Which Scifi Waste Heat Tech is better?

[jjabrams55]

I always try to blend real physics into my scifi writing, since ignoring it tends to break my suspension of disbelief.

The second law of thermodynamics states that heat will go to cold things, and given enough time, the cold stuff will gradually reach the same temperature as whatever is heating it if it continues to be heated.

Radiators are not an option for my scifi starships, because the energies required for FTL/warp travel would require radiators of impractical size anyway (is that a giant radiator with a tiny ship attached LOL).

So I came up with two scifi solutions, one of them ignores thermodynamics and assumes the aliens know more about science then we do currently, enabling things we say are impossible. The other actually follows the second law of thermodynamics and also the law about conservation of momentum.

Scifi tech solution One (follows physics more): Use a portal gate that is connected to a planet and your starship at the same time. Connect portal to a giant block of ice on planet, then blow hot air from ship toward the portal. Use more AC fans to blow the cool air from evaporating ice around the ship's cabin to cool it down. Thus no ridiculous heat build up.

There is only one concern which may make even this idea impossible... conservation of momentum. Your starship, if in orbit of a planet, will have a much faster velocity than the block of ice sitting on the planet's surface, and it may even be traveling in a totally different direction if the starship is orbiting somewhere else light years away. Thus if a chunk of the ice broke off and hit the ship's cabin... the result might be enough to cause a hull breach or maybe even destroy the ship. Velocity/directional difference will kill you in space, physics proves that much. The only way to protect against that would be with powerful forcefields, even magnetic ones would do, since both ice and water are repelled by uber-powerful magnetic fields, and if a ship has FTL capability... it has energy/power to spare. One could use the magnetic fields to both slow and direct water vapor so that it won't be like a particle beam hitting the ship's interior walls at high velocities. It could match the ship's velocity once the ship's magnetic fields are down with it.

Scifi tech solution two (mostly ignores physics): Use an exotic energy field generator that generates a white ball of light that blocks all but a small amount of heat from escaping it's core. Thus the heat the energy ball can hold is much greater than the heat that it radiates. It's essentially a very convenient radiator. Occasionally you would have to release the heat from the energy ball with an energy beam shot (much like a might laser shot, releasing all the stored heat at once). Otherwise all the stored up heat would eventually start to make the energy ball hotter and hotter until... nothing good for your starship occurs.

How a starship could dump heat onto the energy ball would be rather simple. You could do it simply by cycling coolant pipes through the energy ball, which would cool as they passed through the outer layers of the energy ball. You would want to avoid passing coolant pipes through the core though, since that is where the highest concentration of heat is held.


So posters... which tech is better? Which has more applications? Which is more useful?


The only real advantage the energy ball solution has is that you can have smaller starships with it. Adhering more to physics with portal solution requires a big starship. Why? It's easier to cool something with more air than less, and you get more blowing cold air with bigger fans, not smaller ones. Given the fact that a starship has a ridiculous energy level to begin with (FTL? Seriously), you would want as much cool air as you could get blowing around your ship cabin to cool ship systems from overheating. So ironically, we just removed the massive radiator problem and replaced it for massive AC fans inside the starship itself, leading to a massive starship. The only way to avoid a massive starship would be to just link the ship's FTL system to a portal that links to it's power source. That way the ship would not be generating the FTL energies that require massive AC fans to cool off. Then you could have a classic starship that doesn't necessarily need to be massive.

Obviously... the energy ball solution does not have such issues.


Your thoughts and your votes? Which is better? Any more scifi applications for both the portal and the energy ball that I have yet to think of?

 

[zmunkz]

First of all, I have to say, neither solution does much by way of suspension of disbelief if we are talking hard sci-fi. If you just need some hand wavium so you can move on with the story, then sure, either will do, no need to go into it. Put your portal cooling system next to your inertial dampeners and artificial gravity. That said, here are some thoughts.

Option 1:
I don't see that there would be any benefit to discharging the heat onto ice caps... you just need to get it away from the ship. The moment you introduce a portal, you are no longer dealing with a closed system, so the second law of thermodynamics is cleanly side-stepped. You can just dump your excess heat into the near absolute-zero of inter-galactic space. If you are looking for a cold reservoir for some kind of cool-return, you could still use empty space or just regular air-conditioning technology, as long as you are no longer competing with the crazy heat-generation of your engine.

