Cunjo Carl

Oh, thanks! I had no idea. I'm happy to hear people are still giving this mission a shot, it was fun to make. I got whacked with a nasty illness which prevents me from playing games (or surfing much) so I'm almost exclusively in the Science & Spaceflight forum. I hadn't even heard of the mission of the week or the destroy KSC challenge. Cool sounding challenge though! Thanks for letting me know, I'll fix up those broken images soon. Seeing this reminds me, I was originally planning to make a deluge of missions earlier this year. Please look forward to some more creative ones when I can get back to it!

Interesting! Don't count it out too soon, there actually is a thing. A great example is that you can actually see bullets flying through the air if you're along their path (hopefully from the origin!) Though they're normally effectively invisible because they move too fast, from some angles, they're quite plain to see. Let's imagine a game where there are some entities (call them ghosts) that are difficult to notice because they move back and forth along a line too fast and blur out, but if our player moves to the right angle the ghosts are clearly visible. The ghosts' sudden oscillation between near and far would be pretty unnerving. Then suddenly, one gets closer!! Yeah, that could be a fun. Maybe a nice mechanic for a walking simulator or a suspense title? There actually is an occasional advantage (among the disadvantages) for game designers to work with mechanics created by bugs, technical difficulties or obliquely nuanced mechanics. It crops up surprisingly regularly, especially in small titles where the play experience can be short and tightly crafted and high risks are more par for course. They even show up in AAA titles sometimes... I'd give it a go, but I think this video describes it a lot more eloquently. Bugs becoming features. The wonderful results of bizarre mechanics taken seriously. I haven't watched the 4k video yet, I've kinda been avoiding it! I'm assuming he just complains about dpi? For one of my old jobs (MEMS fab) I used to observe the quality of 10um features with my bare eyes, so my opinion is that up to 2500DPI is A-ok :D. (mostly kidding, I've never seen high-res monitors in real life, so I don't know for their case)

Thanks for the word! Awww... That'd be too bad to hear if WASM's switches won't be improving over JS' JIT... I was hoping to atleast get compiled JS speeds out of it. I really think that's the biggest drawback of using JS for a ton of applications, is how idiosyncratic and poorly documented its profilers and compilers are. One wrong move and a whole function gets slapped into the 1% native run speed morass of the JIT interpreter on atleast one of the common browsers. Switches and dispatch functions are the most problematic for sure! Even put within a very simple function with nothing nasty to worry the profiler or compilers (in Firefox for preference for me) and with everything being best case scenarios (like consecutive ints 0-100, no fallthroughs, no cache thrashing, etc) it took ~~80ns per switch. Putting in a nearby eval() to force JIT, didn't make it that much slower, which kinda shows how slow it can get. For everything else though, I'd be a happy camper with WASM running at compiled JS speeds (optimized or baseline). I was really hoping WASM would bring in assembly abilities, like jumps and prefetching! The WASM community seemed really adamant about having only simple code control though, offering only switches as non-binary control. Come to mention it, do you happen to have any idea how WASM's going to emulate C code if it can't do jumps (for the gotos)? It made sense that they could play some tricks with WASM's switches as a hack when compiling, but if they're going to do JIT with any reasonable efficiency, they'll need jumps. Back when I was poking at it (early 2017), the general consensus seemed to be that only bad programmers need the code control of jumps or jump tables anyways, and that jumps would make the syntax ugly. For my case, they weren't wrong on any account , but I'd like to see how they're going to handle this! Maybe I'll get lucky and they'll breakdown and put 'em in after all. I'm mostly just chatting, I can't code at the moment (or even browse more than a hair), but after seeing the 'lexing' thread and I came to wonder if the old roadblocks from that project had been cleared. Sounds like not yet, unfortunately. It's nice to hear the WASM folks are really pushing the whole C/C++ JIT emulation thing though! It wasn't in the plans when I was poking at it, but I think that'll do them well. The UI library support of JS meeting the functional library support of C/C++ should make a killer duo! It feels like it's been in beta for ages! I'm happy with feeding it static memory, but admittedly the setup to even get a "Hello World" out of it was pretty non-trivial. I guess I'll wait another year and see what they do. Thanks for the update and advice! Cheers.

