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  #21  
Old November 12th 04, 03:26 AM
Christian Ramos
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"Kaido Kert" wrote in message
om...
"Christian Ramos" wrote in message

...
There appears little room for payload now, so placing biologicals and
associated life support on those payloads seems a bit ridiculous,

I asked the same question in another online discussion, and got the
number of around 50kg for one rat and its consumables for a six-month
cruise, including associated equipment. I suspect its closer to 100
but still not prohibitely high.


Hmm. I think that would be significant unless it was on its own mission.

let alone the fact that you would have to go to mars to actually

retreive the rats..
Additionally, rats arent really going to cut it in determining the

effect on
humans, plants and other species.

Its not absolutely necessary to retrieve them, is it ? We could simply
pack sufficient health monitoring equipment along. Of course,
returning it back to earth and monitoring the long-term effects would
be even better, so if you have a mars sample return mission, it would
be perhaps possible to return biological experiments from martian
orbit along with surface sample.


I'm not aware of such equipment, you would probably have more luck utilising
cell cultures and such, but again the data would only marginally be
relevant. We're not talking about radiation as comes out of reactor core, it
is a different thing.

Obivously effects on humans would be far from certain with rat
experiment, but we could be a lot more confident, after all we have
used rats for such purposes for centuries. But packing a couple plants
along would be a good idea of course, especially because those wouldnt
cost much in a payload.


We're probably, getting into the realms of where experts in the area need to
comment, however, the documents I've read indicate this wouldnt be viable.
It's more than monitoring their health, you want to see what damage is down
for both different fluxes of radiation and accumulated forms of radiation.
How would you match them. You could probably measure the radiation, a
sophisticated thing when talking space operation, but how would you measure
the impact on cells for each form, how would you determine the secondary
effects and interations between various forms of damage and other biological
processes, how would you differenatiate changes from radiation as opposed to
gravity or environmental.

Eventually some living organism is going to have to take the trip, and
it would be kinda stupid to have the first human crew as test
subjects.

Why..I dont remember Nasa sending rats to the moon before the Apollo
landing.

But they put chimps in Mercury capsules, didnt they. US was in a race
then and didnt have enough time to do it. Were there never plans to
put animals on Surveyors ?

Sure..But the Mercury capsules were LEO that is not that environment of
outer space that the apollos encountered on the way to the moon. As for the
data that was gathered, well I would guess it gave them a systems
integration perspective, ie: does everything seem to work. Space was very
much an unknown which probably drove the chimps and dogs in space, although,
it's an interesting question, why did the chimp go into to space, was it
just a conservative approach to validation or something else.

I'm sure in one of the historical books I've read that the chimp decision
was made by Von braun given his lack of confidence in the boosters, but I
could be totally screwed up there, will have to dig them up once my "lab" is
complete


  #22  
Old November 12th 04, 01:44 PM
John Thingstad
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On Thu, 11 Nov 2004 00:02:36 GMT, Christian Ramos
wrote:


VASIMR, seems to me like a technology toy looking for a real life
solution.
How would you envisage VASIMR being used. Although, given a space based
research program that furthers our understanding into magnetics and
plasmas
things could change, but the benefits are more likely to flow through to
technologies such as the Russian MPD thrusters.



I've looked over MPD and it seems like it produces far lesser thrust per
wight of
gas. I might be wrong.. The idea of VASIMR is to get variable thrust of
significant
% of g force and be able to maintain it over a long time. Getting the
energy from a
reactor greatly reduces the amount of propellant needed. As I've said a
nuclear fission
produces approx 1 000 000 times the amount of energy you would get from a
chemical reaction.
(Not that you can utilize all of it..)

I see it used for manned interplanetary flight.
Particularly continous acceleration means that the peaple are exposed to
cosmic radiation and zero g for much lesser periods of time.

For unmanned flight a ion engine might be a alternative.
(DeepSpace1 et.al)

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  #23  
Old November 13th 04, 03:20 AM
Christian Ramos
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"John Thingstad" wrote in message
news
On Thu, 11 Nov 2004 00:02:36 GMT, Christian Ramos
wrote:


VASIMR, seems to me like a technology toy looking for a real life
solution.
How would you envisage VASIMR being used. Although, given a space based
research program that furthers our understanding into magnetics and
plasmas
things could change, but the benefits are more likely to flow through to
technologies such as the Russian MPD thrusters.



