A list of links that pulls together some ideas from recent posts.
This post started with the idea of safety. Along that line of thinking, one should like to use the Dragon's safety features in case of a massive failure of the main rocket package. The Dragon can fly off to safety in case of a major failure mode.
At the moment though, I am having second thoughts. Actually, I am confused. I thought that it was necessary to always have a thrust ratio of (the vehicle's weight to thrust) greater than one. This is what led to the Mea culpa redux post. That's because I noticed that the NTR in Dewar's book doesn't have a ratio greater than one.
So, I played around with the idea of using multiple engines, ( an idea obtained from the topmost link above ) which led to the idea of an engine out capability for this NTR configuration. For example, if you were to lose an engine on the Falcon 9, it could still get to orbit. But with a single engine in this NTR rocket, you would not be able to get to orbit if it failed. Let's say that one uses 3 smaller engines for the NTR instead. With a loss of one, perhaps you could still get to orbit. That's an important safety feature. You can control events even if you can't get to orbit. The nuclear reactor need not go down where you don't want it to.
But to do this, you have to sacrifice something. In this case, you'd have to sacrifice the Dragon and cut the weight drastically. Maybe you can't have everything, and certain priorities have to be chosen. A greater risk for the crew and a lower risk for everybody else.
Perhaps the radiation issue can go with crew safety thoughts that I've been having. At what point does the insistence upon complete safety become counter productive? Has society become phobic about radiation? A comparison with the psychology of phobias may be helpful in illustrating the irrational fears in general and the fear of radiation in particular. I'm thinking of the movie Vertigo as an example.
The character played by Jimmy Stewart was handicapped by his fear of heights. It made it impossible for his continuance in his job as a police officer and ended the career that he expected to have. As the character Scotty's life was ruined by his disability, so could it be that the fear of radiation in society has ruined our capability to use this source of energy to advance society to a higher level? Scotty's fear was irrational as the video below illustrates. He is in no danger as he looks out the window, but he faints from fright.
In comparison with a phobic reaction as illustrated above, can it be truly said that this culture has developed a radiation phobia which is harming our interests? How much of a real risk is involved in the nuclear power industry? Hasn't it all been overblown to the extent that it surpasses all real risks that would taken if the technology was developed to its full potential?
In other words, would it be worth it to society to overcome this fear and move forward? There may be no real good alternatives. Not for society as a whole nor the space program in particular.
Update:
The J-2 rocket on the S-IVB third stage of the Saturn V rocket was capable of 220k lbs thrust. There was only one of these engines onboard. That means that you don't need a thrust weight ratio greater than 1 for the entire trip to orbit. Since the S-IVB carried not only itself, but also 100k lbs to go to the moon and back, it was lifting far in excess of its own weight.
What that means is that with a 3 engine NTR, you could probably still get to orbit in the event of an engine failure. The only question now is can you get the weight down and make it all work?
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