Ion drives may open up the outer Solar System, but they’re anything but high-thrust. With NASA’s Deep Space 1 mission and the later European Smart 1 moon mission, the idea was to operate for long periods of time with very little kick from the engine. The effect is cumulative, and it works. Japan’s Hayabusa asteroid probe used four ion engines designed to burn throughout its cruise to asteroid Itokawa. 20,000 hours of cumulative operation used up a scant 20 kilograms of propellant, highlighting the efficiency of these engines. NASA has run an NSTAR thruster at the Jet Propulsion Laboratory for over 30,000 continuous hours, almost five years of operation.
Now the European Space Agency has conducted successful tests of a new kind of ion drive, one designed to provide greater thrust than its predecessors. The Helicon Double Layer Thruster (HDLT) uses radio waves to ionise argon gas, creating two layers of plasma between which charged particles can be accelerated in a beam. The HDLT design was conceived by Dr. Christine Charles and team working in the Plasma Research Laboratory at Australia National University. Here’s how an ESA news release describes the process they invented, drawing on an interview with Dr. Pascal Chabert (Ecole Polytechnique, Paris):
To create the double layer, Chabert and colleagues created a hollow tube around which was wound a radio antenna. Argon gas was continuously pumped into the tube and the antenna transmitted helicoidal radio waves of 13 megahertz. This ionised the argon creating a plasma. A diverging magnetic field at the end of the tube then forced the plasma leaving the pipe to expand. This allowed two different plasmas to be formed, upstream within the tube and downstream, and so the double layer was created at their boundary. This accelerated further argon plasma from the tube into a supersonic beam, creating thrust.
How much thrust? At this point, ESA simply notes that at the same level of fuel efficiency as the main thruster on the SMART-1 mission, the new engine would produce “…many times more thrust at higher powers of up to 100 kW…”
The effect is not dissimilar to a natural phenomenon witnessed by many on Earth, as ESA explains:
“Essentially the concept exploits a natural phenomenon we see taking place in space,” says Dr Roger Walker of ESA’s Advanced Concepts Team. “When the solar wind, a ‘plasma’ of electrified gas released by the Sun, hits the magnetic field of the Earth, it creates a boundary consisting of two plasma layers. Each layer has differing electrical properties and this can accelerate some particles of the solar wind across the boundary, causing them to collide with the Earth’s atmosphere and create the aurora.”
Centauri Dreams‘ take: Now that ESA has confirmed the Australian results, the way is open to begin design studies for larger prototypes. The key to the recent ESA tests was to demonstrate that a double plasma layer could remain stable and thus allow for reliable acceleration of the charged particles for thrust. That it can is heady news and points to new sets of options for missions to the outer planets. We need spacecraft capable of delivering maximum payload without being dwarfed by fuel constraints. Coupling ion efficiency with higher thrust is a welcome and necessary step toward that goal.
This sounds like a reduced-capability version of Dr. Chang-Diaz’s VASIMIR variable specific impulse plasma drive. The ESA version would provide higher thrust at the cost of specific impulse, but VASMIR would continuously vary the Isp so as to match the exhaust velocity to that of the spacecraft. Because of how the rocket equation works, this maximizes efficiency such that the vehicle can either go faster, or use less reaction mass.
Yes, VASIMR seems to offer more, particularly in the way it offers modulated thrust and a great deal of control over the plasma even as maximum power is maintained. I’ve seen this compared to the gear-shift in a car with a standard transmission — thrust decreases and specific impulse increases as the vehicle moves into cruise mode, etc. Chang-Diaz was saying at one point that a VASIMR-equipped vehicle with a 200-MW nuclear power system could deliver a 20 ton payload to Mars in 39 days. Of course, getting a workable reactor in that configuration and dealing with the weight issue is not going to be easy!
nuclear electric ion or plasma engines have been around since the
1950s. Simple high powered nuclear electric versions of them can deliver a specific impulse of up to 300,000 seconds. This results from an exchaust velocity of up to 3,000,000 m/sec which is 1% of light velocity.
This is enough to revolutionize interplanetary propulsion in space.
Tim
tmayes… i was just about to sign off then i read the specifications that you posted for an ion propulsion system! just had to say something.a specific impulse of 300,000 seconds!!! whew,would that EVER be revolutionary visavie propulsion in space!!! thank you very much,your friend george ps sorry if my comments where insufficient but i do hope alot of people will add their thoughts on this important and impressive subject. thank you again g
300,000 Seconds = 5000 Minutes = 83.33 Hrs. Anyway I think Tim has put a (or two) zero(s) by mistake; then the duration had been 8.33 Hrs and 0.83 Hrs, which makes it ~50 Minutes. Now, recent practical developements as I’ve noticed in PP is, of DS4G Engine; they achieved a thrust of 1mN (don’t laugh) till 15 minutes, at ESA. Indeed, quite remarkable, when compared to nothing but straight theory of Plasma Confinement of Dr. Chand-Diaz and Co. The guys at JSC are good at arithmetic, but they hadn’t even published the result of their 2003 test. And as far as, HDLT’s concerned; its indeed very practical plus genuine idea. Relatively.
