If I got this right, the reactor engine mass is in part required for radiation
protection. Many science fiction writers (like Clarke in 2001 and before him)
were advised to present their fantasy spaceship reactor mounted on a long stick
pushing forward behind the crew module on top. The stick spacing would then
sufficiently protect without requiring radiation mass penalty. Any calc on
this issue?
The same subject. In the late 50-ies or so, there was a plane based on the B36
bomber configured to fly with a fission (or was it two?) reactor aboard for
propulsion. It did fly a few times before it was concluded it soon became too
“hot” for crews aboard and this could then not be remedied.
So I wonder what the Russians worked out for their recently advertised fission
motor cruise missile bomber with enormous range. Of course such contraptions
are not designed to fly with a crew inside.
John
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of William Claybaugh
Sent: zondag 15 april 2018 17:42
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Circa 1968 video about NERVA nuclear rocket program
On Sun, Apr 15, 2018 at 9:08 AM Perry E. Metzger <perry@xxxxxxxxxxxx> wrote:
On Sat, 14 Apr 2018 22:28:48 -0400 (EDT) Henry Spencer wrote:
On Sat, 14 Apr 2018, Perry E. Metzger wrote:
Specific impulse of around 900 seconds with high thrust seems
like a really useful technology, at least for off-planet use.
Unfortunately, it suffers from high dry mass, because of huge
insulated LH2 tanks and engines that are very heavy for the thrust
they produce, which hurts mass ratio badly enough to quite
significantly reduce the benefits of that appealing Isp. Isp is
about *engine* performance, but it's *vehicle* performance that
actually delivers payload, and they are not the same thing. There
are still benefits, but they aren't as large as you might think if
you look only at Isp. And they come with costs.