At what stages is the development of a nuclear jet engine?

Question

Space

There is an opinion that a nuclear jet engine can reduce the flight time to Mars to 1 month.
However, the Mars 500 experiment, scientific press articles on the effects of radiation during an 8-month human flight, and other studies point to space agencies' plans to use existing engines for future Martian missions. About the prospect of a flight within 1 month in one direction does not go.
If you know, at what stages is the development of such an engine? What problems arise in its design? Negative sides? Why is such a question rarely raised on asterresources?

Answer 1

Nuclear rocket engine has been developed for a long time. There are two working prototypes: the American NERVA engine, and the Soviet RD-0410. Of course, these engines will be able to reduce the time of flight to Mars, but even with them, the flight will take more than one month. Why are these engines not being used? Most likely, because humanity practically does not get out of the Earth's orbit, and using a nuclear engine to put a spacecraft into orbit is harmful to the environment due to its radioactive exhaust. Perhaps if we regularly flew at least to the Moon, then there would be a demand for nuclear engines, and no one would start mass production of such engines for the sake of one mission planned in the distant future.

Answer 2

There has been a race of powers since the early 60s. In the USSR, funding was more modest, since the government considered these technologies only in terms of political use to put pressure on the United States. But the tests were carried out, and very successfully. They say Kurchatov was ultimately against it, since the massive use of such engines would mean atmospheric pollution. The technical problem was the search for materials and structures that can withstand a temperature difference of ~3000 degrees. But our design bureaus also found solutions overseas, although perestroika began here , and all this turned out to be unnecessary.
The danger is the accident of the ship in the Earth's atmosphere, if it is equipped with such an engine. Possible radioactive fallout, and residual radiation for a long time can let you know.
As for the flight speed, I think the payload is more important, and the larger it is, the less likely it is that the flight will be "lightning fast". A good article on YARD is here .

Answer 3

During the Cold War, atomolet projects were developed (aircraft capable of flying from the heat generated by atomic engines). In the USSR, it was possible to create a fairly compact reactor that could easily fit in the fuselage. But there were 2 "small" problems:
1) Exhaust of radioactive substances into the atmosphere (besides, the plane settled for a week in a special bunker);
2) A sufficient amount of anti-radiation protection cannot be put on a flying machine. A lot of lead can be poured onto a submarine or ship, but there are problems with an airplane and a rocket. The crews of those planes received a good dose and many of them died (if not all).
So the problem is not so much in the engine as in the protection of the crew. No one will deliver lead into orbit, and a layer of foil will not save a person.