Zeiss Ikon

I've been slowly learning an important truth in RO: the more engines you have, the greater the likelihood one will fail (and the longer it'll take to build, reducing the likelihood of being able to make a second attempt on a contract). My first orbital rocket in RO used seven RD-103 (no M), boosting a single RD-103 second stage, then a pair of AJ10-27 uppers. It took six tries in sandbox to get one launch in which all ten engines ignited and burned their full duration -- and in career, I had enough failures to have the contract expire (twice in a row!) and sink the program. In my second career (with build time settings changed -- reached orbit in two years), I had one that was the classic Redstone (the A-6 engine running on Ethanol 90, not the Hydyne A-7) and an AJ10-37 second stage, with the three clusters of Baby Sergeants pushing an Explorer I (to around 45,000 km apogee on the first try). My third one (Baba Yaga) had an RD-103 core, two (shorter burn) RD-103 boosters, an RD-103 second stage, and an AJ10-37 upper. It made orbit, it made polar orbit -- and then I had four failures in a row trying to launch to a sun-synchronous, and the program was bankrupt. In my current career, Take Five (hard mode), I'm in late 1958 and haven't yet attempted orbit: waiting for the LR-79 and LR-105, which along with the AJ10-37 or AJ10-42 can pretty readily put a Sputnik into orbit, or an Explorer well beyond LEO. Only problem is, I've reached a point where (with both the 1956-1957 liquid and 1956-1957 solid engines in progress) I have to keep grinding sounding rocket missions to keep the lights on, launch an occasional crewed suborbital to keep the astronauts from retiring (Jeb's dead and Bill retired, but Val and Bob are still in it along with pilot Lagergard and Engineer Maufield -- haven't hired more yet, as the real crewed program is a ways off yet), and hope I don't have another string of failures.

I suspect most of those dead set on replicating real life are celebrating a reasonably playable 1.3.1 RSS/RO/RP-1 combination, and might use Principia as well (which, with n-body physics, make possible orbits that depend on perturbation, like the one that eventually got Clementine to the Moon even after an insertion stage failure, or the one recently used to get TESS to its destination without even enough dV to get to the Moon the standard way).

I've been playing RSS/RO/RP-1 for the past couple months, but as I recall, that's the four-chamber engine similar to the RD-108 the Russians used? It has lower performance with higher weight than a Bobcat (after all, the Russians needed five clusters to get to orbit; Gemini-Titan needed a single two-chamber engine). If it were available at a lower tech node, it might see some use in career before the Bobcat unlocks, but since (as I recall) they become available at the same time, I don't see where the Kodiak will get much spotlight.

Recently, Jeb died in my RSS/RO/RP-1/Principia "Take Five" career. Unreliable hardware is a given with Test Flight in play, but that wasn't what killed Jeb. What killed Jeb was that, after the main engine failed around a kilometer up, and the abort sequence worked perfectly, the Conical Cockpit burst out of the fairing, stabilized flat end first (due to a couple hundred kilos of lead in the base, and a set of small fins on the pointy end) -- and then I realized there weren't any parachutes. I'm playing in "hard" mode, so I have no reverts or even quick-loads; Jeb was dead the moment I released the launch clamps, and with the engine failure, he didn't even get to burn up during reentry.

For those in the United States, that launch time is (aiming for) 8 PM EDT tonight, 11 PM PDT. I might try to watch it, if I remember and can stay awake (I was up at 4:00 AM this morning, so even 8 PM is on the late side for me).

Exactly. I first ran across the technique, specific to model building, almost fifty years ago in Keith Laumer's book, How to Design and Build Flying Models, but I've seen it touted by G. Harry Stine (one of the fathers of model rocketry) as well. I got the impression it was an old technique, dating back to the invention of water soluble glues (casein glue was the first Elmers, introduced in 1947 by Borden -- mainly known for their milk products -- but the production and use of casein glue goes back to Egyptian times). Modern white glue is polyvinyl acetate in water, and has as its main advantage over casein glue that it won't spoil in the bottle (casein glue is still sold in powder form, used mainly for sizing artist canvas). The way I learned it was to rub the first layer of glue well down into the wood grain or paper surface, then when it was just barely still tacky, make the second application and join the parts. Aside from overall joint strength, the other advantage is that the glue grabs very quickly when applied this way -- plain Elmer's will tack hold in ten or fifteen seconds from joining the parts, a process that takes up to a half hour if you apply the same total amount of glue and immediately join the parts. Clamping can almost be eliminated for model construction purposes, total glue amount applied can be reduced (which, once again, helps with finished frame weight), and the finished joint is stronger than balsa, spruce, light-ply, and most hardwood ply.

