I have had a theory for a few years now, that a plane properly designed might be able to fly under water. Years ago a ballistics expert told me that bullets travelling through water actually breaks the waters molecular bonds down so that you end up with nothing but oxygen and hydrogen. Not only does it break down the water but it does it without destroying the structural integrity of the bullet. Because of this I have been thinking for years that a plane flying fast enough should be able to submerge itself and continue to fly in the wake of oxygen and hydrogen.
When I heard of the capabilities of the scram jet, x-43, I thought this might be the prefect opportunity to test this theory. Not only is it fast enough but it also runs purely on oxygen and hydrogen which may allow to fly under water with out using its own fuel. Furthermore, it may even be possible to refuel under the water. As I said this is just a theory, but it does have some evidence that supports the possibility. First, we know that fast enough moving projectiles tear water down to its elemental make up. Second, we know that thanks to inertia, when objects collide at massive speeds it can be predicted which if either of the two substances will survive undamaged. This is reinforced by the fact that ballistic experts fire bullets into a water tank to acquire pristine, used bullets. Even though the lead is soft the water does not deform it. Third, when air to ground missiles are fired into the sea they often continue for a great distance under water.
Given this evidence I have a simple suggestion for NASA when they next test the x-43. Leave the engine on when it hits the water. Just to see what the physical demands are on the structure and engine.

Originally posted by Mo0se
Given this evidence I have a simple suggestion for NASA when they next test the x-43. Leave the engine on when it hits the water. Just to see what the physical demands are on the structure and engine.

...and their budget!?
No dis', Mo0se the underwater theory is quite plausible, but i had to giggle.

Sanc'.

Hrm, any more information about this? It seems very strange that it would actually break down, I would have thought it would be more of a vaporization effect similar to cavitation.

There is also the matter of drag, the drag caused by travelling through water is far far greater than that of travelling in air. Energy wise it would be an incredibly expensive excercise.

the force of impact from hitting the water alone would probably destroy the aircraft. If there were a way to start underwater perhaps this would be more feasable, using fuel on board until a high enough speed was reached to use the physics of breaking down the water molecules.

I think that the overriding question here is WHY!!! Why fly underwater at mach, what is it about 5.5 - 7, apart from being a thrill ride, what purpose would it serve? Its a cool idea though. But governments havent got a habit of risking millions if not billions of dollars on a 'Cool Idea'. Just for fun so to speak....Although picure the scene, its the year 2305, 85 th Jack Azz Wing, Commander Burt Nobbler will attempt to fly hyper sonic scramjet..(audience laugh cos we didn't have plasma drive then)...how primitive! into the Atlantic at the 5.5 - 7 mach mark. (audience in fits), But just incase we've taken a scraping off his cheek for DNA re-assimilation just incase anything goes wrong The scary thing about this scenario is that it is more likely to happen than any government doin anything Cool.....which is a shame.

[Edited on 3-6-2004 by Tigerfeet]

Originally posted by Tigerfeet
I think that the overriding question here is WHY!!! Why fly underwater at mach, what is it about 5.5 - 7, apart from being a thrill ride, what purpose would it serve? Its a cool idea though. But governments havent got a habit of risking millions if not billions of dollars on a 'Cool Idea'. Just for fun so to speak....Although picure the scene, its the year 2305, 85 th Jack Azz Wing, Commander Burt Nobbler will attempt to fly hyper sonic scramjet..(audience laugh cos we didn't have plasma drive then)...how primitive! into the Atlantic at the 5.5 - 7 mach mark. (audience in fits), But just incase we've taken a scraping off his cheek for DNA re-assimilation just incase anything goes wrong The scary thing about this scenario is that it is more likely to happen than any government doin anything Cool.....which is a shame.

[Edited on 3-6-2004 by Tigerfeet]

A simple answer to the 'why' question is: Very fast torpedoes.

Actually, if they could get scramjets working underwater, it would revolutionize the Navy fleet... think about it, a scramjet gets the slingshot/rocket off the aircraft carrier, circles in a wide arc around the carrier to get just the right velocity, turns on the ionizing nose and wing edges, and disappears underwater, able to outrun just about anything launched at it!

I don't think it's just a 'cool idea'. As much as I'm against (especially) military warfare, the countries that still harbor old wars make military a necessity. Why send in a sub loaded with possible casualties when you could have a plane do the same thing, with no more than 2 possible casualties? Of course a scramjet couldn't 'patrol', but they could easily (if able to cruise underwater) take over many of the 'seek and destroy' missions, and get out of retaliation range much quicker than submarines... even the quickest nuclear subs.

Underwater drag: As you may have noticed, I took care of the 'drag' problem above, using technology that they already use to fly at multi-mach speeds.

All though theoreticaly one of the objects should remain intact, it is not plausible for any object the size of a usable airframe to impact any object at any speed. Ever seen an aircraft moving at only 90 knots hit a flock of birds? Also a bullet whether lead or full metal jacket has a consistent density aircraft do not. Any variations in density within an object will cause flex and resonance during the change of the medium in which it is moving. This can and probaly would lead to catastrophic failure within the structure and outer linning. Next even if you could maintain structural integrity how would you collect the now liberated oxygen and hydrogen? Your ballistics friend failed to inform you that this process occurs in the wake of an object moving through water at hypervelocity.