GoSlash27

p1t1o, I've always found this stuff confusing since it's often counterintuitive, so bear with me... I hear "Schwarzchild radius" and "event horizon" used interchangeably, and the sources I've picked up this stuff from insist that they are one and the same. Perhaps this is incorrect? All of the proofs I've seen re. the Schwarzchild radius are straight- up Newtonian; the radius at which Vesc=c. That's where my puzzlement stems from, because I wouldn't *expect* the Schwarzchild radius to be a true event horizon. It would just appear as such from outside the SoI since nothing can reach Ve beyond that point, but within the SoI light and even matter would be able to cross that radius and come back out. From within the SoI, the true event horizon would be at half that, where space gets so bent that escape is truly impossible and all directions point in. I'd love to have someone clear this discrepancy up for me Best, -Slashy

As I understand it, the "event horizon" is the radius where Vesc>C. But if that's the case, then it *is* possible to cross back out, it's just impossible to leave the SoI. Since Vesc=Vorb*sqrt(2), then it'd stand to reason that the actual "abandon hope all ye who enter here" is at half the Schwarzschild radius, where Vorb >/= C. I may be missing something, tho'...

Back in my day... We went outside to play with other kids in person There was no internet The phone was attached to a cord Only rich kids had a computer You had to watch whatever was on TV and listen to whatever was on the radio. Each offered just a few stations. Our "Google" was the index card catalog at the library The Atari 2600 was a high- end home gaming system Get off my lawn, -Slashy

Why do I hate mods? They're a buncha sneaky, underhanded finks who.... Wait... Are we talking about moderators, or modifications? /IKeed

^What Zeiss Ikon said. It's cool if you want to apply some artistic license in order to move a story along, but if scientific accuracy is important to you, then I recommend forgetting about the concept of globular clusters as a basis of empire. There's no planets out there, no rocks, and no resources to sustain life. Best, -Slashy

There's *not* bound to be a few asteroids, though. The lower the metallicity in the stars, the less likely it is that you're going to find rocks. Basically, all you can count on finding in a globular cluster is a lot of old stars. It's just empty desert out there. And yeah... I suppose you *could* bring your biospheres out there to the boonies with you, but in that case, why would you leave in the first place?

This is the problem with these futuristic looking delta designs with a long pointy nose, wing toward the back, and engines in the tail. It looks for all the world like it's balanced, but at high speed it becomes dangerously aerodynamically unstable. At high speed, you have a big light "paddle" of fuselage hanging out in front of the wing, and a heavy aerodynamically clean mass in back. End result: the plane wants to fly backwards. Try placing the wing in the middle of the fuselage instead of in the back, and bring the engines forward with them. It'll be boring looking, but will be a whole lot more stable at speed. Best, -Slashy

A sphere with a radius measured in "x" km is equivalent to "x" miles cubed. ex: If Kerbin were compressed into a cube, it would be about 600 miles wide.

Wumpus, It's been a little while since I designed that one, and I'm a bit hazy on the details... But IIRC the initial t/w was the result of synchronizing the fuel expenditure of the core LF&O engine with the burnout of the SRB boosters. That way, the quasi- asparagus tanks would run empty right at the moment the SRBs burned out. The 1.7 t/w at liftoff was a happy accident, not anything I actually aimed for. Best, -Slashy *EDIT* I forgot to mention up-stream: If the LF&O engine I have selected for cost- effectiveness happens to be more powerful than these figures, then I won't turn them down to match. They are considered minimums. If my engine wants to pull 2g off the pad, I'll let it.