Vishaque
Specific impulse is the rocket engines exchaust velocity in meters/sec devided by the gravitational constant G of 9.81 m/sec.Electric rocket engines can achieve any exchaust velocity up to the velocity of light.The nuclear electric radiator pipes type photon rocket has exchaust velocity C but 300,000,000 joules of light must be reflected into space by the collimator mirror to deliver 4 newtons of thrust. Advanced ion rocket engines can in actual fact generate an exchaust velocity approaching the velocity of light , but immense amounts of electrical energy are required to accelerate the ion exchaust beam. Often each 1/2 pound of ion engine thrust requires up 100,000 joules of electrical energy to produce it. Also a 100 fold increase in the exchuast velocity for a given mass of acclelerated ions ,requires a 10,000 fold increase in the amount of electrical energy expended to accelerate the ions and so on.
Tiim
Have to make one correction on my comment about nuclear electric photon rocket motors here. 300,000,000 joules of reflected light delivers 2 newtons
of thrust not 4 newtons of thrust.
Indeed, it’s quite relatively sad, to announce that the above two posts have not have any relation to rest posts. Nevertheless, I suspect Tim works works for Draper Labs or similar sort of organization, whose budget has still been deduced, and their employees are not finding solace in simple academic calculation, that were once questions of 4th grade science students.
Sorry Tim.
I’ve been fascinated by the prospect of a more advanced prolusion system (than current ion) that could produce particle exit velocities around 25-50% the speed of light or more. I think about gas centrifuges and mass spectrometers and wonder if a design using powerful superconducting magnets spinning an ionized gas would work. Cascading gas centrifuges skim off only the heaviest isotopes (uranium hexafluoride enrichment). In a similar fashion an advanced drive could only allow particles that reach a certain velocity escape from
a spinning mass of gas. The stronger the magnetic vector B the smaller the radius r of a charge q and mass m would take in spinning mass of charged particles (like a small relativistic hurricane and a disk shaped confinement). Lighter ionized gasses like alpha particles (helium nuclei) would take smaller radii and so would be easier to confine and therefore accelerate in the device. A particle would travel a constant velocity in the device unless acted on by some sort of tangential acceleration. Perhaps some sort of orthogonal magnetic field???? I’m probably crazy. Here’s another geometry, how about a hollow torroid and some sort of syncotronic acceleration??? Particles give off syncotron radiation in the upper atmosphere of the Earth as they travel in a helical path along magnetic field lines. Wouldn’t they have to loose some kinetic energy? How about irradiating then to make them accelerate?? Once the particles reach a nice ridiculous velocity they would be allowed to escape from a small opening in the periphery of the device.
Endless power for deep space exploration
by: David M. Freeman
Abstract:
Antimatter: Magnetic Plasma Ion Engine System:
Can be contained by a magnetic flux, within a timed expansion of the magnetic and gravitational fields in mil. seconds, within a given area of space. A spherical containment vessel is where this process will take place. The use of six magnetic rings around the containment area moving in opposite directions and orbiting the containment will create an artificial gravity field, which can be controlled by the use of a magnetic flux, with in the gravitational field around the antimatter. This will hold the process of heat generation in place around the antimatter core. Shielding around the containment will be used to protect the crew and other personal from both heat and radiation produced during the process. Plasma shielding is the main element in use for this level of protection and control. This Containment must be held within a perfect vacuum in order to allow heat generation to be effective in the creation of Ions at a given rate and speed with in the containment and the injector tubes. These Ions will then be stored in a holding area developed to maintain their rate and speed. This vessel will need to handle temperatures of up to 2,000 degrees (K) with in the inter-containment area. Nitrogen will be used to cool the core of the chamber and keep the antimatter stable. This process will produce an endless supply on Ions for use in the Ships Ion engines. This use of antimatter will pave the way for sub-light engine development in the near future. The on broad computers will be used to control the rate and speed of the Ions being produced by using the flux controller to very the magnetic and gravitational fields with in the chambers core. By speeding up the Ions before entering the engine injectors, high speed can be meet with in minutes in stead of in hours. Most Ion engine designs take a long time, before the thrust will push the spaceship at a rate needed for inter planetary travel. This system will make it possible to change all that for the future. By using Plasma as the catalysis to produce Ions the possibilities are endless as far as speed is concerned. As long as you can maintain a stable environment with in the containment and hold the antimatter in check Then sub-light speed is not out of the question.
This sounds like a great thing in regards to interplanetary non-human transport. Human transport still requires the acceleration be kept below maximum limits, as our physical bodies can only sustain 6-7Gs of acceleration and still remain conscious and even then only for a limited time. Ideally it should retain around or below 4Gs of acceleration force maximum. Unless the new research regarding spinning superconductors producing a stronger than expected gravitational field can be utilized to create a converse artificial anti-gravitational effect so the occupants are unaffected by the external acceleration. Then the star trek like scenario described above might be possible. Check out this article:
http://www.sciencedaily.com/releases/2006/03/060325232140.htm