Rune

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Everything posted by Rune

  1. Fire up KSP, install RSS, try it out. Or, you know, have a little faith in the guy that did and commented a couple pages back (not me!), and quotes 9,1km/s as a likelier figure. Rune. It also works if you consider the fraction of kerbin's orbital velocity and kerbin's P2P requirements. Basically >90% of orbital speed.
  2. I just posted this elsewhere, but I think you guys will appreciate the anlaysis better: So, I have run the numbers on that lunar mission. It's mighty interesting! This could be the real intent behind the whole 'paying for it' thing, finding the customer that foots the bill while feeling like he makes a great deal. Let me explain, and hold on to your hats, 'cause I dunno how long this will be: First, assumptions. I will assume that the numbers given in the presentation are true (Raptor Isp=375s, empty weight of the orbiter 85mT, max. payload 150mT, max. fuel load 1,100mT/1,250mT in the tanker version because payload is fuel), that the mission is staged from GTO (Geosynchronous transfer orbit, which is reasonable, analysis as to why later), and that the dV map in the wiki is close enough for government work. Why GTO? Well, according to the wiki, form there it's about 3.2km/s to the lunar surface. Add 2.3km/s to come back to an atmosphere-intercepting Earth orbit, and you get 5,5, well within the 6,4km/s my trusty excel sheet spits out for the BFR orbiter, with full fuel and 150mT in payload. Seems reasonable. That means that we need a full BFR orbiter at GTO, meaning we first have to refuel it in LEO (at least 8 trips of a tanker if a tanker can transfer 150mT of fuel and suffers little losses). Then, we have to refuel it again form fully-fueled BFR tankers, themselves refueled in LEO, each by its own eight tanker flights. How many tanker flights to GTO we need can increase the total number of launches pretty quickly. So, how much fuel can a BFR tanker get to GTO, if starting full at LEO? Well, that is easy. Massaging my sheet, I get that a payload of 590mT of fuel makes it to GTO. Coming back is easy, since perigee is still close to the planet, so the tanker can aerobrake. That means you need only slightly more than one tanker (at least!) to refill the ship with payload in GTO after it spends 660mT of fuel getting itself to GTO (again, that excel spreadsheet is neat). Since everything is a rough first-order approximation, let's call it two tanker flights, and the margin will take care of inefficiencies I haven't taken into account. So all in all, for one to reach the Moon and return, three BFRs must reach GTO, and in turn you have to launch 24 (!) to LEO to get those three up there. Well now, that proposition, at a decent enough launch rate, is starting to sound like a good business market to serve, a single lunar mission a year means two flights each month. There are the high flight rates that could make the whole thing economical, ginormous as it is. Rune. Imagine what that excel spreadsheet is meant for, and why I use it a lot. ^^'
  3. That is a point for them, yeah. But even then, if you think about it, they need the commitment beforehand, right? I mean, they ain't going to be cheap toys to put together. You know, I am usually the one to bring up the "you guys are all a bunch of planetary chauvinists" spin to the conversation, but I had never though about using Aldrin cyclers as an argument and/or intermediate step. That could almost work, right, the two things justifying each other? But nah, on second thought, if you want to learn to live in space for realsies, you don't really want to go to Mars, and one thing distracts you from the other. Rune. Just to clarify, I truly believe that in, say, 2,000 years, living in a planet's surface full-time will be for the eccentric few.
  4. Cyclers are basically a way of overcomplicating the whole thing into the realm of sci-fi. Let's start from the beginning... what are Cyclers for? Well, theoretically, they lower the mass necessary to launch from Earth for a Mars mission... once you have launched a bigger mass to build it in the first place. And yeah, they make a ~6 month travel a bit more comfortable... but then why do we have crews of humans living in a tin can for longer stretches at a time in ISS. Bottom line? They sure are a way to overcomplicate your architecture and increase the cost of the first mission. They add complexity and failure points (what happens if the transfer ship fudges up the rendezvous/docking? How do you send a menteinance crew to the cycler without committing them to a whole mission?). They add to the total R&D cost, because they imply a separate vehicle to be developed and launched (and a big vehicle at that). And all of those compromises, all of those additional costs, for what? To make 'easier' a trip that can be done in a single lousy chemical stage. Yes, I said that. Mars is very much not far away, the dV to land on Mars is lower than to do the same thing on the Moon. And if you ain't landing, a slightly more sophisticated chemical stage can actually do a roundtrip to Mars if you design the architecture smartly (aerocapture into a high orbit on both ends of the journey). Rune. TL,DR: I see no real benefit, and a whole lot of added difficulties.
