# Fusion Rocket.

1. Dec 18, 2005

### Line

Is it a rumor or is the government really devolping a fusion rocket. From what I've heard it's so strong it could get us to Mars in as quick as 8 ays. Not lieing 8 days. If you wondering about the acceleration and deccearation it supposedly would have 1.5 time the force of gravity. So you could literally have artifical gravity in space.

I know they are trying to develop fission rockets but I had no idea about fusion.

2. Dec 19, 2005

### Danger

I've never heard anything about that particular subject. The closest that I can think of is that Robert Forward proposed back in the 70's that a ship using about 4 grams of antimatter to heat a few thousand gallons of water would make it to Mars in a month or so. (I'm not sure about the numbers, but it's something like that.)

3. Dec 19, 2005

### FredGarvin

4. Dec 19, 2005

### Staff: Mentor

Various concepts have been around for few decades, and so far, they are still concepts on paper.

Fusion research has yet to produce excess energy. There is the inertial confinement program at Livermore, and various magnetic confinement programs, e.g. ITER, with US R&D at Princeton, General Atomics, and I believe a few other places.

The problem with fusion systems is the mass - they require massive structures. To get an appreciable acceleration, the propulsion system requires extremely high mass velocities (i.e. high kinetic energy) or high mass flow rates.

Bottom line - fusion propulsion is still hypothetical.

5. Dec 19, 2005

### Line

But Fusion creates enormous amounts of energy. The size of the craft shouldn't reduce velocity that much.

6. Dec 21, 2005

### enigma

Staff Emeritus
Ideal rocket equation

$$\Delta V=-I_{sp}\times g_0 \times ln(\frac{m_f}{m_0})$$

If you've got a huge inert mass, you're going to need to expend even larger amounts of fuel to get the same velocity. Fusion rockets would have an advantage in the specific impulse department (Isp=3000+ compared to 450-500 or so for the very best chemical rockets), but that inert mass is a big problem. Not to mention huge engineering obstacle that we can't get more energy out than we put in.

7. Dec 21, 2005

### finchie_88

This is a little off topic, but are there any rocket designs (which could be realistically made within the next 50 years, none of these hypothetical creations where sace-time in front of the ship is compressed and then expanded behind the ship etc) which don't rely on the expelling of particles at very high velocities?

8. Dec 21, 2005

### kleinjahr

Check out the Orion project. One of the earliest proposals for a fission rocket. Though I wouldn't want to be within a hundred miles of the launch site. Puts all those nuclear warheads to good use.

9. Dec 21, 2005

### Staff: Mentor

An individual fusion reaction produces a large specific energy, e.g. for D (2 amu) + T (3 amu), the energy is 17.6 MeV with 5 amu, or 3.52 MeV/amu. The downside of this reaction is that about 80% of the energy is given to the neutron (14.1 MeV), combined with the fact that the products are released isotropically, with only a fraction going initially in the direction of interest.

Fission e.g. U-235 or Pu-239 produces ~200 Mev or less than 1 MeV/amu. Also, fission has the disadvantage of heavy fission products 91+/- and 141+/-as compared to the light nuclei in fusion.

However, the implementation is not so straightforward, because one needs a population (mass) of atoms undergoing a reaction and they are not all simultaneously reacting. In the fission or fusion process, a fraction of a percent are undergoing the reaction at any one time, and they are doing so at high temperatures and pressures, so that one needs a massive system to contain the reaction.

In addition, one needs a fuel supply (more mass) in order to replenish the reaction chamber as fuel is consumed.

All that mass has to be accelerated and that mass is usually way more than the payload.

10. Dec 21, 2005

### Staff: Mentor

There are no practical rocket designs at the moment which do not rely on expelling a propellant. There are concepts that use the solar wind or photons, but those are not rockets and fairly limited to projects within the solar system, i.e. near a star.

As for compressing/expanding the space-time continuum or something like warp drive, there are numerous papers on such hypothetical concepts, and so far they remain hypothetical.

11. Dec 21, 2005

### Intuitive

Considering all the Technicalities of Fusion engines, Wouldn't an EMP Engine over take a Fusion Engine.

Considering that the EMP engine is made with optimal efficiencies.

Capacitors can be charged over a timed array to give multiple EMP bursts to a super conductive Magnet in which an expanding field collapses off and repels off a diamagnetic shield, Specialized Diamagnetic shielding could help in increasing the EMP pressure by making special active polarization diamagnetic molecule that can change its orientation by electrical induction, This would allow the transparency of a diamagnetic shield to be controllable.

My Space bubble in design uses a type of EMP drive.

12. Dec 21, 2005

### Staff: Mentor

Basically, an EMP system must impart momentum/kinetic energy to some propellant, presumably whatever particles atoms/nuclei are collected in space.

One has to look at the particle density and available mass flow in, which will then constrain the mass flow out, and then on must detemine the $\frac{\partial B}{\partial t}$ in order to determine the energy imparted to the flow. I am not aware that high magnetic fields have been obtained with large solenoids. High fields have been obtained on small SC magnets, however, the maximum field strength is apparently open to dispute.

13. Dec 22, 2005

### Intuitive

Here is a link to energy levels of pulsed Superconducting Magnets for EMP measurements.

http://hypertextbook.com/facts/2000/AnnaWoo.shtml

The strongest so far is 850 Tesla destructive Electromagnetic pulse.

Field density can be controlled by using an array of Superconducting Magnet cells instead of a single Superconducting magnet.

Last edited: Dec 22, 2005
14. Dec 22, 2005

### Staff: Mentor

which has a link to NATIONAL HIGH MAGNETIC FIELD LABORATORY - http://nmr.magnet.fsu.edu/facilities/45T_32mm_TLH.htm

One has to look at the sizes of the SC magnets, and then determine the mass one can collect and energize. One still needs to obtain a high $\frac{\partial B}{\partial t}$ in order to propel a charged mass.

In the case of high field pulsed magnets -
http://www.magnet.fsu.edu/focus/construction.html

and
http://www.magnet.fsu.edu/focus/operation.html

The problem is that depending on the frequency of pulses, the average power could be very low. Furthermore, the system needs an energy supply and heavy capacitor banks to store energy for the pulses. The specific energy may be too low for a spacecraft propulsion system.

Last edited by a moderator: Apr 21, 2017
15. Dec 23, 2005

### Line

I'm still not quite understanding. Arelativly minute amount of fuel is needed to give an superabundant amount of energy in a fusion reaction.
The ;argest hydrogent bomb was around 60 megatons an dcould easily fit into a rocket. One blact from that thing would send you flying off. Only problem is cotaning the heat and the blast.

You shouldn't have to use a huge rocket if you can find a material that can contain the blast. To me the largest worry would be if you hit a meteoroid or loss steering. That's one thing that puzzles me,how do stattelites and probes survive without hiting space rocks and junk?