I have a hard time following your description of the issue with ice falling and hitting the ship. In any case, how the differences in relative speed play out depends on your rules for your portal (and no "real" rules exists to compare to). Whatever the case, the ship needs to be able to withstand impacts from all sorts of space debris anyway, so I don't think a few bits of ice from the cooling system would be any added concern. Star trek solves this with shields and a deflector dish.

I am not sure how practical magnetic fields are as a solution to water protection. This source suggests you would need magnetic fields on the order of 10 million times stronger than the entire planet Earth just to start levitating liquid water at rest. If you need to deflect while at high velocities, I suspect you would need many more orders above that. And even more for ice, as you need to first rupture its crystalline structure before the diamagnetic properties manifest at all. It all seems pretty dubious to me.

Option 2:
As you say, this doesn't seem to play with much existing physics so it is a little hard to comment. I could imagine a small singularity stored in a magnetic well that is extremely efficient at holding radiant heat energy. An array of these around the reactor could "eat" much of the thermal output, but they would need to be dumped before they got too large to remain stable in the wells.

***

This recent thread has a much longer discussion if IF and HOW MUCH science you need to worry about. I would say, if it is cool and serves your story, go into the details. If it is not important to your worldbuilding and your story, maybe just hand-wave. Either of these sounds cool, though the second one seems like you could do more interesting and immediate things with. I can imagine a lot of good plots where this white ball gets overheated or stuck or whatever.

 

[jjabrams55]

First of all, I have to say, neither solution does much by way of suspension of disbelief if we are talking hard sci-fi. If you just need some hand wavium so you can move on with the story, then sure, either will do, no need to go into it. Put your portal cooling system next to your inertial dampeners and artificial gravity. That said, here are some thoughts.

Option 1:
I don't see that there would be any benefit to discharging the heat onto ice caps... you just need to get it away from the ship. The moment you introduce a portal, you are no longer dealing with a closed system, so the second law of thermodynamics is cleanly side-stepped. You can just dump your excess heat into the near absolute-zero of inter-galactic space. If you are looking for a cold reservoir for some kind of cool-return, you could still use empty space or just regular air-conditioning technology, as long as you are no longer competing with the crazy heat-generation of your engine.

I have a hard time following your description of the issue with ice falling and hitting the ship. In any case, how the differences in relative speed play out depends on your rules for your portal (and no "real" rules exists to compare to). Whatever the case, the ship needs to be able to withstand impacts from all sorts of space debris anyway, so I don't think a few bits of ice from the cooling system would be any added concern. Star trek solves this with shields and a deflector dish.

I am not sure how practical magnetic fields are as a solution to water protection. This source suggests you would need magnetic fields on the order of 10 million times stronger than the entire planet Earth just to start levitating liquid water at rest. If you need to deflect while at high velocities, I suspect you would need many more orders above that. And even more for ice, as you need to first rupture its crystalline structure before the diamagnetic properties manifest at all. It all seems pretty dubious to me.

Option 2:
As you say, this doesn't seem to play with much existing physics so it is a little hard to comment. I could imagine a small singularity stored in a magnetic well that is extremely efficient at holding radiant heat energy. An array of these around the reactor could "eat" much of the thermal output, but they would need to be dumped before they got too large to remain stable in the wells.

***

This recent thread has a much longer discussion if IF and HOW MUCH science you need to worry about. I would say, if it is cool and serves your story, go into the details. If it is not important to your worldbuilding and your story, maybe just hand-wave. Either of these sounds cool, though the second one seems like you could do more interesting and immediate things with. I can imagine a lot of good plots where this white ball gets overheated or stuck or whatever.

The orbits and velocity difference is what would be dangerous. Your hull may be able to take a piece of ice hitting it at orbital speed... but an increase of velocity adds a lot more damage potential to anything. Even a bag of kitty litter would do damage in space if it were moving toward you at 110,000 kilometers per hour while you are flying toward it... at 110,000 kilometers per hour.

The vacuum of space won't work as a place to dump waste heat, as we are not going to dump hot air into space... since that is a waste of cabin air. And the ship has no radiators to speak of so that's not an option.

One added benefit of the portal that the energy ball does not have is phone-home radio. My ideas are based on an alliance of three alien races with different ways of handling both waste heat and FTL. With the alliance, they blend their tech together to get the typical classic starship we all know... except they ignore physics a bit less.

