Oolite Bulletins

Hi all,

Quick suggestion - when flying close behind another ship, whether it be dogfighting, or crossing behind a vessel's path how about having some form of 'wake', or vortex effect like you get in planes.

Flying close behind another aircraft with rear engines produces turbulence which can make the plane unstable - similarly in Oolite, flying behind a ship should cause some disturbance.

And what about heat damage from the ships engine flame? - could that perhaps be included? - I know you can purchase additional heat-shielding but for smaller (and older) ships this could cause malfunctions.

Anyway, just thought I would add those....

Px4

The wake would have very little effect outside the visible "flame" from a ship - the matter that the ship is ejecting would have become too dispersed by that point. There would be no vortex effects either (wingtip vortices on aircraft are a function of producing lift by moving air about. There is no air to react against in space).

However, it's reasonable for flying in the flame of another ship to have an effect on shields.

winston wrote:

However, it's reasonable for flying in the flame of another ship to have an effect on shields.

And on cabin and laser temperatures.

winston wrote:

The wake would have very little effect outside the visible "flame" from a ship - the matter that the ship is ejecting would have become too dispersed by that point. There would be no vortex effects either (wingtip vortices on aircraft are a function of producing lift by moving air about. There is no air to react against in space).

Hmm, I've got two counter examples for you.

STS-61, the first Hubble repair mission. They were replacing the old solar panels and couldn't roll up the starboard panel because it was warped. So it was unbolted, and an astronaut at the end of the arm dropped it into space. The Shuttle fired its RCS and pulled away. The exhaust from the RCS clipped the panel and sent it spinning and undulating. Flapping like a bird then tumbling into the void. The single most beautiful space video I've ever seen. Never been able to find a copy of that.

Apollo. We've all seen the video where the first stage drops away, followed a few seconds later by the interstage ring, which tumbles away. What is almost never seen is the same video from a different mission where the second stage fires up a bit earlier. The interstage ring is ripped to shreds. Most impressive. (Also impressive is that those cameras were film cameras which were jettisoned by parachute -- yay 1960s tech.)

Granted both these objects were lightweight. Which a Cobra III is not. Still, I could well imagine that somebody's engine in your face would cause your ship to become jumpy and difficult to point. Not to mention frost your windshield due to erosion.

makes sense getting punished for touching the plume by damage to shield and heatsystems.
and it would be really cool if meant getting a soft-bounced tumble in the oposite direction

Odo987 wrote:

winston wrote:

The wake would have very little effect outside the visible "flame" from a ship - the matter that the ship is ejecting would have become too dispersed by that point. There would be no vortex effects either (wingtip vortices on aircraft are a function of producing lift by moving air about. There is no air to react against in space).

Hmm, I've got two counter examples for you.

STS-61, the first Hubble repair mission. They were replacing the old solar panels and couldn't roll up the starboard panel because it was warped. So it was unbolted, and an astronaut at the end of the arm dropped it into space. The Shuttle fired its RCS and pulled away. The exhaust from the RCS clipped the panel and sent it spinning and undulating.

It's not really a counter example - the panel flapped away like it was in the wind not because of the continued reaction of the engine's wash, but because it was twanging like a string on a musical instrument (i.e. continued to flex long after the initial impulse had ended). It would also drift away because there was nothing to stop it. As you point out, it was also a pretty light object. It was also an unpowered object.

On the other hand, a Cobra Mk.3 is an enormously powerful ship, so powerful it doesn't even feel like flying a spaceship. The wash from another ship is only going to have a noticable effect where this wash is quite dense, like, say very close or actually inside its exhaust "flame". A Cobra is also tough enough to be able to spend limited time in a sun's corona, so we know it's not likely to be physically degraded when it's away from the ship's "flame".

Hmm...particle inertia? particles of plasma could be emitted by the engine exhaust, along with traces of hydrogen, O2 and the like, and could cause a small 'wake' effect. Not enough to affect the flight of a ship or the like, but maybe enough to bounce an escape pod around.

I feel that that example (escape pod) sets the right idea - the possible effects should relate to the size ratio between lead and chase ships, and the consequential engine power.

So, a ship Cobra sized or less, too close behind a Boa at full power, might 'wallow'...? Thoughts?

Selezen wrote:

Hmm...particle inertia? particles of plasma could be emitted by the engine exhaust, along with traces of hydrogen, O2 and the like, and could cause a small 'wake' effect. Not enough to affect the flight of a ship or the like, but maybe enough to bounce an escape pod around.

AHA!

I was wondering how I might implement any of these effects, but of course exhausts emit particles (and we can do that invisibly in Oolite) and I can simple check for collisions with those particles. I feel a TODO coming on.

Wouldn’t it be easier to model an invisible cone of influence?

Star Gazer wrote:

I feel that that example (escape pod) sets the right idea - the possible effects should relate to the size ratio between lead and chase ships, and the consequential engine power.

So, a ship Cobra sized or less, too close behind a Boa at full power, might 'wallow'...? Thoughts?

Yep, that works for me!! Can it be relative to the size of the ships involved? Thus a Sidewinder would get bucked in a Cobra 3's wake, and a Cobra 3 would get bucked in an Anaconda's wake and so on. Maybe the big ships would get bucked in a Behemoth's wake, and a Sidewinder would get toasted in a Behemoth's wake??

The particle densities would be higher the bigger the ships, and the wake cone would be bigger??

I have an idea for this that might satisfy all parties. What if we make the radiation from the engine wake affect the sensors of ships caught in it.

For the player, and for AI, they could instantly lose target lock (for AI this would have to also make them lose track of the primary and secondary threats).

Player's scanner and headup display could vanish.

And if you use witchfuel injectors as you burn a ship, they could suffer a flashbomb effect (thank winston), causing them to fly blind all over the place for several seconds, and for the player too.

Would be nice to be able to use this as a defensive measure against ECM hardened missiles (only for witchfuel exhaust).

Ahruman wrote:

Wouldn’t it be easier to model an invisible cone of influence?

Attempting an implementation I'd say yes.

I thought this would be a quick thing to implement, but it's a little more involved, so I'm going to hang fire on this awhile.

Hrmm… it should probably be doable to express it as a function of the dot product of the exhaust plume’s axis and the distance from the base of the plume, with a bounding sphere or cone to stop the effect from having infinte range. It’d be easiest to scale the co-ordinates for the calculation such that the exhaust plume is a unit size. After that, something like the square of the dot product divided by the distance ought to be a reasonable starting point for an influence density function.