When the Tunguska event occurred almost nobody knew about it for a long afterwards because it occurred in the middle of nowhere, aka central Siberia. Risks might be minimized by launching this engine from a similarly obscure location, with plenty of uninhabited space in the direction of escape trajectory. Albeit if the engine, God forbid, explodes at a high altitude then the radioactive material could scatter over the upper atmosphere and still rain down upon populated centers despite an obscure launch point and trajectory. The commentator said that there can only be a disaster if the nuclear engine is active when it is atmosphere. As I recall many scientists protested when the US launched the Cassini-Huygens nuclear powered probe (which is now exploring Saturn and its moons) was to be launched even though there is presumably no good reason for the nuclear engine to have been activated before it reached orbit. Hence, I am not convinced that you achieve full safety simply by leaving the nuclear engine inactive until it reaches orbit. There are good reasons to feel nervous about this, but it is another large step forward towards Mars. The US may spend a lot more money on space than anyone else, but the US government is in general especially inefficient for an first world government. So in terms of actual contribution, ours likely amounts to less than 80%.

I believe the intention is for the nuclear engine to operate only in space, with the launch from the ground using conventional rocket fuel. If this is the case then the nuclear engine could be designed to survive reentry and impact on earth intact, with no chance of radiation leaks. The problem with conventional rockets is that although they can generate lots of thrust they don't operate very long because of the rate they burn fuel. Conventional rockets are efficient for launching from earth but for long distance space travel they will only burn for minutes when better system will operate for hours or days. Unlike what you see in star trek a flight to Mars with a conventional rocket would mean a few minutes of rocket burn and then coasting 99% of the way till you flip the rocket over and fire the rockets backwards to slow down to enter Mars orbit. A nuclear engine could run most of the way which means overall much higher speed is achieved and some semblence of gravity is artificially created by constant acceleration and decelleration all the way there.

This is a great thing from russia, it is very safe having two way thrust. when the craft reaches the outer space the nuclear powered engines can be given a role to play in outer space. There is no chance of getting radio active material with zero gravity

I love this news site.

They should develope Warp Drive! Then I can get from Yalta to Simferopol faster!!

Actually Petrenko there is already plenty of radiation in space from deep space (cosmic rays stopped by our Magnetic Field) and of course the Solar wind. The shielding required for the nuclear propulsion could be designed in such a way that the crew could use it to shield them from the sun during times of extreme solar activity.

What people fail to realize is that nearly 2000 nuclear bombs have been detonated on Earth. Just as tests. Very few since the nuclear test ban treaty however. And now people seem to think a single nuke exploding would have incredibly massive consequences or whatever. And it's true, a nuke dropped in war would be a truly horrible terrible thing that could escalate into a nuclear war that bombs much of the human race into a new radioactive stone age. But a nuke exploding in a failed attempt to launch a spacecraft is worth the risk.
But I think sending a nuclear rocket to Mars would be a waste and not worth the risk. We can get to Mars with conventional rockets within a year. Save the nuclear rocket for a journey to Europa or some other promising water bearing moon. But that is many decades in the future.