calbiterol

Out of curiosity, why?

Whoops. Past my pay grade.

Would a white laser be sufficient? Given enough power? You can combine red, blue, and green lasers to produce a "white" laser. Lasers are collimated...

That assumes that the sail is opaque to the entire electromagnetic spectrum.

The rapid prototyping field is progressively moving towards being a viable form of manufacturing, particularly since one can now match the density of a forged part. There are currently a number of different methods by which one can RP a metal part. The general gist of the main ones is: Direct Metal Laser Sintering: This is powdered metallurgy, RP style. The working powder is used both as filler material and as part material. A laser then sinters a very small layer of powder, creating a solid metal part. Electron Beam Melting: Replace the sintering laser from DMLS with an electron beam that melts the base powder. Electron Beam Freeform Machining: This is a process still under development by Nasa, but has been proven, and parts are being made. Basically, an electron beam melts a feed wire (like in Fused Deposition Modeling) and "prints" it onto a table that moves in the Z-axis.

AKA, "Am I doing this right?!" Note: I promise I didn't actually multiple post this many times, I'm just making use of the divider as a logical separation between edits! So, some background: I'm currently doing some design work with pneumatic rifles, and I want to actually go about this the *right* way - that is to say, I want to actually put some engineering skills to work - and hence want to describe the system mathematically. The gas under consideration is compressed air, and the temperatures follow the normal range of ambient outside temperatures in North America during anything but winter - aka, roughly 0-30 degrees centigrade. SO, given the fact that projectile acceleration to approximately 315 feet per second (I apologize in advance for the wankered units!) takes extremely little time, I thought it appropriate to assume an adiabatic condition. Since the temperature and pressure range are both moderate, I therefore grabbed the formulae for ideal gas adiabatic expansion and work from hyperphysics. After a little manipulation, I wrote an expression for the optimum length of a barrel for ideal adiabatic expansion to equalize with the ambient atmospheric pressure. I then substituted this equation for length in the adiabatic WORK equation (again, from hyperphysics) to get the final volume. I was then left with an implicit function in terms of initial pressure and initial volume that described the conditions necessary to accelerate the projectile (3.2 grams) to its final muzzle energy (130.5 lbs-in). Then, I fired up MATLAB and started writing a little bit of code... syms x y; syms p0 v0 A k pAtm W0; outputVars = [x y 1.400 .3685 14.696 130.5]; workingVars = [p0 v0 k A pAtm W0]; bL = v0 / A * (( p0 / pAtm) ^ (1 / k) - 1); deltaW = p0 * v0 * ((v0 + A * bL ) ^ (1 - k) - v0 ^ (1 - k)) / (1 - k) - W0; ezBarrel = subs(deltaW,workingVars,outputVars); ezplot(ezBarrel,[0 850 0 15]); ...just to see that everything was working out nicely. WELL, my code told me that .3117 cubic inches of 200psi compressed air should be enough. That, in turn, gives a barrel length of 4.68 inches - which would be completely fine, if I were sure it was correct! But I'm not, so I fired up the Gas Gun Design Tool (GGDT - nifty little app) with settings that as closely approximated this situation as the program would allow! For example, I used a burst disc valve with a 100% flow coefficient; barrel diameter, valve diameter, and reservoir diameter were all equal, etc etc. I then had GGDT optimize for barrel length - essentially repeating my former calculations with different programming and fewer assumptions. The results: ideal barrel length of 7.14 in (instead of 4.68), end muzzle velocity of 238 feet/second (instead of 315), with roughly the same initial volume and pressure. It did, however, give me an energy efficiency of only 13%. My question is: should I assume the discrepancy in the numbers is due to the differences in the situations being described between the GGDT and my numbers, or is there some gross error that I've missed? Also, if it would help, I can post up my calculations so you can all see the equations (and how I got them). Merged post follows: Consecutive posts merged*cough* *cough* I think I figured it out... I missed an exponent when copying an equation down. I should say, I missed it TWICE, since I double-checked everything I was doing. I won't know for sure until I get home from work, but the barrel length is MUCH closer (7.3495 inches). If anyone wants to see the derivations and such (or the end curve), let me know and I'll post them up; otherwise, consider the question answered! *doh!* Merged post follows: Still no diceWell, re-ran the numbers in GGDT. They still don't jive with each other. I tried a number of different data points; it seems like the lower the pressure, the more accurate the velocity prediction is, and the less likely the barrel prediction is. I also checked again to make sure that I entered everything into MATLAB correctly, and I did. So, the question still stands. Merged post follows: My mathsMy maths: Okay, managed to turn it into a .pdf: Derivation

Funny thing, I once met a guy named Jack Hoff. And my high school health teacher? His name was Dusty Seemans. True story.

Well in Germany that doesn't really matter; fireworks are illegal there anyways.

Plus, sure seems to me like one of the biggest reasons we keep getting taller (ever so slowly) is that our nutrition has improved. At any rate, from an evolutionary standpoint, I don't see any reason why it would be advantageous to be smaller or bigger in today's society.

