rubber on the tires and the seals throughout the chassis, engine, etc. all of it will crystallize and outgas. Your electronics are also definitely not going to work.

All of this assumes that you get your road built and carry enough air to power the car - which is ridiculous.

But yes, drag slows the car down. In fact, drag, friction, gearing, and the gas in tank are the only things preventing any car (not just a veyron) from having an infinite top speed.

(damn, treed by Jim)

 

[Jim Prower]

Yes, but you had some more engineering challenges to overcome.

That's why the moon buggies were electric instead of petrol...or even I.C Hydrogen and Oxygen. And had special tires. Hell, the latest rover designs don't even have gas-filled tires, just flexible spokes on the wheels.

 

[Keef]

Yes, but you had some more engineering challenges to overcome.

That's why the moon buggies were electric instead of petrol...or even I.C Hydrogen and Oxygen. And had special tires. Hell, the latest rover designs don't even have gas-filled tires, just flexible spokes on the wheels.

The moon buggies' tires were like chain-link mesh type stuff.

Earth's atmospheric pressure is 1013 hectopascals. The moon's pressure is .3 nanopascals, so... .00000001013 hPa. A steel air tank full of sea-level Earth air would probably explode on the moon. Liquids wouldn't stay liquid. It would be possible to "inflate" a rubber tire on the moon and actually use it as a proper tire. The difficult thing is that the amount of air you would "inflate" it with would be so minuscule it'd hardly be measurable by anything other than whatever NASA measured the pressure with. A tire could go flat like it does on Earth but the process would take a much longer. Think of how quickly you return to Earth after a jump and how slowly a leaking tire goes flat. Compare that to how slowly you drop after a moon jump and you can see that it'd take months for a tire to go flat instead of the few days it takes on Earth.

But why chance it when you can just use tires that won't go flat.

EDIT: After reading Danoff's post, I'm assuming rubber tires wouldn't stay rubber. Rubber has oil in it, among other things, that would outgas and leave behind solid material. It would be like a rock but probably very brittle and generally useless.

EDIT 2: And then I looked at the rover's fender and thought, "Is that plastic?" Plastic has oil in it. Lots of things have oil in them. Lots of things have lots of things in them actually. Did NASA really have to design materials for everything that were completely free of liquid ingredients? What were astronauts' boots made from? Sounds ridiculous unless everything was made of aluminum or some other pure elements.

 

[Danoff]

You have to use a compound that can withstand extreme temperatures and pressures. You're not going to have liquid engine oil if your car is on the moon. Car tires aren't designed to withstand temperatures between -233°C (-387°F) and 123°C (253°F). The rubber used in car manufacturing would freeze at the lower temperatures, and parts of it would burn off at the higher temperatures. That's not to say it's impossible to manufacture a plastic part that will survive the temperatures of space, nor is it impossible to fashion any solid material that uses any oil in the manufacturing process that will survive in space. What it means is that a Bugatti Veyron, or any other production car, does not have materials that were designed for that purpose - and many of those materials will fail.

Cars rely on a lot of liquids and gasses - none of which will behave at zero external pressure and extreme temperatures without redesigning the car so much that it's no longer a car.

 

[niky]

I suppose we'd have to design 600 mph tires that hold up to vacuum. Probably have to make them solid steel, as on many speed record cars.

Forgot about the radiators. Hmmm. We'll have the radiators and heat exchangers redesigned to liquid-to-liquid heat exchangers. Then the oxygen supply will be bolted to the sides of the car in large liquid air tanks. These would feed through the radiators, which would heat the liquid air into gas.

We should remap the engine, though, to use pure oxygen instead of ordinary air. Then we could use liquid oxygen, instead. This reduces the weight of tanks you'll need to carry... but hell... weight doesn't really matter in top speed attempts... only drag does.

The Veyron, thus retrofitted, should actually be a fair bit more powerful than on Earth... and the extra weight won't matter much when the car is at rest... but the extra mass would put undue strain on the suspension if the car hits any bumps. And that's a lot of extra mass. We'll have to beef up the suspension some more.

Then change the final gearing. We should get to well over 400 mph before bearing friction plays a big part. We'll have to use exhaust to cool the wheel bearings, I suppose.

Hmmmm.... anyone have an extra trillion dollars lying around?

 

[Philly]

I think it would be much easier to just throw the Veyron engine into a LSR type car that minimizes the friction due to air.