Hey! Any chance someone here's tried out WASM? I was curious about the performance of its switch statements for ~50 cases? The code would be compact, so instruction cache misses shouldn't be a big deal, and I know YMMV with branch prediction and all, but I was hoping someone could give me a general feel of if it's 'zingy' or 'better if you didn't.' I was really crossing my fingers they would decide to toss in jump tables in the end, but now I'm wondering if I can just kludge it with a switch. The portability of WASM is really enticing, as well as its ability to tie in with JS (and its 10billion libraries) which is why I was hoping for it in specific. Thanks in advance!

Hmmm... I like the ideas of either an inflatable pressurized space on the rover (like the BEAM on the ISS), or an Ikea-style rover to be shipped in a box and assembled on the surface. Maybe a mix of both? Delivery for these cases could be the same as our present techniques: Rockets, sky-cranes, giant bouncy balls... Image from physorg: phys.org/news/2014-01-decade-old-rover-adventure-mars-earth.html NASA can be very Kerbal sometimes.

Interesting, I had thought the SRBs were largely the same as before, save for the extra segment and (I'd assume) some safety updates. Let's see... I remember NASA's 2-page happy facts sheet says they wound up needing to change a few things: 25 percent more propellant New nozzle design New asbestos-free insulation and liner configuration New avionics Improved nondestructive evaluation processes That sounds like a bit of work, but not a ton. They're definitely understandable updates and retrofits for serving on a new rocket. Let's dig a little deeper... Apparently the motor cases and the propellant also need updating!? What would be left of the original? I can see what you mean about the heavy redesign now. It looks like they'll be aiming for yet another redesign as well, the "Advanced Booster", now in a racy black color! If I'm understanding this little tech blurb in the image, it's only supposed to take only 1000 labor hours to produce? Somehow that seems like an underestimate, but I'm sure they have something in mind. Then it seems they're trying to keep the door open for yet another yet another redesign after that... Well, even if the race was over before it really started, it's still interesting from the tech perspective: 'Advanced Booster' SRB 'Pyrios' LRB VS Oh my gosh, the F1-B LRBs are what the Twin Boar was designed after!? I knew I liked them for a reason! (Images originally from https://www.nasaspaceflight.com/2018/05/sls-advanced-boosters-flight-nine-shuttle-heritage/ )

Committee decision, got it. That's too bad! Well, if anyone's got the goods on the tech specs, I'd still be happy to learn about them.

I've recently become interested in the F1-B engine, a radically simplified and modernized revision of the F1-A, which was designed (but as I understand not prototyped) for the SLS as a liquid alternative to the shuttle-like SRBs they went with. I've been trying to get a feel for how these options compared to eachother and why (specifically) they found the SRBs to be the better option. In the absence of a committee, the decision would probably boil down to (in no particular order): Thrust (engineering requirement that both options provide a total of 3.6MN) Dry mass Isp (or burn time) Cost Logistics Safety/reliability Aerodynamic/vibration complexities I'd have to imagine that the F1-B would take an edge from the safety/reliability standpoint, but I'm having a really hard time finding anything concrete to compare them by in the other regards. I've found on wiki that the shuttle SRB has a vac ISP of 260s (pretty good!), but while I know Cape Kennedy can have some nasty weather, I've never heard of it being vacuum bad! Anyways, anyone have some figures I can sink my teeth into? Thanks in advance.

Oh, good point that's true. Rereading my post I'm missing a few things! For the case of Nitrogen, it's fairly ironic given how necessary it is, pretty much only bacteria can utilize it (and maybe that one fungus). It really highlights how interwoven our biosphere is!