  5. Many moons ago, I did a replica of the soviet MAKS spaceplane... an actual serious proposal that even saw some ground test articles built, and some tripropellant engines tested: Rune. I guess having a Mriya built, you just look for stuff to put on it.
  6. Yup, you guys are basically re-deriving the classical rocket science mantras: -The most important figure of merit for a first stage engine is TWR. -The only important figure of merit for an in-space engine is Isp. -SRBs are the thing to get cheap thrust off the pad. The second one is kind of obvious (more Isp=more dV= you get further), but the first one is not any less true. A higher TWR can do absolute wonders to your total takeoff mass, not least because it will minimize gravity losses, which are the ones that dominate in pretty much all but the tiniest rocket designs. Rune. Bottom line: for pure LFO performance, and screw cost and scale, nothing beats a Mammoth (first Eve SSTO, first true SSTA). The Vector is the close second that is actually easy to configure for a given mission.
  7. Yeah, the big drill is a must, since it's the only one that will work anywhere, not just regions of high ore concentration (so you don't really have to scan for ore and have global access), plus it allows you a decent ground clearance. OTOH, no reason to bring the heavy ISRU unless you are interested on 100% efficient ore conversion (i.e: you store fuel as ore to save tankage weight, which can be done BTW on large ships where the 4mT of ISRU are a rounding error), or you want to power the ISRU equipment with the magic of very broken KSP thermodynamics (you can power a refinery with a tiny part of the LFO mix it produces, which is very not like that IRL). But if you are patient and/or nuclear-powered, the small one saves weight and works just as fine. Thanks! I must tell you, I had an inspired afternoon on that one. It just short of fell together without me noticing, and then it was just a bit of polish... after having percolated a lot of info subconsciously in the background, for a long time, I imagine. Still, I have taken much longer to come up with airbreathing birds... rockets are refreshingly simple by comparison. Rune. Always glad to return the inspiration when I can.
  8. Tips? Well, I have one: abandon all hope of SSTOing Eve with an ISRU payload. And even if you did (because yes, it is possible to SSTO Eve, just amazingly difficult), no freaking way in heck you can then reach Gilly to refuel. That is with stock parts, of course, mods are as unlimited as the cheat menu. Other than that, if you want to reach Tylo (which is in itself quite the achievement), go with an all-rocket SSTA. They are surprisingly easy to design, once you realize what you need is a Kerbin chemical SSTO with enough nuke oomph to get itself to Minmus afterwards as a payload, plus the mining equipment, of course. Can be done with a single nuke and just two Vectors, which is a plus since the size (=part count) doesn't have to be ginormous. Mine looks like this, but VTVL could be even more efficient, since TWR is more than one at takeoff, I just wanted to be able to nail precision landings on rocks with atmosphere, easily. Rune. And yes, that thing has made the Kerbin-Tylo trip for realsies.
  9. This is a tiny step, at most. And we might differ on it being the right direction slightly, nukes have a lot of hidden quirks that make them troublesome... Anyhow, 18.8 million dollars is about 1/1000 of the entire NASA budget. That is what they are spending on this. In the same budget, they spend upwards of five times that on education, and that is after massive cuts. Rune. So maybe the new budget is a 5x bigger step into becoming an education agency?
  10. Those are really good-looking. And the Comms relay not having to be actually connected to the base is something that hadn't occurred to me! Rune. Nice!
  11. So yeah, ignoring all the tangents about stealth in space, this is very feasible just as you envision it, because it ain't stealth in space. At least, not in the usual sense. This is, in fact, being a rock and surviving reentry. No one would look twice at a rock reentering, if it was small enough. We miss ~10m impacts all the time, because they are over uninhabited areas. I doubt we will have a good enough early alert system in 50 years to catch them. Make it ~5m across to give you some margin, and you can still fit a small spherical capsule inside (Dragon is three and something meters in diameter). And the 'tech' is dirt simple, the "disguise" of rock would make a pretty good heatshield over your heatshield, until it burned/blew away. Small, cold-gas maneuvering thrusters for small orbit correction could indeed be explained away as comet-like emissions if they are small and far away, if anybody is caring enough to look. During reentry, no one is really looking, so you can pretty much do what you want, as long as it isn't much more (or less) energetic than a typical piece of rock burning up (and there is a wide variety of rocks, so 'typical' is a very loose term). Then pop chutes at the last second, or even better, do a soviet-style parachute jump from a falling capsule, and let it sink in the ocean to hide the evidence. Of course, the long trip to another planet, especially if it is ballistic all the way, on a tiny armored tin can with a limited thermal budget... yeah, not very comfortable (but some small powersource would be feasible as long as it didn't change the IR emission dramatically, after all it could be an albedo thing). But magic away something like suspended animation, and/or drop it close to the target when no-one is looking (say, form a legitimate freighter doing a legitimate cargo run), and you are set. Rune. But people sure like to discuss 'Stealth in Space', which is in itself an interesting data point if you write sci-fi.
