nuclear space engine - would it work ??

Steve Hix wrote:

Actually, as long as you don't require high speed, leg-based machines
would be able to go places that tracked and wheeled vehicles can't go at
all, or only with great difficulty.

I recall seeing a writeup of a new-ish leg-thing in development
specifically to deal with terrain that isn't suited for wheel/track
vehicles. It wouldn't replace wheels, certainly, but it could supplement
them for some environments.



The Army's been playing around with this idea since the 1960's, but the
Humvee's don't have legs on them yet.
The legged vehicle is slow, it's complex, and it's not very energy
efficient at all - compared to wheels in particular.
So you are on Mars and you come to a big pile of rocks that looks
difficult to traverse... if you've got a legged vehicle you can slowly
crawl over them and then slowly walk away from the far side. If you've
got a wheeled or treaded vehicle, you simply drive around the pile at
fairly god speed then drive quickly again once you're on the far side...
in the process of driving around the obstacle you've covered more ground
that you can examine.
Remember Dante I and its trip into the volcanic crater of Mt. Erebus on
its mechanical legs?:
http://volcano.und.edu/vwdocs/vw_news/dante.html
Remember how Danti fell INTO the volcanic crater of Mt. Erebus?
So, they looked things over, and built Dante II, and sent it into the
volcanic crater of Mt. Spur.
Down into the crater of Mt. Spur went Dante II.... down into the crater
where the boulder hit and damaged one of its legs.
Then it tried to climb out...then Dante II fell INTO the crater of Mt. Spur.
So they tried lo lift it out with a helicopter....then Dante II fell off
the helicopter and BACK INTO the crater of Mt. Spur.
Legs didn't seem to work very well for doing stuff like this.
So if you want to look into a volcanic crater what do you do?
Simple, you drive on treads up to the edge of the crater, then you let a
spherical probe on a tether roll down into the crater, as that's what
the incline angle is going to make it want to do. Now you've got gravity
on your side, and it's your helper, not your enemy.
After the probe does its snooping, you reel it back in... if it gets
stuck you just cut it loose and move on.
Dante was trying to do something very simple in a very complex manner.
Look at the angle of the slope Dante I is trying to climb down in this
photo:
http://volcano.und.edu/vwdocs/vw_news/dante_1.jpg
This isn't a job for a legged robot, it's a job for a basketball. :-D

Pat

Jochem Huhmann wrote:


Yeah, but ion (or better Hall Effect Thrusters) were flown since the
70ties by the Soviets. I still can't find more specific data, but some
sources count more than 100 missions.

And then there is also SNAPSHOT, an USAF satellite using a cesium ion
engine in 1965, SERT-2 using a mercury ion engine in 1970...
experimental, but still. Old stuff, actually.



I always thought they'd make a great system for gently nudging a
reconsat around without shaking it up like a RCS would, you could get
some very fine pointing with ion engines.

Pat

Henry Spencer wrote:




The line of what humans can do stays fairly level, aided by equipping
the human explorer with more and more high technology equipment that
must be designed in such a way as to interface with him.



Make up your mind: does it stay fairly level, or does it rise with the
addition of that equipment? In fact, it has risen quite a bit.


Yes it has risen... but it is all equipment that has to interface with
the human explorer- in short you are sort of turning him into a cyborg
with detachable cybernetic parts; at some point you are going to end up
with equipment so sophisticated that the explorer merely has to point it
where he wants and it does all the rest.
At that point you might want to leave out all the display screens for
the operator, and just do it all roboticly.
Our "future warrior" soldiers are already dragging several pounds of
night vision gear, thermal sights, computer interfaces and television
cameras. Soon, the poor guy is going to have no carrying capability for
ammo or food because of all the the electronic crap he has strapped on
him...so the Army is looking into powersuits to increase the soldier's
carrying capability.
And where it's going is obvious: http://www.msnbc.msn.com/id/6852832/
First the recon drones replace the recon planes, then the robot fighters
and bombers replace the manned fighters and bombers, then the war robots
replace the infantry.
And it will go the same way in space.


The most effective approach is to send *both*, and use them together.



I seriously doubt that we can afford a manned Mars flight.
It'd be extremely expensive to do, and I doubt it gives results anywhere
worth the financial outlay to do it.
The same might be said for the return to the Moon mission; it'd be
interesting to do, but it simply isn't that critically important to
justify the cost of it.
On he other hand we can give Mars a pretty good going over in a unmanned
manner at a comparatively low cost compared to a manned mission,
particularly if we come up with some good designs for fairly simple
lander/rovers and then make quite a few of them rather than our current
process of making one or two of a particular design and then moving on
to something new.
By the time we find out that we do have a great design...like our
present two rovers...we simply move on rather than exploiting it.
Although our present rovers can only land and operate on around 5-10% of
the Martian surface we should build some more to the same design and put
them down around the planet's equator where possible. This is something
we could do on the cheap for a fairly low cost with a good chance of
success.

In
particular, the capabilities of robotic systems expand dramatically if
humans are available for repair, refurbishment, and low-lag teleoperation.
They can be used to offload a lot of routine chores, freeing up human
hands and heads for things that robots can't do effectively.


Again... this is today...what about around 2036? Remember what computers
were like in 1976?



and at some future point it first meets
it, then crosses it...and the machine has the advantage and is more
capable than a human explorer would be.



Someday, possibly. Not soon.



I'd bet within 50 years tops, probably sooner.
Dyna-Soar died when the ICBM's arrived, because they could do the job of
getting a H-bomb from point "A" to point "B" at a lower cost than a
manned system could.
Our communications satellites are unmanned yet do sterling service.



