A follow-up to my previous question-barrage: Properties of magnetically confined plasma shielding

After some of the feedback, I'm splitting it into several smaller questions.

In the world I'm building up for a game, one of the factions have magnetically confined plasma shielding technology. I'm changing it up and making the shield an active defense, rather than a passive barrier as most forms of science fiction use them. The way they're defined, the heat from this plasma would dissipate quickly and would likely cook the hull and crew/pilot if the temperature could be maintained for an extended period of time.

Not to mention the other effects:

  • The energy emitted by the shield would saturate the EM sensors, blinding the ship's instruments to all but higher frequency active scans.
  • I imagine this being fairly bright and/or obscuring to the pilot's vision.
  • The shield would block fire in both directions and may even make thrusters useless while active.

How it works

The plasma is stored in a magnetic bottle and kept at high temperature. The gases used for the plasma are the byproducts of the ship's fusion reactor (so anything between helium and iron on the periodic table,) meaning it passively replenishes as the ship's reactor is running. The plasma is vented through a series of ports around the hull then confined in a magnetic field to enclose the ship. The shield lasts up to a few seconds and gives the ship protection to most weapons.

So, what I'm trying to figure out is what this shield would actually look like. Would it look like a miniature star in the shape of the ship's magnetic field? Or would it more resemble a glowing cloud around the ship?

Would the pilot simply see a blinding light from all directions outside their ship?

  • $\begingroup$ It depends upon how dense you want your plasma field to be - which would also determine how effective it is as a shield. At low density it would look like a glowing fog or cloud, but at high density it could be as bright as a star, or even a thermonuclear bomb. Your ship would need to shield itself from the emitting radiation. $\endgroup$
    – Konchog
    Commented Apr 2, 2017 at 13:21
  • $\begingroup$ If it's to be dense enough to block incoming weapons, I imagine it would be more towards the star end of things. And I've already taken the radiation into account by short exposure and proper shielding for the pilot/crew in the hull/cockpit. $\endgroup$
    – Arvex
    Commented Apr 2, 2017 at 14:13

3 Answers 3


The radiance will be very bright. Stefan-Boltzmann law applies to plasmas in thermal equilibrium, and for 10,000K gives us 567,000,000 watts radiation power for every square meter shield surface. By 100,000K it's 5,670,000,000,000 Five freaking terawatt on each square meter. It increases 10000fold for every 10fold increase in temperature.

Altough your engineers could be able to help a little, (who said it has to be in equilibrium) a realistic plasma shield dense enough to have meaningful effect on material projectiles would shine like sun.

Your pilot will not sit behind an armorglass window. He will be in the well armored, closed bridge, and follow the action on screens. Before shield activation armored doors will cover the external cameras, and fire control will be accomplished by X-ray LADARS and computerized extrapolation.

WARNING: I never said that such a shield will work in reality. Even fusion reactors proposed so far are far from the required power, and no calculations were made about the magnetic confinement.

Edit: yes, it would look like a small, very bright star. But with naked eye, simple telescope or camera you wouldn't be able to see it's shape. It is too blinding for this.


enter image description here

The shield would probably be shaped like ferrofluid covering the ship with magnetic spikes. Check this amusingly narrated video that shows some detail features of ferrofluid spikes I've not seen elsewhere.

The shield would not be a round "bubble" but would flow along the contours of your ship, especially along any sharp protruding edges:

enter image description here

Not to mention it is damn sexy and I have never seen anyone use this shape for shields before, so it might be a unique design for your game.

  • 3
    $\begingroup$ Its a beautiful idea, but does not describe a realistic plasma shield. Plasma is not ferromagnetic fluid. However an other faction could have such armor. $\endgroup$
    – b.Lorenz
    Commented Apr 2, 2017 at 19:50
  • 4
    $\begingroup$ I'm honestly of the opinion that that's too freakingly awesome to not use, realism be damned. Sometimes you just have to remember that you're a dwarven gun jockey firing a rail gun at a five headed space dragon. $\endgroup$ Commented Apr 3, 2017 at 16:15
  • $\begingroup$ The spikes would act to deflect incoming energy even as the fluid dissipates it. you could make it work. $\endgroup$
    – pojo-guy
    Commented Aug 25, 2017 at 23:42

A magnetic bottle will do a lot in stopping particulate radiation from the plasma from damaging the ship itself, but you will need to come up with something to stop the ship being damaged by the EM radiation being emitted from the plasma. A plasma kept at high enough temperatures will - as previous replies have mentioned - basically look like the entire ship is aflame, or a star. However, this depends on the temperature of the plasma itself, the color and spectrum of the emission will be identifiable from a combination of the Stefan-Boltzmann laws and the Wein Displacement laws (as an interesting meta, this could be used by an attacker to find the peak temp of the defensive plasma). Radiation from the plasma will not just be limited to the visible spectrum, however, and - even in a vacuum - can cause a huge amount of damage to the defending ship's external hull through infra-red emission.

What is this shield used for? If it is for repelling solid slug ammunition - whose offensive capabilities rely on sheer kinetic energy - it's doubtful this would be stopped by a superheated plasma. Even if it were to be stopped, the resulting momentum transfer would be incurred to the plasma itself. If you can counter momentum change of the plasma with the magnetic bottles, then it behooves that the magnetic bottle itself is going to be a more effective shield. The best application for such a shield would be for dissipating harmful EM fields. As plasmas are extremely high conductors, an EM wave would be critically damped by such a volume of plasma through excitation of plasma currents.


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