I like the idea! Preface, this is how I remember it working, but it may be a bit off... There's two varieties, and both can provide magnetic levitation. The first (and the kind I'm much less familiar with) is a 'linear motor' type, where there's permanent or electromagnets in the track and electromagnets in the train. The other rarer kind is called the linear induction motor where there's electromagnets on the train and a conductive but non magnetized track (like plain old aluminum). As the electromagnets on the train turn on, the electrons in the nearby conductive track experience the sudden magnetism, and (by the way of things) rush in circles (called eddy currents) to create an opposing magnetic force. This causes momentary levitation, but it's not a stable situation. Quickly afterwards though, the electromagnets on the train start to turn off, and just in front of them another set turns on. The new set also opposes those eddy currents , and because it's a little in front of them, pushes forward off of them (moving the train forward), while simultaneously creating a new set of eddies very slightly further forward. The process repeats, and the magnets keep pushing off old eddies while creating new ones. The rate these eddies move within the track is called 'slip' and is a defining factor in how the motor functions. In real situations, the motor will use electromagnets turning on in alternating directions (poles) rather than simply on/off. Also, the above is from a stationary perspective. Because the eddies move much less quickly than the train, the electromagnets on the train need to sweep backwards to keep up with the track. This is all what I remember, and it should be mostly correct but may be off in a little detail. I had to study LIMs for a project a good while back, and wound up prototyping one in my garage. What stuck with me most was how to choose wire gagues and wrappings rather than how the blasted things worked! Sometimes life is like that. An LIM to support 500Tonnes of rocket would be truly gargantuan and require enormous amounts of power. There are, however, many things in this world that can supply and handle enormous amounts of power so it's certainly a possibility! It would be interesting to calculate just how much electric power would be involved, but I'm expecting from a paper I just glanced at ~1-2kW/ton of levitation assuming a typical slip (optimized for pushing the train forward by magnets). So, probably 1/2 to 1 megaWatt for my proposed 500T rocket sled ... As a reference, your house probably pulls ~1kW on average, enough to maybe levitate a very small car. Edit: The 1-2kW/ton value sounds a little low to me. Maybe the ones I made were really low efficiency though! That would certainly sound likely. I think... I could be wrong, but I seem to remember you could get better levitation efficiencies if your track was ferromagnetic (like carbon steel). The downside was magnetic saturation could be an issue, and you couldn't use high slips so forward motion got a little funky. Still, I think the first thing I'd look into would be this. For fun, back at home, It is possible to levitate an object in place using a single electromagnet which simply turns on/off quickly by this same effect. It's a common physics demo, called the jumping ring.

For certain values of the term terraform, for sure there's at least a possibility! Things we need: CO2 <.03atm (more is toxic) O2 ~.20atm (less is uncomfy) Temp > -20C (need green house gasses to maintain) Diluent gas enough to make the O2 not ignite us poor carbon based life forms with a single spark. There's Fluorine on Mars in atleast some amount, so we could imagine converting the deposits into a green house CFC that doesn't rapidly degrade by UV photolysis. That could help drive up the temperatures. There's plenty of Oxygen on Mars, in the soil as oxides and at the poles as CO2 There really aren't any good sources of a diluent gas, like N2 or Ar. This could be a big sticking point. How would we drive up the O2 and down the CO2? Like all rose-tinted plans for Mars habitability, this one involves finding water out there. Once Crispr really hits its stride, we could (atleast in our ambitions) terraform the red planet using highly modified plant life. This plant life could lift O2 out of the rusty soil, and drive CO2 out of the air by affixing it. If they were dark enough, their albedo could help warm the planet (with the help of some potent green house CFCs) . I think the hardest part is that there aren't any suitable diluent gasses. To last on the surface, you'd need N2 or Ar... And there just aren't any good sources for either! Hmmm... By the time we do all this, the human body may be obsolete anyways. Mars as it is could be a get away paradise for the AI human androids certain to be ubiquitous in the near future! Maybe we should just leave enjoying the fun and sun on the red planet to them? ... I'm sure Elon would agree Edit: My plan is missing a few little details.... Hah! Slightly understated of course. I really shouldn't post when I'm so tired.