During my adult model rocketry period (late 1990s), I demonstrated that, at least with plywood and paper as the materials (sufficient for supersonic flights with the correct choice of engines), ordinary white glue (aka Elmer's) is more than strong enough, and there's no reason to use anything else unless you're in too much of a hurry to wait for it to dry (additional advantage: unlike epoxy or cyanoacrylate, about 60% of the mass of white glue applied evaporates by the time it's fully hardened). Using double glue joints (an old, old technique that originated no later than the 19th century, used for furniture construction) and self-bracing construction (fins through the body tube, bonded to the motor tube and centering rings), I flew my NAR HPR Level 1 certification (in 1999) with a rocket in which the structure was bonded solely with Elmer's White Glue. The engine was an Aerotech H128 (29 mm reloadable), rocket kit was a Thug (don't now recall the kit maker). The bond created by double gluing with Elmer's is stronger than the base material -- plywood/plywood bonds will break in the wood when tested to destruction. There is no bond you can make with any adhesive that's stronger than "stronger than the base material." To improve on that construction you'd need to either coat the entire structure in a composite (fiberglass in resin or epoxy, for instance) or change to stronger material.

For the intersecting circles, you can prove you've created a regular hexagon: all the sides are r, and of course that hexagon is made up of six equilateral triangles, also with side length r. You can see by inspection that the distance from the center of each outer circle to its intersection with the original circle is r, since this is the case for any point on a circle relative to its center. Using the intersection points as new centers, then, constitutes a geometric construction of equilateral triangles that share the sides forming radii of the original circle, and, from them, a regular hexagon. Proof by construction, using only geometry, no actual math.

And this is the number one reason not to use metal parts in the motor itself, and not to store a completed solid propellant motor (of any size). There are also Federal explosives regulations that govern storage of rocket propellant, either in or out of an assembled motor, and failure to comply with them is not just a felony, but might be labeled as terrorism in today's climate. For a hybrid, fortunately, the fuel isn't an explosive and the oxidizer is usually something you can legally buy and store (nitrous oxide is used a lot; you at least used to be able to buy the denatured variety -- tainted with sulfur dioxide so folks couldn't get high inhaling it before they got sick from the sulfur -- at speed shops). Even better, in a hybrid design, the pipe can be both pressure vessel and fuel (hence original discussion of PVC, ABS, acrylic, etc.). I've seen a number of hybrid "High Power Rockets" (large, expensive model rockets) launched; they were, as of 1999 or so, commercially available and, in some situations, easier on the legality side than high power solid motors (there's no law against storing a small bottle of nitrous in your home or garage, and the fuel used in those was polyethylene -- which burns clean, being just carbon and hydrogen -- or synthetic rubber, which isn't much worse). The motor casing was aircraft aluminum tube, with screw-in aluminum end caps, one of which held the injector and "pyrovalve" that served as the igniter as well as releasing the nitrouse as it burned away, the other holding the phenolic nozzle. Nitrous makes a great oxidizer for this purpose -- it self pressurizes to around 800 psi at room temperature, stores as a compressed liquid (much like carbon dioxide), decomposes exothermically into nitrogen and oxygen (so adds energy to the combustion), and requires no catalyst, if an igniter is used, as the decomposition can be triggered thermally (nitrous is also used as a monopropellant, with a catalyst or a thermal start).

