[AR] Nuclear Hydrogen Thruster
- From: Craig Fink <webegood@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 9 Jun 2018 12:06:57 -0500
New Horizon Probe propulsion design was driven by History, looking into the
past when NASA had Rocket Scientist willing to take a chance and figure out
an interplanetary propulsion system. But what if New Horizon had not been
restricted to History, but was allowed to look forward into the future .
On Thu, Jun 7, 2018 at 10:17 AM Nels Anderson <nels.anderson@xxxxxxx> wrote:
On 2018-06-07 10:42 AM, Craig Fink wrote:
I wish they had put one of those one the New Horizons probe, low
thrust mid-course corrections, hi thrust planetary burns. Sounds like
it was made for planetary probes.
> On Thu, Jun 7, 2018 at 9:30 AM Henry Vanderbilt
> <hvanderbilt@xxxxxxxxxxxxxx <
mailto:hvanderbilt@xxxxxxxxxxxxxx>>
wrote:
Maybe it would be better to heat the H2
resistively, though that is not nearly so sexy. And one cannot help
noting that resistojet's appeal is limited to a few special situations.
Your right, what if NASA had put a resistojet onboard, what whould it
look like?
First, the power source for the arc jet, has to be nuclear as that was the
chosen power source for New Horizons. The engine must use on average of
less than 200 watts of power of nuclear origin.
Propellant, Hydrogen by far the best propellant for the job. Hydrogen is
"Shelf Stable" at 3 K temperatures of deep space, Hydrazine is not and
requires temperature control of the entire system to keep it from freezing.
Passive "Sun Shield" is all that is required to stop thermal radiation
heating. Space is the perfect Dewar so the pressure in the Hydrogen tank
can be kept very low (vapor pressure of Hydrogen at the boiling point of
Helium), resulting in very light weight storage tank, unlike the much
heavier high pressure tank and pressurization system of the Hydrazine.
New Horizion's mission profile requires 2 types of burns, one for mid
course corrections, one for planetary slingshots.
Mid-course correction type burns being the preferred mode of running, a
pulsed arc-jet that can be repeated for years and years. Extremely high
ISP, low thrust, able to run on 100 watts or less supplied the nuclear
power supply. Sounds like a fun design point for the engine.
Planetary Slingshot type burn being the short large thrust mode deep within
gravity wells. Low ISP (300 to 600) high thrust, blow-down mode so to speak
using an electric powered centrifugal compressor to bring the Hydrogen
propellant up to pressure (variable 100 to 10,000 psi). Two design points
for one engine, sounds like fun.
Battery, yes this engine is going to have a "Shelf Stable" battery to make
the trickle charger useful for the pulse arc-jet and power the pump. Shelf
Stable at 3 K temperatures, superconductor storage works great at Liquid
Hydrogen temperatures, so the battery goes in the the Propellant tank, that
works.
Battery capacity, may as well make this extremely light weight low pressure
hydrogen tank do double duty by choosing the right material to build it, to
enhance and reduce the amount of superconductor required to size the
battery. Fe, hydrogen annealed Iron tank, metal of choice, to increase the
inductance of the superconductor loop of wire attached to the inside of the
Hydrogen Tank.
Pulse Arc-Jet pressure tank, sized for one pulse of the Mid-course
correction. Liquid Hydrogen is pumped into the extremely small 10,000 (or
more) psi engine tank. This tank is heated by the nuclear battery, over
time, bringing it up to pressure ready for the Arc-Jet pulse where all the
energy stored in the superconducting loop is routed thru the Arc-Jet
sending the 10,000 psi extremely hot Hydrogen on its way. Not sure exactly
what the ISP of this engine would be, but I suspect it might be rather high.
Planetary Slingshot, blow-down mode. The Arc-Jet is turned off, all the
energy of the superconducting storage loop is needed to power the Electric
pump to bring the Liquid Hydrogen up to engine pressures. The valves of the
10,000 psi arc-jet header tank are left open, this mode is running on pump
pressure and thermal mass heating supplied by the Nuclear Battery. Yes, may
as well make that heavy Nuclear Battery do double duty, just like the Iron
Hydrogen tank. Temperatures and pressure are much lower, but thrust is much
higher and can be sustained until the Nuclear Battery temperature drops to
low.
Now that would be a sexy engine for deep space missions like New Horizon.
Craig Fink
WeBeGood@xxxxxxxxx
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