Oddity

[discord]

nemo: that is actually not a good thing in a few very specific situations, specifically if it gets INSIDE your body, on the subject of U235 decay.

do note, i am NOT a nuke scare monger, that irrational fear needs to go out in the trash with other irrational falsehoods like santaclaus, DHMO scare(even if that one at least is funny), the absurd idea that guns are silent just because you do not get ruptured eardrums in the cinema or for that matter the belief in the logical impossibility of an all loving all knowing and all powerful old man sitting on some cloud telling people to not enjoy sex or perfectly tasty and safe food(and if you believe in another equally bizarre all powerful being the first kind of believers will want to kill you, or if you just have a different idea of what the all powerful being is telling us, well someone wants you dead for that too.).

why can't people just accept reality?

[Charlie]

Statements about religion aside, all that breeds is hatred and contempt.

Whats wrong with a "falsehood" like Santa? He indirectly brings hope and happiness to millions, I can live with the fact he isn`t around. Even when I knew the Santa wasn`t real, I played along for the sake of my sister.

Should the day come when I have children, I will lie about Santa. Why? Because I would want them to look forward to the day when a magical jolly fat man in a red suit brings them the presents they wanted. Shouldn`t everyone get a chance to be happy? Even for a little bit? Even if it`s not real, it`s real enough for the children.

[Turrosh Mak]

Whats wrong with a "falsehood" like Santa?

I think Terry Pratchett said it best in this speech by Death in the Hogfather. Humans need fantasy to be human.

[Nemo]

nemo: that is actually not a good thing in a few very specific situations, specifically if it gets INSIDE your body, on the subject of U235 decay,

Absolutely, and for both the radiological and heavy metal reasons. Alpha radiation is utterly ineffectual outside the body and dangerous inside, more so than any other form of radiation. We could discuss that at length and run some math and find the dosing needed to be harmful. But while we can say that u-235 poses risks under certain circumstances, the .66 tons of uranium-235 bromide in the fuel in question would not in real world scenarios. Its rough math in my head, but you can just about rely on standard launch procedures to protect the launch crew and the spectators are already far enough away. No one gets exposed to anything harmful at a launch failure and the exposure decreases with altitude and speed.

[Absalom]

2020... I assume you mean ITER?

No, I mean the Polywell, a non-Tokamak design. 2020 may be jumping the gun a bit, but I've also heard that the reason why fusion perennially "will take 20 years" is because that's how long it'll take to get ready to use it after a big breakthrough. My understanding is that the Polywell is simple enough that if you have a convenient coil reprocessing facility nearby, you should mostly be set.

Its being engineered with a maximum acceleration tolerance of .2g.

At which point, bearing in mind that I thought you were talking about "as a surface-to-space stage", I'd be suggesting a ground-based reactor, with microwave power transmission. Not the direction you'd normally direct your microwave power broadcasters, but for a quick "pop and kick" system it should be fine. However, since you're apparently talking about in space, the only "acceleration tolerance" problem would be creating a design variant intended to work in zero-gee to 0.2 gee (this would probably mostly relate to restraining things that you didn't previously have to restrain).

Even after you generate the power from the reactor, you still need ways to turn it into impulse. Either with heat radiation or lasing I suppose? Sides, if youre going through all that trouble to generate all that plasma, may as well just simplify things and stick with vasmir.

"Stick with Vasmir" is a misnomer, since a power source would be required for that to work anyways.

IIRC a vasmir engine would only take you 6 months to transfer from LEO to lunar. The benefits of such systems are the reduced mass requirements for fuel, theyre more efficient but not as strong as chemicals. Either way provides too little thrust to be useful for travel in human time frames. A NSWR could get your child to alpha centauri, assuming there was any reason to actually go there.

A reactor-powered Vasimr used as the "plasma injector" for a larger MHD-ish engine (Hall effect thruster derivative, perhaps?) would at sufficient power levels and engine lengths presumably be useful for much the same thing, and a fusion reactor would work even better. At any rate, why exactly are we talking about Alpha Centauri? Did SpaceX ever say they wanted to go there?

And that was kinda my point. Its unacceptably risky because its evil atom splitting radiation, sievert scale need not apply. Its like watching Columbus going to the Spanish and getting turned down in favor of a plan to reach China by digging a tunnel. Because it can work, we just need to throw enough resources at it.

The risk isn't in Sieverts per say, it's in the fallout risk. The US Airforce has blown up defective satellites so that they wouldn't spew poisonous non-radioactive propellants in an area that would be vulnerable to them. If the radiation was quickly gone then it would be much more likely for the idea to be accepted, so a bomb is better than fallout.

