Three of my Icarus Interstellar colleagues, Kelvin Long, Richard Obousy and Tabitha Smith, are attending the Nuclear & Emerging Technologies for Space conference. Lots of innovative engineering for nuclear power and propulsion – new energy conversion systems that turn radioisotopic heat (usually from Pu-238) into electrical power, and new designs for space-capable fission-reactors.
Plus some alternative technological work is being reported on. At least two Icarus Interstellar presentations, one with my name on it as co-author (I did a lot of background research for it, but Rich and Kelvin did the writing and Power-Pointing.) The second covers ignition of fusion via antimatter. Tabitha Smith is our resident nucleonics expert and is very keen to see a revival of nuclear thermal propulsion for space applications. Another concept – which I didn’t see an abstract for – is the fission-fragment rocket, which also has potential as an advanced fission reactor.
Then there’s the real fringe, but with solid experimental work to back it. Low-Energy Nuclear Reactions (misnamed “cold fusion”) were represented by two papers, one which discussed the physics and another which described a new “cold fusion” radiothermal heat-source. LENRs work by funky solid-state physics which confines deuterons in much closer proximity than they would ever experience in free states, like gas or plasma. This allows fusion tunnelling probabilities to go way, way up and so-called pycnonuclear reactions to occur. Small particles of palladium or platinum can soak up large amounts of deuterium gas and, once suitably “loaded”, in the right conditions, emit large amounts of heat for indefinite periods of time. Xiaoling Yang & George Miley’s battery produces about ~350 W/kg – a bit less than Pu-238′s 550 W/kg, but without the very nasty radiation. Not as power dense as a fission reactor, but enough to power space-probes. Given better thermoelectrics (also presented on at the conference) that heat might produce ~50 W/kg of electricity to power a probe’s electronics or even a low-thrust engine.
What kind of engine though? The presentation by Harold (“Sonny”) White and Paul March presents a propellantless drive, which they dub the Quantum Vacuum Plasma Thuster or Q-Thruster. It works… in test-rigs. The idea is simple – it uses the virtual particles of the vacuum to create an “ion wind” for push. Thus no onboard reaction mass required. Whether it will work in space is something they’re seeking to test in an orbital payload in the near future. Presently they quote the Q-Thruster making 0.1 N per kW of power, massing about 10 kg per kW. That’s pretty good compared to the current generation of ion-driven probes like “Dawn”, currently orbiting Vesta, which turns 2.6 kW(e) into 0.092 N thrust at maximum jet-power. Better still, there’s no propellant involved. No tanks, no piping, no flow-controls. Given power, a Q-thruster will push and push…
Imagine a nano-satellite, about 10 kg mass. Its power source is 3 kg of Miley battery – thus 100 W(e) to power the Q-thruster, and 50 W(e) for the probe’s instruments. That gives it a push of 0.01 N. A mass of 10 kg, that means ~4 kg of power/propulsion and 6 kg of instruments. The acceleration is ~0.001 m/s2, which sounds low, but isn’t really. “Dawn”, for comparison, masses ~1,290 kg at injection into deep-space and yet gets a top thrust of 0.092 N. “Dawn” also holds 450 kg of Xenon propellant in its tank, which it would exhaust in ~4.65 years at top thrust. Its maximum acceleration is just ~7E-5 m/s2, or 14 times less than our nanosat.
How long would a Miley LENR battery last? If 0.1 of the mass is deuterium (palladium really does soak it up) and the energy is from D+D -> He4 fusion (as suggested), then 100,000,000,000 seconds of heat is available at 350 W/kg. About ~3,170 years. How far would it go in that time at 0.001 m/s2 acceleration? By that stage it has reached 1/3 lightspeed (100 million m/s) and travelled over 520 light-years. In theory it could go into orbit around Alpha Centauri in 404 years, or fly past in 286 years at 0.03 c. Closer to home it would whizz past Pluto in a bit over a year.
Enough speculation for one night. Ciao!