I'd argue in this case that we need it. The verticality of the sled is one of the hugest technical hurdles. It would ideally be at like 80 degrees! Putting it even at 45 is adding in a lot of technical constraints on the launch vehicle, and that's still an enormous challenge on the sled end as well! A nice flat rail and a HOTOL SSTO (horizontal takeoff and landing) are peanut butter and chocolate. It's the high ISP of the air breathing mode that allows for the slow, low angle of attack climb. Zeplins launching rockets? Now we're talking cool While the rocket sled idea has numerous technical hurdles, I'd contend that these particular ones aren't the biggest of deals. The space plane would need to be able to structurally survive transonic conditions, but given it's designed for surviving the considerably greater aerodynamic pressures of MaxQ (up at mach 3-5.5 somewhere) the transonic region wouldn't place any new design constraints. It's a freebe! That is, unless ground effect causes massive amounts of excess lift that somehow aren't experienced in other regimes (like reentry). Next, the rocket sled will certainly experience drag, but even a (very) highball estimate would be .5G worth when at top speed in addition to the of the 2G acceleration. On the other hand normal rockets generally work up to many G of acceleration in addition to both gravity and aero drag. By comparison this sled's gonna be toodling! Fuel-wise, since it's only responsible for ~450m/s deltaV, the aerodrag won't kill us through the exponentiality of the rocket equation either. Just bring along some more fuel. On the flip side, plane-based launchers would need to deal with both its own drag (parasitic), as well as the lift induced drag to keep everything floating. The current state of the art, VMS Eve, isn't able to break the sound barrier-- It provides the height without a ton of speed. Adding in the further constraint that it would be carrying an enormous Hydrogen-fuelled vehicle makes it a tricky sort to imagine. It's already the biggest composite air frame ever built, but it would need to get much larger! Spruce Goose eat your heart out, style thing. It would definitely provide the additional advantage of dropping off the launch craft at a higher altitude (= lower pressure) so perhaps the added difficulties are worth it? Let's actually put some numbers on these engines and the fuel mass of a rocket sled. Now given this is fantasy, of course I want them to be raptor engines! Sadly, I think those will be massively overkill. Let's check. Skylon wet mass: 325T (wiki) Raptor SL Thrust: 1700kN (wiki) Raptor SL Isp: 330s (wiki) Sled Fuel Mass (approx): ~80T = (95+325)*(exp(450*1.25/(330*9.8))-1) -- Includes 1.25 factor of drag Sled Total Mass (Guess): ~175T = 80T Fuel + 95T Everything else Sled+Skylon Wet mass (iterate): ~500T = 175T + 325T Sled numEngines: ~7 = 500*(2*9.8*1.25)/1700 -- Includes 1.25 factor of drag Sled numEngines including a 15 degree outwards cant: ~7.5 = 500*(2*9.8*1.25)/(1700*cos(15deg)) Round it to 8 Well! Lucky me, it looks like we'll get to use raptors after all . These figures include a healthy margin for aerodynamic drag, but do assume fairly high grade components for the sled. On the other hand, a -very- heavy sled might end up being more like 350T fully fueled (240T dry + 110T fuel), and require 10 raptors to push it including the outwards cant. I'm assuming that most of the mass will be attributed to (in order) the frame, wheels, tanks, plumbing, control surfaces, motors+suspension+breaks, rocket engines, and lastly the seats for crazy tourists who might be named Jeb. Now while I think the above aspects are circumventable by available technology, there's quite a few that aren't. Q: How do we keep this sled stable on the track without lifting off or slamming down at any point? A: Uh... Canards+Spoilers? Q: How do we keep the sled's exhaust plumes from scorching the track? A: Maybe put the sled's rocket engines on pylons with a slight outwards cant? Q: How do we account for most of the mass being mounted on top? A: Having the rocket pylons up on level with the mutual center of mass would probably be the way. Q: So Skylon just flies off this thing without trouble? A: For sure! Q: Where can you build 15km of track without bothering nearby populations with all the sonic booming? A: There's a few places, but they're admittedly almost as rare as a nice mountain people wouldn't mind you launching rockets up the side of. Q: What if a kangaroo or an emu gets on the tracks? A: Just build the fences around it high... like reeeeaaly high.