I've looked over MPD and it seems like it produces far lesser thrust per
wight of
gas. I might be wrong.


It may, although it would be interesting to compare end to end conversion of
the energy to thrust output. MPD is also on my list of a propulsion system
that I "should" be able to build at "home", VASIMR on the other hand is not.
My thinking was along the lines that further research into plasma dynamics
and magnetic fields is going to have more direct bearing to MPD first and
then vasmir later. That is, their is much more room for performance
improvement on the MPD side which may then flow through to things such as
VASIMR.

.. The idea of VASIMR is to get variable thrust of
significant
% of g force and be able to maintain it over a long time. Getting the
energy from a
reactor greatly reduces the amount of propellant needed. As I've said a
nuclear fission
produces approx 1 000 000 times the amount of energy you would get from a
chemical reaction.
(Not that you can utilize all of it..)


Well the question I would ask is, if you have a reactor on board your craft,
would you not be better to pump the fuel directly through the reactor rather
than convert to electricity then convert back to heat the propellant. This
is a numbers question though, have you ever compared?

Also, given our limited understanding of plasma and magentic sciences, are
we even sure that such a device would work well in "Outer Space" with all
kinds of external plasma and magnetic interactions This later is a question
I've never seen addressed so perhaps I'm being paranoid.

I see it used for manned interplanetary flight.
Particularly continous acceleration means that the peaple are exposed to
cosmic radiation and zero g for much lesser periods of time.


I always have a problem with these types of solutions of long term
acceleration. Once you get to such speeds that make Interplantary travel
viable, arent you also going to be at a speed where even the impact of dust
particles could devastate your ship. Your ability to maneuver is also
compromised with such a solution.


  #24  
Old November 13th 04, 12:18 PM
John Thingstad
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On Sat, 13 Nov 2004 02:20:38 GMT, Christian Ramos
wrote:

. The idea of VASIMR is to get variable thrust of
significant
% of g force and be able to maintain it over a long time. Getting the
energy from a
reactor greatly reduces the amount of propellant needed. As I've said a
nuclear fission
produces approx 1 000 000 times the amount of energy you would get from
a
chemical reaction.
(Not that you can utilize all of it..)


Well the question I would ask is, if you have a reactor on board your
craft,
would you not be better to pump the fuel directly through the reactor
rather
than convert to electricity then convert back to heat the propellant.
This
is a numbers question though, have you ever compared?


Well utilizing the heat from the reactor directly is certainly easier.
It was the first idea and explored already back in the 50's.
Of course then it was though to be used in the atmosphere
something we would never consider today.
But a atomic reactor can generate electricity with good efficiency.
(Except the RORSAT reactor (Russian..) mentioned elsewhere)
Heating has directly you could not possibly put as much
energy into the gas. Then there is the fact that the gas
flow would have to be high to have a cooling effect.
P = m*v and we want m as small as possible and v as large as possible.
(I am talking about the propellant not the ship per se though the same
applies here.)
Seems to me magnetic induction of ions wins hands down.


Also, given our limited understanding of plasma and magentic sciences,
are
we even sure that such a device would work well in "Outer Space" with all
kinds of external plasma and magnetic interactions This later is a
question
I've never seen addressed so perhaps I'm being paranoid.


Knowledge of magnetic's is (or really electro-magnetics) is
decidedly where our science is the most advanced.
Plasma flow seems sufficiently well understood to make a
working motor.
(Not that you should be asking me about this..
http://www.ae.utexas.edu/design/phoenix/vasimr.html
and references should give you an idea.)

I see it used for manned interplanetary flight.
Particularly continous acceleration means that the peaple are exposed to
cosmic radiation and zero g for much lesser periods of time.


I always have a problem with these types of solutions of long term
acceleration. Once you get to such speeds that make Interplantary travel
viable, arent you also going to be at a speed where even the impact of
dust
particles could devastate your ship. Your ability to maneuver is also
compromised with such a solution.


