Two Questions

[Spacescifi]

QUESTION ONE:

Ever heard of the direct fusion drive?

It sounds really awesome, like it seems to put VASMIR to shame.

Is it better than VASMIR?

 

https://en.m.wikipedia.org/wiki/Direct_Fusion_Drive

 

QUESTION 2:

Just curious if one could rapidly magnetize air as it passes through the intakes would that help rocket SSTO's at all?

I say this because in 2019 researchers claim they magnetized room temperature air with a circular configuration of lasers!

So the obvious scifi route for me is to metaphorically see how far down the rabbit hole goes.

I tend to think if we could magnetize air rapidly though the intakes then perhaps we could create an airbreathing engine that that could work equally well at both supersonic and subsonic, since the magnetized air could be slowed to subsonic as needed with magnetic fields,  or directed whereever in the engine faster.

What do you think?

Perhaps we could even have bladeless props?

Basicallty like a dyson fan only it magnetized oncoming air and threw it back as exhaust.

It would either need to be huge or have uber magnetic fields, meaning it would be cheaper to scale up than down.

Actually either way it needs uber magnetsm, it's just that being smaller in radius makes that requirement even higher 

Edited April 19, 2020 by Spacescifi

[Scotius]

Indeed, it looks very promising. Fusion drive and power plant in one package? Yes, please!

[Shpaget]

Bladeless fans are a gimmick and most certainly not bladeless. The blades are just hidden.

VASIMR (not VASMIR) is a just a "motor" it needs a power supply. Direct fusion drive is both "motor" and power source so comparison is fuddled.

That being said, the difference in energy density between whichever chemical energy source you fancy and fusion is several orders of magnitude.

[Guest]

DFD is a promising technology and the only fusion drive that is actually being tested. It's not particularly impressive compared to some other, more theoretical proposals, but it's far closer to actually being usable on a real spacecraft.

[sevenperforce]

5 hours ago, Shpaget said:

Bladeless fans are a gimmick and most certainly not bladeless. The blades are just hidden.

That's what I originally assumed too, but...

https://insideunmannedsystems.com/going-bladeless/

 

[Wjolcz]

I would take antimatter, use it to ionize water that charges anti-iron batteries and then those batteries boil that water which turns into steam and drives a steam turbine that spins a submarine propeller to fly in the atmosphere.

And then have a magic drive to go from Sol to Alpha Centauri and back twice in 0.000000374628264s.

Edited April 20, 2020 by Wjolcz

[sevenperforce]

17 hours ago, Spacescifi said:

Just curious if one could rapidly magnetize air as it passes through the intakes would that help rocket SSTO's at all?

I think this has been addressed before but air cannot be magnetized without being ionized. Ionization either requires extreme voltages or extreme heat.

[Spacescifi]

7 minutes ago, sevenperforce said:

I think this has been addressed before but air cannot be magnetized without being ionized. Ionization either requires extreme voltages or extreme heat.

Perhaps. Here is article:

A dense molecular gas has been rapidly magnetized using light. Done by physicists in Canada, the experiment involves using an “optical centrifuge” to rotate the molecules. This causes the electronic spins of the molecules to line up in the same direction. The technique could have a wide range of applications including the production of large amounts of spin-polarized electrons.

Creating a magnetized gas in which electronic spins point along the same direction is very difficult to do by simply applying a magnetic field – even using the strongest laboratory magnets. Magnetization can be achieved by shining circularly polarized light on a gas. If the light is resonant with the molecule’s electron energy levels, a high degree of spin polarization can be achieved in about 100 ns. However, this only works if a high-intensity source of light at the correct resonant frequency is available. Another problem is that the technique is only practical for relatively diffuse gas samples.

Corkscrew-like pulses

Now, Alexander Milner, Alexsey Korobenko and Valery Milner at the University of British Columbia have used a non-resonant optical technique to magnetize a sample of oxygen gas. Called an optical centrifuge, the method involves firing broadband laser pulses into an optical system that outputs corkscrew-like pulses. These pulses are then able to deliver large amounts of angular momentum to molecules. A process called spin-rotational coupling then causes some electron spins on the molecules to become polarized and point in the same direction, thereby magnetizing the gas.

Although only a few percent of the oxygen molecules are actually centrifuged in the process, the number of polarized electrons created is about 1000 times greater than achieved using resonant techniques. The magnetic field created in the sample is on the order of tens of milligauss – which is about one tenth of the Earth’s magnetic field.

Other benefits of the technique are that it works in less than one nanosecond, and that it can be deployed at room temperature in relatively dense gases. The team also found that the process can be enhanced by placing the gas in a magnetic field.

Chemical reactions

According to the researchers, the optical-centrifuge technique could be useful for nuclear magnetic resonance (NMR) imaging because the electron-spin polarization can be converted to a nuclear-spin polarization for NMR. A spin-polarized gas could be used as a source of spin-polarized electrons for particle-physics experiments as well as for probing the dynamics of chemical reactions and analysing the electronic properties of materials.

The research is described in Physical Review Letters.

[magnemoe]

7 hours ago, Shpaget said:

Bladeless fans are a gimmick and most certainly not bladeless. The blades are just hidden.

VASIMR (not VASMIR) is a just a "motor" it needs a power supply. Direct fusion drive is both "motor" and power source so comparison is fuddled.

That being said, the difference in energy density between whichever chemical energy source you fancy and fusion is several orders of magnitude.

Note that real prototype fusion engines also require an power source its not an fusion reactor. However we get extra energy from the fusion process who help increase the ISP. 
An vasmir engine is in in many way an fusion engine without fusion. 

[Guest]

This is an advantage in its own way, though. We haven't managed a proper breakeven so far, especially not in continuous operation. A fusion thruster doesn't really need breakeven, though, it just needs to fuse things and make exhaust particles go very fast. Of course, you then require a power source to go with it, probably a hefty one, at that, but the Isp gain might be worth it, and you can load some power heavy equipment to give your reactor something to do when it's not powering the engine.