My experience has been right in line with Ohio Bob's suggestions. The advantage of choosing a lower T/W is in mass and cost savings, not pure efficient attainment of orbit with the least possible expenditure of DV. Some other reasons to throttle back during the launch: -Controllability issues around Mach 1. All the drag inherent in going too fast too low can manifest itself in a rocket that doesn't want to turn or doesn't want to fly straight. Keeping your t/w under 2 during the steeper portion of the flight can make a rocket easier to fly. -Heating issues at supersonic speeds. If you keep the hammer down for too long while in the atmosphere, you *may* overheat to the point where parts start blowing up. -Precision/ repeatability of launch trajectory. It's a whole lot easier to place your payload into a specific orbit when you slow the process down a bit. You find that you can follow a narrower launch corridor and expend the exact same DV every time. This helps with planning purposes, both during mission planning and vehicle design. So I generally follow these guidelines when designing stages: SRB booster: 1.2 initial t/w, 1,800 m/sec DV LF&O booster: 1.4 initial t/w, 1,700 m/sec DV Second (transstage): 0.7 initial t/w, 1,600-1,800 m/sec DV (larger diameter lifters have lower drag per mass) Orbital and interplanetary ops: 0.5 initial t/w. During launch, I climb vertically to around 80 m/sec V, then initiate a 5° pitchover and follow prograde. LF&O engines are throttled back to maintain acceleration IAW the formula 2sin(pitch). Pitch/acceleration 90/ 2 75/ 1.9 60/ 1.7 45/ 1.4 30/ 1.0 This is generally where my first stage conks out, around 800 m/sec, 30 km altitude, and pitch= 30°. Conveniently, this is where aerodynamic control no longer matters, so any control surfaces or streamlining stuff can be ditched here. Second stage then kicks in, and I can firewall it at 0.7g. I pitch and throttle as necessary to keep my Ap 45 seconds ahead, and place it at the orbital altitude. Once it starts running away from me, I shut down, ditch the second stage if there's no further use for it, coast to about 5 seconds short of the Ap, then circularize. SRB first stages are cheaper, but also a bit more cantankerous, since they can't be throttled. A booster that starts out at 1.2g on the pad can be cooking over 3.5g when it finally burns out, so you may have to force the turn early and ride it through the heating. The acceleration can be artificially "throttled" by clustering SRBs and staggering their throttles, so they burn out at different times. Best, -Slashy

daniel l, The stars in globular clusters are mainly low metallicity. It's not just a matter of finding habitable planets, but finding planets at all. Best, -Slashy

I'm not "against" mods (actively campaign against their use), I just don't use them myself. I *suspect* that the people who are against your particular collection of mods are either hardcore purists or are angry that their collection of mods aren't the same as yours, and so can't enjoy your creations the same way you do. Best, -Slashy

Nothing; you'd be dead. The tidal forces approaching the event horizon would rip you apart like taffy.

Ah, but your second stage was like 1.7, ramping up to 3.8 as the fuel burned. I understand in your case that you'd need around 1g to start with, given the early termination of the boost phase, but 1.7-3.8 is still way more acceleration than you need. Likewise, the 3rd stage is 3.4 minimum, where 0.5 would be fine. Best, -Slashy

Starchaser, If you tone down the thrust, you won't have to worry about that because you won't be flaming on the way up. Best, -Slashy

Starchaser, That's cool. Still a dramatic improvement over where you were. A few pointers I can give you: *The DV to LKO should be roughly split evenly between the first and second stage. First stage DV calculated at 1,800 m/sec DV at 1/2 ATM, and 2nd stage 1,700 m/sec DV at vacuum. This results in a good approximation of a minimum total launcher mass. *I think you can rein in your t/w quite a bit. I generally use 1.4:1 t/w for LF&O first stage (1.2 for SRB), 0.7 for transstage, and 0.5 for orbital ops. Where this allows you to use lighter and cheaper engines, the benefits will compound backwards down the stack. If you wind up with the same engine, don't bother throttling back once you're past Max Q. * For this short a DV budget, you should check to see if a 2 stage rocket is a more efficient solution. Best, -Slashy

Green Baron, FWIW I'm inclined to agree with you. But at the moment, I wouldn't call this disparity "comfortable" (I know, not your words). At *best*, I'd call it "an oddity explainable by error and/ or false assumptions". Either the universe is older than they assume or this star is younger than they assume. Possibly both. But whatever the cause of the discrepancy, they've still got work to do. Best, -Slashy