Yes. Impact with debris is a problem. Maneuvering less so.
But, as I mentioned, going slow isn't safe either...
Still the area between earth and mars is mostly empty.
It seems to be less of a problem than in earth orbit.
For dust to sand size particles segmented shielding should do the job..
Anything bigger... Big enough and you can see it and maneuver around it..
If you are unlucky and hit something the size of a pebble let alone
rock.. Big trouble. Don't know the exact odds but I believe your
chances of getting there are still pretty good.
(I mean by not getting hit.)

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  #25  
Old November 14th 04, 12:25 AM
Christian Ramos
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Default


"John Thingstad" wrote in message
news
On Sat, 13 Nov 2004 02:20:38 GMT, Christian Ramos
wrote:


Well utilizing the heat from the reactor directly is certainly easier.
It was the first idea and explored already back in the 50's.
Of course then it was though to be used in the atmosphere
something we would never consider today.
But a atomic reactor can generate electricity with good efficiency.
(Except the RORSAT reactor (Russian..) mentioned elsewhere)
Heating has directly you could not possibly put as much
energy into the gas.


WhileVasimr puts much more energy into the propellant, I'm interested in
doing the numbers, since you'll lose energy in the conversion to electricity
and back again to heating in Vasimr. Would you assume such a beast would
utilise a rankine or stirling cycle for electricity generation?

Then there is the fact that the gas
flow would have to be high to have a cooling effect.


Not necessarily. If the the reactor also serves the function of electricity
generation you would likely have an independant cooling system given the
propulsion system will not be constantly in use. Although balancing that
could be tricky.

P = m*v and we want m as small as possible and v as large as possible.
(I am talking about the propellant not the ship per se though the same
applies here.)
Seems to me magnetic induction of ions wins hands down.


I think you need to take into account the conversion losses. Thermal energy
available in the reactor to heat propellant versus amount of thermal energy
available to input to Vasimr after losses.


Also, given our limited understanding of plasma and magentic sciences,
are
we even sure that such a device would work well in "Outer Space" with

all
kinds of external plasma and magnetic interactions This later is a
question
I've never seen addressed so perhaps I'm being paranoid.


Knowledge of magnetic's is (or really electro-magnetics) is
decidedly where our science is the most advanced.
Plasma flow seems sufficiently well understood to make a
working motor.


It may be advanced from a relative perspective, but still along way to go.
Sure you can produce a working motor, I've can produce a working launcher
from a softdrink+bottle, but we are talking about it's viability as a
propulsion solution. If you also add in the immature technologies it
utilises such as superconductors etc, well...

(Not that you should be asking me about this..
http://www.ae.utexas.edu/design/phoenix/vasimr.html
and references should give you an idea.)


Yep. I'm familiar with the engine from tech papers. Again, it still seems a
high tech toy looking for a solution. Some references that may be of
interest to you,

The Development of the VASIMR Engine -International Conference on
Electromagnetics 1999
Rapid Mars Transits With Exhaust-Modulated Plasma Propulsion - NASA TP 3539
Accuracy Improvement in Magnetic Field Modeling for an Axisymmetric
Electromagnet - NASA/TP—2000–210194


I see it used for manned interplanetary flight.
Particularly continous acceleration means that the peaple are exposed

to
cosmic radiation and zero g for much lesser periods of time.


I always have a problem with these types of solutions of long term
acceleration. Once you get to such speeds that make Interplantary travel
viable, arent you also going to be at a speed where even the impact of
dust
particles could devastate your ship. Your ability to maneuver is also
compromised with such a solution.


Yes. Impact with debris is a problem. Maneuvering less so.


A problem inplies a solution. I dont think we are anywhere near such a
solution, so I would call it a unaddressable problem currently.

But, as I mentioned, going slow isn't safe either...
Still the area between earth and mars is mostly empty.


My comment was directed at interplanetary, in the case on intraplanetary
such long acceleration methodolgies could be useful. Although, I have a
suspicion that its more useful for unmanned activities in which case you
probably would want to use something with less failure points.

It seems to be less of a problem than in earth orbit.
For dust to sand size particles segmented shielding should do the job..


At the speeds needed for interplanetary travel, segmented shielding simply
means a bigger bang when it hits, the energy in such particles at those
speeds wont be mitigated by whipple shields with current materials.

Anything bigger... Big enough and you can see it and maneuver around it..


At those speeds and with such low acceleration forces, I suspect you would
be toast before the computer could even analyze the situation, but we are
getting too heavy into hypotheticals I think.




 




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