Theoretically, the top speed of the car would be infinite, since the only force acting against the car is the acceleration of the mass. So if you had an infinite gear ratio, all of the force from the engine would be put to use accelerating the car, with no friction acting against it. Acceleration would be small, but it would never stop.

 

[Keef]

Forgot about the radiators. Hmmm. We'll have the radiators and heat exchangers redesigned to liquid-to-liquid heat exchangers. Then the oxygen supply will be bolted to the sides of the car in large liquid air tanks. These would feed through the radiators, which would heat the liquid air into gas.

An aluminum radiator like we use here probably wouldn't withstand the cold like Danoff mentioned. While the metal itself might fare fine, the structure wouldn't. It would shrink so much the welds might fail.

We should remap the engine, though, to use pure oxygen instead of ordinary air. Then we could use liquid oxygen, instead. This reduces the weight of tanks you'll need to carry... but hell... weight doesn't really matter in top speed attempts... only drag does.

A problem with using pure oxygen in the engine is that engine's already run fairly inefficiently with a 10 psi vacuum. If you used pure oxygen you could have a good oxygen/fuel ratio, but because all the other stuff in air is absent the vacuum the engine would be operating under would be ridiculous. To use the same volume of oxygen as a typical engine on earth, the sealed and pure-oxygen fed moon engine would need the tiniest cylinders to avoid having a huge vacuum.

If you were to create the same volume of intake air with pure oxygen, not only would the engine theoretically be capable of tremendous power, but it would also destroy itself while attempting that output. Maybe even before it devoured all that oxygen 5 times faster than it would on Earth.

but the extra mass would put undue strain on the suspension if the car hits any bumps. And that's a lot of extra mass. We'll have to beef up the suspension some more.

The moon has very little gravity. You could probably hold up a Veyron with springs from a mountain bike.

Hmmmm.... anyone have an extra trillion dollars lying around?

No matter how much money you have, it would be impossible to "retrofit" any Earth car to work on the moon. This would be a tremendous from-scratch engineering project, probably more so than your typical space robot.

Theoretically, the top speed of the car would be infinite, since the only force acting against the car is the acceleration of the mass. So if you had an infinite gear ratio, all of the force from the engine would be put to use accelerating the car, with no friction acting against it. Acceleration would be small, but it would never stop.

There is air, or whatever collection of gases, on the moon, and there is gravity. This moon engine would still have a redline, and you can only fit so small a final gear with only so small of teeth before it's simply too weak to handle the power being sent to it. Top speed would never be infinite, just like the top speed of a rocket engine is never infinite. You can only go as fast as the stuff shooting out of the engine.

 

[Boundary Layer]

To answer the original post: The car would hit a much higher velocity on the way to the moon than it ever would on the moon.

There, done. The rest is all an exercise in futility.




I think it's great though.


Lets say you have spent a few years and a few hundred million dollars to:

• avoid all the mass loss problems associated with putting 'crap' in a vacuum by sourcing alternate materials
• find suitable lubricants and fluids and fuels to make all the 'stuff' on board actually work almost as intended
• redesign the electronics packages with rad-hard space-grade parts and conduction cooled vibration tolerant housings and boards
• make the vehicle single fault tolerant by duplicating almost everything on it (you can't just call a tow-truck if something goes wrong)
• covered the majority of the vehicle in special silvered teflon blankets for insulation... and maybe left a few key spots clear for a few tiny radiators to be added to thermally isolated equipment
• installed an anchor that you throw out the window to slow you down because conventional automotive brakes without convection will melt before they bring this thing to a stop

Well... the engine cooling problem is still massive, and as far as I'm interested the biggest problem facing such a vehicle. I think it's a game breaker (not that there aren't others). There is a LOT of heat being generated there.

All the waste heat generation will have to be rejected to space by huge HUGE radiator panels (not automotive radiators, but a panel with a high emissivity surface finish). Dozen's of square meters in area, I'm sure. And these radiators will have to be deployable because you probably won't find a launch vehicle with a payload cavity large enough for them if they don't.

hmm... and to keep radiator size to a minimum, it probably means you can only drive in straight lines that keep the radiator pointed away from the sun and earth.

I seriously doubt you could ever get these radiators on to the vehicle, and make them sturdy enough to withstand the vibrations they'll experience by bouncing around with this moon-car without, at least doubling the car's mass. More mass means you need to bring more fuel for the car... but you also have to pay the launch provider much much much more money for the extra fuel THEY require to get you to the moon.