There are a number of supersonic gas-pressure gun designs around. One I'm aware of is used to do things like shoot ping pong balls through ping pong paddles (leaving a neat, round hole, at least on the impact side). Another uses hydrogen to accelerate tiny projectiles to six or seven (or ten?) times the speed of sound to study high velocity impact (like micrometeoroids hitting the ISS). All of these have in common that the barrel is held in a vacuum before a rupturing diaphragm releases the high pressure driving gas. Now, ordinary spring-piston air rifles can reach modestly supersonic velocities by compressing the air at the time of the shot, and using the compression to multiply velocity (the piston is, say, ten times the area of the barrel, so the barrel can drive at tein times the piston's velocity on the same volume flow) -- but this would require some massive apparatus to produce the needed pressure/flow on an instantaneous basis. You can't make it from liquid nitrogen on demand; it takes time to transfer the heat needed to boil off the liquid into gas. And all that said, you have the same problem with this kind of launcher that Jules Verne did with his underground cannon in Florida, written to fire men at the Moon in the 1860s: the acceleration needed to build up useful velocity in a manageable barrel length would be enough to liquefy bone and flesh. It's possible to build electronics that can be fired from a gun (they did it with vacuum tubes in the Second World War) -- but humans couldn't survive the tens of thousands of G that would come with launching to orbital speed in a barrel short enough to actually build.

Yesterday, I closed out my "Take Four" career in RSS/RO/RP-1/Principia. Not intentionally, mind you, but it was getting well into 1958, I was still flying LOX/Ethanol and LOX/Hydyne because the LOX/Kerosene engines were still under development. I'd flown two craft to orbit, one at Canaveral's natural inclination, one to polar orbit (still with battery life problems -- those procedural avionics needs lots of power!). I took the contracts for both sun-synchronous and solar powered satellite. I still don't fully understand how an orbit at 95-99 degrees inclination can precess to remain aligned with the sun (the claim is that the Earth's equatorial bulge produces the necessary ~1 degree per day precession), but I can launch to the required inclination without a problem and find out later if Principia models the Earth accurately enough to make it actually work. Except that after six launches in a row I couldn't get the booster core, both side boosters, the second stage (all RD-103, LOX/Ethanol) and the upper stage (AJ10-37, aniline/furfuryl and IRFNA) to all ignite on the same launch. With the clock running down and funds on hand significantly less than the combined failure penalties for the two contracts, I quickly grabbed an easy contract for a crewed mission to 120 km, hoping to save the program. As I was rolling that rocket out to the pad, however, nearly a month after the two orbit contracts expired, something else ran down, my funds hit zero, the rollout stopped, Val retired, and I was done. I may have missed a short expiration on the "X-Plane High" mission, but I'm pretty sure it was the usual 90 days, and my vessel took only 62 days to complete; even with rollout time I should have had at least a couple weeks of leeway. Regardless, it was over. I salvaged the vessel designs, deleted the save, started up a new one, "Take Five" ("hard" level, except I turned off "hide unpurchased parts" to cut down the switches back and forth between VAB/SPH and R&D -- "hard" in RO doesn't make game play harder in terms of increased failure rates, reduced performance, etc.; rather, it reduces rewards and/or increases failure penalties and cuts the safety nets of quickloads and reverts), and resumed burning the fins off WAC Corporals (because the only suitable fins available at start are B9 Procedural Wing (Early), which overheat at around Mach 2). I did find a solution, however: I stretched the propellant tanks on the WAC enough to give a ten second overburn (beyond rated burn time) on the engine. That reduced acceleration early in the flight enough to keep the fins on, and incidentally allowed the liquid fuel stage to reach 90 km (instead of the 68-69 available with the version that burns only the rated time). I chose "hard" because I think it'll reduce the temptation to attempt orbit too early -- it's very possible to perform early orbital missions with LOX/Ethanol engines like the RD-103, but the reliability of those engines is so poor that doing so will either require going back to grinding sounding rocket missions (very heavy payloads to fairly high altitudes, by that time) until the LOX/Kerosene LR-79 unlocks, or risk sinking the program with a long string of engine failures (as happened in "Take Four"). Meantime, I need to learn how to use MechJeb properly to manage orbital ascent in RSS. I'm able to fly a pretty efficient gravity turn, but MechJeb ought to be able to do a better job of hitting a specific inclination, and can fly a chosen ascent path with avionics that won't permit manual control. The times I've tried using MechJeb to control a launch, it's gone completely haywire, either completely failing to turn over for horizontal velocity, or turning over much too soon, leaving my craft near horizontal at only 50-60 km (with atmosphere extending to 140 km in RSS). Watching Grayduster and Nathan Kell do it on YouTube isn't doing the job, so I need to find some written information.

