Go Back   Science Forums > Physical Sciences Forums > Space > Spaceship design
Reply
 
LinkBack Thread Tools
Old 10-09-2007   #131 (permalink)
TheBigDog's Avatar
Doing the Impossible

Moderator
Gallery Curator

Location:
Madison, OH (when not in fantasy land)
 
TheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond repute
Send a message via MSN to TheBigDog
 



Not Ranked  0 score     
Re: Hypography X Prize Entry

Camera's and radios can be tested on any platform. We will move toward final rover designs with higher associated expense over time.

If 5 kg proves too low then we can change that. I think that the total engineering challenge will be similar in all sizes, but some of the costs can be constrained by keeping to a small size. A great deal can be done with 5 kg.

Bill


----------------
aka TheBigDog - Hypography Full Freaking Moderator
Become a Hypography sponsor!
The truth is incontravertible; malice may attack it, ignorance may deride it, but in the end there it is. - Winston Churchill

TheBigDog's recommended reading: The Science of Success - Charles G. Koch

A neutron goes into a bar and asks the bartender, "How much for a beer?"
The bartender replies, "For you, no charge."
Reply With Quote
Old 10-09-2007   #132 (permalink)
Turtle's Avatar
Percipient

Platinum Subscription
Sponsor

 



Not Ranked  0 score     
Arrow Re: Hypography X Prize Entry

Quote:
Originally Posted by freeztar View Post
Wouldn't you need an anti-centrifuge?
I don't think so? From the drawing below, doesn't the "downward" force on the pan lesten as the centrifuge spins it to a 45 deg angle?


Quote:
Originally Posted by freeztar
You might be right, but we need a definitive parts list first to make that call, yeah?
Affirmative

Quote:
Originally Posted by freeztar
Very good point! It would indeed require the same amount of joules to accelerate/decelerate the mass of the rovers wether here or on the moon. But weight should make a difference, particularly if we used a "hopper" design like CraigD suggested.
Since we have in mind to have multiple rovers, I see no reason to not have them all different? People can work on whatever team or teams they fancy. yes/no?

Janus gave some masses for operational LEO launch systems and I wonder if there is any advantage is going below what a particular system is rated for? Keeping in mind we will have a considerable amount of mass involved beyond that of the individual rovers.

Quote:
Originally Posted by Freezta
Acknowledged.

Quote:
Originally Posted by Freezemeister
Which cars have you been looking at? I remember from my days as a kid that the higher-end RC's were almost exclusively metal (once stripped of their body). Of course, they are much more expensive and I'm not sure about their power.
I borrowed a big electric car (Jeep Grand Cherokee body which I removed). It is 2-wheel drive with fat off-road tires & powered by a 9.6 volt battery. Manufacturer is Scientific Toys LLC & made in China (I have not put it in my mouth. ) It has a two-channel radio. The motor has a metal case, but it is entirely contained in a plastic gear-box and has a protrudung cooling fin array. I think the all-metal cars you have in mind are the gas-engine models?
Attached Thumbnails
Hypography X Prize Entry-centrifuge01.jpg  


----------------
semantics is not always just pedantic quibbling. ~ douglas r. hofstadter

Last edited by Turtle; 10-09-2007 at 01:24 PM..
Reply With Quote
Old 10-09-2007   #133 (permalink)
Turtle's Avatar
Percipient

Platinum Subscription
Sponsor

 



Not Ranked  0 score     
Arrow Re: Hypography X Prize Entry

Quote:
Originally Posted by TheBigDog View Post
Camera's and radios can be tested on any platform. We will move toward final rover designs with higher associated expense over time.

If 5 kg proves too low then we can change that. I think that the total engineering challenge will be similar in all sizes, but some of the costs can be constrained by keeping to a small size. A great deal can be done with 5 kg.

Bill
Acknowledged. What I see as a problem for a small wheeled rover the size of an RC is that the terrain is then much rougher by scale. When making my prototype video, the car high-centered at the end on a small hummock of grass on a 2 inch "cliff" down to raked garden soil. I drove it all of 20 feet. The Moon's surface is no backyard.


----------------
semantics is not always just pedantic quibbling. ~ douglas r. hofstadter
Reply With Quote
Old 10-09-2007   #134 (permalink)
freeztar's Avatar
M.C. Grillmeister

Moderator
Editor
Basic Subscription
Sponsor

Location:
ATL, GA, USA
Latest blog entry:
 
freeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond reputefreeztar has a reputation beyond repute
 



Not Ranked  0 score     
Re: Hypography X Prize Entry

Quote:
Originally Posted by Turtle View Post
I don't think so? From the drawing below, doesn't the "downward" force on the pan lesten as the centrifuge spins it to a 45 deg angle?
I see what you are getting at, but you have to consider the x-axis vector as well, no?
Quote:
Since we have in mind to have multiple rovers, I see no reason to not have them all different? People can work on whatever team or teams they fancy. yes/no?
I agree, to a point. I think the basic chassis and electronics should all be the same for manufacturing cost reasons, but it would definitely be great to have versatility in functions.
Quote:
Janus gave some masses for operational LEO launch systems and I wonder if there is any advantage is going below what a particular system is rated for? Keeping in mind we will have a considerable amount of mass involved beyond that of the individual rovers.
My guess would be that the advantage would be more velocity, but we only really need "enough".

