[ExI] specific thrust

[spike]

... On Behalf Of Adrian Tymes
Subject: Re: [ExI] specific thrust

On Fri, Dec 10, 2010 at 8:06 PM, spike <spike66 at att.net> wrote:
>> ... This would provide enormous *specific* thrust, but the total thrust
is 
>> in the milli-newton range.

>...I think I recall reading about that.  This was why I was specifying that
the thrust-to-weight of the engine needed to include the power source, so
you can't get away with claiming "enormous" thrust without including
everything that would need to scale up in order to scale the engine up...

Ja, ion engines are only good for enormous specific thrust.

>> So you could eventually use something like that to navigate in  space, 
>>but it requires patience.  It could be scaled up, but everything  
>>scales together.

>...  So I wonder if it would be possible, using today's technology, to
build an ion engine that could deliver 1G+ of thrust - again, including
something to power said ion engine for about 10 minutes.  Adrian


I'm having a hard time imagining it.  State of the art for ion drives would
be in the microG range, if you optimize everything.  It's easier to imagine
a solar powered ion drive, or perhaps a standard solar powered hot xenon
drive, but both will still be down in microG territory.  We have those
already too, but they do take a long time to make anything happen.  Once you
take the cost of money into account, most of the time they go ahead and
choose old fashioned chemical propulsion, accepting low specific thrust in
exchange for high maximum thrust.

spike