I'm a bit disappointed that nobody so far has reacted to the second part
of my reply to Anthony (repeated below): That near-term usefully faster
space transport will probably need to offload the mass of the power
generating machinery to combine high-enough energy propulsion (on the
rough order of 2000 seconds Isp) with high enough thrust-to-weight and
thus acceleration (on the rough order of one km/s per day) to allow
reducing transit times to, say, Mars, from months down to weeks. Goes
without saying? Too nuts to even react to?
Or, just not something we've been thinking about? If so, it's time that
started changing. Anthony is 100% correct that conventional chemical
rockets can take us only so far (even if he is a bit more pessimistic
than I about just how far that might be.) The time to start planning
how we move past that point within this generation is now.
Henry
On 8/22/2019 10:09 PM, Henry Vanderbilt wrote:
Yes, agreed, in the long run we must get past conventional rockets to something orders of magnitude more energetic.
Of course the common problem with higher-energy propulsion is that generating and handling that higher energy without melting takes too much mass, resulting in what I am inclined to call "the mousefart thrust problem." The power supply masses far too much so it takes too long to get up to speed. And intermediate cases, like nuke thermal rockets, just don't gain enough Isp to make up for the reactor mass. Yeah, you can get to Mars in four or five months - but you can do that with chemical rockets also, given depots and local propellant spent profligately - which would likely be cheaper overall than developing and fielding the thermal-rocket reactors.
NSWR is an interesting attempt to combine high energy and high thrust-to-weight in an onboard nuclear powerplant. Practical? Who knows. I'll happily watch the tests - via video, from a LONG way off.
I tend to think that the most promising near-term approaches to usefully-better-than-chemrocks space transport involve offloading as much of the high-energy machinery as possible to fixed power-beaming stations at either end of high-traffic routes. That way you can just throw mass at gaining the efficiencies needed so your power generating and beaming machinery doesn't melt. The two power transmission methods I currently like are laser array, and neutral particle beam. Lasers you can convert to electricity then use in electric thrusters, with useful fast-transport performance at ship-end power-handling-to-mass ratios only (only!) a half order-of-magnitude better than current SOTA. (It may also be possible to use laser beams to directly energize reaction mass in other-than-material containment, but that has a whole lot lower TRL.)
Neutral particle beams I only last spring became aware of as an option - I gather the ship needs to apply a charge to the approaching beam, then magsail on it - others can no doubt shed much more light on the concept (so to speak).
My bottom line though is that self-contained ships that can zoom around like the Millenium Falcon require several (human) generations more advanced low-mass power-handling than an external beam-powered transport net. Subway cars in space, if you will - far less sexy. But we can build them a whole lot sooner, within this generation, and we should, IMHO.
(RE your opening question, FWIW, I've never heard of any NSWR-specific nuclear experiments. As you say, this isn't the fifties, there is no known funded program, and I would think it'd be really hard to do a proof-of-concept on that on any likely discretionary budget.)
Henry
On 8/22/2019 8:01 PM, anthony@xxxxxxxxxxx wrote:
Have any experiments been conducted using Zubrin’s nuclear salt-water rocket (NSWR) concept to verify the design or has it fallen into the ”anything that’s nuclear” black hole?
The cost to even get to the experimental stage wouldn’t be trivial seeing this isn’t the 50s. I subscribe to the model that if we are going to accomplish anything *really* significant in space flight in the next generation, we have to get the known chemical reaction approach monkey off our back. That’s just my opinion. The Zubrin citation is only an example BTW.
I’d like to hear some thoughts about this.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