  12. Speaking as someone that has worked a modular base concept a lot... yeah, I concur. I also dislike putting modules in an orientation where the IVA doesn't fit, which means pretty much everything goes vertical. But that doesn't mean that it has to look bad! On the contrary, lots of concept art out there with cylindrical modules upright. Makes for a more efficient use of pressurised space (and flat floors). I guess you have already seen my stuff elsewhere (I've posted like, a lot of different versions over the years), but if I can recommend you just one thing, it's to go with the method of assembly that I learned from @Temstar a lot of moons ago: grab the modules by a docking port on the base. That way you have a common base that your construction rover crawls under, and dropping the landing gear on the base part makes the connection. With that as a standard, you can build your individual modules on top, on say, a common 2.5m base with the same clearance above the ground, and you can use the dcking port there to standardize the delivery method (in my case, the very awesome Orca, or a disposable reentry package for Eve). As a plus, with lots of construction rovers you can make your whole base a wheeled contraption, for relocation. These days, I'm toying with the idea of using KIS to build stuff on-site, with cranes and the like, from small landers with modest payloads. But, you know, mods. I really really wish KIS/KAS became stock at some point, it adds a ton of gameplay. (Edit: this is what I mean by awesome gameplay, imagine building bases that way!) Rune. But dang if it ain't hard to come up with something better after refining my Base-In-A-Box for so long.
  13. If you can fish the file, I'd be happy to reverse-engineer it to my needs... but I'm afraid I wouldn't know how to code it from scratch. Those are seriously awesome. Might take a gander when you post them, I've never gone the HTHL route with chemical rockets, and it will be nice to peek under the hood for the dV and TWR ratios. Rune. MTFBWU!
  14. Must have edited out the need for air. This is not stock, I doubledare you to prove me wrong.
  15. Depends entirely on your payload size. If you are pushing an O'Neill style habitat, 20kms wide is just about good enough to cover both cylinders with some margin for the low-grav farms around them. But yeah, structurally speaking it would probably be more efficient to use a Medusa-like tractor system, especially at those sizes. Of course the sail (much better to think of it that way) would be just as thick as it is required, plus margin (and could be a good radiation/debris shield during flight). Daedalus assumes colonies mining fusion fuel by the million metric tons, from the atmosphere of Jupiter. I think I can assume free solar orbit construction form asteroid material, conveniently manufactured into aerospace-grade parts, to build such interstellar behemoths. Rune. Fission fuel would be probably cheaper to manufacture on Earth, but a starship that has to brake at the other end should be able to manufacture its own bombs, 'cause half-life.
  16. It's not really that necessary (heating from LKO is not that big of a deal), but it looks really cool. It looks even better with a ring of aerospikes! Now, does anyone know of a way of changing the fairing's texture to something a bit less... crappy? It would be really cool if there was a mod to do so through tweakables... Rune. If googled for it, but all I find are dead ones, or procedural fairings.
  17. A personal thread where everything gets archived is a great way of not forgetting about your own crafts. Other than that, the likes come with time, and the good layout, with time spent editing. Rune. I encourage it, because it's nice to go back to it for the memories.
  18. Hi there! I think this goes here: 40mT of payload @100km circular, throwing nothing away. Well, actually the heatshield when you come back to land, but that's because I didn't like how the landing gear had to extend trough it in the 20mT version. This is supposed to be the launcher for a short-of-realistic RP'd architecture! That means no reaction wheels to magic things into behaving, no non-storable fuels being, well, stored, and everything is modular and a tidy 10mT in weight, so you can mix and match payloads to missions, yet still don't have to launch the same rocket a gazillon times per mission. You can see some examples of those payloads in both payload bays, I think they are turning out cute. Rune. I have channeled mi inner Bono here, I think.
  19. The Isp of an Orion is a tricky thing to work out. For starters, the only designs seriously studied were the tinier ones possible, and thus atrociously inefficient. But in a few speculative papers (like this one), Dyson outlined the true limits of the tech when you have the right size. Of course, by "right size", he meant enough to use efficient thermonuclear (1MT/mT) pulse units, and a big spherical plate (and I mean big, like 20 kms wide, radiation cooled, and made of solid copper). In any case, cruise speeds of 1-10% of c are often considered plausible for nuclear pulse propulsion. That is more than comparable with theoretical fusion engines, which is not surprising, since those big "pulse units" are thermonuclear bombs deriving their energy mostly from fusion. And as plus, the payload can be city-sized. Rune. Which has always made me wonder, why study fusion-powered starships and their heat issues, if we already know the shortcut to ignore waste heat and have stupendous efficiency with fusion-like Isp.
