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#26 2004-08-12 13:48:03

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

Metalfoam is more stable than carbon composites. A smelter and continuous casting machine could provide structural parts, while the harder to manufacture items would be Earth made.[/quote:post_uid0]
More stable??  I'm not sure what your meaning is here but carbon composites are not radioactive so they are just as stable as anything.  You link did not provide any information on the metal foam but I can assume it is made of metal which would lose a great deal of internal heat.  Heat loss=energy loss meaning longer running times for the fuel cells simply to keep the crew from freezing.

Also I doubt the metal foam is stronger and lighter than carbon composite but if you make the vehicle there it really doesn't matter as long as you make it strong enough.

The idea to smelt metal and somehow assemble a vehicle on mars is not efficient and full of risk.  It's also not necessary.  Why would NASA or anyone else want to do this?  Your proposal's are driven, not by the goal of science and exploration of mars, but by your desire to colonize mars on the very first landing. 

This simple mars vehicle is intended to give a crew of two the ability to go out maybe 500-600 miles to take core samples and then return.  That is all.  I doubt the vehicle would be in a fully operational condition by the time the next humans landed back on mars.[/color:post_uid0]

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#27 2004-08-12 20:05:56

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

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#28 2004-08-13 02:23:23

karov
Member
From: Bulgaria
Registered: 2004-06-03
Posts: 953

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Metal foams appear to be perfect bulk structural material for buildings, return interplanetary rocket vehicles, the frames and the modules of the planetary ground rovers...

The tech seems simple enough, so compertivelly lightwigt equipment could allow Mars Direct - likee programs to achieve entirelly new dimension: The return ships and the cars can be produced/assembled there such way decreasing the innitialy landed mass 'investment' to bigger nuclear reactor, chemical and metal processing plant + lightweight parts which can`t be made there. It seem wherever the lander descends the necesarry resourses would be present - Al, Fe, H and Si from the regolith, C and O from the air to make the bulk structures of the rockets and rovers and buildings, to fuel and breathe them...

In my 'case of mars' the landers predecesing the humans arrival should carry also several methanol burning combustion engines. The metal foam could be used for the tires, too. AS major in-situ produced plastic ( for enclosing the foam sandwiches, etc.) could be pointed out the polyethylene, consisting only of C and H and easily producable from CO2 , H2O via mathane to methanol. How the extreme cold reflects over the phase structural properties of the polyethylene?[/color:post_uid0]

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#29 2004-08-13 05:49:05

mboeller
Member
From: germany
Registered: 2004-05-08
Posts: 53

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Hi Dook;

I think I had an idea how you could improve the efficiency of the SolarCells without any new technology:  Use an Heliostat. smile

See here my idea: http://www.8ung.at/mboeller/Heliostat-S … System.jpg

With this system you should be able to produce max. energy from sunrise till sunset. So instead of the 3 KWh/m² on an flat surface you could produce up to 0,59KW/m² x 12h = 7 KWh/m² or more than 2 times the normal amount of energy. An added advantage is, that the driving direction will no longer affect the energy production, cause the Heliostat will allways face the sun in an opimal way.

The SolarCells here are even a little bit bigger than in Your proposal. So with the (2 x 2x5.6 m² smile 22.4 m² x 7 KWh/m² x 20% efficiency for the GaAs SolarCells you can generate more than 30KWh per day. Enough for 2 hour of driving at full speed!

I hope you like it.

Manfred[/color:post_uid0]

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#30 2004-08-13 14:00:35

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]As in the spacesuits, cold temperature, flexible materials will have fluorocarbon composition.
-
Non-crystalline, glass like steel is a recent development. Lack of crystals make it non-magnetic and possibly better at low temperatures.
-
Starting point for tires is the Moon Buggy piano wire concept.[/color:post_uid0]

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#31 2004-08-13 14:19:17

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

Hi Dook;

I think I had an idea how you could improve the efficiency of the SolarCells without any new technology:  Use an Heliostat. smile

See here my idea: http://www.8ung.at/mboeller/Heliostat-S … System.jpg

With this system you should be able to produce max. energy from sunrise till sunset. So instead of the 3 KWh/m² on an flat surface you could produce up to 0,59KW/m² x 12h = 7 KWh/m² or more than 2 times the normal amount of energy. An added advantage is, that the driving direction will no longer affect the energy production, cause the Heliostat will allways face the sun in an opimal way.