I'm as big a fan of NSWRs as anyone, but launching from a populated atmosphere with one seems like sheer insanity. I'd rather try an Orion drive and then do some tests with NSWRs far from anything important. Orion may have its own potential for mess, but at least we've got a lot of practice in making atomic bombs. Getting practice in making NSWR reaction chambers... even with a lot of computer modeling, that's a hair raising prospect.

For that matter, if you're willing to restrict it to ground-to-space you could attempt a purely-fusion interpretation of the Orion, powered via either a reactor, or a microwave power transmitter. That wouldn't even have the fallout worries of a "clean Orion".

[discord]

charlie: the problem with such is when grown ups believe in santa and that we have a democracy, a ruler of a people bloody well should be informed about and base decisions on reality not fairy tales or other non factual data, given that we live in a democracy EVERYONE is the ruler, therefor no one of voting age should believe things which are blatantly not true....

not talking about moral values, which is what terry pratchet mentioned but simple things like gravity exists and in most cases if you throw a ball it will fall down, or other basics of reality....another fun one, "war can't happen to us"...it may be unlikely but it bloody well CAN, especially if you go around pissing everyone off, when you grow up leave childish illusions and fantasies where they belong, you may very well enjoy a good book or movie, i do, but i do not BELIEVE in it.

and finally, everyone has 'fantasies' and some kind of crazy, in my case i believe humans are better than they are....more tolerant, more honest, etc. but i try to keep my crazy to myself.

[Arioch]

I love fantasy. I don't believe that knowing the difference between fantasy and reality in any way reduces my love of fantasy and imagination. Kids know the difference between make-believe and reality; that doesn't stop them from pretending. If I had kids, I would tell them about Santa and observe the customs of setting up stockings and leaving milk and cookies, but I would be clear that it was pretend. I'm pretty sure they would still enjoy Christmas just as much as if I lied to them and tried to trick them.

Luckily, most democracies (like the US) are republics rather than direct democracies; the people are not the rulers, but they vote for the ruler. Direct democracy tends to devolve into mob rule. That's why I'm not a fan of the California proposition system; ordinary people are barely qualified to vote for leaders, and are certainly not qualified to decide on specific issues.

[fredgiblet]

I've long thought some for of limited suffrage would be better, the problem is designing a limited suffrage system that isn't discriminatory. The only setup I can think of that would be fair would the Starship Troopers path where you're required to volunteer for civil service (usually miilitary) before you can vote.

[Arioch]

I think it's important that people not feel disenfranchised... for a democracy to work, people need to feel invested in the system; they need to feel like they could have a say, even if they usually choose not to. So I don't think limiting suffrage would work very well.

I think the current republican system works pretty well. There will always be ups and downs... when things aren't going well, people need to wake up and take an interest in what they think the government isn't doing right. But I don't think the electorate should be involved in making the day-to-day decisions of how to run government. The California proposition system is rendering the elected government impotent by heaping more and more voter-imposed restrictions on it. At some point you have to let your elected officials do their job during the term for which they're elected; if you don't think they did well, then elect someone else when the time comes.

Otherwise there's no point in having an elected government at all. I'm for small government, but I'm not for no government.

[Charlie]

I discovered early on that the world can be harsh and unforgiving, sometimes life just isn`t fair. I will do my best to make sure that the same would not happen to my children, if that means pretending about Santa, dragons, cops-n-robbers and what not then so be it. Almost everyone grows out of it at some point, why not let them live in pretend land. They will eventually learn whats real and whats not, everyone grows up.

As for governments, more voter power isn`t a good thing. Since anyone whom meets the requirements can vote, people who might be considered "disruptive elements" would be able to effect change in large numbers. Fortunately, there arn`t enough of these types to be a concern. If only service members were allowed to vote, the recruitment process would screen out all of the undesirables.

Police states and dictatorships can sometime be far more stable than current "western" government.

[Arioch]

Telling children that dragons are real is not wonderful or fanciful or imagination-fueling. It's terrifying.

Children have no trouble at all being imaginative while knowing full well that imaginary things are quite different from real things. There's no need to deceive them about it. This notion that knowledge stifles creativity is absurd. If anything, I've found the exact opposite is true; it's the well-educated people who are the most imaginative.

Police states and dictatorships can sometime be far more stable than current "western" government.

But that's a myth; they aren't. Functioning democracies are far more stable than authoritarian governments, which have to deal constantly with suppressing insurgency.

