Jan 4, 2008

NXT and Lunar X PRIZE


Okay, here's a little thought experiment. Ignoring getting the robot to the moon (the rocket side of the equation), what would it take to get an NXT robot to win the Lunar X PRIZE?

Here is the contest objective described in the simplest terms (taken from the official website):

"To win the Google Lunar X PRIZE, a team must successfully land a privately funded craft on the lunar surface and survive long enough to complete the mission goals of roaming about the lunar surface for at least 500 meters and sending a defined data package, called a “Mooncast”, back to Earth."

So, a few things:

From Ask an Astronomer: The temperature on the moon varies from -387 Fahrenheit (-233 Celsius), at night, to 253 Fahrenheit (123 Celsius) during the day. Because the moon has no atmosphere to block some of the sun's rays or to help trap heat at night, its temperature varies greatly between day and night.

This leads to some questions:

1. At what temp will plastic (specifically, LEGO NXT Technic plastic) shatter?
2. At what temp will rubber shatter?
3. Can the NXT Brick be insulated somehow to protect it from these temps? Does circuitry degrade at these temps?

I think most of us will agree that sending an NXT robot to the Moon's surface is probably a bad idea. But there's a saying that I'm going to modify a bit - "The only difference between the difficult and the impossible is cost."

So, given some funding, how would a dedicated group of LEGO NXT fans go about building a robot that is NXT based that could participate in the Lunar X PRIZE? Cast components out of metal? Insulate the Brick inside some sort of shell?

(Don't take this too seriously, folks... have fun with it and keep the discussion positive)

13 comments:

peter hoh said...

Recently, my son discovered that his camcorder's battery ran out rather quickly when he was using it in the cold. He started thinking about insulating it, but I didn't think that would buy him much time. Scarves, hats, and jackets keep us warm because, unlike camcorders and robots, we generate heat.

So I think that a moonbot would need a heat source to keep its batteries functioning in extreme cold.

David Levy said...

I believe that was already achieved some years ago by a Mr. R. Kramden
"Bang Zoom!"

David Levy said...

Seriously...that sounds like an exciting challenge for kids to simulate here on Earth.

Brian Davis said...

As a physicist, I have lots of thoughts on this, but to answer Peter's point briefly... robots *do* have an internal source of heat - the electronics. The core of some spacecraft is called the "WEB", or Warm Electronics Box, and these are usually kept warm by the waste heat from the electronics (& a few back-up radioisotopic thermoelectric heaters in some cases). Normally, the problem with consumer electronics (and even some spacecraft) is heat *dissipation*; it's not keeping warm that's tough, but getting rid of the heat before you cook your electronics (& batteries)...

--
Brian Davis

peter hoh said...

Brian, following up on your comments, I'm guessing that the problem with the camcorder is that it's built to lose the heat that it generates.

But really, would putting a wool cap over the back of a camcorder make it last much longer in extreme cold temperatures? (i.e. single digits, Fahrenheit) My son was using it on a tripod. Perhaps it might have lasted longer if someone was holding the camera while filming.

peter hoh said...

My favorite robot on the moon is Cooker, who can be seen in Wallace and Gromit's Grand Day Out.

aaron said...

Harumm...

Examining present "robots" might help. Both the lunar rover (ok, it's not a "robot" but it's electrics/tires/etc had to endure the moon) and the mars rovers (not quite as harsh an environment) could provide clues on what'd be needed.

Metal wheels are a must.
Moon dust was a real issue...so airtight seals around the motors would be necessary.

If the mars rover has to use a heater to keep it's electrics from freezing, that'd probably need to be standard equip for an NXT rover as well.

Anonymous said...

This really does seem like it could be modified to be a great challenge for kids. Does anyone know what is required of the data package.
Also, since the moon rotates so slowly, and the robot only has to go 500 meters couldn't it just be landed on the near side to perform it's tests? This would eliminate some of the need for insulation due to cold, no? Or vice-versa?

CATpit contractor said...

In addition to the question of a shattering point... at what point will abs/rubber melt? If the robot is exposed to 253 degree temperatures, it's going to have serious issues dissipating all that heat.

Brian Davis said...

OK, a few more thoughts...

No, the ABS couldn't cut it as far as the thermal issues go. It has a rather narrow range of temperatures that it can handle, while the range on the lunar surface is huge. Even the Apollo missions landed near lunar "dawn", so that the temperatures of the rock surfaces were moderate, and yet they still had to contend with plastic-shattering cold in the shade, and plastic-melting heat in the "morning sun".

But in that case, take out the ABS... the electronics in the NXT alone are a significant improvement in terms of processing power, speed, memory, and power consumption, to the entire Apollo CSM. The problem here might be they are not radiation-resistant (Apollo memory, based on ferromagnetic cores or "donuts", was). Still, you might get around this by using several and "voting out" the proper result. So that *might* be doable.

DC motors are, well, DC motors - they should function fine in a vacuum (at least for a short time or at low power... again the thermal management issues get tricky). Lunar dust probably isn't a huge worry - yes, it will eat the motors, but if you make sure the motors are near the front, ahead of any wheels, and you only drive forward, then the front stays fairly dust-free (no air means no billowing dust... just ballistic dust).

Batteries are an issue - yes, they need to be warmish to work, and unless you keep them warm the entire cruise phase, you've got a big problem at the end. But you might reasonably manage a short surface stay using banked capacitors as a power source, charged from the delivery vehicle just before landing (hey, if Jim says I don't need to worry about the rocket, I'll let the same folks who are building the rocket build my custom cruise stage ;) ).

Sensors, well... the US sensor & sound sensor are clearly out, and the light sensor might be close to useless (talk about a place with shadow issues...). The touch sensor would work fine... but if it's based on resistance, temperature swings are perhaps a very critical problem (& sensor tend to be exposed, not in the warm electronics box). Possibly mechanical touch mechanisms that move something over a fiber-optic transmission to a light sensor internal to the WEB might work, and the Hitechnic gyro & accelerometer would be critical (they can function inside the WEB as well), but the compass would be pointless. Hmm...

This is a fun little problem, how to take the NXT to the Moon. Literally :)

--
Brian Davis

Kirk Backstrom said...

An idea that just might work is to have a "space suit" for the NXT rover. What I envision is an enviromentally controlled sphere that has the NXT on the inside to drive it (sort of like a hamster in a ball). If the space suit contained air at ambient temperatures, me thinks the NXT would operate just fine.

Christopher R. Smith (Littlehorn) said...

Peter, I've used those sealed re-usable Heat Packs (w/ the little metal 'clicker' inside to activate the chems) to keep my batteries warm. It works for a few hours.

Lunar X Prize:

To add some to what Brian has already said about electronics heat..

Many of the Space Shuttle's avionics boxes are attached to 'cold plates' to maintain a nice temp. Air-ducts flow chilled air directly to many units as well.

I remember a discussion we had back in the old MINDSTORMS forms that went on for years....about how the RCX would fair on a spacewalk.

Kirk has it... a space suit.

..or a pod. Though, an All-LEGO solution is possible in simulations. However, being a LEGO purist, I would like to send one to the Moon anyway.

Chris

Michael302 said...

I like the Moon trip idea but I've always thought that sending a Mindstorms on a trip to the ISS would act like a stepping stone to the the Moon or even, dare I say it, Mars. It wouldn't offer certain challenges like temperture difference or dust problems but it would help us understand how weightlessness would affect the Mindstorms. There could be fans blowing air on all three axis at certain levels of power and so it would move certain directions depending on motor speed and direction.

With some modification almost anything is possible.

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