Impulse Drive: What do we know? (Non-canon speculation)

[Crazy Eddie]

That description doesn't really match the facts, though. Impulse engines are at the wrong place to be rocket nozzles. We never hear of impulse engines spewing out anything that would blast out like a rocket jet; instead, they fart out plasma like a tailpipe. There's the whole reversing and maneuvering thing. There's the defiance of the rocket equation, the insufficient propellant mass. And there are the numerous ships that move at sublight without the benefit of anything that might be a rocket nozzle.

A mini-warp drive with a tailpipe would be a better match for what we see than a maxi-rocket in almost every sense.

Timo Saloniemi

Except that the addition of the driver coil neatly provides that needed "fudge factor" for the rocket equation, either by lowering the mass of the ship or raising the mass of the exhaust. At a specific impulse of, say, 300,000 seconds, impulse engines would be able to do everything we see them do and more.

Of course, every science fiction show in the history of the genre has failed to take realistic fuel requirements into account, so I'm not sure why we should expect Star Trek to be any better in this regard; if we wanted to be THAT realistic about it, most of the things on the ship could not logically exist to begin with.

 

[Santaman]

^^Except in ships like the D'Deridex or Nebula who do not have impulse engine exhausts at all, no exhaust no thrust which makes moving a few million tons of D"deridex quite problematic don't you think?

 

[Crazy Eddie]

^^Except in ships like the D'Deridex or Nebula who do not have impulse engine exhausts at all

Nothing visible, at least. On a ship that is designed for stealth, I wouldn't expect there would be. Federation RCS thrusters don't have any visible exhaust either.

 

[Bill Morris]

^^Except in ships like the D'Deridex or Nebula who do not have impulse engine exhausts at all, no exhaust no thrust which makes moving a few million tons of D"deridex quite problematic don't you think?

But Andy Probert, who designed the D'Deridex, was kind enough to weigh in on that in this forum when I was working on the MSD and said the reason you don't see impulse engines is that they grabbed the drawings off his desk before he had a chance to put them in, and the Greg Jein didn't do anything about that on the model, either. He also told us on in the same post where they would have been if things hadn't been so rushed: in the tail. I had already drawn them differently but then changed the drawing as per his instructions.

Here's the result. Even though you don't see them on screen, this is designer intent. He also confirmed the locatioins of the disruptors and said that the scenes where you see disruptor blasts coming from the main deflector are against designer intent. One such case is in VOY: Message in a Bottle. And he said the greebles along the spine were escape pods.
http://lcars24.com/schem41.html

 

[John O.]

I was just curious if anyone had attempted to explain the use of the term "sub-impulse" in DS9 when they used a couple of older ships that had been used as raiders by Bajoran underground against the Cardassians. It made it sound like there was an actual benchmark for impulse engines rather than 'impulse' being just a general term for sublight.

 

[Crazy Eddie]

It was just an overly simplistic attempt to make the raiders sound very very primitive. The producers didn't give that much thought to it.

 

[Santaman]

^^Except in ships like the D'Deridex or Nebula who do not have impulse engine exhausts at all, no exhaust no thrust which makes moving a few million tons of D"deridex quite problematic don't you think?

But Andy Probert, who designed the D'Deridex, was kind enough to weigh in on that in this forum when I was working on the MSD and said the reason you don't see impulse engines is that they grabbed the drawings off his desk before he had a chance to put them in, and the Greg Jein didn't do anything about that on the model, either. He also told us on in the same post where they would have been if things hadn't been so rushed: in the tail. I had already drawn them differently but then changed the drawing as per his instructions.

Here's the result. Even though you don't see them on screen, this is designer intent. He also confirmed the locatioins of the disruptors and said that the scenes where you see disruptor blasts coming from the main deflector are against designer intent. One such case is in VOY: Message in a Bottle. And he said the greebles along the spine were escape pods.
http://lcars24.com/schem41.html

Cool!

 

[John O.]

It was just an overly simplistic attempt to make the raiders sound very very primitive. The producers didn't give that much thought to it.

Well... YEAH, I knew that but you guys seem capable of legitimizing anything, so, I expected an actual explanation

 

[Crazy Eddie]

Oh.

Er...

