Why the large differential in trips to Mars?

On 24/08/2012 3:52 PM, JF Mezei wrote:
When Nuclear is mentioned to power a mars surface expedition, what are
we talking about ?

Nuclear batteries (much like on Curiosity) or a nuclear fission reactor
that heats water up into steam which drives turbine which drives a
generator ?

Can nuclear batteries (not sure if right words for it) produce
sufficient power to run human activities such as ECLSS, experiments etc ?

In the case of a proper reactor, how much water would it really need ?
Can them make them in a truly closed loop system that requires very
little water be added to it ?


Right term for a nuclear battery is RTG (Radio-isotope Thermoelectric
Generator) - it uses thermocouples to produce heat from radioactive
decay - not very efficient at about 3-5%.

A nuclear reactor on Mars would be quite safe for humans as there is no
magnetic field to protect them from cosmic or solar radiation; people
would still have to wear heavy protective suits like on the Moon. That
would help protect them from radiation.

I'm not a proponent of nuke anything; but the futher we go into the
solar system, the more such things are going to be needed. Mars is
about as far as is practical for a solar-powered facility.

On 24/08/2012 2:59 PM, Hg wrote:
Using Solar will mean -

. Sending large and heavy batteries to Mars for storing electricty
in the day for usage during the night.

. Dust storms last for weeks (sometimes) cutting Solar energy output
drastically. Sure you could store energy during sunny periods for
use during dust storms - though you'd need absolutely gigantic
batteries for that purpose.

. The most useful scientific experiments generally require megawatts
of power to provide conclusive results. Not sure at all solar could
provide this science power - and power our life support systems at
the same time.

If there was a safer option that existed instead of nuclear I'd be
all for it and give it a big thumbs up. If we had to launch a human
mission to Mars today unfortunately nuclear seems to be the only
option.

Still, as somebody else mentioned we're many decades away from doing
that so hopefully there will be an energy breakthrough in the time
it takes. Just like I'm hoping there will be a propulsion
breakthrough that will let us go to Mars in just a few weeks. If
we could do that then we could launch a mission much sooner.


A nuclear reactor isn't going to be light weight either. I suggest
ultracapacitors - light but bulky for energy storage. They are also
made mostly of carbon and could be easily made on Mars with a small
manufacturing facility. Such a thing would be a form of bootstrapping.

"Alan Erskine" wrote in message
nd.com...

A nuclear reactor isn't going to be light weight either. I suggest
ultracapacitors - light but bulky for energy storage. They are also made
mostly of carbon and could be easily made on Mars with a small
manufacturing facility. Such a thing would be a form of bootstrapping.


Ultracapacitors still aren't as impressive as some think.


http://en.wikipedia.org/wiki/Energy_...ergy_densities is a
very useful chart.

Note, some assumptions are made here, but still useful.





--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net

On 24/08/2012 11:56 PM, Greg (Strider) Moore wrote:

"Alan Erskine" wrote in message
d.com...

A nuclear reactor isn't going to be light weight either. I suggest
ultracapacitors - light but bulky for energy storage. They are also
made mostly of carbon and could be easily made on Mars with a small
manufacturing facility. Such a thing would be a form of bootstrapping.


Ultracapacitors still aren't as impressive as some think.


http://en.wikipedia.org/wiki/Energy_...ergy_densities is a
very useful chart.

Note, some assumptions are made here, but still useful.

You're talking mass, not volume. Ultracaps are moving along nicely and
will eventually surpass LiIon batteries.

"Alan Erskine" wrote in message
d.com...

On 24/08/2012 11:56 PM, Greg (Strider) Moore wrote:

"Alan Erskine" wrote in message
d.com...

A nuclear reactor isn't going to be light weight either. I suggest
ultracapacitors - light but bulky for energy storage. They are also
made mostly of carbon and could be easily made on Mars with a small
manufacturing facility. Such a thing would be a form of bootstrapping.


Ultracapacitors still aren't as impressive as some think.


http://en.wikipedia.org/wiki/Energy_...ergy_densities is a
very useful chart.

Note, some assumptions are made here, but still useful.

You're talking mass, not volume. Ultracaps are moving along nicely and
will eventually surpass LiIon batteries.

Umm, no, I'm talking density.





--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net