Quote:
I borrowed a big electric car (Jeep Grand Cherokee body which I removed). It is 2-wheel drive with fat off-road tires & powered by a 9.6 volt battery. Manufacturer is Scientific Toys LLC & made in China (I have not put it in my mouth. )
I suppose we should start testing the effect of Hg on regolith.

Quote:
The motor has a metal case, but it is entirely contained in a plastic gear-box and has a protrudung cooling fin array. I think the all-metal cars you have in mind are the gas-engine models?
Yes, now that I think of it, I am thinking of the gas-powered models.


----------------
Hypography Science Forums Moderator
---
"There are no passengers on Spaceship Earth. We are all crew." - Marshall McLuhan

"We must not forget that when radium was discovered no one knew that it would prove useful in hospitals. The work was one of pure science. And this is a proof that scientific work must not be considered from the point of view of the direct usefulness of it." - Marie Curie
Reply With Quote
Old 10-09-2007   #135 (permalink)
TheBigDog's Avatar
Doing the Impossible

Moderator
Gallery Curator

Location:
Madison, OH (when not in fantasy land)
 
TheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond reputeTheBigDog has a reputation beyond repute
Send a message via MSN to TheBigDog
 



Not Ranked  0 score     
Re: Hypography X Prize Entry

I was thinking that the wheels would be very oversized compared to an off the shelf RC, but I get your point about the scale of obstacles. I need to get my hands dirty with this.

Another thought I have had... what if the drives are hydrolic, and the motor is submerged in the fluid to absorb the heat? This could provide both the cooling for the motors and the ability to have other ways of moving the rover around.

Bill


----------------
aka TheBigDog - Hypography Full Freaking Moderator
Become a Hypography sponsor!
The truth is incontravertible; malice may attack it, ignorance may deride it, but in the end there it is. - Winston Churchill

TheBigDog's recommended reading: The Science of Success - Charles G. Koch

A neutron goes into a bar and asks the bartender, "How much for a beer?"
The bartender replies, "For you, no charge."
Reply With Quote
Old 10-09-2007   #136 (permalink)
Turtle's Avatar
Percipient

Platinum Subscription
Sponsor

 



Not Ranked  0 score     
Arrow Re: Hypography X Prize Entry

Quote:
Originally Posted by freeztar View Post
I see what you are getting at, but you have to consider the x-axis vector as well, no?
I haven't a real clue. Just looking for an excuse to build an expensive science thingy.

Quote:
Originally Posted by Frezolith
I suppose we should start testing the effect of Hg on regolith.
I wonder if the contest rules will have environmental standards we have to meet? No oil spills allowed!?

Quote:
Originally Posted by Bill
I was thinking that the wheels would be very oversized compared to an off the shelf RC, but I get your point about the scale of obstacles. I need to get my hands dirty with this.
Then there is the matter of wheelbase length (front-to-back) and the "width" between wheels side-to-side(can't think of any automotive term for that measure just now). Another problem with smaller wheels is that for our given distance goal of 500 meters the smaller wheel/tire will experience more wear than a larger wheel/tire.

That's all I got. Ohh wait...it's not all. I found this camera looking for "miniature high resolution color video cameras". The only industrial source I found required registration. >> Sony EVI-HD1 HD High Definition PTZ Camera at a low price


----------------
semantics is not always just pedantic quibbling. ~ douglas r. hofstadter
Reply With Quote
Old 10-09-2007   #137 (permalink)
Janus's Avatar
Understanding


 



Not Ranked  0 score     
Re: Hypography X Prize Entry

Quote:
Originally Posted by Turtle View Post
I don't think so? From the drawing below, doesn't the "downward" force on the pan lesten as the centrifuge spins it to a 45 deg angle?
No, the force felt on the pan will be the result of the vector addition of the centripetal acceleration and the gravitational acceleration. For the pan to tilt at 45°, the centripetal acceleration must be 1g. The resultant acceleration felt by the pan will then be 1.414g and your 5kg mass will "weigh" 7.07 kg.


----------------
"Men are apt to mistake the strength of their feelings for the strength of their argument.
The heated mind resents the chill touch & relentless scruntiny of logic"
-W.E. Gladstone
Reply With Quote
Old 10-09-2007   #138 (permalink)
Roadam's Avatar
Questioning


Location:
Slovenia,Europe
 
Roadam is a jewel in the roughRoadam is a jewel in the roughRoadam is a jewel in the rough
 



