Re: starship-design: Interstellar Probes

["Kyle R. Mcallister" <stk@sunherald.infi.net>]

Gene Marlin wrote:
> 
> Using current and near-term technology, how fast could we get a 2
> kilogram probe to nearby stars such as Tau Ceti, Epsilon Eridani,
> Proxima Centauri, and 61 Cygni?

Depends on what kind of propulsion you use. To get it there fast is
virtually impossible with current technology. 

To give you an example of how bad it really is, this is how much it
would take to send a school bus sized payload past Alpha Centauri in 900
years:

Propellant:       Specific Imp.:            Fuel mass:
=======================================================
Chemical           500                      10^137kg (not enough mass in
universe)
Nuclear fission    5000                     10^17kg (a billion
supertankers)
Nuclear fusion     10000                    10^11kg (a thousand
supertankers)
Antimatter         50000                    10^5kg (ten railway tankers)

If you want to get there faster that 900 years, it gets worse. If you
want to actually stop at the destination, it gets even worse. That's why
I don't believe we will make it with any of these propulsion systems. It
would be better for a 2 kg probe, but not good.

Kyle R. Mcallister