[ExI] Power satellites

[Stefano Vaj]

On Sat, May 2, 2009 at 12:11 AM, spike <spike66 at att.net> wrote:
>> Stefano Vaj:
>> In fact, were the earth more massive, it might even be
>> impossible, if I am not mistaken, to achieve escape velocity
>> with chemical-reaction rockets, given that any such fuel
>> would not contain enough energy to lift itself, let alone any
>> useful payload and the necessary vehicle...
>
> No.  Well, not exactly.  If the earth were more massive, there is not a
> point where achieving escape becomes *impossible* but rather it does quickly
> approach impractical.  The process is exponential, but with no brick wall
> stopping the whole parade.

Please forgive me if I am saying something stupid in terms of
elementary physics, but let us say that chemical reaction x liberates
energy y for any kilo of reagents. If you keep increasing gravity, the
work required to lift any given quantity of reagents may well sooner
or later exceed the work that can be obtained from the same quantity
thereof, or not?

In other terms, when the gravity is strong enough, a Saturn V does not
take off at all, let alone gets to orbit, irrespective of its payload,
right?

I insist on this concept because I am afraid that on earth we are only
marginally distant from this scenario. This is why I am attracted by
Project Orion-like vehicles, in spite of their obvious
inconvenients... But of course the ablation system sounds like a
brilliant solution, at least on paper, since you would not have to
bring all the energy along.

-- 
Stefano Vaj