Nice. I'm playing a career (called "Take Four" -- one guess why) in RSS/RO/RP-1/Principia, and I've actually managed to put two satellites into orbit (so far) with only ethanol fueled main engines and sounding rocket engines in the upper stage(s) -- RD-103 core and two RD-103 side boosters, RD-103 second stage, and two AJ10-27 upper stages. If they all ignite and don't fail in some other way, they'll just about put the final empty tank and motor, some RCS thrusters and a couple tiny peroxide tanks, a probe core and battery, and a Geiger-Muller counter into orbit. The second one got an upper stage upgrade (to a single AJ10-37 with a larger tank, a little bit of over-burn) and managed a polar orbit. Now I'm trying to get into a sun-synchronous with 246 tiny solar cells (which still don't come close to meeting the spacecraft's power requirements and cost a mint; I should probably cut the number down to ten or so, make the flight a demo -- and save myself ten-plus kilos where it matters most). It took me until 1958 to do it with 1955 technology, though. Even in "normal" difficulty, research time is killing me. The whole KCT is killing me, really. Put your upgrades into VAB, research will have you into the 1960s before you can fly a real space capsule; put 'em into R&D, and you'll be in 1959 and still building sounding rockets because you can only launch three a year. Or, you can spend hours and hours and still more hours grinding sounding rocket contracts to earn the funds to buy upgrade points to be able to launch to orbit in 1955, never build anything in the SPH, and have pulled all your hair out before you can actually launch anything interesting (I'm watching Nathan Kell's RP-1 video series on YouTube on my breaks at present). If you managed to launch to orbit in 1955 with standard RO settings, my hat's off to you.

If you can get something with the aerodynamics of a sounding rocket (i.e. long and slender, with a long pointed nose cone and tiny fins for stability) up to Mach 10 or so, and launch from Colombia at a suitable upward angle, it would climb out of the atmosphere before losing too much speed or burning off the fins, then ought to come close to coasting to the African coast before reentering -- and which time, it's likely to either burn up or break up. Of course, if you're trying for orbit, you'd start the rocket engine a little before apogee. Starting from, say, Mach 6 (after aero losses climbing through the atmosphere), a high performance sounding rocket equivalent could just about make a very low, short-term (before it decays) orbit. Of course, building the rail only makes sense if you plan to launch these on a near-daily basis, which itself only makes sense if you have some pressing need for very short-lived (on the order of weeks, barring electric ramjets to keep them up) low-altitude satellites.

I had in fact tried right clicking both the avionics core and one of the antennae during the flight, nothing there that I could transmit or review. I found the problem, though -- but I still don't understand why it's a problem. I compared the two versions of Baba Yaga in the VAB and found one difference that might be significant to the avionics -- the core on the orbit stage was set as the root part on the original, but due to some experiments with core and battery sizing and test fitting a Sputnik PS-1 during the upgrade, the root was the tank below the core on the Ic version. I rerooted and launched again (there was a convenient contract to send a "sounding rocket" to 3500 km -- on the second try, when the third stage engine did not fail, I was able to push just over 4000 by running the ullage thrusters for a while after third stage cutoff, though I had 3500 nailed when the UDMH/IWFNA ran out in the AJ10-42). On the way up, I tested by doing a telemetry analysis -- and the data transmitted as expected (though it had no science value; I was "in space above Earth's shores" which gets a lot of traffic). Now, the only thing I can think of that would cause it to matter whether the avionics were root part or not is if the science automatically transfers to the root part -- and science data landing in a empty propellant tank isn't very useful, and difficult to remove. Important thing, for me, is knowing how to deal with the problem. I still think this is a subtle bug, but it's now one I know how to work around. For my game play, I'm much more concerned about edits for SPH craft, even just "fill tanks," causing a 0% completion condition. Meantime, I need to launch another polar orbiter (or take the sun-synchronous contract) to get the cosmic ray and "space near" telemetry science from all the remaining biomes.