Green Baron, I wouldn't exactly call it "comfortable". The low end of the estimate is 13.7Gy, which is only 100My after the currently accepted age of the universe. Cosmologists place the first stars at 300My after this one, and this is a second generation star. I think they still got some 'splainin' to do. Best, -Slashy

Very nice! V1: $33,700/ 62.5t V2: $26,500/ 47.0t V3: $19,000/ 7.37t That's some serious savings! -Slashy

This was so baffling, I had to look it up myself. It's true, but what's even more confusing is that it's not even from the first generation of stars. Either cosmologists suck at estimating the age of stars that aren't really far away, or they suck at estimating the age of the universe. Best, -Slashy

Green Baron, I should also point out that I'm not either Best, -Slashy

Again... We are using the word "civilization" as if it is a fixed percentage of "life". I'm not convinced that this is so, given our own history. Civilization requires intelligence, which must be a product of either natural selection or freak accident. In the entire history of evolution on our planet, natural selection has favored bigger/ stronger/ faster over smarter. The most enduring alpha predators on this planet have never developed more intelligence, they've simply been effective dumb eating machines. The anthropologists are still scratching their heads over how humans ever wound up evolving braininess and ( more importantly) why. The most popular theory right now is that intelligence was an accidental by- product of upright bipedalism and the ability to perspire and was never favored by natural selection. Even in today's society, intelligence seems to be of fairly low value in the genetic "dating" market. It could be that the evolution of intelligence is not the norm, but rather a freak accident. And if that's the case, then civilization may be exceedingly rare (or nonexistent) even if life is fairly common. Best, -Slashy

Yeah, they're not necessarily a night and day difference. In some payload ranges, pure SRB first stage is the cheapest. In others, the LF&O is cheapest. In all cases, however, LF&O is lighter and easier to fly. In the case of "lighter", a pad limit or part count restriction may dictate chucking SRBs (such as in my example). In the case of "easier", the designer may opt for a more friendly LF&O design, particularly when the prices are close. Best, -Slashy

Helmetman, I was insisting on this same point a little over a year ago myself. I have since learned that this isn't quite correct. The cheapest disposable boosters are actually a quasi-asparagus arrangement of SRBs around a LF&O core. The cheapest solutions were in the $500 per tonne range, and about 150t payload. At the other end of the spectrum, the Flea and Hammer are not cost-effective when employed as first stages. LF&O designs will not only be lighter, but also cheaper. SRBs come into their own as first stages with the BACC and the Kickback, and can be very cheap... but it comes at the price of throttlability and steerability. Clustering boosters helps with the throttling issue, since the thrust can be tapered over the course of the flight. Unfortunately, by the time clusters come into play, you're getting into some pretty large payloads. All of that to say this: In the range of small rockets (such as the one I posted), SRBs aren't the best option. Too heavy, too expensive, and too temperamental. And since Starchaser's mission can be accomplished by a small rocket, SRBs are not viable in this case. Best, -Slashy

Absolutely. The emphasis on "cheap" would be greatly reduced if the entire LV could be recovered. At that point, you run into fuel expenditure (or payload fraction) as the overriding economic concern, as we do in SSTO spaceplane design. You also run into a gamble with reliability, as you are betting that you will never lose a vehicle, which instantly erases the savings. This is the basis of a counterpoint I was going to post in regards to a point raised upstream; "A stock monoprop design can never outperform a LF&O design".(Edit: A misunderstanding on my part. Nobody actually said this) One case this is not necessarily true: When the payload has monoprop tanks you weren't going to use and the DV budget is low. In this case, the monoprop engine has the advantage because the tankage is free. Even though the Isp is lower for the LF engine, there isn't enough burn time to make up for the mass of the fuel tank in fuel savings. On an even shorter scale, it may not be worth it to add the monoprop engine at all, as the reaction thruster itself is sufficient to provide the required DV. In this case, the monoprop engine would have to save more fuel than the engine itself weighs. On a short enough DV budget, there's not enough fuel expenditure to make this happen. Best, -Slashy