Ionizing Atmosphere on the nose of a rocket, missile or aircraft to reduce drag

[paul3337]

I heard of a strange engineering concept that was mentioned to me by someone who claimed to be a retired aerospace engineer. It was a guy I met on the internet so I took what he said to me with huge grain of salt.

He said something to me that I barely comprehend and I haven't heard from this guy in a year or so but it has got me curious to ask about it here.

This guy stated one time that if you were to ionize the atmosphere on the nose of a missile, or possibly the nose of an aircraft such as that one passenger jet that was once used that could fly faster than the speed of sound, that it would create a sheath of plasma that would reduce drag and enable a missile or an aircraft to go beyond mach 10 without overheating or breaking up.

I call nonsense on this but curiosity has gotten the better of me and now I got to ask:

Is there something to what he said?

If so, if SpaceX somehow ionized the atmosphere off the nose of the first stage of their rocket ship/superheavy vehicle, would it reduce drag? If so, would that lead to better fuel efficiency for the sea level raptor engines?

I just thought it would be wise to ask about it on a forum like this before completely discarding the idea. :)

 

[FactChecker]

I know nothing about it, but I would refer you to this mention of Project DRIFT: "Project DRIFT (Drag Reducing Ionized Flow Technology) aimed to improve aerodynamic performance and efficiency by ionizing the air that flows over an aircraft’s wing in subsonic, compressible regimes." here

 

[paul3337]

just read it. that's really cool!

 

[Benjies]

So, first thing's first, let's see if it's even feasible that we reach ionization temperatures at the tip of an aircraft. Let's look at the SR-71, flying Mach 3.2, as a test case for your question, here. The max body temperatures found on that craft are lower than 1,000K- this is ignoring the engines and purely looking at the body. At that low of temperatures, I don't think the craft is ionizing anything.

So, let's look deeper. Let's look into the DARPA HTV-2; Mach 20. Now we should get to see some ionization. 2,200K surface temperatures. Okay, some ionization. Non-zero ionization:

After some reading in 'Physics of Electric Propulsion' (Jahn), ionization is discussed at great length. Electrothermal thrusters undergo a similar process to what you're describing, as propellant is ionized by passing it through a high-temperature medium. The temperatures discussed therein were citing similar temperatures due to the necessity for the resistor to not melt at operating temperatures, so, 2,500-3,000K was cited. Granted, the elements used in these thrusters are radically different than air, but it does give us some guidance for a ballpark on the temperatures where we can at least expect to start seeing ionization. HOWEVER, we've had to climb to Mach 20 to see 2,200K and start scratching the bottom surface of the temperatures seen in these electrothermal thrusters, therefore, for practical hypersonic applications that do not involve an external ionization source, your drag-reduction theorist guy is grasping at straws for a feasible system, yet he is touching on an important aspect of hypersonics (some argue the definition of hypersonics): ionization and the effects of air dissociation on aircraft behavior.

So, let's step into the arena: We are engineers at NASA hired to design the X-43A. This is a scramjet engine with an 'integrated propulsion unit', in which much of the aircraft is actually serving as a source of thrust and lift at precisely the same time. We've got to game this ionization that we see occurring on the spacecraft to maximize Lift/Drag, and thrust... Unfortunately, it turns out that the degree of ionization at the temperatures of this Mach 10 engine is too low- the engine requires external sources of ionization.

Unfortunately, what you are touching on Paul3337, is largely classified space. You bring up a great head-scratcher, as we talk about future capabilities in hypersonics that may even require knowledge and fielding of ionized flow mechanics, we are but lowly citizens who iz 2 dum to know of what actually exists for these sorts of capabilities. I'll check back into this thread after the next war or in 40 years.

Oh- and to your SpaceX question- that's a great aero question I'd like to echo. I understand why we don't do an arrowtip shape up there to avoid terrible temperatures, but how do we optimize the shape of the fairing nose for an entire flight corridor? My hunch, honestly, Paul3337, is that there are great papers out there that go into great depth on the nose design. I'd strongly assume ionization temperatures are not realized on the surface of the nosecone during flight for commercial launch vehicles. If you attempted to induce ionization through an external power source, you would almost certainly increase the inert weight of the vehicle far too much to justify the technology. Weight is king.