[Nemo]

A reactor-powered Vasimr used as the "plasma injector" for a larger MHD-ish engine (Hall effect thruster derivative, perhaps?) would at sufficient power levels and engine lengths presumably be useful for much the same thing, and a fusion reactor would work even better. At any rate, why exactly are we talking about Alpha Centauri? Did SpaceX ever say they wanted to go there?

Because when dealing with humans time matters. Its contrasting the best available plasma based drive to a NSWR. Vasmir's 6 months to the moon is unacceptable. Contrast that with the jaw dropping realization that we are within reach of the nearest star using NSWR. I even pointed out we have no reason to but it is possible. If you followed the rest of the thread Titan, the moon, Mars, and Phobos were the focus of in system destinations. Using the other kinds of drives mentioned is simply not practical for human transit. Hall effect thrusters are even worse in this regard than a vasmir. Yes they're efficient, but have no thrust. High ISP low thrust is fine for long running probes and satellites, or maneuvering engines on a station but not for a human rated primary drive.

The risk isn't in Sieverts per say, it's in the fallout risk.

*snap*





Someone please help me.

[Absalom]

Police states and dictatorships can sometime be far more stable than current "western" government.

But that's a myth; they aren't. Functioning democracies are far more stable than authoritarian governments, which have to deal constantly with suppressing insurgency.

The key word is "functioning".

A reactor-powered Vasimr used as the "plasma injector" for a larger MHD-ish engine (Hall effect thruster derivative, perhaps?) would at sufficient power levels and engine lengths presumably be useful for much the same thing, and a fusion reactor would work even better. At any rate, why exactly are we talking about Alpha Centauri? Did SpaceX ever say they wanted to go there?

Because when dealing with humans time matters. Its contrasting the best available plasma based drive to a NSWR. Vasmir's 6 months to the moon is unacceptable. Contrast that with the jaw dropping realization that we are within reach of the nearest star using NSWR. I even pointed out we have no reason to but it is possible. If you followed the rest of the thread Titan, the moon, Mars, and Phobos were the focus of in system destinations. Using the other kinds of drives mentioned is simply not practical for human transit. Hall effect thrusters are even worse in this regard than a vasmir. Yes they're efficient, but have no thrust. High ISP low thrust is fine for long running probes and satellites, or maneuvering engines on a station but not for a human rated primary drive.

6 months to the moon, yes, but is that for the actual route, or is that to adjust the orbit to follow the path that you want? As I best recall, on a cycler orbit you can go from the Earth to mars in 2-3 years. I somewhat suspect that if you used the Vasimr to induce a cycler orbit between Earth and moon, the actual transit time after orbital "finalization" would be less than the time mentioned (which is not to say that I know cycler times between Earth and Moon). At any rate, the 6 months is for a specific model of Vasimr, so you shouldn't be treating it as some maximum limit.

As for Hall thrusters, if you look back, I was suggesting them as a possible technological basis for producing an MHD effect to further accelerate the exhaust from a Vasimr. The Wikipedia page said that the exhaust tops out at ~10% of lightspeed, so even if you ignore relativity you can get better thrust if you can just produce more acceleration (and if you keep adding energy after relativistic effects become noticeable, then you keep dragging more thrust out of it). The main question is what you'd need to do to avoid component damage. If you're already running it from a fusion or fission reactor than you shouldn't lack for power capacity, the question will simply be how to use all of it.

Would it be enough for interstellar flight? Maybe not, but I wouldn't dismiss it unless someone did some actual analysis. For that matter, if it doesn't need to sustain itself, the basic Vasimr design could be modified to act as an honest-to-goodness fusion engine, and those have been suggested for interstellar travel before.

The risk isn't in Sieverts per say, it's in the fallout risk.

*snap*





Someone please help me.

Request denied. But seriously, a massive nuke with no fallout would be more acceptable than a small nuke with lots. Not that it matters, since that comment was prompted by my previous misimpression that you were talking about using NSWRs for planetary launch.

[Nemo]

The Wikipedia page said that the exhaust tops out at ~10% of lightspeed

Here again, you do not understand specific impulse and thrust and are confusing exhaust velocity for vehicle velocity. I gave a link to ISP, read it. The appeal of these engines is their high fuel efficiency not their thrust. You must understand this concept and that of mass requirements for fuel affecting mission parameters before we can continue. They provide very very very very small amounts of delta v over long periods with only a little mass used. As I said before, unmanned vehicles and station keeping devices only.