  20. Fairings have internal nodes since... ¿1.2? Nothing stops you from attaching stuff to one of those nodes (say, a shielded docking port), then building the fairing so it attaches to that part, and you are left with a nice 'shielded' conical space to put unaerodynamic stuff into. You can always get rid of the fugly, humongous fairing base by ofsetting it inside another part. Rune. Great to build Mk3 spaceplane noses that are not like every other Mk3 spaceplane.
  21. I kind of get the service bay, but I usually just use a fairing ever since we got the fancy internal nodes. If only those nodes were made 0.625m wide (even better, in a tweakable way), this part would become kind of irrelevant. Have the art repurposed as texture options for the fairing/internal structure instead! Rune. Is it too much to ask for a way to stop the fairings expanding in the VAB, while we are at it?
  22. Well, I have a few things that I just can't improve. The last one is my Orca: Try as I might, it just does everything I ask of it, better than stuff designed specifically for it. Built to ferry up and down base modules to Duna, it turns out that it is also an amazing SSTO in Kerbin, and a very heavy-duty lander for airless moons. Basically, it can handle everything except Tylo and Eve. It is a tough, big, VTOL and sea-capable, extremely maneuverable with RCS on, and although it eats fuel like a hog, it has the endurance to return to a base to refuel from the land (that it probably set it up itself). My best jack of all trades, by far, and it was built in 1.1. But really, in SSTOs, the king of endurance is my Claymore: With small variations, I still use it, and it is basically a post-porkjet conversion (and considerable enlargement) of my Broadsword. And that one is really old. It may not look like it, but the weight distribution and design principles are the same. Maybe you can see the lines if you squint? And although the porkjet pass and, especially, the end of the souposphere brought many changes and a serious increase in payload, my big workhorse SSTO still traces its lineage to this beautiful bird that I used for the first reusability challenge, in those days before recovery was a thing that you could choose. I don't even remember the version, and I must have flown both like a gazillion times. I run a mostly reusable space program since I built them, basically. But really, if I really really go for the spirit of this thread, I have to go with two little gems, which I think have always been rather underappreciated: subassemblies. Note these two pictures: The second one was uploaded to imgur three months ago. The first one, two years ago. And the only thing that has changed there is that the Drive Pods now have a radiator shroud (because heat became a thing in the meantime), and I took out the RCS... because the other subassembly, the Klaw pod, was just so good (it is the thing that is holding the asteroid in the last pic, incidentally, and it is exactly the same design nowadays). I haven't changed them, I don't expect to, and frankly, I don't want to. They are just that awesome, and have seen me through a lot. Edit: now that I see the pics full size, look at the kerbal moving around the orange tank with a EMU-type thing in the background of the Broadsword pic: I still have that same 10-part subassembly in some of my stations!! I think that must take the crown for longest-living thing in my space program. Here's another shot of it: Rune. So yeah, I guess you could say I'm "a bit" conservative.
  23. With a Terrier for an upper stage, I'd move more fuel to it, moving the mass ratio closer to the ideal e. That would give you more dV at the cost of less TWR (when you no longer need it), boosting the core to lower velocity and saving the energy for the upper stage. That little engine sure packs a punch. You'd get more total dV, and who knows, maybe that means you can drop the first onion stage, dramatically lowering total liftoff mass, and most importantly, drag (by about 30%). BTW, can't that fairing have a smaller, flush cross-section? For other drastic weight reductions, you could fit a whole other stage inside the fairing: Chair, tiny fuel tank, ant engine. More dV that you'll know what to do with, tough control becomes complicated. That way you can certainly drop two spikes, since final mass on orbit is truly ridiculous(-ly small). Rune. The eficientest stage always has the golden mas ratio.
  24. Gotta wait for me mods (especially now that I have a graphics card from this decade), but everything smells pretty good from here. Caught a couple of bugs I was interested in, got a couple of mods I use stockified (give me KAC and KER, polish the graphics, and I'll stop using mods! ), general polish... Good update, maybe a tad light in content, but that's because I cared little for the localization personally. All in all, good job guys! Rune. Now get cracking on Making History!
  25. Dude, you tamed Eve. And you did it using Rhinos! Mad math skillz there, many kudos deserved! Rune. Not seeing nukes in there was the most disconcerting thing of it all.