Again, I'm a fan of the rocket sled idea, and I do like the approachable aspect of the page, but I'll point out the following challenges: Launch Escape System Building with roller coaster technology Launching an orbital rocket through a tunnel It's fun to imagine how we might approach these challenges, but the one thing we can say for sure is that they're not cut-and-dry as presented. Some researchers would get to make their careers by them! Nothing wrong with that. Why am I a fan of rocket sleds though? I used one on an SSTO in KSP once, and it worked amazingly! So I hatched a plan... and as we know, if it works in KSP it'll work in real life too, right? Now this isn't the *Best*Plan*Ever* (tm), it's just my rough sketch idea of a cool thing to be done with a rocket sled. Rather than being based on the X-33, it's based on Skylon, the fully reusable SSTO space plane coming out *soon* (tm). The rocket sled (Methalox or turbojet powered) is supported on a ~15km long, perfectly flat and level high gauge rail with one rail electrified. The rocket sled cradles the fuselage of a space plane that is exactly the hopes and dreams of what Skylon could be. A few launch clamps hold the two together. Skylon spools up its engines while the rocket sled fires, pushing forward at 2G! 5km down the rail (22 seconds later) they're traveling mach 1.3, then the launch clamps unlock and Skylon lifts away by aerodynamic forces. The rocket sled engages brakes (reactive brakes maybe) and slows down at 2-3G over another few km, dumping most of the power into the rail, where it's used for something cool back at base camp... lasers maybe? Then, after stopping, the rocket sled uses electric motors to drive back home. Meanwhile, Skylon does what Skylon does (why mess anymore with an already awesome plan). It picks up altitude and velocity up to mach 5 with its miraculous jet engines, then it switches to closed combustion and rockets into orbit. Once there it drops off a payload (or acts as mothership to a returning GTO second stage) , and then flies home. Because it's nice and light weight by now, it'll have an easier time of this than the shuttle. Finally, it uses powered flight to land back at the starting blocks. A crane or something drops it off on the rocket sled again, they're refueled and flown again! It'd have no launch escape system, because it wouldn't have passengers! Just cargo and a computer at the helm. In the case of an emergency, it would try to save the spaceplane by having it lift away, or having the rocket sled put on the breaks, but it definitely wouldn't be human rated. What advantages does this have over Skylon as it's currently envisioned? This would let the designers optimize the aerodynamics and engine profile for super sonic flight without worrying about takeoff, subsonic and transonic conditions. It would need to be able to fly in subsonic conditions on return, but not efficiently! As much as the free deltaV, removing the subsonic design constraints is what would really add value to the system. Also, the landing gear (= dead weight) could be made much smaller because they would only need to support the spaceplane _after_ it lands without the fuel/cargo. Additionally, there wouldn't need to be a large launch-abort braking system in the landing gear, because it would be on the rocket sled instead. All of this translates to a huge boost in deliverable payload fraction, which translates to money money money. Advantages over contemporary flyback boosters: Fully reusable, no lost upper stages. Less assembly required per flight. Disadvantages: Plenty. I really like the idea though!

Yeah, understood. I had mentioned early on that the purpose of each stage of the compressor was to incrementally boost the pressure and someone corrected me saying each stage was instead for incrementally accelerating the flow (speed) in preparation for a single sudden pressure boost just before the flow enters the combustion chamber. Given continuity and the influx conditions that sounded unusual (like a good recipe for choked flow), but it's been a good while since I did pump/compressor design so I was asking. Thanks! It's kinda funny, when we were learning compressor design in chemical engineering, we were taught that axial compressors were so expensive that you could optimize the cost of your entire plant by just considering them alone. Aerospace is quite the industry, strapping 2 of these onto a chunk of metal and just tossing them up into the air!

Rocket sleds are an awesome concept, and as a total layman I prefer them quite a bit to hyperloops, but they do have a number of interesting issues. The main things that stick out in my mind are that the ground effect (uneven aerodynamic drag/lift because the ground is so close) is going to get really crazy when the rocket goes transonic! Also, and there'll be notable mechanical stresses on the rocket just from being supported and propelled from the side. Plus, after release the launch vehicle would require much more aerodynamic control than your typical 'flying cylinder' vertical launcher. All this sounds like a lot of extra structural requirements on the rocket, which'll raise drymass considerably. The question is, are these increased structural drymasses somehow less than the drymass of the extra fuel tank that would have been needed to hold the 'wasted' fuel of a normal launch.... despite being less awesome somehow I think the normal launch would win out. There's a lot of stuff on this particular site that doesn't quite sound right to me, though I'm admittedly no expert on the topic. One example as case and point, they posit that the first stage speeding up along the ground is actually a good thing for the crew's safety, and to be honest, that's bizarre! With a proper LES, your chance of escaping a rocket catastrophe is really quite good. If you were traveling mach 2 only a few dozen meters off the ground, and the launch vehicle or its rocket-sled breaks or explodes or otherwise falls from track, what could you possibly do to save the crew? The webpage says the crew could "... eject from an escape capsule, similar to aircraft ejection seats". At mach 2 just off the ground? With the upwards inflecting track? Really? Also, I found these statements particularly funny: " There are other bogus space launch concepts that are proven failures, yet continue to be advocated and funded, like maglev launch and reusable boosters. " " Shooting a spacecraft upward off a rocket-powered sled a better alternative. " " Building a ramp up a mountainside may seem complex, but it's simple compared to the difficulties of building massive rollercoaster tracks. " " Some people have expressed concern about air pressure build-up if a tunnel is used. One solution is to make the tunnel wide enough so its not a problem. " Thanks for sharing, @farmerben! I do really like the concept of rocket sleds by the way. It's mostly that they have a lot of technical difficulties that would need to be addressed (like anything), and this particular page tends to call them "minor problems" and not really deeply discuss them, while also ascribing them many benefits which I don't think they really have. I do like it as an introduction to the topic though!