I like both ideas, but I will admit that the portal system is more flaw inherent. Since it actually requires a network of portals since portals only reach a LY out. A chain of orbiting portals every LY results in well traveled routes, and less freedom of movement than the energy ball design, but at least it allows instant communication.

The other awesome thing about the portal is that it can offer resuppy to the ship on the go.... so long they point the portal to outer space and wait for the ship to rendezvous with the drifting supplies (since it's direction/orbit will no doubt be different than the starship... since it's based on the homeworld LY's away).

 

[Montero]

Why is there so much heat in the first place?
A space ship has finite resources, so why are you throwing away energy?

That is what would bug me regarding suspension of disbelief.

 

[jjabrams55]

Even though reality often makes scifi boring and less spectacular when applied, sometimes it does just the opposite. You know the amazing heat sinks starships use that don't require any outside radiators? If you have a super heatsink, you're not radiating anywhere near the amount of heat off your hull that you're conserving inside your heat sink. So what happens when you fly down for reentry on a planet? No scifi shields, just your starship hull taking atmosphere to the face and trying to tank the heat with your heatsink. On second thought... you will need a little scifi magic if you're not even using ablative shielding (pop scifi rarely ever does, and it certainly doesn't look anything like ablative shielding that we know, just like like metal).

So let's add a structual integrity field to the hull, so that the oncoming air WON'T ablate it. So the hull absorbs all this heat as the ship comes down through the air. You should get cooked alive, but you don't. The outside of the hull glows red-hot, but the super heatsink ensures that the heat is absorbed before it heats the crew cabin area, even though the outer hull is glowing red-hot. Eventually air friction slows the ship enough that you can hover in place or just fly where you need to go on the planet. Gradually the hull's color goes back to normal as the heatsink absorbs the excess heat.

Why am I so sure a scifi heatsink combined with a structural integrity field could do this? Because whatever it's using for warp/FTL should IMO reasonably produce WAYYY more waste heat than anything reentry could put out. If your heatsink can absorb that, reentry should be child's play.


More often than not scifi does not explain HOW they do what they do. This is just one explanation of how they COULD do it. Even if it's not shown this way, this is one opportunity where physics would add to the special effects instead of take away from them. Most scifi just shows ships SOMEHOW not burn up every time they fly down, even if they do this repeatedly. I know, I know... scifi shields are in play. But I think shields are a cop-out and unnecessary when you don't really even need them to survive reentry. Not using my method anyway.


Your thoughts?

 

[jjabrams55]

Why is there so much heat in the first place?
A space ship has finite resources, so why are you throwing away energy?

That is what would bug me regarding suspension of disbelief.

Ahem... this is is scifi. Reality does not know how to make legit starships. It's all theoretical right now anyway. What reality DOES know is that getting rid of waste heat in space is a BIG problem when there is a LOT of heat.

Current physics does not suggest ANY way of making power without SOME waste heat. And given the energy levels required for something like FTL/warp/insert your fictional FTL here, they should produce some MONSTER waste heat.

Even the calcs that have been done on the energy levels for alcubierre warp are staggering, even when reduced. Since waste heat is unavoidable (unless future physics says otherwise), I include waste heat that needs to be dumped.

The other option is to straight up ignore it like the problem doesn't even exist. Much like Star Wars. Which also has 'airplanes in space'. Can't do that. I can't. Hate that.

 

[Mirannan]

One possibly relevant fact: Not even all current-technology spacecraft use (or used, to be accurate) ablative heatshields. For example, the Space Shuttle didn't; what it did use was a ceramic-based material a little like mineral wool loft insulation (except more so, of course) so that the heat didn't get anywhere near the spacecraft's structure in the first place - as long as the tiles stayed intact, of course.

 

[chrispenycate]

If you prevent the hot atmosphere (adiabatic compression heats as much as friction) from contacting the shell of the ship (since it's plasmolysed it can be manipulated by magnetic fields, MHD) you'll get relatively little heating of the ship. Of course, none of my starships land - they're manufactured in space, and go from orbit to orbit, and carry spaceplanes for orbit to surface transfers, so the problem is massively reduced. There would be some radiant transfer with temperature differentials like that, but no more than you'd expect from a close flyby of a star - mirror plating would reject a lot of it. And cooling down would be fast in atmosphere when the shock wave moves on.

