Leonard Erickson:
(referring to my last post)
>>10Kg/s at Isp 600,000 produces energy equivalent to a 50 KT bomb every
>>second. This will NOT produce "*small* holes". Unless you define
>>*small* as comparable to Hiroshima or Nagasaki. Keep in mind that it
>>takes you 6g rocket 6 seconds to reach 1Km+ altitude. So you'll dump
>>the equivalent of a 300 KT bomb on the launch site. This will not be
>>dealt with by "blast pits".
>Once again, you are assuming that the energy is "just there". Look upon
>it as a plamsa arc torch with a 10 Kg/s flow rate. It'll vaporize the
>hell out of anything that gets in the way, but it is *directed* energy
>(at least at first).
Look on it as a directed energy hydrogen bomb. It will only be directed
until it hits something (like the ground), then it will begin dispersing.
Which dispersal will have an effect not unlike a nuclear explosion.
>Compare this with a Saturn 5. The first stage of the Saturn V was good
>for quite a few kilotons if it blew. But in a normal launch, the the
>exhaust damage wasn't that hard to contain. A fusion rocket with the
>same thrust (6 million pounds) would use 10 *pounds* of fuel per
>second. The energy release is of the same order of magnituide., it's
>just more concentrated. (yes, I picked that thousand ton ship in the
>original message *specifcly* because it was "equivalent" to a Saturn 5!)
No. For a rocket of a given thrust, energy release is proportional to Isp.
A Saturn V (with an Isp of 270 more or less) has a power rating of
4.4E10 Watts (about. 7,500,000 Lbs thrust, BTW, not 6). A fusion rocket
with Isp 600,000 has a power rating of 9.8E13 Watts. I personally do not
consider a factor of 2000 to be "the same order of magnitude".
>Stop and think, a 10 kg/sec jet is going to be fairly small. *Easily*
>less that 10 meters. More like *one* meter. Especially considering the
>exhaust velocity (roughly 2% off lightspeed!). (anybody know enough
>plasma physics to rough out an answer? If not, I'll just treat it as
>hydrogen gas, and work it out that way...)
>
>It may bore a hole 100 meters deep in the rock of a class X starport,
>but the hole will be fairly narrow.
Have you ever seen a shaped charge warhead go off? I have. It
(theoretically) makes a very small needle jet of plasma. But after
it hits something hard, it looks just like an HE shell exploding. If
a fusion jet burns a hole in the ground, the jet will transfer it's
entire kinetic energy to the launch site before it's through. Which will
look like a small hydrogen bomb. And what happens after you get more
than 100m in the air? You give the jet time to diffuse before it hits
something solid, and make the effects on the countryside worse. Keep in
mind that we are still talking 50KT/s here. Dumped into the atmosphere
for at least 25 seconds (you actually won't be above 20Km in only 25s).
So you dump energy equivalent to a megaton bomb into the starport. Frankly,
if the starport can take that kind of abuse routinely, then nuclear attack
should be no big deal to the worlds of the Imperium.
---Steve Higginbotham