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Thread: Speculating on a Hobby Lunar Rover

  1. #31
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    Re: Speculating on a Hobby Lunar Rover

    Quote Originally Posted by metaform3d View Post
    Just to deep-end a little more, a lunar rover mission can be characterized by several phases: boost, traversal, descent, roving.

    Boost: the most expensive phase and, unless you're an aerospace firm or a major government, the one you have the least control over. You probably need to get your vehicle to GTO -- geostationary transfer orbit -- to start the next phase. I can't find stats for that, but it's probably between $10K and $12K per pound, the cost for getting satellites to LEO and GSO, respectively.

    Traversal: getting from Earth orbit to Lunar orbit or Lunar close approach. Here you have a lot of opportunities to save on mass. Ion engine or solar sail are probably your best bets; slow and steady but very light. Also really complicated and can easily fail. You can either try to use the same engine to ease into Lunar orbit or you can "fall" into a fast close approach.

    Descent: decelerating to the Lunar surface and touching down. The lander needs retro rockets to kill all its orbital speed so it won't smash on impact, but this causes it to fall so it needs braking rockets as well. Airbags have proven to be good shock absorbers which cuts down on fuel mass for landing. Still, a large fraction of your mass budget will be allocated to this phase.

    Roving: making a 500 meter trek and sending some video. The rover on the surface is the ultimate payload, and it would be nice if it could do a lot while it was there, but to claim the prize it really has to do very little. Survive the trip and the landing, send telemetry, take some pictures, drive around the block. As I said before, the main goal of the rover, as with all the other systems, is to be a light as possible.

    To break even I'd shoot for a $12 million boost, which puts the total vehicle mass at 1000 pounds. I'd allocate another $7 million on transfer and descent, and maybe $1 million on the Lunar package, including the base station and rover. The total Lunar payload can't be more than about 50 pounds, of which the rover should be about 5.

    OUCH -
    my visa nearly imploded upon reading the figures for LEO and GTO....
    So when you factor in the cost to get you there $20 million prize is not even enough to recoup launch costs.

    edit: She weighs in at a sleek 11.5kg (25lbs) and is about the size of a milk crate - Pathfinder on Mars
    http://mars.jpl.nasa.gov/MPF/roverpwr/power.html
    Last edited by lildreamer; 01-19-2009 at 02:11 PM.

  2. #32
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    Re: Speculating on a Hobby Lunar Rover

    Quote Originally Posted by lildreamer View Post
    OUCH -
    my visa nearly imploded upon reading the figures for LEO and GTO....
    So when you factor in the cost to get you there $20 million prize is not even enough to recoup launch costs.

    edit: She weighs in at a sleek 11.5kg (25lbs) and is about the size of a milk crate - Pathfinder on Mars
    http://mars.jpl.nasa.gov/MPF/roverpwr/power.html

    Dude I would be extremely surprised if you could build the hardware for under $10 million once you get all the of the testing labs involved.
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  3. #33
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    Re: Speculating on a Hobby Lunar Rover

    my outburst - is really based on the prize Google is providing and the amount of time, money and effort that would have to go into this project. Since it's really a mental exercise - money is no object then
    I figure since Pathfinder was such a success; using a rover and base station combination maybe would be an ideal start.
    Mimicing what NASA did basically means staying with tried and true.
    Realising you are entering 1/6 the gravity well of Earth as compared to Mars which is a little over 1/3 of Earths we might save a little on fuel cost.

    soo what have we accomplish so far....

  4. #34
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    Re: Speculating on a Hobby Lunar Rover

    The money isn't to be made on the Google prize. The money is to be made on the endorsements.
    I Void Warranties�

  5. #35
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    Re: Speculating on a Hobby Lunar Rover

    Sorry, Meta, we've already figured out that we're spending 7.9lbs of your 5lb budget on a laptop, and another 3lbs wrapping your laptop up in foil...

    Independant studies by the SRI Group rate the OPERATING temp range of the Toughbook from -20F to +140F. I'm not sure how we decided the toughbook was adequate, btw. According to: http://www.solarviews.com/eng/moon.htm - Max surface temp is: ~253.4deg F and min surface temp is: -387.4deg F.
    The means are 224.6deg F [day] and -243.4 deg F at night.