Get the heat from the engine to these panels however you like... through a pumped fluid loop, heat pipes, conduction through a metallic frame, whatever. I think that is a secondary detail. - but pumped fluid loop would get my vote.

 

[Danoff]

Way to take it to the next level of detail. Forgetting the foldable radiator panels for a moment, I wonder if you could actually get a Veyron inside any rocket payload fairing. I'd bet shuttle could carry it, but good luck getting it on one of the remaining shuttle launches. And if you could squeeze a veyron into the payload housing, what would the vibrations and accelerations of launch do to such a veyron?

Let's take a step back and remember that we don't have any rockets capable of getting that kind of mass to the moon right now (definitely not shuttle). The Saturn V is what we need, but I believe NASA has misplaced the design specs for that - so there isn't currently a designed rocket (let alone one being built) that can get anything like the mass we're talking about to the moon's surface - primarily because it's not good enough just to smack the veyron into the side of the moon. You have to enter lunar orbit, and then descend to a gentle landing on the surface. Removing the propellant and stages, we're talking about something not too dissimilar in mass from the apollo lunar lander.

If you were capable of landing something on the moon, something with wheels, and on a road that you presumably built, and you wanted to set the land-speed record on the moon - what you'd basically want is an ion rocket with wheels attached. Not a Bugatti Veyron. You'd probably need a nuclear powered ion rocket (which means more thermal radiator panels).

At first, your rocket car would start out very slowly. 0-60 miles per hour in like... an hour. But it would constantly be gaining speed. Eventually, after rolling around the moon's surface for a while, the rocket car would no longer need the road or the wheels attached to it, because it would have achieved the necessary velocity to be in orbit just millimeters off the moon's surface. But that's not the maximum speed. The ion rocket could then continue to thrust straight down, toward the moon's surface, continuing to speed up, staying in the same orbit but moving faster than orbital velocity through it. This would be ultimately limited by the thrust of the rocket. If we got really motivated, we could actually calculate the theoretical maximum speed of such a vehicle. Maybe I'll crunch the numbers tomorrow.

 

[niky]

An aluminum radiator like we use here probably wouldn't withstand the cold like Danoff mentioned. While the metal itself might fare fine, the structure wouldn't. It would shrink so much the welds might fail.

Oh... we'd have to scrap the thin-walled heat-exchangers, anyway. We'd have to have sealed custom heat-exchangers for this, or replace them with radiators that actually cool by radiating the heat out into space.

A problem with using pure oxygen in the engine is that engine's already run fairly inefficiently with a 10 psi vacuum. If you used pure oxygen you could have a good oxygen/fuel ratio, but because all the other stuff in air is absent the vacuum the engine would be operating under would be ridiculous. To use the same volume of oxygen as a typical engine on earth, the sealed and pure-oxygen fed moon engine would need the tiniest cylinders to avoid having a huge vacuum.

The engine will be boosted, right? Creates its own atmosphere. All we have to worry about is the seals holding in vacuum.

If you were to create the same volume of intake air with pure oxygen, not only would the engine theoretically be capable of tremendous power, but it would also destroy itself while attempting that output. Maybe even before it devoured all that oxygen 5 times faster than it would on Earth.

That's where the remapping comes in... we'd have to run incredibly rich to keep the engine from eating itself alive.

The moon has very little gravity. You could probably hold up a Veyron with springs from a mountain bike.

Gravity isn't the issue. If the Veyron hits a bump or an oscillating motion starts up on an uneven surface and the vehicle is carrying one or two tonnes of tanks and vacuum-proofing, it will overstress the stock suspension.

No matter how much money you have, it would be impossible to "retrofit" any Earth car to work on the moon. This would be a tremendous from-scratch engineering project, probably more so than your typical space robot.

It's possible. Tremendously impractical, but possible. Heck... since the atmospheric pressure of the moon is negligible, I could even build a pressure tank around the car to hold air in. Simply have an air-tight seal around the suspension parts, which have to hang outside the tank.

There is air, or whatever collection of gases, on the moon, and there is gravity. This moon engine would still have a redline, and you can only fit so small a final gear with only so small of teeth before it's simply too weak to handle the power being sent to it. Top speed would never be infinite, just like the top speed of a rocket engine is never infinite. You can only go as fast as the stuff shooting out of the engine.