 

[VinceK]

I think this may have more to do with materials then theory. The three types of heat transference: diffusion, radiative and convection, would all advance with the discovery of new materials, which I assume would be available in an FTL universe. In all probability, as @chrispenycate has mentioned, FTL ships would by necessity require some form of external shielding, otherwise the inadvertent contact with a dust cloud could turn that shiny intergalactic cruiser into a molten slug.

 

[jjabrams55]

I think this may have more to do with materials then theory. The three types of heat transference: diffusion, radiative and convection, would all advance with the discovery of new materials, which I assume would be available in an FTL universe. In all probability, as @chrispenycate has mentioned, FTL ships would by necessity require some form of external shielding, otherwise the inadvertent contact with a dust cloud could turn that shiny intergalactic cruiser into a molten slug.

That is true, yet I also think that people miss an important fact about shielding. For every action there is a reaction. Assuming you're using a traditional deflector shield (bend gases/air around the front of the ship so it don't hit your ship in the face), then your action WILL create a reaction.

What you're doing is the same thing a propeller/jet engine does... throwing air from the front to the back (granted, they suck air/heat it out the back, but same basic propulsion force more or less). Which in turn ACCELERATES the ship even FASTER through the atmosphere. Sure, the air isn't hitting you, but the ground sure will when you hit it in excess of orbital velocity!

Even a ship in a warp bubble, assuming it was deflecting gases hitting it in the front, should experience the same propulsive effect. You just wouldn't notice any speed change until the ship exits the warp bubble. Then you would have tp use gravity assist/atmospheric braking to avoid exhausting all your rocket fuel (assuming you even use reaction engines at all) for course corrections. Which is quite easy to do BTW with ANY FTL/warp drive that conserves momentum. All you do is keep warping next to the gravity well, while letting gravity pull you in each time to bleed off speed.

Atmospheric braking has it's own issues, as I already discussed. But it is faster.

 

[Montero]

Erm. Well. "This is scifi"

Humph.

You start a thread asking for input because you want to blend in physics to keep your disbelief suspended. When I tell you that part of what you are doing seems illogical to me, you say "This is scifi".
That is really annoying.

I find your latest post rather illogical too, as you are saying in the first paragraph that "reality dos not know how to make legit starships" and in the second paragraph "current physics etc". Well yes, current physics and engineering is struggling to make the kind of space ships that would enable rapid travel of the kind where you could trade with another solar system. One of the problems is the vast energy needed to get out of the gravity well. So wasting any in heat is illogical. One of the advances needed would be far greater energy use efficiency. So going in for complex methods of getting rid of waste heat - that would crash my disbelief suspension. You need complex methods so as not to generate lots of waste heat in the first place.
You don't "straight up ignore it" - you say things about "space travel became widely available only after the Haroldson modification so increased energy use efficiency that heat generated was tiny."

 

[Dulahan]

Ok, lets point out the basics to answer this question: A celestial body burns up entering the atmosphere because of fiction with molecules in the air. As there are no air molecules in space, the celestial body is receiving no friction and there for traveling at a greater rate of speed than it otherwise would. The body hits the Air molecules like a wall, friction happens and heat is generated.

Now the equation escapes me but speed and angle of descent directly correlate to the fiction generating heat. NASA has tackled one of these issues by calculating the optimal angle for re-entry but they cannot control the shuttles speed -- the space shuttle is not flying but its falling, hence the nickname "The Flying Brick".

Too me, the science says that a craft with the ability to control its own descent (angle AND SPEED) would barely need protective shielding at all. It would wade through the Air Molecules as every else does on our little blue planet. Protective shielding was first conceived for Ballistic Missiles and later Space Craft, it's relevance is based the inability for these objects to control their descent speed.

The Atmosphere isn't some kinda magical being that destroys whatever it touches .. you need to aggravate it first.

 

[jjabrams55]

Erm. Well. "This is scifi"

Humph.

You start a thread asking for input because you want to blend in physics to keep your disbelief suspended. When I tell you that part of what you are doing seems illogical to me, you say "This is scifi".
That is really annoying.

