Zeiss Ikon

Now, that Bi-elliptic transfer @AHHans linked is very closely related to the cheapest way to make a large plane change: go way the heck out where your orbital velocity is very small, and you can make a 180 degree plane change for a very small amount of dV.

To expand on @Signo's answer, hot staging is something you do because of ullage. It's manifestly unnecessary in the stock game -- stock engines and tanks don't care about ullage in any way. If you're playing Realism Overhaul, or pretty much anything using RealFuels and real world engine parts packs, you'll need to pay attention to ullage. "What's ullage?" Glad you asked. Ullage is the "empty space" in a propellant tank. There's always some; usually filled with some kind of pressurant (even pump-fed engines need pressure in the tanks, just not as much as pressure-fed engines). This can be bad if the pressurant winds up near the rear/bottom of the tank, where there should be propellant, when your engine needs fuel (or oxidizer). Let's say you launch a basic sounding rocket, like a WAC Corporal (1948 technology here, hang onto your hat). This is a primitive two-stage rocket, with a high thrust Tiny Tim booster (originally an air-to-ground unguided rocket from WWII). Your basic WAC Corporal stack will pull something like 30 G off the launch pad with this booster -- but the booster burns out after about 0.6 seconds, leaving you falling upward at roundly 200 m/s. If you now want to stage and ignite your (pressure fed, hypergolic liquids) upper stage sustainer, you'll find it doesn't work. EVER. Because the air drag at 200 m/s results in enough deceleration to immediately slosh all the propellants to the nose cone end of the tanks, and the nitrogen that's supposed to push the aniline/furfuryl fuel and red fuming nitric acid oxidizer into the thrust chamber instead runs straight out through the injectors. This is why ullage has to be managed. The WAC Corporal method, as of 1948, was to ignite the upper stage at the same time as the Tiny Tim, and time the staging decoupler to fire at the exact same time the Tiny Tim burned out. That gave the sustainer engine most of a second to come up to thrust, and ensured the booster wasn't hanging on creating drag that could (even with the sustainer fully ignited) lead to pressurant in the feed lines instead of propellants. Done this way, the WAC Corporal worked about 95% of the time, and would fly as high as about 120 km (less if it was carrying a payload, of course). And that's hot staging. As Signo noted, the Soviet space program used hot staging a lot -- it's the reason you see many of their rockets with open strutwork interstage structures, so that the next stage exhaust has an exit to prevent either choking the engine before it's fully ignited, or blowing out the interstage fairing with potential to lead to a structural collapse as maximum G load. By contrast, the American space program almost never used it (can't say for certain they never did, but I think that's true). Look at a Saturn V -- specifically at the base of the S-II second stage. It has (relatively) small solid propellant "ullage rockets" -- there to ensure there's a (small) positive acceleration after the staging event, so the ignition of the next stage can take place successfully. And there are no ullage rockets on the Service Module, because it was intended to fly in vacuum and needed RCS to point before a burn anyway, and RCS works just fine for ullage management. I think there are even Apollo recordings where the crew mentions the ullage burn start, several seconds before the burn to return from Lunar orbit to Earth. Ullage can be managed other ways, of course. One way (used often for things like attitude jets/RCS and long-term station keeping thrusters) is a bladder tank. This stores the fuel (usually a monopropellant, most commonly hydrazine or a derivative these days) inside a bladder, much like a water balloon inside the rigid tank structure; pressure is applied to the outside of the bladder, and the inside is carefully debubbled before launch, so that every time you open the valve, the propellant flows into the catalyst pack and turns into thrust. In the case of Voyager 2, even if the last time was thirty years ago. If you're launching from the ground (even if that "ground" is Lunar regolith), gravity (even if it's a fraction of a G) does an admirable job of managing your ullage. I don't know that it's actually been done in a rocket, but another possibility would be an aerospace version of what I learned to call a "clunk tank" when I was flying radio control models (before they were electric). This had the fuel pickup in a weight on the end of a flexible tube which would always find its way (with an audible "clunk" if you checked it on the ground with the engine stopped) to the current "bottom" of the tank. Works great when (as with an aerobatic model) you aren't sure where you local gravity will be any given moment; won't work any better than a fixed pickup in microgravity (so probably not very useful in actual rockets).

A Kerbal stranded in her space suit shouldn't show as debris. Debris would normally be a spacecraft fragment, and when it's not showing an orbit ellipse, it may be "landed" on the surface of the Mun. The antenna on your ship only affects how far you can communicate back to Kerbin, it has nothing to do with targeting. Lack of targeting ability is likely due to not having upgraded your Tracking Station (or Mission Control, but I think it's Tracking Station in this case). To rendezvous with a Kerbal who likely has no EVA fuel left, without the ability to target the rescuee? You've got your work cut out for you. I don't know that I could do that, and I've done a bunch of rescue contracts in LKO and Munar orbit -- but never tried them before I had targeting ability.

I don't know offhand whether the Kerbol system supports this, but you might explore a Kerbal version of an Aldrin Mars Cycler. Invented by Buzz Aldrin (yes, the second man to step on the Moon), an Aldrin Cycler rides an orbit that passes Earth and Mars once each cycle (either outbound or inbound -- you need two of them to travel both ways faster than a Hohmann orbit), and uses gravity assist from both Earth and Mars to keep the orbit synchronized with very small dV expenditures for corrections. This depends on the near-resonance of the orbits of Earth and Mars, with a conjunction every 26 months -- the outbound cycler will pass Earth, and then pass Mars, then spend some time out in the main Asteroid Belt, at every conjunction (the inbound cycler will do the same, but pass Mars, then Earth, while inbound). As I recall, transit one way is about 3 months, and almost two years for the "idle" portion of the orbit. The encounter at each end is at a fairly high velocity (a good bit above Hohmann transfer value), best matched at the Earth end by launching passengers and cargo from the Moon, to slingshot around Earth. Going to Mars and returning to Earth would obviously benefit from aerobraking, but I'm not sure how the Mars colony is expected to match velocity (though starting from a much shallower gravity well doubtless helps).