The SolarCells here are even a little bit bigger than in Your proposal. So with the (2 x 2x5.6 m² smile 22.4 m² x 7 KWh/m² x 20% efficiency for the GaAs SolarCells you can generate more than 30KWh per day. Enough for 2 hour of driving at full speed!

I hope you like it.

Manfred[/quote:post_uid0]
I think the Heliostat is a good idea.  The mirror could be made of reflective mylar so it would be very lightweight and the control system shouldn't add too much weight.  Actually the vehicle would probably weigh the same since the solar panel array could then be fixed and not have extra parts to make it move to face the sun.  For launch the heliostat could easily be folded down on top of the solar array.  Also the solar panel array could then be mounted slightly lower, closer to the vehicle because it would no longer have to swivel.

The heliostat would have to be held up by a bar or tube that has two swivel points.  One at the bottom of the bar where it connects to the vehicle and one up high where it connects to the mirror.  This would allow it to reflect the sun when the sun is directly overhead.  The heliostat would be hanging out from the vehicle-sort of like this:

\
  l\    <-heliostat
  l  \
  l --------l      <-heliostat mount and swivels
              l
 

The heliostats own support would then put shade directly onto the solar array (if it was mounted to the vehicle in the center of the solar panel array) but that would not have much of an affect. 

I am going to include this change into the vehicle's design.[/color:post_uid0]

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#32 2004-08-13 15:08:08

karov
Member
From: Bulgaria
Registered: 2004-06-03
Posts: 953

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]DOOK!!!

"...Power Source: Options
1a) Methane-Oxygen Air-Turbo Rocket driving Turbo-shaft electric generator
1b) Methane-Oxygen Internal combustion engine driving electric generator

2) Methane-Oxygen Fuel Cell (Recommended for backup and surge power requirements)
3) Emergency Solar ..."

from http://www.angelfire.com/md/dmdventures … grade.html

Mars Direct of Zubrin itself includes fueling of the expedition rover with part of the methane/oxigen produced for the ERV!!![/color:post_uid0]

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#33 2004-08-13 15:12:54

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]What if the heliostat where a circular mirror instead?  Folded up it would be a long slender cone of reflective mylar, the point of the cone would connect to a swivel and the mount for the heliostat.  It would be maybe 10 feet long and lie on top of the solar panel array for launch.  This mylar roll could then be raised up and unfold itself in a circle creating a round reflective mirror 20 feet in diameter.[/color:post_uid0]

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#34 2004-08-13 15:23:31

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]DOOK!!!

"...Power Source: Options
1a) Methane-Oxygen Air-Turbo Rocket driving Turbo-shaft electric generator
1b) Methane-Oxygen Internal combustion engine driving electric generator

2) Methane-Oxygen Fuel Cell (Recommended for backup and surge power requirements)
3) Emergency Solar ..."

from http://www.angelfire.com/md/dmdventures … grade.html

Mars Direct of Zubrin itself includes fueling of the expedition rover with part of the methane/oxigen produced for the ERV!!![/color:post_uid0][/quote:post_uid0]
[color=#000000:post_uid0]That design is the most insane thing I have ever seen.  It's going to cost $1 billion on it's own and it's just going to break.  It's unnecessarily complex.

I don't know what the CELSS modules are but I'm going to do some research.  They sound like they may be of use.

Their power sources sound great for drag racing but they do not say anything about the amount of fuel supply usage and storage.  A rocket engine that uses oxygen?  No way you could carry enough to supply it for more than a few seconds.  I really would wish that you do a little math yourself and then you will see that combustion engines use too much fuel.  The methane/oxygen fuel cell and the emergency solar are the only thing that is of any use but the design does not go into more detail.

Also there is no weight given for this vehicle.  For it to be included in Mars Direct it must be 2.2 tonnes or less and this thing is probably over 20,000 pounds (over 10 tonnes).[/color:post_uid0]

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#35 2004-08-14 12:32:46

mboeller
Member
From: germany
Registered: 2004-05-08
Posts: 53

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

I think the Heliostat is a good idea.  [/quote:post_uid0]
Hi Dook;

Thanks. smile

Originally I had something else in mind. Not an real Heliostat, but an Heliostat-like Mounting for the Solar Cells. All of the blue-shaded area's and lines where intended to represent the Solar-Cells in different positions.