Just don't swallow it. It doesn't get a chance to evaporate if you swallow it. And that's NOT good.

Not if it truly evaporates - I think dry ice would sublimate under those conditions. However, the visible difference between sublimation and evaporation could be difficult to detect. I think Phoenix has equipment to test for exactly this kind of thing, doesn't it? ... I've always wanted to go to Mars...

Anybody here participate/compete in FSAE? For those of you unfamiliar with the competition, it'd be interesting to note that there's a new hybrid competition as well.

So that people know what DH is talking about, I made reference to generating electricity by dropping rubbish down a shaft. I actually think I already mentioned this somewhere on the forum, but it's been so long since I was active here that I don't really remember! EDIT: Oh jeez, didn't realize the rest of this thread was so old. I thought I remembered something like it... Scratch that, reverse it. I'll remove myself from what appears to be a buddingly unproductive argument. Cheers!

That's besides the point. And he could, it would just make bombing irrelevant for him! I wonder if that policy will ever change. Meh, off topic now.

?! That's the biggest load of horse refuse I've heard outside of the "Border Fence Project!" Wow, I hope Tancredo is stupid enough to visit Mecca while it's being bombed.

Don't get killed.

ITER's made some progress. At least they know WHERE they're going to build this thing - Cadarache, France. Here's the proposed timeline.

Wow, I didn't even think about that, and that sure isn't trivial.

Please take none of this personally. I'm going to say things bluntly, but I am attacking your point, not you; please read it this way. This is just my little disclaimer to keep things civil - which is something I've rarely had a problem with at SFN, but it's been a solid year since I've posted here regularly, so I thought I'd say it again. I beg to differ. I cite the Vietnam War. We had every possible military advantage over the Viet Cong / NVA. We even had a real, practical experience in the jungle by the war's end that equaled that of our enemy. And yet, we still lost the war. Why? Because Ho Chi Minh convinced the American people that the war was not worth winning. If al Qaeda does the same thing, we are finished. They sure wouldn't. I wouldn't be surprised at all if it's some of those very tribes that are truly harboring terrorists in their homes. No. The military did not fail. The military bureaucracy failed. This is a subtle, but very important, difference. It was not until much later that the "failure" of Operation Eagle Claw was fully understood. The operation was needlessly complex and, more importantly, there was no adequate air contingent to match the skills and requirements of Delta Force, as well as the general Special Forces. This spawned the creation of the 160th SOAR and USSOCOM. The ultimate deciding factor that caused the abortion of Operation Eagle Claw was mechanical failure. Too many of the helicopters had become inoperable for the mission to be given the go-ahead. During the evacuation staging, a helicopter pilot became disoriented and crashed into a C-130. I have spoken to one of the more superior officers among the Special Forces who were at Desert One, and he was extremely confident that, had there been no technological failures, the mission would have been a resounding success. That is all largely off-topic and irrelevant but I couldn't leave it alone. But fear can. You said it yourself: "In my very strong opinion, people are so scared that they might be killed in a terrorist attack that they have lost all judgement and are advocating policies to keep them 'safe' that are disastrous." In my equally strong opinion, fear merits nothing - not action, not inaction, nothing - and I think you would agree. However, motivation by fear is one of the many principles behind terrorism, and it is working. When any American decides not to do something because of fear of attack, terrorism has a small victory. When any American voices support for security legislation that curbs his rights as a US citizen out of fear for an attack, terrorism wins. Terrorism can and will destroy the United States as we know it, but only if we let it. And we must not let it. Fight legislation made out of fear. "He who would trade liberty for some temporary security, deserves neither liberty nor security." Not a military action when called such. Simply rephrase it to a police action, however, and it becomes forgivable. Also, keep in mind that the US has definable, protected borders. The border of Pakistan in question is neither pronounced, defended, secured, or protected. There is NO analogy between the two, and any comparison is apples to oranges. Absolutely false. Our rights as a sovereign nation never cease, no matter where we are. This is often the reason that wars start in the first place. The right and responsibility of a nation to protect its citizens DOES NOT STOP when a citizen visits a foreign nation. The right and responsibility of a nation to secure its economic well-being through the procurement of resources DOES NOT STOP when those resources come from overseas. The right and responsibility of a sovereign state to defend itself DOES NOT CEASE when the enemy is in another sovereign state. Soft diplomacy is the preferred method, but (and I say again) military diplomacy is not out of the question. This is a basic principle of international relations. This is absolutely false. The statement that every operation has collateral damage is a skewed perspective brought on by the fact that the ONLY operations we hear about are those with collateral damage because of a number of very complicated political reasons within the news media. Military diplomacy is a synonym for hard power, also know as hard diplomacy or certain types of power politics. In short, it is the use of military force, aggression, provocation, or the threat thereof to coerce another nation to the will of the aggressor. I agree with you 100% on this notion. HOWEVER, terrorist organizations are highly compartmentalized. By killing the high-ranking leaders, you eliminate the few people in the entire organization that are aware of more than just a small amount of information. That means that another person must be found that can be trusted, then that person must be brought up-to-speed on a vast amount of information previously unknown to him. This takes a lot of time and causes a lot of temporary confusion, which can be taken distinct advantage of to attack the cause behind the organization. Furthermore, the ideal operation in the event of a meeting of high-ranking officials is NOT to eliminate them. Ideally, these officials would be captured for interrogation, which, when concerning high-value targets, is extremely valuable information. These are the few people who know where bin Laden is, and the capture and trial of bin Laden would, without a doubt, remove the public leader of al Qaeda and severely cripple its cause. The symbolic meaning of bin Laden's capture, trial, and execution would be so significant that al Qaeda would be hard-pressed to recover (under that name, at least). From an illegal standpoint, the BEST outcome of such an operation against high-ranking leaders is to capture them, stage their deaths, and then torture the information out of them. Wrong. Absolutely deniable. The point is that, if done correctly, no one would even know that there was a bomb or missile in the first place. The event would simply be a massive explosion. No muss, no fuss, and absolute deniability. Black ops. You have just contradicted yourself. I'm talking about operations with absolute deniability. When I say "The mysterious explosion or execution of a number of high-ranking al Qaeda," I mean just that. There is no attributable source of this event, it just happened - as far as anyone other than the target and the aggressor are concerned. If it "just happened," it cannot be criticized without backlash. If any Special Forces team(s) were involved, then the mission would involve a capture scenario. The targets would then simply be missing or captured, and the location of capture would be stated as Afghanistan, and the world would say, "Oh how nice, al Qaeda leaders were captured in Afghani caves!" and go about its dinner. Again, please don't take this as an attack ad hominem, as it is anything but. I can deal with this. I don't like it, but I can cope. It's when people's real deaths become entertainment that I am sickened. If you are reporting on a war to inform people about it, if you are showing the cost of war in a way that makes people stop and listen in silent reverie, then that is one thing, but reporting on war death to raise ratings, with no other good reason, is disrespectful. Honor the fallen. Don't make a mockery of their sacrifice. George Stephanopoulos' segment "In Memoriam" on This Week does an excellent job of avoiding this. Cheers, Calbit