Having a single impeller do all the work winds up being thermodynamically lossy unless it's quite long and very -very- well designed. You wind up creating a ton of heat! Having many smaller compression stages helps keep all the energy you put in turn into pressure rather than heat. It's true what I've been calling pressure for clarity is better called 'head'. In real life the turbine increases the energy of what it's pushing on and that energy can take the form of either pressure or velocity depending on what's going on downstream (namely the cross sectional area of the chamber). I thought jet engines primarily boosted pressure, given the air is already enterring a right fraction of the speed of sound. Was I wrong about that?

Not really sure. I only know the term from other industries, but it has a pretty standard meaning. The impeller (or impellers in this context?) should just be another word for the compressor fans which boost the pressure of the incoming air to make the combustion work better. They're something that turbojets have and ramjets don't. The word impeller could also be used to refer to part of the pump which pressurizes the fuel in order to squirt it into the combustion chamber, but I think in this context they're talking about the air compressor fans. EDIT: @Cheif Operations Director Using a blade turning the other direction to act as a stator and also the next stage of the compressor/turbine is a great idea, and I seem to recall seeing a system that worked like that, but it was definitely a terrestrial application. The main reason it's not done more is probably the mechanical issues involved... counter rotating fan blades can be surprisingly hard to make, because that means their shafts need to be concentric (one inside the other) and the bearings to hold all this in place suddenly become much more touchy and expensive. It would however theoretically boost thrust to mass on a plane... Ah! Here's a paper of people doing exactly that. http://softinway.com/wp-content/uploads/2013/10/Comparison-of-Counter-rotating-and-Traditional-Axial-Aircraft-Low-pressure-Turbines-Integral-and-Detailed-Performances.pdf They have some ideas to make it work with a parallel shaft rather than a concentric one... interesting. Anyways, good idea!

I'm a bit out of my depths here, but I believe the unholy union of a turbojet and a ramjet into a single engine is simply called a turboramjet. I think.... I think Sabre technically counts as one (the rocket that KSP's Rapier is based on.) It also has closed-cycle functionality where it turns off its airbreathing abilities, and turns into a rocket engine. It's basically the coolest possible rocket plane engine. As for turboramjets, I don't think they've ever heard of one in practical application, it's mostly a fun idea. There's a few prototypes around though. Likewise, ramjets don't really appear on airplanes except as extra engines on a normal plane for use in research and novelty, though I have heard of a ramjet missile once. Anyone correct me if I'm wrong though, has anyone heard of a production ramjet plane? Also along these lines are air augmented rockets, which don't bother with any of that silly Oxygen stuff in the air and just use the stream of air coming into the engine for added reaction mass = Isp. They also haven't seen practical use, but also sounds totally awesome!

Your idea would work as a stator, for sure! Actual ones in turbines are apparently just a bunch of metal slats all pointing in to the center like an asterisk * . This said, I've never seen one in real life besides on pumps, so I only know what I've heard here. If someone know more specifically, feel free to chime in!

A mixture of direct pushing and a little centrifugal force. Same as a ceiling fan! Think about sticking your hand out the car window to use it as a 'wing'. If you tilt your hand up, it catches air and pushes it down. It's the same with the turbine blades, except they spin in circles and push the air toward the combustion chamber. If you want to keep boosting the pressure higher and higher though, you need to put things called stators between them, which keep the air going straight back (and pressurizing) rather than just spinning in circles. *sniped*

Here it's all about pressure. The layers of turbine blades (and stators) will boost the air pressure higher and higher until its driven into a very high pressure reaction chamber to burn with the jet fuel. The advantage of high pressure is that the fuel burns faster, more completely, and yields more mechanically available energy. It's an identical story to the pistons in a car by the way! They compress the gas+air before igniting them.

