# Honor Harrington's Impeller Wedge -- conundrums **URL:** \ **Category:** Cafe Society\ **Created:** [June 2, 2011, 12:53am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026 "2011-06-02T00:53:11Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 12:53am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/1 "2011-06-02T00:53:11Z")
I’ve just started reading David Weber’s _Honor Harrington_ book series. I’m in the middle of the 3rd book (_The Short, Victorious War_) at the moment. I can live with the fact that the Impeller drive blatantly violates the Conservation of Momentum. (Hah! Take _that_, Sir Isaac Newton!) But the indestructible dorsal and belly wedges created by the impeller drive … well … Missiles use their own miniature impeller drives, which generate their own top and bottom impeller bands. I read somewhere that a countermissiles destroys a missile by intersecting the target missile’s impeller bands with its own impeller bands. This overloads and shorts out the drive rings on both the missile and the countermissile. So … why can’t a missile’s impeller bands do the same thing to the impeller wedge of a ship? It would certainly make warships less invincible when they roll to face their belly wedge toward their attackers. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 2, 2011, 1:20am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/2 "2011-06-02T01:20:33Z")
It’s a matter of scale. Anti-ship missiles are larger than countermissiles, but only by something like a factor of 10 or so, and countermissiles have disproportionately large wedge nodes anyway. An actual ship, however, is so much larger than any missile that the fluctuations induced by a missile’s wedge are lost in the noise. Presumably, a ship _could_ ram another ship, but that’d be both suicidal and insanely expensive. Alternately, a ship could be designed to produce an extended wedge that would protrude far enough out to attack another ship, without damaging the attacker: That’s what the gravlance Honor used in the first book was. It’s still not enough to actually kill an enemy’s wedge, but it _is_ enough to instantly take down sidewalls. While we’re at it, the restrictions on wedges and sidewalls: A wedge can only be produced on two sides of a ship. A sidewall can be produced on two more sides without sacrificing thrust: This is how warships are usually configured. Additionally, you can also protect the front or back (but not both) with sidewalls, but doing so prevents the ship so protected from using its wedge to accelerate. Or, you can completely surround a ship (or more likely, stationary space station) with sidewalls on all sides, again with no acceleration. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 2, 2011, 1:52am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/3 "2011-06-02T01:52:35Z")
> [@Chronos](#): > > It’s a matter of scale. Anti-ship missiles are larger than countermissiles, but only by something like a factor of 10 or so, and countermissiles have disproportionately large wedge nodes anyway. An actual ship, however, is so much larger than any missile that the fluctuations induced by a missile’s wedge are lost in the noise. Presumably, a ship _could_ ram another ship, but that’d be both suicidal and insanely expensive. Alternately, a ship could be designed to produce an extended wedge that would protrude far enough out to attack another ship, without damaging the attacker: That’s what the gravlance Honor used in the first book was. It’s still not enough to actually kill an enemy’s wedge, but it _is_ enough to instantly take down sidewalls. Agreed. Tonnage given in this webpage [Missile | Honorverse | Fandom](http://honorverse.wikia.com/wiki/Missile) state that a capital ship missile masses 80 tons. A destroyer class ship weighs 1000 times that. Weber also has his own website and discussion forum. I don’t know how fast conversations move there… > [@](#): > > While we’re at it, the restrictions on wedges and sidewalls: A wedge can only be produced on two sides of a ship. A sidewall can be produced on two more sides without sacrificing thrust: This is how warships are usually configured. Additionally, you can also protect the front or back (but not both) with sidewalls, but doing so prevents the ship so protected from using its wedge to accelerate. Or, you can completely surround a ship (or more likely, stationary space station) with sidewalls on all sides, again with no acceleration. Spoilered for tech that comes in later books. Weber did come up with “bow walls” on the graser armed LAC’s. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 1:57am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/4 "2011-06-02T01:57:20Z")
> [@Chronos](#): > > Additionally, you can also protect the front or back (but not both) with sidewalls, but doing so prevents the ship so protected from using its wedge to accelerate. Is this why fixed installations (e.g. space stations) use onmidirectional sidewalls, instead of projecting the much-tougher top-and-bottom impeller bands around themselves for protection? Because they’d have to leave one side completely open? EDIT: And I just had a thought – wouldn’t an impenetrable impeller band make an EXCELLENT shield for a ground-based installation on a planet? Why haven’t I seen anything like that yet? Just 'cause it can’t move doesn’t mean it couldn’t have its own impeller rings installed. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 2:05am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/5 "2011-06-02T02:05:13Z")
