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Comment: Re:It is (Score 1) 123

by Rei (#49378241) Attached to: SpaceX's New Combustion Technologies

Wow, this is great to hear - I'd never heard of you guys before. :)

And looking at your site, I like what you're doing even more - direct 3d printed aerospikes? Pretty darn cool. What sort of 3d printing tech are you using? Have you looked into the new hybrid laser spraying / CNC system that's out there (I forget the manufacturer)? The use of high velocity dust as source material gives you almost limitless material flexibility and improved physical properties that you can't get out of plain laser sintering, and the combination with CNC yields fast total part turnaround times.

And you're working on turbopump alternatives? Geez, you're playing with all of my favorite things here.... ;)

What sort of launch are you all looking at - is this ground launched (and if so, do you have a near-equatorial site) or air launched? I'd love to see more details about your rockets, what sort of ISP figures you're getting so far, how you're manufacturing your tanks, and on and on. But I guess I'll have to wait just like everyone else ;)

I wish you lots of success! And even if you don't make it, at the very least you'll have added a ton of practical research to the world :)

Comment: Re:Wrong Focus (Score 1) 123

by Rei (#49378083) Attached to: SpaceX's New Combustion Technologies

Note that it's technically possible to have something like this with a slow reactor; you could for example use steam as a moderator, which will transmit a reasonable proportion of near infrared through it (the hotter you can run your fuel particles, the better transmission you'll get). But not only will you lose some light, but just the simple act of neutron moderation is a very heat-intensive process, meaning big radiators if you want big power (not to mention that the moderator itself for such a slow reactor is also far heavier than the core). The whole point of my variant is to avoid the moderator and avoid the ship having to ever capture anything but incident heat lost due to generation, transmission, reflection, etc losses.

One possibility for a slow reactor, albeit only directly applicable to the rocket mode above, is to have your propellant be your moderator, absorbing both IR and moderating fast neutrons. The fact that it's heating then becomes irrelevant (actually an advantage), since you're dumping it out the nozzle for thrust. If one wanted mission flexibility in such a scenario you could have such a moderator-ejecting rocket mode used to get to orbit, and then switch to retaining the moderator once in orbit and cooling it instead in order to make use of the fission fragment operating mode.

But a fast reactor would obviously be highly preferable so you don't have to worry about a moderator at all. :) I'm just pointing the above out because slow reactor versions have already been simulated.

Comment: Re:Wrong Focus (Score 1) 123

by Rei (#49378039) Attached to: SpaceX's New Combustion Technologies

Wait a minute, no, I entered it right into the calculator the first time around. Argh, this interface is confusing. Radiative equilibrium for Tunsten at its melting point 3300C according to the calculator is 92MW/m. A "cool" 1200C radiative temperature according to the calculator 2,6MW/m. According to the calculator, 10kW/m is about 380C.

Comment: Re:So What (Score 2) 298

by hey! (#49376609) Attached to: Poverty May Affect the Growth of Children's Brains

It is your choice to make your eventual obliteration the focus of your life. That's something you can either try to change (good luck with that), or it's something you can choose to accept. But choosing to accept that doesn't mean you have to sit around being miserable and resentful while you wait for the Grim Reaper. The world is only as cold and hard as the things in it you choose to focus on. There's also more wondrous and amazing and even funny things in the world than you an get around to thinking about in a lifetime.

It's like summer vacation when you're in school. You only get ten weeks or so of it, not nearly enough to get to all the things you want to do. And there are some people who will react to that by spending the whole time from day 1 unhappy about going back to school. What a waste of existence! But that's definitely a choice open to you.

Imagine your last few seconds of consciousness before you die. How would you like to spend them? Being angry? Sad? I think that's a waste of precious time. I'd like to have someone I love very much tell me a very funny joke.

Comment: Re:So What (Score 1) 298

by hey! (#49376541) Attached to: Poverty May Affect the Growth of Children's Brains

No, we all make the choice of the kind of world we want -- or maybe it'd be better to say the kind of world we can live with. It just so happens that some people can live with a world that they don't like very much, so long as that doesn't demand very much of them.

Anyone can by choice have an immense effect on the world around them. Maybe they can't change the *whole* world very noticeably, but they can transform their own neighborhood.

Comment: Re:Wrong Focus (Score 1) 123

by Rei (#49375327) Attached to: SpaceX's New Combustion Technologies

The cornerstone of it is the dusty fission fragment rocket, so I'd start there. Another key aspect is the use of a accelerator-driven subcritical fast reactor rather than a critical slow reactor. Lastly it's a variant of a nuclear lightbulb, albeit (as mentioned) without the primary drawbacks of them (containment and radiation blackening of the chamber blocking the light). This latter aspect is due to the spectrum changes of fused silica (I can't find a paper on short notice that shows the IR spectrum, but you can see that for most types of fused silica / fused quartz, there's little loss of transmission on the red side of the spectrum; this holds true but is even more pronounced in the IR range).

Comment: Re:Nonsense (Score 1) 1029

by hey! (#49374839) Attached to: Apple's Tim Cook Calls Out "Religious Freedom" Laws As Discriminatory

Oh, yeah. The rational actor theory. But by the same postulates that underly that theory there should be no human being who eats unhealthy, boozes or gambles excessively, or picks fights he obviously can't win.

I have an alternative theory which states that going by actual behavior most people discount their future welfare to zero when there's an immediate reward, even a trivial one. It's almost impossible to resist an immediate burst of pleasure a nasty habit's got you hooked, whether it's a relaxing smoke or that glow of self-righteousness you get when you act on your bigotry.

People will literally kill themselves for a little short-term reward. Forgoing a little profit is nothing compared to that. If you look at places where segregation was historically sanctioned, you'll see you're entirely right: it's economically irrational. That didn't stop people from doing it.

Committees have become so important nowadays that subcommittees have to be appointed to do the work.

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