Sadly... yes... though I expect with a custom gearbox and wheels that will hold the strain, we could still hit an ungodly number (Mach One? Mach Two? Is there a speed of sound in space? )

 

[Danoff]

Ah, orbital velocity at the surface of the moon is 3756 mph. To 0th order, that's the speed limit.

 

[daan]

So is it just a coincedence that the Veyron can do 253mph? Or was it designed to achieve moon orbit?

 

[Danoff]

So is it just a coincedence that the Veyron can do 253mph? Or was it designed to achieve moon orbit?

Check again, 253mph was based on a much larger orbit. It's almost 4000 mph at the surface of the moon to achieve orbit. Now, keep in mind that when I say orbit, I'm talking about an orbit that's just barely off the surface of the moon the entire time. To do this on the earth you'd have to get your car up to 17,671 mph - but you'd also have to fight the atmosphere the whole way (and would burn up doing it).

 

[Boundary Layer]

Way to take it to the next level of detail. Forgetting the foldable radiator panels for a moment, I wonder if you could actually get a Veyron inside any rocket payload fairing. I'd bet shuttle could carry it, but good luck getting it on one of the remaining shuttle launches. And if you could squeeze a veyron into the payload housing, what would the vibrations and accelerations of launch do to such a veyron?

I'm certain you could fit it in an Ariane5, or Proton, even Falcon 9, or any of the other competing heavy lifters for big satellites. This is roughly car sized. The trouble is that all of these LV's will only get you to LEO. You would need something equivalent to a Saturn V, as stated.
...and you still need room for a lander, and the huge thermal subsystem.

If the lander interfaces with the payload clamp band adapter it should be no trouble to protect at the car from pyrotechnic shock due to stage separation or payload separation.

I'm almost willing to wager that the random/acoustic vibrations would not be a problem for the car, though it depends on how the lander grabs it... but it's not like theres potted inserts all over it that will get ripped out if a few of the body panels starts resonating together, or sensitive imaging equipment or star cameras with that will become misaligned if something deforms by a few thousandths. I think it's just the batteries and solder joints in the electronics that would really be at risk. Then again I'm not sure how severe the random vibe levels would be since this is a fictional LV we're talking about (use NASA GEVS + arbitrary FS? maybe 16 Grms for 2 mins for qualification?)

What's a typical first fundamental mode for a fully assembled car anyways?

 

[Danoff]

Yea, looks like a Veyron would fit the Falcon 9, Atlas V, Delta IV Heavy etc. etc. Interestingly enough it looks like it might fit in a car-like manner - with the wheels pointed to the ground during launch. All that would need to be done would be to secure it from hitting the roof during staging and you could actually count on the suspension to damp the rest of the forces.

Anyway, yea, without on-orbit assembly we need a launch vehicle that doesn't exist to carry it with a descent stage that will put it on the moon without crashing.

Edit: Maybe Johnson Space Center will let us borrow the one they have on their lawn.

 

[Boundary Layer]

I think I just saw Richard Branson viewing this thread...

 

[gary31]

Oh... we'd have to scrap the thin-walled heat-exchangers, anyway. We'd have to have sealed custom heat-exchangers for this, or replace them with radiators that actually cool by radiating the heat out into space.



Gravity isn't the issue. If the Veyron hits a bump or an oscillating motion starts up on an uneven surface and the vehicle is carrying one or two tonnes of tanks and vacuum-proofing, it will overstress the stock suspension.


Sadly... yes... though I expect with a custom gearbox and wheels that will hold the strain, we could still hit an ungodly number (Mach One? Mach Two? Is there a speed of sound in space? )

the best heat exchangers i can think of would be to use a water to water, ie have the radiators submerged in water, have this 'bath' water take have values that regulate the relese of water to the vacum of space, the relesed water would evaporate and absorb energy (heat) from the tank. this is the same method of cooling that was used in the spacesuits used by appollo astronuts.

the oscilation motion shoudl be engineered out with the use of dashpots (shock absorbers)

there is no sound in space (not strickly true but it is in this case)

 

[Keef]

I think I just saw Richard Branson viewing this thread...

Yeah. He's probably running to Burt Rutan right now saying "I have no idea what these people are talking about, but we can probably make money off it!"

 

[Jim Prower]

The new Ares series of rockets should fit the bill...

if they ever get off the launchpad.