cthia wrote:I'm not really certain where the two navies were located in reference to each other and the planet. The Admiral's ships were hiding somewhere away from the planet I think. And the SLN's ships were headed towards the planet.
The SLN task force was in orbit of the planet and had been for a week. The RMN detachment was sunwards, between the orbits of the second and third planets, accelerating outwards towards Hypatia (though I guess not exactly towards). This detachment was destroyed still short of the planet, so their debris continued into interstellar space.
BTW, I also think we might not be on the same page about what constitutes the front and rear of the debris field . . .
Front = leading edge in the direction of movement. Also happens to be the same direction as the "front" of the ships and throat of their wedges as they're accelerating.
Rear = trailing edge.
In this configuration, after they've passed the planet, the trailing edge is the closest to the planet.
ThinksMarkedly wrote:For pods launched while the ships were inertial but still intact, I'd expect the pods to quickly accelerate away to exactly be far enough from debris and the debris field if that gets created. But not too far, you don't want to be a very dark needle in a huge haystack of space, in case you're not rescued before your beacons go dark.
Aren't you describing pods which have a headstart, hence, are way ahead of the pack. . .of junk? The front of the pack?
Headstart in time, but not position. Since the ships are still accelerating, those pods launched earlier have lower velocity and thus are behind the ships and most of the debris field. And as a consequence of the geometry, they're also closer to the planet.
If the ships had been decelerating, the pods launched earlier would have higher velocity and would thus have moved more than the debris.
I wouldn't think it mattered whether the ship was accelerating or decelerating. The velocity imparted upon the launched pods should always be greater than the velocity of the ships. I always imagined that a pod is shot out of the pod bay like a bat out of hell to escape the incoming missile storm and resulting debris. Which is why, I assume, that Relax feels they should have a compensator to protect the occupants from such a high imparted velocity.
That would be ideal but it's physically impossible. The ships' wedges are far more powerful than any acceleration that a non-wedge system could produce. Even the MAlign's vaunted spider drive could only reach 250 gravities; a pod being pushed by thrusters could maybe do 5 gravities for a minute or two. The ship formation was moving at its slowest ship's maximum acceleration: HMS Phantom, at nearly 674 gravities.
I agree that a pod is shot outwards of a ship with sufficient delta-v compared to the ship to quickly clear the ship's wedge. But the ship's own acceleration or deceleration will make most of the difference. It depends therefore on whether the ship's acceleration is adding velocity to the direction the missiles are coming from or in the opposite direction. That is, if the ship is accelerating towards the missiles (like they were in this case), any pod launched will be quickly left behind the ships, so the missiles will not threaten it. On the other hand, if the ship is decelerating towards the missiles, as a traditional pre-MDM missile exchange was, any pods launched would be between the ships and the missiles. The other two cases, of ships moving away from their attackers, are dual.
So the velocity imparted by the launchers and the pods' thrusters is irrelevant for ships under power. They are needed only to get away from the wedge quickly enough and when the ship is not under power. If the ship has lost its impellers, the damage may be sufficient to warrant getting out of Dodge as quickly as possible.
Forgive me for such a simple analogy. But if five bullets are shot out of a nine millimeter and the sixth shot causes the gun to explode, the five bullets should be found far away from the fragments of the explosion which are bringing up the rear, certainly if the event happened in the vacuum of space. Regardless of whether the gun is accelerating or decelerating. What am I missing?
The magnitudes of the time and the acceleration. You're focused on a gun, which usually accelerates very little and fires bullets very quickly.
Simple Kinematics says at any time
t, the last bullet will be at position:
x = v t where
v is the relative velocity that the gun imparted on the bullet upon firing, and the gun will be at position
x = ɑ/2 t² (we are adopting the inertial frame of reference of when the last bullet was fired). That gives us the equation
ɑ/2 t² = vt for when the gun and bullet are at the same position at the same time. One solution is the trivial one:
t = 0, which is when the bullet was fired. The other one is [t] = 2v/ɑ[/t], which is positive if
v and
ɑ have the same sign.
Conclusion: gun and bullet will be at the same position again at some point in the future (
t > 0), if the gun hasn't exploded before the time
t = 2v/ɑ.
Let's say a ship imparts a 10 km/s delta-v instantaneously to the pod. A Nike-class ship like HMS Phantom accelerates at 6.613 km/s². So if the pod was launched ahead of the ship, the ship will catch up in 3.02 seconds.
That brings up more questions. One of them I asked in the How to Abandon Ship thread. I don't recall it being answered. In a system which is inhabited, are the pods automatically launched towards the planet?
I'd say so, even if there's no hope of reaching the planet on its own. You can always help the SAR ships, even if your help is negligible.
There's a question on whether the pod should use its finite supply of resources to steer towards the planet. If the pod was launched from a position or velocity from which it cannot reach the planet on its own power, it may be best to not manoeuvre at all and instead use the batteries to keep the occupants alive for another week.