Would it be enough for interstellar flight? Maybe not, but I wouldn't dismiss it unless someone did some actual analysis

It has been. Its not workable for human rated drive systems. You need more thrust.

The risk isn't in Sieverts per say, it's in the fallout risk.

*snap*

Request denied.

*twitch*

Please please...


Im going to try to do this again. What is "fallout"? A derogatory term implying any exposure to radiation is a Bad Thing™Martha Stewart Living. In short, exposure to radiation. What is a Sievert? The measurement of exposure to radiation. Useful for determining exactly what is and is not a harmful exposure to ionizing radiation. Therefore as you said, "The risk isnt in 'measured exposure to radiation' per say, its in the 'exposure to radiation' risk."

[Absalom]

The Wikipedia page said that the exhaust tops out at ~10% of lightspeed

Here again, you do not understand specific impulse and thrust and are confusing exhaust velocity for vehicle velocity. I gave a link to ISP, read it. The appeal of these engines is their high fuel efficiency not their thrust. You must understand this concept and that of mass requirements for fuel affecting mission parameters before we can continue. They provide very very very very small amounts of delta v over long periods with only a little mass used. As I said before, unmanned vehicles and station keeping devices only.

The higher the exhaust velocity, the higher the ISP, yes I know. To rephrase, the higher the exhaust velocity, the more thrust from that same mass of exhaust. If you have an engine that doesn't destructively interact with it's exhaust, and has an exhaust velocity limited only by it's power supply and "active length", then it has the potential to take it's exhaust up to ~99% of c. If such an engine is long enough, then you should be able to use the output of your power supply to calculate the thrust of the engine, I believe with f = exhaust mass * square root( ( reactor output - power losses ) / exhaust mass ). I'm talking about using the Vasimr as an internal component of a higher-thrust via-higher-ISP engine, not as the sum-total of the engine. Are you claiming that this cannot, in fact, be done to the exhaust of a Vasimr, no matter how far to the "thrust" side of the equation it's dialed, due to an inherent engine constraint (as apparently happens with gridded ion engines)? Or have you actually just not spent enough time reading to figure out what I wrote?

Would it be enough for interstellar flight? Maybe not, but I wouldn't dismiss it unless someone did some actual analysis

It has been. Its not workable for human rated drive systems. You need more thrust.

You'll have to convince me that you actually understand what I wrote before I'll take this seriously.

Im going to try to do this again. What is "fallout"? A derogatory term implying any exposure to radiation is a Bad Thing™Martha Stewart Living. In short, exposure to radiation. What is a Sievert? The measurement of exposure to radiation. Useful for determining exactly what is and is not a harmful exposure to ionizing radiation. Therefore as you said, "The risk isnt in 'measured exposure to radiation' per say, its in the 'exposure to radiation' risk."

Saying "radiation falls" seems rather ludicrous to me. Fallout is persistent radiative pollution. Gamma radiation? Once it's gone you just pick up the pieces. Fallout? You can't live there again until it's decayed, and the knowledge that it was ever present pollutes the mind-share of that plot of land for years, or decades, thereafter.

[Nemo]

If you have an engine that doesn't destructively interact with it's exhaust, and has an exhaust velocity limited only by it's power supply and "active length", then it has the potential to take it's exhaust up to ~99% of c.

Not precisely, no. Seems you may be applying mechanical physics here. The limit on Vasmir is the strength of the magnetic bottle b-field which is derived from the super conductor used. Granting an infinite power source is insufficient without accommodating the physical limits of superconductors and the mass of the cooling systems needed. These are low thrust to weight drives that deliver delta V over long periods.

Saying "radiation falls" seems rather ludicrous to me. Fallout is persistent radiative pollution. Gamma radiation? Once it's gone you just pick up the pieces. Fallout? You can't live there again until it's decayed, and the knowledge that it was ever present pollutes the mind-share of that plot of land for years, or decades, thereafter.

Gamma radiation moves at the speed of light. As soon as you measure it, it is gone

So fallout is bad because its scary. Not because it presents physical bodily harm. "Fallout" is a boogeyman. To illustrate my point again, you separated Gamma radiation and held it as a distinct case from fallout. This is inaccurate. Gamma, as well as beta and alpha, are different modes of decay of the physical material which constructs 'fallout'. Alpha decay is when an unstable element spins off a helium-4 atom. Beta spins out either an electron or a positron and either increases or decreases (respectively) the atomic number without altering atomic mass. Gamma radiation consists of high energy photon emissions. The source of which, for this discussion, is the excited state of the atom resulting from the other two forms of decay. In the end, the only thing that matters is the measurable harm from exposure, which is measured in Sieverts. Uranium Bromide enriched to 20% posses no radiological risk in the worst case scenarios here.

