DFD is not suitable for high-thrust applications, at least based on the MHD models we are using. If you try to get too high a thrust, the thrust goes to zero.

]]>Thanks! I did start at 1G just to get a laugh. I knew the numbers would be astronomical (groan). Is there a compromise that reduces fuel by 2 orders of magnitude but reduces each way to a few weeks, a lot of the Human issues are reduced and less supplies needed for the trip itself.

I tried to come up with realistic alternatives. One thought would be human centric. I wonder what it would take in fuel and time to start the journey at 1G from earth and taper off the acceleration such that at the flip point which has now moved, we would be about .65G and they would arrive in orbit with gravity being .376G.

Another idea comes from another persons blog post. from a fuel point getting rid of mass reduces fuel needed to slow down so if a “tug” was able to disconnect from the capsule and a short(er) duration high G like 5G’s for 30 min and continue on an ellipsoidal path would it re-cross the mars orbit at the time needed to go home. A short burst from the launcher High G chemical 🙁 , would allow the return capsule to catch up for the ride home.

One more question has been bothering me, if I may? I see the thrust equation for a rocket is linear relation for exit velocity and mass flow rate. And exit velocity is often used almost interchangeably for specific impulse. So 1000kg/sec and exit velocity of 200m/sec vs 20kg/sec @ 10000m/sec are both 200KN of thrush, what is the mass flow rate of the 10MW dfd at full thrust agumentation. I saw those in talks Stephanie gave and will review but even to come up with .1G the number of engines seemed unreasonable. If they cannot scale in diameter and only perhaps in length, can the dfd ever be used for high-thrust applications?

]]>Thanks Jeff! Check out this blog post

https://www.psatellite.com/doing-the-mars-run-with-fusion-propulsion-at-1-g/

It will allow you to do the calculations you need.

]]>I was playing in a google spreadsheet with a rather ridiculous “what if” we could do constant acceleration, how long to get from earth to mars. It made me realize I was ignoring thrust to weight ratio of the drive itself. I have come to think that we need to begin separating fuel from reaction mass. In a Chemical rocket, they are one in the same. But independently of how you put the energy in, it is the reaction mass that generates the acceleration to change the Velocity.

Picking a mass out of the air like 12000kg (crew dragon) and assuming an infinity long fuel line and straight line distances, I was calculating just the reaction mass for .1g to 1g. So just the .1g would be fantastic for trip time of 70 to 90 hours to flip and burn. The extremely low thrust of the DFD means the number of engines needed would be unreasonable.

So could a possible design for high a thrust fusion rocket be, from left to right, a frc plasma injected into an area where it is heated to fusion conditions and then the plasma is ejected out the back outside the magnetic containment as a new frc replaces it in the heating chamber. This region is a nozzle that is cooled internally and with a film of hydrogen(just h2 reaction mass). I was thinking that injectors outside the dfd section could grow the fusion region and the isolation instead of magnetic could be a balance of amount and direction of H2 with injected fuel. Can a fusion region exist like this or would the non ionized H2 just dilute the plasma and snuff out the reaction?

]]>Thanks!

]]>If you recapture the expended fuel, you are reversing the momentum transfer process which gave the spacecraft momentum in the first place, thus bringing the spacecraft back to square one: no momentum transfer.

]]>Actually the momentum is there and the expended fuel is captured in such a way that there is no momentum loss. Fibonacci system.

]]>If you capture the expelled fuel you will not gain any net momentum. The rocket only works if the fuel carries momentum away from the spacecraft.

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