As the spaceship reached 99.999998 per cent of the speed of light, "hydrogen atoms would seem to reach a staggering 7 teraelectron volts", which for the crew "would be like standing in front of the Large Hadron Collider beam".
humans in the path of this ray would receive a dose of ionising radiation of 10,000 sieverts, and as Bones McCoy would doubtless confirm, the lethal dose is 6 sieverts. The result? Death in one second.
The spacecraft's structure would do little to mitigate the effects of the killer hydrogen. Edelstein "calculates that a 10-centimetre-thick layer of aluminium would absorb less than 1 per cent of the energy", and the intense doses of radiation would damage the ship's structure and fry its electronics.
As noted in the Bussard ramjet work, the hydrogen in interstellar space are positively charged ions.
Having an electrostatic ion scoop or electrostatic shield could either deflect or collect hydrogen ions.
It should be noted that a civilization that can make a ship go very near light speed would definitely have fully mature molecular nanotechnology.
Also, a spaceship does not have to be one solid mass. You can a fleet of components that act as one ship. Using molecular nanotechnology and powerful superconducting wires and magnets would provide several options and configurations.
A cloud or shell or web of molecular nanotechnology dust can be held in front the main ship. A leading edge which could be several astronomical units out in front of the main ship could be for sensing, colliding, blocking or collecting hydrogen ions or particles or any obstacle that could not be detected by the advanced radar and sensing systems.
If the leading cloud cannot process the obstacle then a warning would be transmitted back and the main ship would either change its course and/or shape shift to create an opening to allow the threat to pass through and not hit anything. The cloud can be held in place magnetically and/or with molecular nanotechnology connections (like utility fog).
The light speed warning would have to have sufficient difference with the near light speed travel to still provide time to respond. It is 500 seconds for light to go from the Earth to the Sun (1 AU). So 99% of lightspeed would provide about 5 seconds to react if the warning systems were 1 AU out in front. With time dilation effects, the warning systems will have to be farther forward.
I think that with molecular nanotechnology and powerful superconductors of 100 tesla or more that would definitely be available to a civilization that can send spaceships to near light speed that the ions would not require evasion. We can guide high speed ions now. Having a configurable particle guiding system up front that was both light and adaptable seems well within the capabilities of equivalent technology to near light speed travel. The components of the cloud can generate any electrical or magnetic field that is needed and in whatever configuration is needed.
So the lessons are
1. Do not design your near light speed spaceship in the shape or form of a chemical rocket (ie one big cone or cylinder)
2. Do not use low tech "blocks of aluminum" as your radiation shielding for an interstellar spaceship. Edelsteins 10 centimeter block of aluminum
3. If you are going to look at projected designs of a near light speed spaceship then do a better assessment at where the other capabilities will be at when dealing with the "threats"
4. Also, if you have to design big to be safe then design big