    If the toughbook is able to withstand OPERATING temps from -20 to +140 and our means are -243 (10+ TIMES the capability) and 224.6 (almost 2 times the capability) - how was it we decided that was a good idea again?
    I Void Warranties�

  6. #36
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    Re: Speculating on a Hobby Lunar Rover

    In other words make the rover look like a Giant Coke a Cola can and have it transmitt "I like to teach the world..."
    I'm Sure Coke would love that ...????? hmmmm and make the base station look like a vending machine....

  7. #37
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    Re: Speculating on a Hobby Lunar Rover

    NOW you're thinkin'!
    I Void Warranties�

  8. #38
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    Re: Speculating on a Hobby Lunar Rover

    Quote Originally Posted by lildreamer View Post
    my visa nearly imploded upon reading the figures for LEO and GTO....
    So when you factor in the cost to get you there $20 million prize is not even enough to recoup launch costs.
    No one's going to make a profit doing this. My breakeven figures are kind of a joke too. Realistically you'd need at least $20M for boost and the same again for the vehicle. The prize can be thought of more as an R&D credit. It's an incentive for investors who think that someone else is going to pay part of the cost of developing valuable patents. If you can get Coke to pay a few million to get their logo on the moon that doesn't hurt either.

    A non-traditional approach that might be interesting to explore would be using micro rovers. Instead of a big multi-wheeled box you send one or more tiny lightweight bots. If you can the mass down to a few grams it takes only hobby-scale rockets to get it from GTO to the Lunar surface, and a small amount of thrust and shock absorption to make a survivable landing.

    For roving instead of wheels you make it jump. A tiny motor winds up a spring, and releasing the spring propels the robot forward. It could easily cover 100m at a time, albeit without much accuracy, but the prize doesn't specify where you go just how far. You snap a photo at the apogee of the jump when it's moving slowest. So the whole thing is just a camera, a transmitter, one motor, a spring system, a solar cell, a battery and maybe accelerometer.

    The signal would be weak so you'd need a relay of some sort. Something small could be sent trailing the probe by a day or so, and it would relay the signal until it crashed on the moon.

  9. #39
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    Re: Speculating on a Hobby Lunar Rover

    Ok...two things.

    I don't think we have to worry about cost so much, because all that was asked about and for was a rover. Second, we are not actually going to make the rover! I say we may explore making parts of it if possible...but only to see if they will or will not work for some aspect of the project.

    Metaform...the idea of a lot of tiny jumpers is cool...but would possibly amplify the original problems of dealing with:

    A) huge temperature ranges...
    B) Radiation
    C) Launch and impact

    Now one thing we can consider would be a hybrid of the original and metaform's ideas.

    What if the rover had little pucks that it could drop. The pucks would have a small motor, and be capable of taking a 360 degree panaramic shot of their surroundings. They could then transmit back to the rover/base module. The pucks would only have to work for a half minute or so, and if the robot had enough of them...

    Now as for temperature regulation, I was thinking...all of the sensative electronics could be sealed inside of a gold plated aluminum box. The box could be filled with nitrogen to keep it pressurized. A supersaturated saline solution or oil of some kind could be heated or cooled using a thermocouple attached to the solar cells. The solution would then be pumped through the electronics chamber either helping to cool it off in there, or heat it up. The whole thing would have to be painted white to reflect sunlight...

    DB

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    Re: Speculating on a Hobby Lunar Rover

    Here's some numbers. Worst-case lunar approach is lunar escape velocity: 2400 m/s. Soft landing using solid rockets (250s specific impulse) takes a mass ratio of 2.7. So a 10-gram payload would need 27 grams of propellant. Adding support electronics, overhead and safety margin let's assume a conservative 75 grams for the lunar-descent package.

    Low Earth orbit to lunar approach requires a delta-V of about 2500 km/s, about the same mass ratio again. So to send our 75 gram payload moonward takes 200 grams of solid propellant. That makes the lunar transit package say 350 grams total.

    We want to send three rovers for redundancy, plus another 75 gram package for the relay transmitter, plus 25% overhead is 1.8 Kg -- 4 pounds. Lifting that to LEO would take no more than $8K per pound -- $32,000. That's in the high-end hobby range, and could make a profit if development costs could be kept low.

    Anyone want to try to make a 10-gram lunar flea?
    Last edited by metaform3d; 01-19-2009 at 04:37 PM.

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