Possibly "sub-impulse" might be a portmanteau of "sublimation-based propellant impulse," related to a specific type of impulse engine that uses the heat from a fusion reactor to vaporize a solid reactant mass. Essentially, a very specific type of impulse engine that has reasonably good performance for virtually no maintenance and will still operate even if the ship has been crashed, burried, soaked underwater for a month, lost, found, lost again, eaten, crapped out and then neglected in a damp cave for fifteen years.

Kinda like the Honda Civic.

 

[Timo]

It made it sound like there was an actual benchmark for impulse engines rather than 'impulse' being just a general term for sublight.

Not only that, but the episode suggested that impulse-driven ships would be at a disadvantage against a sub-impulse one when operating down in the atmosphere. Or at least that any propulsive advantage for the impulse craft would be gone.

Might suggest two radically different operating principles, then. Or perhaps a "performance ceiling" that an atmosphere imposes on everybody, probably through air resistance, that can be used as a dividing line between impulse propulsion (anything that has to slow down because of the atmosphere) and sub-impulse propulsion (anything that wouldn't go faster or accelerate better even if the atmosphere were replaced by stark vacuum).

If impulse is based on "improved rocketry", it might be that the exhaust jet is a hypervelocity one - and essentially hits a brick wall when exhausting into thick air rather than vacuum, and thus has to be drastically throttled down.

If impulse is based on subspace fields or gravity manipulation, it might be that the exotic fields will do too much damage to the surrounding air, make it behave in nasty ways that hinder rather than help movement. Or perhaps the fields will refuse to work properly if at all deep down in gravity wells.

Timo Saloniemi

 

[YARN]

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070031912_2007031208.pdf

 

[Crazy Eddie]

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070031912_2007031208.pdf

Interestingly enough, this would imply that all things being equal, a field-only drive would be more effective than rockets/thrusters just about everywhere. Lack of precise control would probably account for the inability of starships to use warp drives for, say, lifting off of planetary surfaces of hovering in place for long periods of time (though the Bird of Prey is apparently capable of going to warp inside a planet's atmosphere and the NuEnterprise is capable of stopping in one).

This part I found kind of cute, though:

B. Inertial Modification of Rocket
To illustrate another misleading use of the rocket equation, consider the notion of manipulating the inertia of a
rocket. If such a breakthrough were ever achieved, the implications and applications would likely extend beyond
rocketry. Even if used on a rocket, there are a number of different ways to envision applying such an effect, each
yielding considerably different conclusions; (1) apply the inertial change to the whole rocket system, (2) just to the
expelled propellant, or (3) just to the rocket with its stored propellant. Just comparing two of these options can show
the pitfalls of such analyses; the case where the entire rocket system's inertia is modified, and where just the rocket
with its stored propellant is modified. In that latter case, it is assumed that the propellant resumes its full inertia as it is accelerated out of the rocket. This notion is similar to the science fiction concept of "Impulse Drive with Inertial
Dampers" as presented in the Star Trek series.

 

[John O.]

When you say NuEnterprise are you talking about NX-01 or the Enterprise from Abrams Trek? I couldn't remember either doing it, so I'm j/c. I'm sure it's my faulty memory.

I think that it is safe to say that in a world where the Reason-For-Being for millions of dollars of funding and hundreds of engineers' lifes' work is reducing noise emissions from supersonic jet engines by 15% in order to make transatlantic supersonic transit flight a feasible reality once again, the idea of any level or measure of inertial manipulation of a flight system would be considered magically awesome from a performance perspective.

As an engineer if I could suddenly call a propulsion system mass 25 kg with respect to the reference frame instead of 25,000 kg, I'd jump for fuckin joy

 

[Crazy Eddie]

When you say NuEnterprise are you talking about NX-01 or the Enterprise from Abrams Trek? I couldn't remember either doing it, so I'm j/c. I'm sure it's my faulty memory.

Abrams Trek: Enterprise dropped out of warp inside of Titan's atmosphere.

I think that it is safe to say that in a world where the Reason-For-Being for millions of dollars of funding and hundreds of engineers' lifes' work is reducing noise emissions from supersonic jet engines by 15% in order to make transatlantic supersonic transit flight a feasible reality once again, the idea of any level or measure of inertial manipulation of a flight system would be considered magically awesome from a performance perspective.

As an engineer if I could suddenly call a propulsion system mass 25 kg with respect to the reference frame instead of 25,000 kg, I'd jump for fuckin joy

Amen to that.