Moving a ship with less engines

SFAndroid's picture
SFAndroid
July 13, 2016 - 11:29am
My example:

HS 6 Freighter with only a single B Ion Engine.  Could it move? Could it jump?

IMO, move = yes, at somewhere near 1/3 ADF. Jump? No. I don't think the reaction mass could apply enough thrust to offset the weight and push the ship to 1%C.

Thoughts?
You can't argue with the invincibly ignorant. - William F. Buckley
Comments:

Stormcrow's picture
Stormcrow
July 13, 2016 - 12:12pm
"Any ship equipped with ion drives must have the full complement of engines for that hull size in order to accelerate and decelerate normally. The ADF of a ship with ion drive always is 1." (Knight Hawks Campaign Book, page 12.)

Maneuvering ships with fewer ion drives is not detailed in the rules, but it's not forbidden by the above either. It just can't accelerate "normally."

It would be a simple matter to say that having fewer engines will reduce the ship's acceleration. A hull size 6 ship with a single ion engine would move 1/3 ADF.

But note that "any hull that is outfitted with chemical engines must have the full complement of engines for that hull. For example, a ship with a hull size of 13 needs four chemical engines." (p. 12) This language says that you absolutely must have all engines. It is possible that this was intended for ion engines as well, in which case "accelerate and decelerate normally" really means "accelerate and decelerate at all."

So the answer comes down to, "Do you, the referee, want it to?"

SFAndroid's picture
SFAndroid
July 13, 2016 - 3:42pm
In part, the reason I ask is, what happens if you have 3 engines and 2 get shot off? Can you limp away or are you just plain screwed? IMO again, the "normally" thing should come into play. Full compliment = Full movement. One engine, limp...and I mean LIMP along.  I mean, if you get lucky against a pirate and kill him before you die...but he knocks out 2 of your engines, the third *should* move you a bit. If your players are off the spacelanes, do you just leave them to starve or suffocate? They may not be able to jump, but given time, they could get closer to civilization.

Again, thoughts?
You can't argue with the invincibly ignorant. - William F. Buckley

TerlObar's picture
TerlObar
July 13, 2016 - 4:14pm
You absolutely can still move.  If you have any thrust at all (even rocket packs) you can change your velocity.  Maybe not by much but you can do it (a rocket pack won't don't hardly anything for a ship but hardly anything isn't nothing).  In the case of a ship losing some fraction of its engines, I'd just reduce the max ADF and MR by that same fraction.  So if you had 3 engines and 2 are damaged beyond repair, your max ADF is simply 1/3 of what it was.  If it was originally 1, you have 0.33, if it was originally 3, it's now 1, etc.

Can you still jump?  Yes.  There's no friction in space.  If you can accelerate, and you don't run out of fuel, you will eventually get to 0.01 c and enter the Void.  It will just take you longer to get there.  You might want to vary the fuel consumption as well.  How that varies depends on your assumptions and the type of engines but you can work it out.

There is another thing to consider, and it is more from a vermissilitude direction.  <puts on physicist hat> If you have only one of three engines, your thrust is now off center.  Assuming they were equally spaced around the hull the thrust vector will be offset from the center of mass which will introduce a torque on the ship causing it to rotate around the center of mass.  The exact amount depends on the mass, the thrust, and the size of the displacement but just turning on your engine full blast will cause you to fly in a (possibly very large) circle and not in a straight line.  However, this is relatively easily solved from a thrust vector point of view by spinning the ship around it's axis.  You then will travel a very small corkscrew path but will go the direction you want to travel, even with only one engine.  Depending on how fast you have to spin (smaller ships and larger engines = more) this introduces a rotating reference frame in the ship.  Basically you're working on a slowly rotating merry-go-round for the rest of the trip.  It's definitely an added complication to throw at the players.  Or you could solve it by not rotating the ship constantly but rotating 180 degrees every so often.  This will result in you flying a zigzag pattern as you start to curve away from your path, rotate around, curve back and got past the planned trajectory, rotate again, and repeat.
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Shadow Shack's picture
Shadow Shack
July 13, 2016 - 7:22pm
TerlObar wrote:
Can you still jump?  Yes.  There's no friction in space.  If you can accelerate, and you don't run out of fuel, you will eventually get to 0.01 c and enter the Void.  It will just take you longer to get there. 

Depending on the jump, maybe even long enough for the astrogator to finish calculating the jump before you reach 1%C. ;)
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