Remember how we first had to build a space station with many cargo
rocket launches, and then head for the Moon? Everyone thought that would
be the case back in the fifties, but we improved our rockets enough that
no space station was needed, and we could do the whole mission with a
single rocket launch.



Yes, but we can't any more. The one-big-rocket approach was driven by a
political imperative for haste, and the capability was lost once that
imperative was satisfied. Building a space station as an assembly base is
*still* the right approach for sustained spaceflight. We didn't bypass
the assembly station because that approach became obsolete; we bypassed it
because political expediency overruled technical merit.


I can guarantee if the aim was to get people on the Moon, and Moon rocks
back to Earth ASAP and at the lowest cost, Saturn V beat the hell out of
assembling a moonship at a space station von Braun style.
God knows how much all that would have all ended up costing once you
start figuring out all the things that would have had to be developed to
make the concept work.

Pat

"Pat Flannery" wrote in message
...


Neil Gerace wrote:

I doubt that a robot can solve differential equations in three dimensions
fast enough to catch a ball let alone drive a tank


The tank would be the robot; just as those robotic vehicles the army has
the test for every year would work.
Everyone keeps picturing something like this:
http://www.umich.edu/~umfandsf/film/...en-robby-1.jpg
dismounting from its vehicle and going around picking up rocks with its
metal hands, but it will probably look more like a larger and souped up
version of one of our present rovers...maybe with treads rather than
wheels now that we know it can get stuck in the dust, and has a hard time
going up hills.

The sort of robot I was thinking about would still get stuck, but could get
itself unstuck without anyone on Earth having to work out how.

"Robert Kolker" wrote in message
. ..

Robots can go into an environment that would kill or disable a human.

Vice-versa, too.

"David Spain" wrote in message
...

The question is, in a time when everything under the Sun has a political
price in the US (I'll exclude Canada for now)

No need to exclude it. Canada probably has a political price in the USA too

Henry Spencer wrote:
The significant fact is that those people didn't bother showing up. Their
numbers and importance have been vastly exaggerated, in the past, by a
handful of noisy extremists. They are disappearing into footnotes in the
history books.


Importance is in the eye of the beholder. I think it is significant that they
didn't bother showing up. But if this mission launches and there is a mishap,
I don't think that crowd will remain invisible for long.

Prove to me that democratic governments have a good track record of opening
frontiers. (I'm *not* talking about freely operating private enterprises).

Why do we care about democratic governments, when freely operating private
enterprises can do a much better job?

Agreed! But I have other concerns. See the new thread I started called
Can Democracies Open the Space Frontier.

I look forward to hearing your opinions there...

Dave

"Pat Flannery" wrote in message
...
Yes it has risen... but it is all equipment that has to interface with the
human explorer- in short you are sort of turning him into a cyborg with
detachable cybernetic parts

And we can improve reaction time by then *attaching the parts*- hell, let's
just send Robocop in the first place!

First the recon drones replace the recon planes, then the robot fighters
and bombers replace the manned fighters and bombers, then the war robots
replace the infantry.

Saw that one already. "Battle of the Planets". The last episode I saw had
Mark pull the helmet off Zoltar, and we saw long flowing hair come out
before Zoltar's boss popped a strobe and helped Zoltar escape.

In article ,
Pat Flannery wrote:
Steve Hix wrote:

Actually, as long as you don't require high speed, leg-based machines
would be able to go places that tracked and wheeled vehicles can't go at
all, or only with great difficulty.

I recall seeing a writeup of a new-ish leg-thing in development
specifically to deal with terrain that isn't suited for wheel/track
vehicles. It wouldn't replace wheels, certainly, but it could supplement
them for some environments.

The Army's been playing around with this idea since the 1960's, but the
Humvee's don't have legs on them yet.

Nor are they ever likely to have them. That's not at issue.

The legged vehicle is slow, it's complex, and it's not very energy
efficient at all - compared to wheels in particular.

Did you bother at all to read what you quoted above your comment?

Where you *can* use wheels, there's not much that can compete with them.

Most places where you can't use wheels, wings are a better solution.

There may well be some niches where leggy gadgets might be better than
either; perhaps severe broken terrain in an area where any small flying
device used for intelligence collection is going to either get shot
down, or would compromise data collection.

In fact, we do use leg-mobile data collection equipment, it's just that
so far, it's been men hauling the gear and setting up and doing the data
collection.

Machines that could be used to cover terrain where wheels can't go might
be pretty useful. Especially in applications where speed isn't critical,
and long-term observation might be.

Not that I expect to see them in the near future.

"Henry Spencer" wrote in message
...
Fuel cells generate water only if you lug along LH2 to feed them, which is
no longer seen as a particularly useful approach for most applications.
Note that NASA's current Apollo remake is going to be solar-powered, with
nary a fuel cell in sight.

Fuel cells seem to fit well only when there is a use for the water and when
the mission duration is on the order of a week or two. Fuel cells,
reactants, tankage, plumbing, and etc. does tend to be fairly heavy.

The lunar version of Soyuz, the 7K-LOK, used fuel cells. It was a first,
and a last, for fuel cells on (planned) manned Russian spacecraft until the
Buran Shuttle. From the article on Astronautix.com, it sounds like there
were procedural/bureaucratic issues with LH2 fueling on the pad. From
memory, pretty much all other Soyuz and Progress spacecraft used a
combination of batteries and solar arrays to provide power.

http://www.astronautix.com/craft/soy7klok.htm

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)