Rocket plumes and magnetic nozzles

[Spacescifi]

 

 

Magnetic nozzles to my knowledge have yet to be implemented for space travel.

What are the pros and cons as opposed to using a regular rocket nozzle?

Pros I can think of: it can have hotter exhaust up to a point, since the exhaust won't hit the nozzle in space. Hotter exhaust gives longer acceleration times, which usually means lower thrust unless one is mixing metallic hydrogen or antimatter into the propellant.

Cons: Does no good in an atmosphere, as the air is all around it and will heat up the lattice nozzle. Also, even in vacuum the radiation from the exhaust alone is enough to heat the nozzle too. If the exhaust is bright enough (antimatter may qualify).

 

Rocket plumes: Would they even look normal with a nagnetic nozzle? Because it seens to me that if you have a super high exhaust speed and low mass flow you won't even see the exhaust, kind of like the glowing nozzles I see in space videos but with no obvious exhaust plume.

Chances are magnetic nozzles would be the same, the lattice nozzle may glow red as the particle exhaust is shot out at lighthugger speed. Don't wanna be in it's path, but you will probably miss the classic rocket plume look?

 

Am I right or wrong? Both?

[linuxgurugamer]

What is a magnetic nozzle?

[steve_v]

25 minutes ago, linuxgurugamer said:

What is a magnetic nozzle?

Uhh, this? Only applicable when one's exhaust stream is ionised plasma AFAIK, so comparisons to conventional chemical rocket nozzles are a bit meaningless.

OP might want to provide some links to designs/studies etc so we know what's being discussed...

[kerbiloid]

1 hour ago, linuxgurugamer said:

What is a magnetic nozzle?

This

Spoiler

 

[JadeOfMaar]

11 hours ago, linuxgurugamer said:

What is a magnetic nozzle?

A magnetic nozzle cannot be used for a chemical rocket, and vice versa.

As you can tell from its shape (see @kerbiloid's spoiler) it's not a fully contiguous structure. It's a criss-cross of beams.

Magnetic nozzles

• 
  • Why these exist is to produce magnetic confinement to keep the exhaust from touching and melting the nozzle itself. As @Spacescifi mentioned, these can handle unbelievably hot exhausts, and exhaust temperature weighs heavily on Isp.
  • Isp ranges over 1000s are very much needed if there is to be any hope of manned space travel or interplanetary probe travel in convenient measures of time (days vs decades). Currently we're stuck on the order of 290 ~ 340 seconds but it's going to be a great day when we can measure a rocket's performance in fractions of light speed. This is the kind of nozzle those rockets will have.
• 
  • Unfortunately, magnetic confinement only works with the ionized plasma kind of exhaust which will respond to the magnetic fields, and this will obviously demand of a lot of input current to power the magnetic fields. This demand is easily met by the fusion reactor feeding the engine, though.
  • In addition to thermal problems in atmosphere, due to their "wire mesh" frame, air will all too easily disturb the exhaust stream while the craft that owns it is moving. Since these things tend to be very long and wide they can serve as an unwanted super grid-fin and produce a lot of drag.
  • The nozzle itself is thick from every angle and probably weighs so much that it would be the last thing you ever want on an aerodynamic vessel.

Chemical rocket nozzles

• 
  • A chemical rocket nozzle is fully contiguous and functions by providing surface area for the exhaust to touch and push against as it expands. These nozzles are sufficiently cooled by the fuel itself (see all the piping on the outside of it) or an ablative coating. Example in spoiler: The RS-25 engine (i think it's the SSME) turns white due to being super-cooled by Liquid Hydrogen.
  • By comparison to magnetic nozzles, these don't weigh much or take up much space to produce CoM or drag issues.
• 
  • These need to be designed for various roles, propellant combinations, and narrow atmosphere pressure ranges. We have so many sea level engines but they suck in vacuum, and so many of the opposite.
  • What's more, there's no proven or commercially ready aerospike engine which is supposed to surpass all of these, but no rocket company is willing to test it because profit means everything at the end of the day, and the investment required to prove an aerospike is an immense gambit so we're going to be stuck with bell nozzles for far longer than anyone's really aware of.
  • While vacuum nozzles are very long or wide, they can quickly reach a point where there's no more point to extending it. Either exhaust problems are introduced, the bell itself becomes too heavy or Isp no longer gains any direct benefit.

Spoiler

 

 

[Cheif Operations Director]

On 8/5/2019 at 1:24 AM, kerbiloid said:

This

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What mod?

 

 

——

Moving to a new thread since it is kind of off topic

 

Edited August 13, 2019 by Cheif Operations Director

[kerbiloid]

4 hours ago, Cheif Operations Director said:

What mod?

 

[Cheif Operations Director]

2 minutes ago, kerbiloid said:

 

Thanks