I find your latest post rather illogical too, as you are saying in the first paragraph that "reality dos not know how to make legit starships" and in the second paragraph "current physics etc". Well yes, current physics and engineering is struggling to make the kind of space ships that would enable rapid travel of the kind where you could trade with another solar system. One of the problems is the vast energy needed to get out of the gravity well. So wasting any in heat is illogical. One of the advances needed would be far greater energy use efficiency. So going in for complex methods of getting rid of waste heat - that would crash my disbelief suspension. You need complex methods so as not to generate lots of waste heat in the first place.
You don't "straight up ignore it" - you say things about "space travel became widely available only after the Haroldson modification so increased energy use efficiency that heat generated was tiny."

Wanna know the funny thing? That is what would break my SOD.

I rather 'invent' ways to manage around current physics than totally overpower/ignore them. Just my style, and you have yours.

It's like me saying, "I like peanut butter!"

You, "I hate peanut butter! I LIKE almond butter!"

Me: "You can keep your almond butter. I hate that stuff!"

For me, scifi is a a vehicle to say/ask "What if THIS was possible?" I can be prescient if I so choose, but that tends to lowball what may tech can do, since modern tech is hopelessly outdated compared with... STARSHIPS!!!

In the end I don't care much how prescient or NOT prescient my fiction is. Because no man can reliably predict the future because no man has created the present and all that happened before them which they had no control over. Anyone that makes a car can predict what will happen to it if it does this or that. But we didn't make the car sooo... ya get my point?

For what it's worth, the ancients drew pictures of men hovering in baskets suspended by flying birds. Da Vinci was closer to the truth, with his winged vehicles, but even he knew hadn't thought to apply fan/propeller tech.

Meanwhile, even before Da Vinci came along, the Romans invented a steam engine which could have lead to mechanical fans/jet engines if they kept up their engineering. They did not. Probably blew all their time on gladiator combat/fighting over who would be the next emperor. The roman empire fell for several reasons after all, and infighting was just one among many.

http://kotaku.com/5742457/the-ancie...steam-engine-cybernetics-and-vending-machines

 

[jjabrams55]

Ok, lets point out the basics to answer this question: A celestial body burns up entering the atmosphere because of fiction with molecules in the air. As there are no air molecules in space, the celestial body is receiving no friction and there for traveling at a greater rate of speed than it otherwise would. The body hits the Air molecules like a wall, friction happens and heat is generated.

Now the equation escapes me but speed and angle of descent directly correlate to the fiction generating heat. NASA has tackled one of these issues by calculating the optimal angle for re-entry but they cannot control the shuttles speed -- the space shuttle is not flying but its falling, hence the nickname "The Flying Brick".

Too me, the science says that a craft with the ability to control its own descent (angle AND SPEED) would barely need protective shielding at all. It would wade through the Air Molecules as every else does on our little blue planet. Protective shielding was first conceived for Ballistic Missiles and later Space Craft, it's relevance is based the inability for these objects to control their descent speed.

The Atmosphere isn't some kinda magical being that destroys whatever it touches .. you need to aggravate it first.

I don't disagree with you. But as I said, controlling your speed of descent (angle doesn't even matter really if you can control your speed... it's just a comfort thing, do you want to fall upside down or not?) takes more time than pop scifi ever shows.


All I do is show what would happen if we did things the fast way and allowed physics to still be in play OUTSIDE your spaceship.

 

[Dulahan]

I don't disagree with you. But as I said, controlling your speed of descent (angle doesn't even matter really if you can control your speed... it's just a comfort thing, do you want to fall upside down or not?) takes more time than pop scifi ever shows.


All I do is show what would happen if we did things the fast way and allowed physics to still be in play OUTSIDE your spaceship.

A powered ship, I would assume, wouldn't have any more difficulty slowing for entry than a car would slowing for traffic or a stop light. I would imagine that the transition would be rather seamless. I could, however, see something where the ship had some kind of reactive armor that would activate during a rapid descent.

Anyone ever see the action film, Demolition Man? There was a seen where the car was out of control and crashed into a sign or display. On impact the car was flooded with a protective foam to save the occupants. If you're hitting the brake before traffic or a stop sign then something sprays out and insulates you from the danger.

 

[jjabrams55]

A powered ship, I would assume, wouldn't have any more difficulty slowing for entry than a car would slowing for traffic or a stop light. I would imagine that the transition would be rather seamless. I could, however, see something where the ship had some kind of reactive armor that would activate during a rapid descent.