Not Ranked  0 score     
Re: Hypography X Prize Entry

Well why do you all think that heat from the motors will be such a problem? A 5kg rover on the moon would have about 5N of force more than enough for driving(I think). If the motor is a stepper one like in GHADs thread then you dont even need high rpm. Consequentially mounting motors directly onto the axels. It doesnt need to be so speedy as earth counterparts, but maybe not so slow as mars rovers. Sojourner, weighing 10 kilos could move 1cm/s. Mars exploration rovers: 5cm/s. MSL : 2.5cm/s. Well the old Lunokhod2 had 50cm/s, and apollo rover something over 200cm/s.
Wow the more I read the less I see which speed would be the best. But given the delay in connection, which is about few miliseconds, I guess one could drive such rover at about few kph. It depends on refresh rate of the video and wether the rover is programable.
Lets say that it goes at speed .2m/s. And lets make even one more assumption that friction koeficcient with lunar regolith is .1(big, really). Then with rover weighing 9N, the power output of the motor is at about .2 watts. Not a lot, is it? Then with efficiency of the electical motor at about 90%(not really good motor), you get only about .02 watts of heating(radioisotope heater units on Spirit&Opportunity produce 1 watt of heat).
As for the battery consumption. Lead-acid battery has rating of about 30 watt-hours per kilogram, so if the rover had 1kg batter of such type it could operate its motor for 600 hours. At the speed of .2m/s or .72 km/h it could make about 400 kilometers . That of course is only motor power requirement, I dont even suspect how big would actual demand be.
If I made any mistake, please correct me.
Reply With Quote
Old 10-09-2007   #139 (permalink)
Turtle's Avatar
Percipient

Platinum Subscription
Sponsor

 



Not Ranked  0 score     
Arrow Re: Hypography X Prize Entry

Quote:
Originally Posted by Janus View Post
No, the force felt on the pan will be the result of the vector addition of the centripetal acceleration and the gravitational acceleration. For the pan to tilt at 45°, the centripetal acceleration must be 1g. The resultant acceleration felt by the pan will then be 1.414g and your 5kg mass will "weigh" 7.07 kg.
Thanks Janus. I knew the right answer had a "v" in it.

Quote:
Originally Posted by Roadam
...As for the battery consumption. Lead-acid battery has rating of about 30 watt-hours per kilogram, so if the rover had 1kg batter of such type it could operate its motor for 600 hours. At the speed of .2m/s or .72 km/h it could make about 400 kilometers . That of course is only motor power requirement, I dont even suspect how big would actual demand be.
If I made any mistake, please correct me.
I have a deep cell battery charged by solar panels for home emergency and camping use. First, the liquid acid type is out for space I think, but they do have gel-type that function in any orientation.

My 12 volt battery is rated in "amp-hours" , not watt hours and has a 100 amp hour capacity. (Watts = Amps * Voltage) My panel is 15 watt (~ 1 amp/hr) for ~ 3 square feet of surface. The battery weighs 52 pounds. So without recharging I could run a 1 amp load for 100 hours or a 5 amp load for 20 hours, etcetera. With my single panel a full recharge takes 100 hours. :

edit: addendum: Mars Exploration Rover Technical Data
The Mars Exploration Rover Maintenance Manual

MER Technical Data


----------------
semantics is not always just pedantic quibbling. ~ douglas r. hofstadter

Last edited by Turtle; 10-09-2007 at 06:27 PM.. Reason: add NASA rover technical data link
Reply With Quote
Old 10-09-2007   #140 (permalink)
Jay-qu's Avatar
Ancora Imparo

Moderator
Editor
Gallery Curator

Location:
Australia
 
Jay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond reputeJay-qu has a reputation beyond repute
 



Not Ranked  0 score     
Re: Hypography X Prize Entry

Excellent thanks for the info Janus!

Assuming we go with the russian option.. 673kg to lunar orbit should be more than sufficient. How do we go about calculating the mass we could deliver to Moon surface? this will place our limit on the rover/lander mass.


----------------
Jay-qu
::Hypography Moderator of..
Chemistry, Physics & Mathematics, Astronomy & Cosmology, Space and Technology & gadgets Forums

"I don't think much of a man who is not wiser today than he was yesterday."
-Abraham Lincoln

Physics Guides - Physics Resources and help
Reply With Quote
Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Re-entry to earth from space question OzAnt Space 12 04-16-2007 01:28 AM
Which entry page? Tormod Community Polls 21 10-17-2005 08:10 AM
M Prize Breaks One Million Dollars! whoa182 Medical Science 5 03-11-2005 04:43 AM
March Quiz Prize Winner Tormod Announcements 0 04-03-2002 11:56 AM

» Advertisement
» Current Poll
Who's the sexiest man alive? Johnny Depp or Robert Pattinson?
Johnny Depp - 27.27%
3 Votes
Robert Pattinson - 0%
0 Votes
Someone else (please specify) - 45.45%
5 Votes
I'm too macho to think a guy is sexy - 27.27%
3 Votes
Total Votes: 11
You may not vote on this poll.


All times are GMT -8. The time now is 11:37 AM.

Hypography?

Hypography [n.]: A combination of "hyperlink" and "bibliography" - ie, a list of links to electronic documents. Comparable to discography and bibliography, but not cartography.

We have been online since May 2000, and aim to be the best place to find and share science-related content of all kinds.

Share the love!

Please add more science to your life. Use our RSS feeds on your blog, your portal, or your favorite feedreader!


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2009, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.3.2
Copyright © 2000-2009 Hypography
Part of the Hypography - Science for Everyone Network