You're going to be very disappointed. First, they're approximately as loud as a pulsejet, because they are a form of pulsejet -- resonant pressure waves in the three stage intake act as the "valves", operation is generally similar to a valveless pulsejet like a Thermojet or Lockwood type. The supersonic nozzle that injects the fuel just acts as the impeller to allow a static start (with correctly tuned intakes), exactly similar to a well tuned Lockwood pulsejet. The inventor built a helicopter, but hardly anyone has seen it fly -- in SIXTY YEARS. Second, like any pulsjet, they won't work at supersonic speeds -- front intake pulsejets will either destroy the reed/flapper valve, or lose too much flow due to intake choking; rear intake types (like most valveless designs) will simply die of air starvation. In neither case is the exhaust supersonic, and an air breathing jet can't exceed its own exhaust velocity in still air. The Gluhareff jet, like other pulsejets, is impractical for tip-jet helicopters for most of the same reasons ramjets don't work well for this: because specific fuel consumption is too high, it's hard to get both jets ignited simultaneous, and they're too noisy (even compared to a conventional helicopter). For the same reasons, neither pulsejets nor pressure jets are practical for any other kind of propulsion, unless budget is an extreme driving factor -- because the one advantage valveless pulsejets have is that they're cheap to fabricate (Colin Furze made one by welding two flat pieces of sheet together and using a pressure washer to blow up the resulting part into a tubular shape). the Gluhareff lacks even that advantage, because it's complex and finicky to build and tune.

I'm currently running a career in 1.3.1 RSS/RO/RP-1 (Dev branch)/Principia installed a few weeks ago via @Bornholio's Golden Spreadsheet. I've seen a number of what seem like minor bugs, the kind of thing you might expect in a mod set still under development (edit an SPH craft and it starts over, 0% completion, even if it was 100% done and all you asked for was to fill the tanks, etc.). Today, I ran into another one, and I'm not certain whether it's a bug or just me not knowing what to expect. I'll provide the .craft files if needed. I built a vessel a few days ago (Baba Yaga Ia) that flew the first orbital launch of my "Take Four" career. Relevant to this question, Baba Yaga Ia had a procedural avionics core, "start" level, booster type, set for minimum 10 T control and sized just below 100% usage, at the top of the final orbit stage, along with multiple A-4 Guidance Units in the booster and second stage. Once I got into orbit, I was able to transmit my science (Telemetry Analysis and Geiger-Muller counter cosmic ray science from various biomes) until the battery ran down. Fast forward to today; upgraded craft Baba Yaga Ic made it to polar orbit (with a 20 second over-burn on the AJ10-42 final stage and a little help from RCS), with a procedural avionics core in the orbit stage, configured as "Post-War Avionics", Booster, and 15 T capacity around 100% usage -- and after this cropped up the first time, I added a quartet of Sputnik PS-1 antennae. Even when I have connection and full pitch/yaw/roll/forward control on RCS, I don't even get the science data popup offering to reset experiment, keep data, or transmit data. It seems the avionics core is now automatically storing the data, thus rendering an experiment like the Geiger-Muller Counter a one-shot, rather than letting me transmit the data each time the craft passes over a new biome. As far as the avionics go, the only change here is upgrading to "Post-war" from "start" grade. Did I accidentally change a setting, or is there a bug in the "post-war" grade booster avionics core?

The very general rule, if you're still under boost (which you likely are, if you're playing at "real scale" as with RSS or a 6.2x Kerbin), is to dump the fairing as soon as the dynamic pressure is low enough not to damage your payload. On Earth, that's generally taken to be the Karmann Line, 100 km high -- but then, Earth's atmosphere is dense enough to cause orbital decay on a scale of years out to at least 250 km. The general definition of the Karmann Line is the height at which orbital velocity is the same as the speed needed for wings to support the weight of a craft. This is obviously based on a number of assumptions (an airframe that can handle high Mach numbers is top of the list, since you're around Mach 22 equivalent to get an orbit), but effectively, it's the point beyond which the atmosphere doesn't matter in the short term. Now, Kerbin's atmosphere is shallower than Earth's (half the height used in RSS), so one might make a first approximation of 50 km as the height at which the atmosphere doesn't matter for the short term, and in fact I've read a number of posts indicating people blow their fairings around 50 km if still under boost, when launching from Kerbin. So, if you're launching from Kerbin, you might reasonably discard the fairing at the end of any coast phase that ends above 50 km. This could vary depending on the payload -- that big dish antenna might be a good candidate to hold onto the fairings until 70 km (times your atmosphere scale factor), while a tank of ore or fuel might not even need a fairing, just a nose cone.