So when you drive fast the "Heliostat-Mounting" of the Solar-Cells would swivel down and the Solar-Cells would align with the roof of the Rover ( see upper picture with the blue line ) and when the Rover is standing or only moving slow ( maybe <5mph) then the "Heliostat-Mounting" would swivel up and the solar-cells on this hugh mounting could face the sun regardless of the movement of the Rover and the position of the Sun.

But I like your idea too. smile

Manfred[/color:post_uid0]

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#36 2004-08-14 13:31:39

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]The vehicle's top speed would be around 20-25 mph but with mars atmosphere this would be like a 2 mph wind on the earth.  I don't think you need to lower the heliostat when the vehicle is moving.  It would experience more shock and vibration from the rough mars surface but I think it would be okay. 

I'm trying to figure out how to make it swivel and what kind of electric motors or actuators would be needed to move the heliostat.[/color:post_uid0]

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#37 2004-08-18 02:44:46

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]On a previous post I thought the Titan system produced 70% efficiency but I believe the Titan systems are 100% efficient when it comes to converting the water to oxygen and hydrogen.  There is energy lost to heat but the inefficiency comes at a cost of electricity, not water.  So this means the amount of hydrogen and oxygen carried does not change except when the crew drinks some of it but this could be reduced by loading extra drinking water into the vehicle once you get it there.  The energy lost is made up by the solar panels so essentially you would have a vehicle that has a range only limited by the amount of food it could carry.  As long as there are no prolonged dust storms and nothing breaks.[/color:post_uid0]

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#38 2004-08-18 14:17:42

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 17,333

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid14]While not being a 100% on target with this topic it does have some details of interest.
Next-gen rover to practice searching for life
Researchers prepare Zoë for test in Chilean desert
http://msnbc.msn.com/id/5725501/[/color:post_uid14]

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#39 2004-08-18 16:10:00

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]A very large version could be designed to be a fuel generating robot. Unfolding extra large solar cells to produce Methane and liquid Oxygen, ahead of the expedition vehicles.[/color:post_uid0]

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#40 2004-08-18 21:01:23

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Slight change in the design.  The forward gearbox has 3 motors that give 6 kw (8 horsepower) each through the reduction gear of 11:1 to turn the front wheel shafts.  The aft gearbox has the same motors but a reduction gear of 6.53:1.  I think the vehicle movement pedal should initially send 80% of the electricity to the front wheels and 20% to the rear then as the pedal is depressed farther more electricity is sent to the rear.  When the pedal is almost to the floor 100% of the power would go to the aft gearbox.

EDIT:  On further thought 100% of the available power should go to the front gearbox at first then as the pedal reaches half way it would be split 50/50 from front to rear.  As the pedal nears the floor 100% of the power would go to the rear.[/color:post_uid0]

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#41 2004-08-19 23:49:22

RobS
Member
From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Check out this website with several very detailed reports in pdf format:

www.umrover.org

Today at the Mars Society Convention the University of Michigan rover design team gave an updated report of their work and referred to their website. The "Initial Papers" link has a 13 page description of their 3 tonne (dry mass), 4.5 meter by 2.7 meter by 3.4 meter rover. Fascinating.

          -- RobS[/color:post_uid0]

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#42 2004-08-20 11:14:46

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Just a large converted military 4 wheel drive truck.
Good guess at the size of vehicle for a comfortable around Mars vacation.

For missions exceeding 30 days (such as circumnavigating the planet) a Dynamic Isotope Power Systems, perhaps mounted on a trailer, could be considered. [/quote:post_uid0]

The trailer adds unlimited range.[/color:post_uid0]

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#43 2004-08-20 11:33:03

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Yes, I've visited the University of Michigan site before and looked at their ideas.  There are a few things that I disagree with them about.