I apologize if this post comes across as beating a dead horse, but I felt the need to say it. Obama never says that he would ignore diplomatic efforts with the Pakistani government. In fact, he emphasizes that he WOULD pursue a diplomatic solution - albeit a "tough love" solution - and that he would encourage the Pakistani government to act. And if the Pakistani government ignored these recommendations? A nation has every right and every reason, especially in the international legal community, to defend itself against sovereign threats and to seek prosecution and retribution against those who attack it. Al Qaeda has already attacked Americans on American soil, and as long as the Pakistani government refuses to take action and no Pakistani citizens or property are harmed, in my mind, America has every right to defend herself. Aside from that statement, I have this, and only this, to say: Where does Obama mention invading Pakistan? Military diplomacy is always a last resort, and Obama mentions this in his speech. He never uses the word "invade" or any form of it, and nor does he ever imply it. Military action against terrorists is just that - small-scale military action against a localized enemy. The missed opportunity that Obama referenced with "actionable intelligence" on "high-level" al Qaeda operating in Pakistan would not have required an invasion. A simple air strike with a single smart missile would have accomplished such a mission, and a stealth bomber, although violating sovereign Pakistani airspace, would most probably have remained undetected. Likewise, a small special forces operational detachment (such as Delta or Navy DEVGRU / Seal Team Six) could have been tasked the mission, with the same net result - the internationally deniable assassination of al Qaeda officials with no provable origin. The mysterious explosion or execution of a number of high-ranking al Qaeda, while extremely suspicious, could not publicly be criticized by a government without fear of extreme political backlash among the international community. Obama was merely putting into public words the policies that most American presidents abide by under extreme circumstances in what is labeled "black ops" military action. Cheers, Calbit P.S.: The potential innuendo here is so great that I could not ignore it

I decided to resurrect this for a status report. I fixed the problem during winter break - right after New Year's methinks, although it might have been closer to Christmas. I managed to get Windows to boot after a long an arduous labor of frustration. My CD-ROM drive had also failed. I replaced it with a jury-rigged CD-ROM out of an old laptop that hardly (but indeed does) work, even though it's 5-6 years old, and backed up my files (again). I then reinstalled Windows. The computer seems to be okay and has been running (mostly) stably since then. At this point though, there's no sense in replacing the CD-ROM, so I'm just getting a new computer.

Haha, DONE!! It's about time. Everything went well, methinks.

Well, my last day of high school (or secondary, for all you foreigners ) is tomorrow! That's followed by an AP test Thursday, but after that, I'm out - then graduation, then on to Cleveland for Uni in the fall! I've been waiting for this moment for the past 3 years. 9th grade / freshman year, I just didn't know any better. Yippee!!!! *Insert Childish glee*