Fusion Propulsion

Presentation by Jason Cassibry, PhD, prepared by Mike Lapointe, PhD, absent

Why the interest in fusion propulsion?

Going far, getting there fast and taking lots of stuff with you

Magnetoinertail fusion

electrothermal loss, introduction of a magneto inertial field cuts down on that loss

Paths to MIF compression:

Z-pinch azithumal field

Theta pinch linear field

Liner materiaal

Equivalent view - magnetic flux implodes target

Theta pinch:

Hooves on a cylindrical piston drive the reaction into a nozzle

Replace the time-varying magnetic field with a stationary field

Induce image currents equation for production

Two stage-like gas guns that can achieve the concept are extant

Ast the pellet runs through the magnetic fuel coil, heat expands the fuel to fusion levels

Accelerator >>> pellet >>>> electromagnetic field >>>> expanding pellet

Target can be accelerated to the required velocity, simplified system helps in many ways 

Phase 1 understand the dynamics between the rapidly moving target and the gradient field

Dynamics between target and gradient field

Fuel target design

Accelerator

…

Target fuels

Deuterium Tridium, seems to be the best route, but many choices to look at

Accelerator trades

Light gas, rail guns

Electro thermal acceleration

…

Laser acceleration

Reduce compression requirements

Higher initial temperature is positive to reduce field investment.

MATLAB modeling

Numerical modeling, includes high-temperature tabulations of state, resolving vacuum charging interface, electromagnetic equation solutions..

Convergence divergence modeling to find fuel gradients.

Looking at 100 microseconds where the target comes in, you can see the density contours as the expansion occurs

Note: not a fusion model, that tried first, code-blue right away.

Payload mass delivered to Mars, preliminary field modeling of both NIAC PUFF …

Initial vehicle concept with Orion.

Developing the tools to evaluate the concept in a mission context

Analytic models to provide initial performance estimates.

Updating fusion vehicle analysis with new engine design and performance parameters…

How will it be kept cold?

We are still working on getting a target to ignite and burn, that will be phase 2

What are the power requirements and what is the power source?

For any. System we will need a battery, this has a 100 Mw nuclear reactor, especially for deep space missions.

What is the density times time target?

Looking at solid density targets, we have not settled in a loss in criteria , still working with basic models.

 Competing with laser confinement fusion?

Partially, but those need a large initial, 3 football field, power and energy requirement… we look to reduce that.

If you strip your system down and compute the energy efficiency, what fractional efficiency do you have?

We look at the kinetic energy invested into the nozzle, vs. the energy returned, but that is not what you are asking for.

It seems asymetric to use Copernicus? High-fidelity tool for a low-fidelity outcome?

That is putting the cart before the horse. Hard to do insertion with a low thrust system. Straight-liine trajectories etc… injection delta v is equal to the velocity at the destination.

What is the jet power? Specific impulse and dry mass?

10k to 30000 for the specific impulse. 200 to 300 metric tonnes. Jet power would be in the order of maybe 100 Mw but probably not that big.

How much of the fusion power hits the plume?

Temperatures get hot, and radiate in the X-ray, but 25-50% depending how large the system

OK so 20 MW of jet power in 100 tonnes?

Yes, but not certain of the number.

What is the liner made of?

We are exploring that as a parameter. This is a derivative of the PUFF concept, so a layer of uranium would give exothermic reactions and an additional boost. Other heavier elements such as lead have been considered.