jackssmirkingrevenge wrote:Lolcat physics states that [Moar heavy=Moar momentum=MOAR POWER!], besides the increase in surface area should more than compensate for the increased weight.
Not really. Firstly, you then have a heavier piston to stop.
Secondly, it's not so much about the momentum as the energy. I should really be talking about the inertia of the piston, not the momentum.
I'm being an idiot and using the public "understanding" that inertia = momentum, which is not the case.
Thirdly the speed of the compression also matters, because it's this rapid compression that heats the gases, so you can't sacrifice piston velocity for extreme mass, there needs to be a compromise.
Alternatively, you could keep Hotwired's design, however incorporate substantial vents midway down the chamber in order to allow the piston a period of non-compressing acceleration in order to gain momentum.
That would also ensure there was no accelerative force after the vent holes. The energy lost to compression for the first half of the travel is pretty insignificant anyway.
On an interesting note however, I once used almost that exact technique to try studying the effects of extreme acceleration on various projectiles.
Basically, I fired something from HEAL into an attachment (fixed straight on the end of the barrel), which incorporated vents to bleed off the firing pressure, and then after the vents, there was another length of 22mm copper about a foot long, capped off at the end.
In this 30 cm section, the projectile compressed and heated the air ahead of it to extreme levels, bringing the projectile from it's full velocity to a halt in just centimetres.
If I'd only modified the end cap so that there was a barrel coming from it, then this would have been almost exactly what your second method describes. However, I was interested in the effects of the acceleration on the projectile, not the pressure built up ahead of it.
I did it that way because although I can generate some pretty fancy accelerations, they were clearly not enough, and they also resulted in a projectile that was travelling at some speed and was therefore difficult to study. The rapid deceleration was a far more useful way to put such forces on the projectile.
The peak deceleration Gs on the projectile were vastly more than any I could have levelled on it during acceleration, into millions, I think my eventual estimate was - so many in fact that I'm highly surprised the projectile survived.
However, it proved that things could withstand accelerations of patently ridiculous levels for short spaces of time.