Over the past couple days, I've been working on the "first satellite" contract in my "Take Four" RSS/RO/RP-1/Principia career -- but meanwhile, one still needs to have "interesting" missions to keep the Big Four from retiring too early (apparently, astronauts get bored if they just sit on the ground for years at a time -- who knew?). So, I built this (slightly handicapped by the time it takes to build, and, what I consider a bug in KCT, the fact that the tiniest edit to an SPH craft resets build progress to zero -- need to repack a parachute or refuel? Scrap the vessel and build a new one, takes the same time). Two J85-GE4 turbojets, on detachable hardpoints. All the kerosene is in the tip tanks, a bit less than 30 minutes at full throttle (and it has to fly at full throttle to get anywhere or climb decently; these early jet engines are pretty weak, at about 12 kN each). The fuselage holds a little over 4 minutes of LOX and Ethanol 75 for the XLR-11 four-chamber, "throttleable" rocket engine (from the X-1 -- canonically, throttling was accomplished by shutting down one or more chambers, and was generally not done in flight except for sequential ignition), which is supposed to push this monster past the speed of sound. It's cranky on take off, because with full rocket tanks it's too heavy to fly well; liftoff, with the "help" of bumps in the runway, is around 60 m/s (if the runway were smooth, it'd be more like 75 m/s). With the jet pods at full throttle, it can fly at around 240 m/s in level flight. Unfortunately, with a large enough wing to make a ground takeoff possible without burning most of the rocket fuel just to get off the ground, there's too much drag to reach the speed of sound. Top speed in level flight appears to be around 320 m/s with both jets and rocket operating, about the same after dumping the jets. Worse, the CoM shifts aft a tiny bit when the rocket tanks are near empty, rendering the machine almost unstable in pitch (very, VERY touchy to fly). I doubt there will be further attempts to fly this craft. While Val (and Jeb, now pictured) were trying to tame this beast, the build crew in the VAB were hard at work. The result of their efforts was Baba Yaga. Named for a Russian witch of myth, partly because the RD-103 engines were a Russian design, and partly because they're unreliable enough that it took six launches to get a flight in which all the RD-103s ignited on cue. The rocket is long and slender because the tanks were sized for the 1.65 m diameters of the A-4 Guidance Units -- three in the booster core, another in the second stage -- which were the most convenient way to have control through most of the flight (there's a brief control lock after second stage ignition, but either SAS or Smart A.S.S. can still hold, I just can't make profile changes during that time). Notice the available dV? Yep, this 4 1/2 stage craft can make orbit on Ethanol 90, if everything goes right. The sharp-eyed might note that the dV readout shows the craft will actually lose velocity briefly after the boosters stage away -- it's not as bad as it looks. TWR for the core is about .98 (due to core fuel burn) by the time first staging takes place, and the vessel is close to 15 km high and angled well over by that time (and horizontal velocity continues to build) -- and TWR quickly rises above 1 as more fuel burns away. Flight profile is more or less a traditional gravity turn, near vertical for the first several kilometers to get out of the soup, turnover enhanced by the low-TWR period. No photos of the second stage burn, sorry. With two AJ10-27 upper stages, there's roughly 3000 m/s on tap after second stage burnout. That allows even a manual flier enough to get an orbit (if I'd been watching apogee a little closer, I might have shut down the final stage a little early, but hey, I wasn't being paid for low eccentricity -- that'll come later). The 26 units of HTP in the final stage, with a pair of ullage thrusters, was plenty to raise perigee out of the atmosphere (this shot is about halfway through that burn). Final orbit: 1090 x 156 km, subject to variation due to perturbations. Unfortunately, the battery ran down after less than one full orbit (this is no Sputnik or Vanguard, with batteries for days or weeks -- that avionics core is pretty power-hungry). Bear in mind, though, that this was done with essentially 1955 technology -- LOX/Ethanol booster, surface-optimized engine in the second stage, and sounding rocket motors for the upper stages.

"Heroes of the Soviet Union today had great success. It is not permitted to reveal what they actually did, but they had great success, and have once more demonstrated the superiority of communism over capitalism." Soviet style missions, good. Soviet style reporting, perhaps not so much.