Oh, and I just thought of yet ANOTHER conundrum: Impellers imply FREE ENERGY MACHINES. There’s no way the fusion power plants on a starship are generating anywhere near as much power as the Kinetic Energy gains their starships are undergoing when they’re accelerating at 500 _g_. 0.3 _c_? That’s an enormous amount of kinetic energy per unit mass. I mean, _enormous._ The starship would have to burn _several times its own mass in fusion fuel_ to expend that much energy-per-unit-mass. This means you could put an impeller drive on an electric generator turbine, run it off of a tiny bit of fusion fuel, and use the resulting impeller-propelled generator to power a small city. Or even better, instead of powering the impeller drive on your generator with fusion, power it with a _smaller impeller-powered electric generator_! Voila. Something for nothing. Bottle it and sell it! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 2, 2011, 2:37am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/6 "2011-06-02T02:37:27Z")
That part, I think we’re supposed to just politely ignore. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [June 2, 2011, 2:54am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/7 "2011-06-02T02:54:24Z")
> [@tracer](#): > > EDIT: And I just had a thought – wouldn’t an impenetrable impeller band make an EXCELLENT shield for a ground-based installation on a planet? Why haven’t I seen anything like that yet? Because it would have spectacular effects on the atmosphere, and because the opposite wedge would stick into the ground and that would be even messier. They don’t seem to use wedges in-atmosphere for anything bigger than missiles. > [@tracer](#): > > Oh, and I just thought of yet ANOTHER conundrum: > > Impellers imply FREE ENERGY MACHINES. Yes, they draw energy from hyperspace; most of the energy for moving the ship doesn’t come from the fusion plant, it comes from the wedge. He’s called it a primitive version of the Core Tap from his Dahak books. For the curious, [the5thImperium.com](http://jiltanith.thefifthimperium.com/) has a bunch of collected ‘infodumps’ from Weber about the Honorverse and his other settings [here](http://infodump.thefifthimperium.com/). ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [June 2, 2011, 3:11am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/8 "2011-06-02T03:11:56Z")
Hell, it’s the inertial compensator that seems more like magic to me than the wedges. I can see using extreme gravity wedges to propel a ship, assuming you could generate the field. And, assuming you could do it, I could see how they could be impenetrable. But how do they keep the crews from turning into paste with every maneuver? Well, with inertial compensators of course. But how would those work?? How do you dampen inertia at all, let alone dampen it when you pulling 500 gravities and making radical turns and such?? Squish like grape. It’s the same thing in most sci-fi stories involving star ship combat. They all use the same thing to get around the fact that making any sort of radical maneuver in space when going at high speeds would kill the crew. -XT ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [June 2, 2011, 3:17am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/9 "2011-06-02T03:17:10Z")
Well, in the Honorverse at least the inertial compensator works by dumping inertial effects into the wedge somehow. Which is one reason why the missiles accelerate at tens of thousands of gs and the ships only a few hundred; compensators can’t handle that kind of acceleration and the crew are squishier than missiles. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [June 2, 2011, 3:39am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/10 "2011-06-02T03:39:55Z")
Like I said, I could see how, if you could control gravity and produce a high gravity field (which is what a wedge is IIRC), you could push a ship or whatever else at high velocity. I could see how such a wedge would act as a shield (be like trying to fire something into a neutron star or even a black hole). I can’t see how you could dump inertia into such a sump, though as you say that’s how it works in the books. Hell, I just love the books and simply suspend belief when I’m reading them, going with the flow. Sort of like the Lost Fleet series…it’s pretty cool, but at a certain point you just have to nod and accept if you want to get into the story. -XT ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [June 2, 2011, 3:54am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/11 "2011-06-02T03:54:33Z")
Actually, I find it more contrived that dumping inertia is a problem at all; with most gravity based drives in SF it isn’t an issue because the field pulls on everything equally. You don’t feel any inertial force for the same reason you don’t feel any while in free fall. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [June 2, 2011, 4:04am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/12 "2011-06-02T04:04:17Z")
I don’t think you’d move in that case. Basically, if you have a field that can generate high levels of gravity (or, I suppose, anti-gravity) then it needs to be directional in order to move the ship. Inertia though is inertia…it’s not about the gravity driving the ship, it’s about making radical turns at high velocity. I can’t wrap my head around how you could do that no matter what fantasy tech you had. How do you ‘dump’ that into anything? You are making a radical right turn at 500 gravities…what do you do? What do you do?? -XT ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [June 2, 2011, 4:37am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/13 "2011-06-02T04:37:44Z")
Squish happens when the vessel is accelerating at a different rate than the human inside. If you could generate a gravity field, gravity would act on the vessel and the human and accelerate them at the same rate. Ergo, no squish. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 2, 2011, 5:09am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/14 "2011-06-02T05:09:44Z")
