# Fusion Rocket.

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.

Danger
Gold Member
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.)

Astronuc
Staff Emeritus
Line said:
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.
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.

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

enigma
Staff Emeritus
Gold Member
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.

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?

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.

Astronuc
Staff Emeritus
Line said:
But Fusion creates enormous amounts of energy. The size of the craft shouldn't reduce velocity that much.
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.

Astronuc
Staff Emeritus
finchie_88 said:
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?
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.

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.

Astronuc
Staff Emeritus
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.

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.

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

NHMFL's 45 Tesla hybrid magnet is the highest continuous magnet field available in the world. The outer superconducting coil produces static field of about 11 Tesla, with the rest of the field being generated by water-cooled resistive insert. Bore size diameter is 32 mm. This magnet was not designed with NMR homogeneity in mind, and its field instability is not to NMR specs. Field stability in resistive magnets is compromised by fluctuations in power supply and in temperature of the cooling water.
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 -
A typical non-destructive pulse coil used at the NHMFL consists of about 300 turns of rectangular cross-section wire (2 x 3 millimeters) in ten layers. The bore (the hole at the center of the magnet) for the experiment is usually between 10 and 25 millimeters (mm) and the height of the magnet is about 100 mm.
http://www.magnet.fsu.edu/focus/construction.html

Pulse magnets come in two forms: destructive and non-destructive. Non-destructive pulse magnets can generate a magnet field pulse as high as 70 Tesla. The average life span of a non-destructive magnet is 500 to 800 pulses. Destructive pulse magnets, as their name implies, are violently ripped apart by the massive stress placed on them when they are switched on. To reach field in excess of 100 Tesla researches set up explosives around the magnet that detonate as the magnet is powered. The explosion compresses the magnetic field allowing scientists to attain fields as high as 1,000 Tesla for a split second.
and
During the creation of these magnetic fields, the magnet heats up dramatically. In order to keep the magnet from melting down, it is cooled to temperatures around -200 °C, using liquid nitrogen. Even at this initial temperature, however, the coil heats from -200 °C to room temperature in just a few milliseconds.
The energy used by the short pulse magnets is stored in capacitor banks. These banks store up immense amounts of energy that can be discharged, or pulsed, through the coil very quickly. To keep the magnet from creating so much heat that it melts, the banks are pulsed for a very brief time-a few milliseconds-in order to keep the temperature under control. The energy expended by these capacitor banks is around 1 megajoule, or the energy of about two sticks of dynamite, and the electricity delivered to the magnet could light 20,000 household lightbulbs at once.
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.

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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?