NASA looks at reviving atomic rocket program

[hunter]

David Szondy August 10, 2017

When the first manned mission to Mars sets out, it may be on the tail of an atomic rocket engine. The Space Race vintage technology could have a renaissance at NASA after the space agency's Marshall Space Flight Center in Huntsville, Alabama signed a contract with BWXT Nuclear Energy to develop updated Nuclear Thermal Propulsion (NTP) concepts and new fuel elements to power them.

The Apollo missions to the Moon demonstrated many things. They showcased human ingenuity, determination, and courage. They proved what American engineering and industry could accomplish in short order when let loose on a goal and demonstrated that humankind need no longer be confined to a single planet.

Unfortunately, it also showed the fact that chemical rockets, even at the dawn of the conquest of space, had reached their technical limits. True, they could send astronauts to the Moon, but only by using a disposable rocket the size of a skyscraper of which only a capsule with the roominess of an SUV returned. And even this was in no shape for anything except a museum.

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http://newatlas.com/nasa-atomic-rocket/50857/

Ah, like the Discovery One of Kubrick and Clarke's 2001



Or maybe you'd prefer the electric model, which requires the large cooling fins for the nuclear electric power plant.

[krispos42]

1. It's inevitable, really

Energy per unit mass is critical for spaceflight, and chemical reactions can't cut the mustard.

Solar sails and solar cells give you a good energy-to-mass ratio but the total energy isn't very much.


We're probably going to have to build some sort of nuclear-powered "tugboat" in orbit that we would attach payloads to (using chemical rockets) then do the in-system travel with the tugboat. Maybe by superheating water and blasting it out the back, or something similar. Maybe mercury would be better; very high material density (less storage area needed per unit mass), low specific heat (easier to boil), reasonable boiling temperature (674°F), and lord knows we don't want it on Earth.

Get the mercury vapor hot and under high pressure from the nuclear reactor (probably by using the mercury as a cooling fluid) then just vent it out through a conventional-looking rocket engine bell. Maybe put some sort of electromagnetic coilgun type thing after the exhaust to increase the velocity.

It would be a pain in the ass to built a nuclear reactor to power this tugboat, but once built it could serve for hundreds of missions, enabling mass transit for us. Being able to achieve .01g acceleration for months on end would be spectacular.

If it's, say 70 million miles to Mars each way (distance traveled on a trajectory there), then .01g would give you, let's see...

D=½at²

35 million miles = 184.8 billion feet (halfway point)
a = .322 ft/s²

t² = 2*D / (.322)
t² = 369.6 billion /.322
t² = 1.148 trillion seconds²
t= 1.072 million seconds = 17,856 minutes = 298 hours = just under 12½ days.

So, 12½ days acceleration, flip ship, 12½ deceleration. 25 days total.


Do the same math for Jupiter, let's see... 4.2 AU from us equals 390 million miles, say. Halfway is 195 million miles, or 2.062 trillion feet.

Doing the same math as above...

t² = 2*D / (.322)
t² = 4.125 trillion /.322
t² = 12.81 trillion seconds²
t = 3.579 million seconds = 59651 minutes = 994 hours = 41½ days.

Times two for total trip, 83 days. 12 weeks.

[eppur_se_muova]

2. Nuclear to electricity to VASIMR would be more efficient ...

The supposed 200 megawatt engine could reduce the duration of flight from Earth to Jupiter or Saturn from six years to fourteen months, and Mars from 6 months to 39 days.[26]

https://en.wikipedia.org/wiki/Ion_thruster#VASIMR

Mercury was originally used for ion thrusters, but ditched in favor of xenon. Turns out it's hard to control the flow of mercury, and contamination of the spacecraft also becomes a problem.