Anyone ever see the action film, Demolition Man? There was a seen where the car was out of control and crashed into a sign or display. On impact the car was flooded with a protective foam to save the occupants. If you're hitting the brake before traffic or a stop sign then something sprays out and insulates you from the danger.

So basically an inflated heatshield? Which... without scifiing it up (making stuff up via the author's imagination), it will be limited to whatever physics allows.


So something like this: BTW, they survive.

 

[Montero]

Mm. Well, as I said in my previous post I find the LOGIC of your arguments contradictory. On the one hand you say that current physics shows lots of waste heat, and then you say current physics can't provide space travel in the way you want it. I agree with the truth of both those statements - separately - but used together they do not support your argument. To me this is not an argument about what people like or dislike, it is an argument about the logic of world building. I think there are holes in your logic. You have ignored that part of my post and changed the argument to saying we have different tastes. I am sure that we do have different tastes, but that is not the point. Your proposed world building is contradictory - you want to invent cool tech to get rid of waste heat - and you are not prepared to discuss the logic of the waste heat. I think the points I have made regarding waste heat are valid and are not a matter of taste.

 

[jjabrams55]

Mm. Well, as I said in my previous post I find the LOGIC of your arguments contradictory. On the one hand you say that current physics shows lots of waste heat, and then you say current physics can't provide space travel in the way you want it. I agree with the truth of both those statements - separately - but used together they do not support your argument. To me this is not an argument about what people like or dislike, it is an argument about the logic of world building. I think there are holes in your logic. You have ignored that part of my post and changed the argument to saying we have different tastes. I am sure that we do have different tastes, but that is not the point. Your proposed world building is contradictory - you want to invent cool tech to get rid of waste heat - and you are not prepared to discuss the logic of the waste heat. I think the points I have made regarding waste heat are valid and are not a matter of taste.

There is really nothing to discuss about waste heat... unless you know something I don't?

To make up something saying we figured out how to NOT make MASSIVE amounts of waste heat from our FTL system is as valid as making up a way to deal with such heat.


Current physics science doesn't really allow for either of our ideas... only time will tell.

If you don't think I argue well enough... well then that's something entirely. But I don't really care. Since I didn't post with any intent about discussing critiques on how well I argue. I came to discuss scifi concepts. Nothing more. Nothing less. G'day.

 

[Montero]

I still hold that my idea of increasing efficiency has greater logic - because it uses less energy. The less energy needed, the more likely something is to be achieved. All engineering heads towards greater efficiency.
On this forum we try for well thought out debate about science fiction ideas, and science fiction storytelling. I see nothing wrong in pointing out that you have not made a logical argument. After all - for suspension of disbelief in story telling you need a consistent internal logic to a story. So you started a thread asking for help, I and others spend time giving you help, you don't like what I've said and have not only been dismissive to me, you have been rude about this forum. Not what I'd call a winning strategy for getting further help.

 

[chrispenycate]

We seem to be addressing two completely different problems here - FTL, about which we know very little, and quite possibly doesn't involve a realspace velocity at all, and atmospheric re-entry (well, entry, I suppose) which we know pretty well. Both are utterly real problems, but the first we can't plan for much.

Personally, I would never land a starship, any more than I would beach a schooner. Leave the mothership at anchor offshore - umm, in orbit round the planet - and carry pinnaces - specialised atmospheric craft - to go down to the planetary surface. Now, if we put the main ship in geostationary - yeah, I know it's not 'geo', but the Ancient Greeks didn't know about other planets - the spaceplane/shuttle/whatever is traveling at negligible velocity relative to the top of the atmosphere (maybe a few hundred kpH, but compared with Mach 25 this is negligible) and gently slow it down and spiral it down. Pleas note, we are flying backwards, drive aimed in the direction of travel. The exhaust plume from the reaction engine (basically a rocket, as we have no atmosphere to use as reaction mass for thousands of kilometres).

Speed of ejection of exhaust is many times that of sound, so when it hits the planetary atmosphere it generates a shock wave, pushing back on the drive and increasing the temperature to plasma levels, so it can be manipulated with magnetic fields. Or not - we won't have the same amount of atmospheric friction as the 'straight in' approach, and it's being pushed by the drive, so hasn't the same tendency to contact the hull. And then you can spin on your axis, and glide in at normal aircraft speeds.