If you launch one craft with X amount of dV, when you dock it to another, the dV of the pair will be significantly less -- if they have equal mass, it'll be half what it was. This is because dV is mass dependent -- you can see this in the VAB if you use Mechjeb or Kerbal Engineer; take any craft you like, add some mass, and watch the dV drop. You'd have to have both craft carrying X dV in order to still have the same amount when you dock. Of course, this is more complicated than that simple case; if the two craft have engines with different Isp, the same fuel that would give one 8400 m/s might give the other only, say, 6000 -- or might give it 10,000 if it has much more efficient engines that use the same fuel (are you using Real Fuels?). But bottom line is that dV is impulse divided by mass (impulse is thrust times time). Your impulse is constant (unless you spend some of it by burning propellants), but the more mass it has to push, the less dV it produces.

Last night (in my RSS/RO/RP-1/Principia campaign) I attempted to meet a contract to launch a sounding rocket test to 1700 km altitude. I had a rocket that would do the job, in simulation; Super High Step, an A-9 booster and two upper stages that I call "Fat Aerobee" -- an Aerobee XASR-1 engine and a tank that holds a full rated burn of Aniline/Furfuryl/IRFNA, but short and squat to fit inside a fairing instead of long and slender like an Aerobee. The ullage motors on the lower of the two are canted to spin the stages, which helps keep them in line (just in case there's a kilogram out of place somewhere in the payload). Unfortunately, the A-9 on the first attempt conked out with about 15% propellant remaining, and on the second attempt both upper stage motors failed before they ran out of fuel (curse you, Test Flight!). There was barely time for a third attempt before the contract expires; and for this I rolled out a new design, which I call Super Green Giant. This one is an RD-102 booster, running on Ethanol 90 and LOX (instead of the Hydyne/LOX the A-9 consumes). The upper stages are the same Fat Aerobees as on the Super High Step, because I don't have the tech for anything better (the Green Giant booster can't lift a full A-4, never mind A-9 stage off the pad, and clustering seems to be asking for trouble at this tech level). Super Green Giant is waiting on the pad for me right now -- time to go launch!

I haven't put fuel in wings to date, though I'm not against it. I've only used the Fat 455 wings once, for a glider (one of the newbie mini-challenges), and filling them with fuel would have been counterproductive in that case. Since then, the only wings I've used with tank capability are the B9 procedural wings in RO, and their capacity is so small (at least in the aircraft I've designed so far) that it's not worth bothering.

I'm playing an RSS/RO/RP-1/Principia career (on KSP 1.3.1, so yes, I'm aware that some of the mods are in pre-release states) -- currently in mid-1954, sounding rockets going high with heavy payloads, and the first tentative crewed suborbital flights (using an A-9 upgraded A-4 to get an X-1 cockpit to around 200 km -- Jeb and Val don't quite black out during reentry, and it's better if I angle over a good bit). I've noticed a couple things that don't seem to work the way they should. First, when I was flying a fairly sedate "X-Planes (Low)" contract (hold altitude at, in this case, 3000+ m, within a 1 km height band, for three minutes on the MET clock), when I landed I found I'd been awarded both the 5 km altitude and 350 m/s speed "world's first" FAI records. Never went above 4200 m, and never exceeded 240 m/s (the airplane I used will just about hit that figure in a steep power dive). The same thing happened on a later flight, when I was awarded 10 km altitude and, IIRC, 500 m/s speed records (same airplane, though I did actually fly above 5 km on that flight). I'd have had those awards soon, anyway; the Single Step ("A journey of a thousand miles begins with...") A-9 launcher was under construction while the pilots were flying contracts to keep them from retiring. This one, I'm fairly certain is a bug, though it would take me more than a week to reproduce (start a career, unlock the appropriate tech, build a jet). For the other situation, I'm not certain this is a bug, but if it's as intended, I'd like to know why this behavior occurs. I'm running Kerbal Construction Time, of course (it's part of RO). If I edit a rocket that's under construction, or completed and in storage, the completion date is set back by a more or less reasonable amount of time, based on how extensive the change was. Change the size of a payload tank -- hardly any effect. Upgrade an engine and change the tanks for the new propellant mix, big hit. By contrast, editing aircraft (specifically, ones that have been put back into storage with "Recover Active Vessel" from the KCT menu for SPH) doesn't seem to have any level of "this is barely any change." If I land the jet above, perfectly (zero damage), "recover active vessel" to get it back in storage, then edit the craft, first, it loads in the SPH in nose-up vertical attitude (like a rocket -- and if I don't reset it, it'll then load on the runway that way next time I launch); second, before I make a single change I see 0% progress on what had been a completed aircraft (in other words, I may as well scrap it and build a new one); third, clicking "fill tanks" resets the build clock like a full rebuild, and doesn't even refill the fuel. Now, I'd expect to be able to haul an undamaged airplane back into the hangar, fill up the tanks, and have that process take no more than a few hours after the recovery process completes -- not 120 days to build a whole new airplane, using the same parts, and without even filling the fuel tanks again. Obviously, the length of time is mostly due to having spent few upgrade points on the SPH -- but taking as long to check the tires and forget to fill the tanks as to build a completely new airplane certainly seems wrong. So, something connected with contracts seems to have a bug related to FAI awards for airplane flights, and KCT seems to have a much uglier bug (in terms of playability), also related to aircraft. I'm presuming I've got everything installed correctly; everything else seems to work fine (except that there's no good reason researching the tech to launch crew to orbit ought to take 12-15 years of game time -- our history did it in six and a half years from the 1951 game start date, or about thirteen years from the first WAC Corporal launch, fourteen from the first A-4 tests, which are long in the past by game start -- but that's another issue entirely).