[Mayhem]

So fallout is bad because its scary. Not because it presents physical bodily harm. "Fallout" is a boogeyman.

The "rational" concern about fallout as I understand it is of radioactive particulates entering the body (in sufficient quantities) via ingestion or inhalation and decaying inside the body. Also some(/many?) of the elements in various radioactive decay chains are toxic in their own right.

So it becomes a question of effectiveness and availability of filtration vs initial quantities/concentration, half-life, biomagnification, etc.

The problem is one of risk assessment - which humans are notoriously bad at - and education vs drama - ditto.

So "boogeyman" instead of somewhere on the scale: trivial - inconvenient - annoying - not worth the hassle - harmful - deadly.

[Nemo]

So "boogeyman" instead of somewhere on the scale: trivial - inconvenient - annoying - not worth the hassle - harmful - deadly.

Which as I have maintained throughout is properly expressed on the Sievert scale. It is this measured approach which is being rejected and that is what I am reacting to. When 'fallout pollutes the mind-share' is a direct reference to people's fear not the potency of the radiological effects, which, again, are trivial in even the worst case scenario launch pad chemical booster detonation.

[Mayhem]

Which as I have maintained throughout is properly expressed on the Sievert scale.

Indeed, however it is also necessary to explain to people - the education problem I mentioned - the difference between a becquerel, a gray and a sievert.

Simply (perhaps overly so) put:

• Becquerel is number of decays per second
• Gray is the energy (per kilogram) imparted by radiation to a (nonspecific) mass
• Sievert is the effective/equivalent energy (per kilogram) imparted by radiation to a human taking into consideration the nature of the radiation - alpha, beta, gamma, etc - the nature of the exposure - internal, external; localised, full body - and the nature of the human - age, gender.

Once that is explained you can talk meaningfully to Joe Public about fallout and sievert reducing precautions and evaluate their effectiveness vs inconvenience.

For example: Fine particulate alpha emitters could be lifted into the air by wind and represent an inhalation hazard.
A suitably fine dust mask worn when outdoors would massively reduce the exposure in terms of sievert (but not in terms of gray).
The discussion then becomes whether the advantages of being able to operate in the affected area are outweighed by the inconvenience of needing to wear said dust mask.

[Nemo]

Precisely. Now as to why Im so certain that current launch procedures are adequate to protect launch pad workers, let me introduce the rubber room and the NASA firefighters.



Link: http://scriptunasimages.wordpress.com/2 ... bber-room/

Launch Pad 39A was the starting point of all the Saturn V rockets to the moon except for Apollo 10. Before each mission, each astronaut was trained on how to use the room. An exploding Saturn V was calculated to have the power of a small nuclear bomb and an explosion would have completely destroyed the 36-story rocket and leveled the launch pad. NASA needed to come up with a series of contingencies to keep astronauts and pad workers safe in the case of a suspected problem that would lead to an explosion. One of these contingencies was a room located 40ft under the top of the launch pad. The room was accessed via a 200ft long slide from the base of the mobile launch platform. In the event of a possible explosion, astronauts would have exited the capsule and entered into a rapid descent elevator that would have got them to the base of the MLP in 30 seconds (this doesn’t seem very rapid to me). After reaching the base, they would jump into the slide taking them to the rubber room. After arriving inside the rubber room, they would take a few short steps over to the Blast Room, closing the armored door behind them. The room, with its floor mounted on a series of springs, has 20 chairs, enough for the astronauts and closeout crew and could be accommodated for 24 hours.

Link: http://www.redorbit.com/news/space/2021 ... efighters/

Basically a bunker on tracks, the M113 is a Vietnam-era armored personnel carrier that offers the astronauts a safe vehicle to get out of danger. It also offers firefighters heavy protection in case they have to go into danger to retrieve the flight crew and launch pad personnel.

"These things are virtually indestructible," said David Seymour, battalion chief and the lead for the pad rescue team at NASA’s Kennedy Space Center in Florida.

Talk about over engineering. The radiation effects of enriched Uranium Bromide weve been so focused on for two pages can, as noted, be stopped by a simple piece of paper. In any catastrophic situation the radiation is a non issue, and especially so when compared to the difficulties dealing with the catastrophic fault of a rocket.