Oh, I was assuming it was your fuselage choice, but it sounds like it was also your engine housing? When I was younger we also used PVC for a bunch of medium pressure applications. It's tough, cheap, mildly fire resistant (though not terribly heat resistant), and can withstand a good range of chemicals and solvents, so we were always finding creative applications. We'd never considered using it for a fuselage or a rocket motor. I just liked the idea! I'll actually be using clear PVC soon to make a prototype vacuum 'distillation' reflux extractor unit a family friend wanted.... it's really versatile stuff.

I also used to build rockets and out of more garden variety materials, but for someone starting off rocket candy is a little bit of... well trial by fire. Good for those that have a lot of non-burnable space and eyebrows to spare! I think a happy in between for cheap home built rockets are water rockets (which can apparently get pretty powerful if taken seriously), and alcohol rockets. I'll never forget my first water rocket. That thing... uh... really moved! I live in a safety culture, so "Wear eye and ear protection, and operate in a safe, open environment with responsible adult supervision." If you're an irresponsible adult, goodness help you I suppose! How high did you get with those rockets @sevenperforce? Did the mixtures treat you well? I like the choice of PVC, by the way!

Oh, I used to do a lot of amateur rocketry with my folks. For what it's worth, it's a very fun hobby. If you have funds to build from a kit, the 1-2ft (~30-60cm) -ish sized rockets launched with engines at the low end of their range tended to be the best experience for value. Loading higher power motors into a rocket make it go higher and faster, which mean you get to see it for less long, and it drifts on its parachute dramatically farther away. Most rockets that are lost are lost to parachuting into distant trees! Since they go pretty high, there can definitely be stiff breezes up above that you don't feel on the ground. It's not a big deal, and chasing after them is part of the fun! But if you're going on a budget, losing a rocket to the wind is pretty obnoxious. When you use a bigger rocket with a smaller engine, it's helpful to get a shorter-end delay for the parachute charge so the chute will still pop at the rocket's apex. Most kits will provide recommendations. Choosing your motors can be hard at first. Fortunately, experience in KSP will make it a lot more intuitive! Another bit of good news is there's some very common and standard sizes. Most rocket engines are Estes brand, or atleast conform to their standards. The way they're designated is by a letter and 2 numbers. From a super simple perspective, the letter tells you how high the rocket will go (total impulse), and the first number tells you how fast (roughly proportional to thrust within a given letter). The second number tells you how much delay there will be between the engine burning out, and the parachute-popping charge from firing. All of the common starter engines (1/2A , A , B , C) are the same diameter, which gives you a good degree of flexibility. Naturally, choosing an engine too 'small' causes the rocket not to lift and too large causes... more exciting problems! Here's a list of some favorites for comparison: http://www2.estesrockets.com/pdf/Estes_Engine_Chart.pdf When you glue together rockets, proper glue choice is important! For a first rocket, I'd recommend 5min epoxy. It has its own troubles, but they're less than that of the cyanoacrylates (crazy glue), the urethanes (rubber cement) or the longer cure epoxies (which are a better choice in the long run). I wonder if anyone has experience with gorilla glue? It came out after my time. Packing chutes is really an art form. Most rockets will have instructions, but the one thing I'll add is that a light dusting of baby powder really helps them open up consistently. If you do a smaller rocket with a streamer, powder up that thing too! Nothing beats the smell of burning gun powder SRBs in the morning! If you do decide to give it a try, I hope you have fun, @Opus_723. As for stories, I once had a tiny rocket named the minnow (or perhaps the mosquito?) Anyways, it was a tiny thing that was barely large enough to contain its engine. My family and I were out in the desert, and figured if we were ever going to try overpowering it, this was the day! So we loaded the poor 1/2A rocket with a high thrust A, and hit the ignition! There was a faint "zwip" noise and the thing simply disappeared! No smoke trail, nothing. A good half hour of searching lead us to find it a hundred yards away, but it was a good lesson in F=ma!

Oh, cool! There's a difference between our results so it looks like we'll get to have the question turned around on its asker . Nothing to do but keep going back and forth to see who hits their target first, eh? Yeah, whether you attack the problem constructively or deductively I guess is a matter of taste. I went constructive because I wanted the general solution, and as always, it took 10 times longer to write out than it did to scratch on paper! I agree, it looks more complicated written out. Either works of course, but I think there's a little wrinkle missing from yours...