In my RSS/RO/RP-1/Principia "Take Four" career, I flew another "X-Planes Low" contract. These are boring, especially with a yellow clock (six real time seconds per MET second, roughly, when at cloud height), but not difficult, and let me practice landing my Jet Trainer. The big deal here was that, for the first time, the Jet Trainer landed without damage; Jeb managed to grease it on (on the large, flat grass field north of the Space Center, since the level 1 runway is useless due to the transverse ridges) so gently I wasn't sure the wheels were on the ground for a moment. After that, I made two attempts at a sounding rocket mission, both failed. One, with A-4 booster and "Fat Aerobee" upper stage pushing an "Early Film Camera" and "Biological Sample" experiment, suffered a main engine failure too low for the upper stage (built to fit in a fairing and spin stabilize, so no fins) to work, the other on an Aerobee didn't quite make the altitude -- too much sounding payload. I also spent some time designing a rough analog to the Aerobee 350. Four of the Aerojet solid boosters (the upgrade from the Tiny Tim, I don't recall the designation and don't have the game open at present -- why don't we have a Nike motor in RP-1?), interstage adapter, staged to four XASR-1 with a minimum diameter common tank, and another interstage staged to a single Aerobee with added ullage motors (so I don't have to hot stage it). Launch performance is much like the most recent updated Aerobee -- 4+ G off the pad on the solids, just under 2 G from the main stage with tanks full, and just under 2 G from the upper stage immediately after staging -- but with a combined burn of 2 m 10 s and average acceleration above 3 G (peak is close to 6 on the main stage, almost 8 on the upper), the upper stage burnout occurs at around 160 km and (according to the sim) apogee ought to be above 800 km. That ought to get me some more altitude record payouts...

Can't say for certain on Gemini, but the Mercury heat shield was built to jettison. This caused some drama during John Glenn's flight -- after launch, while running down a checklist, he turned the heat shield jettison switch (a rotary knob) the "wrong" way to be sure it was off -- and it turned a few degrees, apparently due to a defective stop in the switch itself. This caused the "jettison" light to come on at the telemetry board in Mission Control, and resulted in Glenn being told to keep the retro pack attached to the spacecraft through reentry, instead of cutting its straps and letting it fly away after it had done its job -- the hope was that the retro pack's straps would help keep the heat shield in place. Glenn wasn't told why this procedure change was made, however, and during reentry he noticed something flopping outside the capsule window (most likely one of the retro pack straps, burned free at one end). Once the capsule could be examined, it was determined that when the heat shield release switch was turned the wrong way, it would make contact on the status light, but not on the actual jettison system, but NASA had no way to know that while Glenn was in orbit. As a result, Glenn's capsule was the only one from which the heat shield was recovered after flight. Oh, and I generally do jettison heat shields, and I do it as soon as the parachutes pre-deploy (doesn't bother me to have it stick to the command pod until final deployment) -- just that little bit less stress on the parachute system, a fraction of a m/s lower descent velocity. I'm probably subconsciously thinking that, in a multi-parachute system, it might make a big difference if one parachute fails to deploy or tears off from aero loads.