DDE

Radiation problem is severely overblown. While I don't quite trust,Zubrin's assessment, data from Curiosity shows that an unshielded pressurized habitat is enough to keep the dose within ESA tolerances on a regular Hohmann. If the crash of the Soviet US-A radar sat is of any indication, a local radiation containment situation. The Soviets had given it thought, though; while the Tu-95LAL/Tu-141 only had a directional shadow shield for its reactor, when designing An-22PLO they decided to try and add a reactor jettison and recovery system. It would be a radiation hazard for some time anyway, but no fallout. Finally, we have proposals from the heydays of NERVA to just drop the damned thing into the ocean, claiming that no shielding is required for the reactor to reenter and be recovered for reuse because it's already stupidly durable.

Yeah, but I haven't seen good info on how well it scales down. There are very few reasons to use it over current electrostatic thrusters. I mean, do you really want to deal with liquid hydrogen or liquid lithium when compressed xenon does the job well enough? Not to mention the ISPs can be forced through the roof (~12000 sec). Also, VASIMR isn't being developed for probes. It's touted as a manned interplanetary craft engine, possibly because it overcomes the inherent thrust limitations of ion thrusters (although it's not fully clear why an array of a few thousand of them is off the table).

VASIMR is not an ion thruster, it's a wholly different family, electromagnetic (pondermotive, to be precise) as opposed to electrostatic. No, the magnets aren't the element accelerating remass in a Hall-effect thruster. Therefore your appeal to Dawn is invalid. Efficiency is always a big deal, because the requirement for a reactor results in your propulsion system mass bloating; sure, you can have high ISP, but the hit to the ship's mass ratio still results in your dV tanking, pun intended. No, there appears to be no way to power a VASIMR with solar panels; or, if there is, it is even heavier than a reactor.

Lower efficiency (50% vs 70%), requires superconducting magnets and a nuclear power plant that isn't anywhere near the drawing boards and is likely impossible. http://spacenews.com/vasimr-hoax/ Remember those 'uses' of government financing? It sounds very much like one. Just when I can't watch a T-foot vid...

Furthermore, most rocket engines cannot throttle down as easily, and cannot be fired more than once. And then we have ullage and lOx boil-off. We have it really easy in KSP.

Simple. That is improper use of government money. At best the Central Bank can take them as very low-interest deposits.

It's not like the US Armed Forces have to do the same. If you don't spend it this quarter, next quarter they'll cut your budget!

Ah. Like MIT's ARC reactor? Well, I imagine it wouldn't have gamma-decay materials, so it wouldn't need serious shielding. I dunno, but as a Russian, I know how desperation to throw government funding on some stupid idea looks like. Hence titanium instead of steel.

Pff. Try SCP-022-J. Hm, I realize many designs end up having a fission reactor for start-up, but why would an aircraft have it? Oh, come on, since when except people who know basic science care about thermodynamics?

Mainstream media tries to science again. Results predictable. I mean, it's pretty much the same people who a) say VASIMR is worthwhile and b) call it a warp drive.

Have you ever sold a spacecraft to the Queen of Naboo? Well, it's still missing blackjack and hookers.

And that's still slower than expected. Not to mention those goddamned hydrogen tanks, which will likely be designed as close to structural limits as possible...

That's a good start. Missiles, drones and Autonomous Kill Vehicles should be kept onboard thin-skin carriers. The best propulsion system for a "battleship" is obviously the Orion nuclear pulse drive. Immediately we get a worked historical example - 3 x 127 mm, a few hundred city-buster reentry vehicles... I also suggest Niven-Purnelle-style x-ray laser "fascii" pumped by the drive explosions, alongside multiple radial railgun mounts as rapid-fire weapons for close range (100-1000 km) and area denial barrages; a mixture of CASABA-HOWITZER shaped nuclear charges and high-frequency lasers for inner point defense.

Doubtful. It's need a whole lot more dV. So they're half a century behind the Soviet Union. Again.

Nuclear-powered lighter-aboard/container icebreaker-class ship? Done. https://en.wikipedia.org/wiki/Sevmorput

Well, I wasn't quoting you, was I? I'm just all too aware of the high risk of slipping into this. For instance, when I developed five factions, one's from Earth, one are Earth rogues who signed a treaty on Kapteyn b, one comes from a halo subdwarf, one suffer from a 3.12 time dilation factor due to a Kerr-metric black hole primary, and the incomplete one get a loose binary sun and crimson oceans of ammonia-contaminated CS2.

http://www.bbc.com/future/story/20160713-could-this-be-the-first-nuclear-powered-airliner Aside from multiple nuclear physics errors like this There's this Whiskey Tango Foxtrot?

Well, I guess it's more thoroughly discussed in Ignition! and Things I Will Never Work With. Apparently, though, they also tested chlorine trifluoride:

Your post is being pretty damned chauvinist by assuming that "life" necessarily exists in Earth-like conditions.

Wasn't it the one they considered shooting in order to safely disable?

'fraid there're faster ones. Can't beat Mach 25. I'll make a dastardly mention, then.

Can't go wrong with anything from the Apollo 13 OST.

At this point, I'm tempted to drop H2 and bring up H, which is implied to have been one of innovations of Project SUNTAN. Sure, it requires supercooled tungsten matrices to store, but it should be a lot more compact.

Size creep. Few nations build "cruisers" and "destroyers", but then you have pretty nasty "frigates" being rolled out instead. Right now a littoral combatant can have 2000 km effective range on her cruise missiles. OP, care to say whether you're talking about a battleship or a warship in general, and define "battleship"?

Dead weight. It's what kills jet-assisted orbital SSTOs and it's going to wreck the life of a suborbital SSTO as well, because the airbreathers would be off and the wings wouldn't be providing significant lift for much of the acceleration stage.