> [@xtisme](#): > > Hell, it’s the inertial compensator that seems more like magic to me than the wedges. I can see using extreme gravity wedges to propel a ship, assuming you could generate the field. And, assuming you could do it, I could see how they could be impenetrable. But how do they keep the crews from turning into paste with every maneuver? Well, with inertial compensators of course. But how would those work?? How do you dampen inertia at all, let alone dampen it when you pulling 500 gravities and making radical turns and such?? Squish like grape. > > It’s the same thing in most sci-fi stories involving star ship combat. They all use the same thing to get around the fact that making any sort of radical maneuver in space when going at high speeds would kill the crew. > > -XT I think the idea is that the technology is mastery of gravity and gravitic theory. They even use gravitic lenses to achieve fusion in their reactors. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 2, 2011, 5:12am UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/15 "2011-06-02T05:12:41Z")
> [@xtisme](#): > > I don’t think you’d move in that case. Basically, if you have a field that can generate high levels of gravity (or, I suppose, anti-gravity) then it needs to be directional in order to move the ship. Inertia though is inertia…it’s not about the gravity driving the ship, it’s about making radical turns at high velocity. I can’t wrap my head around how you could do that no matter what fantasy tech you had. How do you ‘dump’ that into anything? You are making a radical right turn at 500 gravities…what do you do? What do you do?? > > -XT They rotate the ship, and continue accelerating forward. (In a new direction.) You would only have to cushion the effects in generally one direction. Edit: Actually, I like **Tabby’s** explanation better. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 6:30pm UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/16 "2011-06-02T18:30:03Z")
> [@Tabby\_Cat](#): > > Squish happens when the vessel is accelerating at a different rate than the human inside. > > If you could generate a gravity field, gravity would act on the vessel and the human and accelerate them at the same rate. Ergo, no squish. And since we already KNOW they can generate gravity fields – it’s why the crew can walk around on board a docked starship, instead of floating through the hallways – all a starship accelerating at 450_g_ needs to do is generate a 450_g_ field directed toward the front of the ship. I think the U.S.S. _Enterprise_ uses something similar when they engage their Impulse Drive. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 2, 2011, 6:38pm UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/17 "2011-06-02T18:38:37Z")
[QUOTE=tracer] I think the U.S.S. _Enterprise_ uses something similar when they engage their Impulse Drive. [/QUOTE] That’s not correct, **tracer**. > **[Impulse engine](https://memory-alpha.fandom.com/wiki/Impulse_engine)** > > An impulse engine or impulse drive was a common propulsion system used on starships used to create impulse power in order to achieve impulse speeds. In Federation starships, the impulse drive was essentially an augmented fusion rocket, usually... > [@memory alpha](#): > > The impulse drive was a propulsion system used for sublight speeds. In Federation starships, the impulse drive was essentially an augmented fusion rocket, usually consisting of one or more fusion reactors, an accelerator-generator, a driver coil assembly, and a vectored thrust nozzle to direct the plasma exhaust. The fusion reaction generated a highly energized plasma. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 2, 2011, 6:49pm UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/18 "2011-06-02T18:49:24Z")
> [@](#): > > Yes, they draw energy from hyperspace; most of the energy for moving the ship doesn’t come from the fusion plant, it comes from the wedge. That’s explicitly stated to happen when they’re “under sail” in a gravwave, but it’s never mentioned for normal space, or even for quiet hyperspace. It’s as good a fanwank as any, though. And any technology that can manipulate gravity like they do can also, inherently, manipulate inertia, so that’s not a problem (or at least, not a _new_ problem: Gravity control is an indistinguishable-from-magic tech as it is). ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 7:25pm UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/19 "2011-06-02T19:25:35Z")
> [@mlees](#): > > That’s not correct, **tracer**. > > [Impulse engine | Memory Alpha | Fandom](http://memory-alpha.org/wiki/Impulse_drive) I didn’t mean the Impulse Drive used gravity-control technology to acheive propulsion – I meant that the starship had to engage an _internal_ counter-gravity field in the opposite direction to keep the tremendous thrust of the Impulse Drive from turning everyone on board into crepes. (I believe they referred to it as the Inertial Dampener.) ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [June 2, 2011, 7:27pm UTC](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026/20 "2011-06-02T19:27:21Z")
> [@Chronos](#): > > And any technology that can manipulate gravity like they do can also, inherently, manipulate inertia, so that’s not a problem (or at least, not a _new_ problem: Gravity control is an indistinguishable-from-magic tech as it is). Still doesn’t explain why, if they can violate the Conservation of Energy like that, they don’t built impeller-powered Power Plants. [Next page](https://boards.straightdope.com/t/honor-harringtons-impeller-wedge-conundrums/584026.md?page=2)