1) They say there should be two pressurized rovers on mars, one primary and one as a backup in case the primary one fails and the crew gets stranded.  While I admire their focus on safety and wouldn't disapprove of one extra Ares launch to have two rovers I think if you build enough redundancy into one vehicle that it would be acceptable.
3) A three person crew increases the need for food, oxygen, CO2 removal, water, and maybe most important of all, space inside the vehicle.  Two crewman is enough.
4) They estimate a pressurized rover to weigh 5,000 kg!!!  That's 11,000 pounds.  I guess they plan to build it out of lead. 
5) They expect a power usage of 90kw!!  No way they need that much power.
6) Each wheel have 360 degree steering?  I just don't think it's necessary.  Off road vehicles on the earth travel over terrain just as rugged as mars and they don't need it.  It's just going to cause problems and likely break.

They feel the rover will become hot inside and it may.  I am trying to come up with a simple, lightweight, way for the crew to cool the vehicle if necessary.  Also I believe my idea will have some radiation protection from the hydrogen bottles mounted on the outside but it may need a layer of polyethylene they mention.[/color:post_uid0]

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#44 2004-08-20 11:37:09

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Just a large converted military 4 wheel drive truck.
Good guess at the size of vehicle for a comfortable around Mars vacation.

For missions exceeding 30 days (such as circumnavigating the planet) a Dynamic Isotope Power Systems, perhaps mounted on a trailer, could be considered. [/quote:post_uid0]

The trailer adds unlimited range.[/color:post_uid0][/quote:post_uid0]
[color=#000000:post_uid0]RTG power plants are just too heavy, thousands of pounds alone.[/color:post_uid0]

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#45 2004-08-20 12:01:01

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

RTG power plants are just too heavy, thousands of pounds alone[/quote:post_uid0]

Mobility power requirements were estimated to be .1 W-h per kg per km traveled (from Human Spaceflight, Larson, p. 467)[/quote:post_uid0]

1 cubic meter Methane expands 630 times.
Which produces 6616 KWH.
For 2,000 kg Mobitat the range is:
6,616,000/(2,000*0.1)= 33,080 km[/color:post_uid0]

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#46 2004-08-20 22:40:12

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

Mobility power requirements were estimated to be .1 W-h per kg per km traveled (from Human Spaceflight, Larson, p. 467)[/quote:post_uid0]

1 cubic meter Methane expands 630 times.
Which produces 6616 KWH.
For 2,000 kg Mobitat the range is:
6,616,000/(2,000*0.1)= 33,080 km[/quote:post_uid0]


33,000 km is pretty far.  I really doubt it.  We would all be driving methane powered vehicles if it was true.[/color:post_uid0]

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#47 2004-08-21 02:05:30

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]I think Lithium-Ion batteries should replace the NiMH ones I previously wanted.  The Lithium-Ion batteries have an operating temperature down to -20 degrees.  There would need to be a battery warmer beneath them to keep them from freezing and it probably would have to be on from launch till the crew leaves the vehicle on mars.

700 pounds of Lithium-Ion batteries should be enough and it will bring my weight down to almost within limits.  Just a few more pounds to go.

http://www.saft-batteries.biz/120-Tec....HPliion[/color:post_uid0]

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#48 2004-08-21 02:51:36

MarsDog
Member
From: vancouver canada
Registered: 2004-03-24
Posts: 852

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Do you disagree with " .1 W-h per kg per km traveled".
Or the energy in a cubic meter of liquid CH4 ?

Another interesting electric car link.[/color:post_uid0]

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#49 2004-08-21 10:59:59

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]

Do you disagree with " .1 W-h per kg per km traveled".
Or the energy in a cubic meter of liquid CH4 ?[/quote:post_uid0]
I disagree with your explanation that you can go 33,000 km on 1 cubic meter of methane.  What kind of engine?[/color:post_uid0]

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#50 2004-08-21 18:44:47

Dook
Banned
From: USA
Registered: 2004-01-09
Posts: 1,409

Re: Simple Mars Vehicle Part 1

[color=#000000:post_uid0]Another modification to the original idea.  Of the eight external storage bottles, six will hold hydrogen gas and two will hold oxygen.  The fuel cells use more hydrogen than oxygen to make water.

Also discard the kevlar rock guard by the wheels.  Not really needed.[/color:post_uid0]

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