Generally, the original contract document (visible under the "active" tab in Mission Control) will show you details like that thAt don't t appear in the summary. They'll give a tolerance, like "inclination 93-97 degrees, eccentricity .02-.04" for the sun synchronous orbit - - but some of those details may not show in the in-game summary.

if you're flying the craft, you can point to the "contract" (looks like a document) in the menu (upper right, if you haven't moved it) and then scroll down to see the contract conditions. There will be green checks on the completed conditions, and empty checkboxes beside the ones that still need to be completed. Most likely there is a "stable orbit" requirement, which is usually ten seconds to two minutes, and you'll see it count down in the conditions. Otherwise, there'll be something like "eccentricity less than X" or "eccentricity between X and Y", "inclination less than X" or "between X and Y", or similar conditions that haven't yet been met if the contract hasn't completed. Fix your orbit for whatever unmet condition may apply, or wait for the "stable" check time to expire. Also, a mod might want to move this to the "Gameplay Questions" section...

Yep, making VTO SSTO rockets in KSP is almost trivial. There was a challenge thread on this (over in the Challenges board) a couple years ago; I've got a fairly trivial entry there. These days, I mostly play in Realism Overhaul -- which includes Real Solar System. Orbital velocity around Earth is about 7800 m/s, the atmosphere is 140 km high (though that last 40 km is pretty danged thin, it will eventually bring down a vessel), and we're playing with real engine performance, mass, fuel choices, and (un)reliability. Making an SSTO on Earth is just about possible, but making one that can carry useful payload requires the most current engines you can get, and choosing the correct fuel/oxidizer combination (Isp trades off against density, which affects tanks size/mass, storability -- yes, cryogenics boil off -- and toxicity, in the form of increased costs to roll out a completed launcher to the pad). Short version: there are good reasons almost all modern rockets use kerolox, with a few going for Mixed Oxides of Nitrogen (MON) and a hydrazine derivative, and methylox being the popular new kid. Yes, hydroloxhas much higher engine performance, but a Space Shuttle burning kerolox could have had an external tank barely bigger than the orbiter, and one burning methylox could probably have had a similar launch profile and payload, still with a much smaller ET. Want to make a Delta Clipper, X-33, or Skylon in RO, you'll have your work cut out for you (as witness that NASA, ESA, and all those private companies are still flying simulators and making CGI videos). Meanwhile, the workhorses in the real world are all two stages to LEO. As noted above, your dV on the pad needs to be 8900-9100 m/s (depending on TWR), and you need a highly efficient launch profile. I let MechJeb do the flying from ground to orbit, generally...

@capi3101 I see you took some names from Gilligan's island, but I haven't read all of every one of your reports, so might have missed this -- why isn't Gilligan named Denver, since you have Backus (Howell) and Hinkley (Professor)? Or am I not supposed to ask that?

Can't say for sure what the .ORIGINAL files are. You might look at things like last modified date, file size, or even try opening them with a text editor to see what's inside. I have a suspicion they might be files for the craft that are included in a new game (if you choose to allow them in settings), or craft provided by a parts mod, with the .ORIGINAL so you can't accidentally save back over. Or they might be files that you currently have open in an editor, with the .ORIGINAL indicated the pre-edits version (so the game can restore that if you close without saving).

Um... Very carefully?

I think those store the tiny thumbnail image in the VAB/SPH "Open" dialog. I've noticed that if I import just the .craft file, the .meta file appears after I've opened the file in one of the editors. Likewise, if I create and save a new design, there's no .meta file initially (and no thumbnail image), but after I reopen the file in one of the editors and go back to the Open menu, the thumbnail appears, and now there's a .meta. If you open the .craft file in a text editor, you'll see it contains a bunch of heirarchical information about parts and their properties -- it might be a form of XML, but if not, it's some kind of database file that tells the game what parts to load, in what order, attached to what, and offset how far in what direction, and rotated how, and recolored which way. Like DNA, it contains all the information a working game of the correct version (and mod set) needs to recreate the craft.

I love Principia, and it's not a terrible load on your computer (or at least on my FX 8350 with 16 GB). What clinched it for me was when I launched into a sun-synchronous orbit and I could see (in heliocentric view) the predicted orbit lying right on top of itself for hundreds of orbits, where ordinary orbits spread out into a "ribbon" as perturbation moves them around. Six months later, the orbit was still right over twilight. Sadly, I'm not running Principia at on my 1.6.1 RO career, because it requires upgrading my Linux version; too big a job to do before I get a long weekend again...

Don't forget that if the orbit has very low eccentricity and is perfectly equatorial, it doesn't matter if it encounters the "hoop" at different local times on each orbit -- it'll be at the same height every time and always directly above the equator, which are the same parameters as a fixed building has. I've been launching with MechJeb recently, orbit and Lunar contracts in RSS/RO, and I've seen MJ nail an orbit to a few meters of altitude variation on several occasions. If you launch from the body your hoop is built on, using MJ, the real challenge will be getting the last couple meters ironed out, then build the building around the craft's orbit. Anyone remember reading "The Holes Around Mars"?

I think the board software rescales the link images for both pictures and video links -- I sometimes read this board on my tablet (Kindle Fire HD10), and the thumbnails are quite a bit smaller relative to the page on that device than they are on my desktop computer.

Well, in fact, sometime during the construction of the replacement craft, the contract did complete out -- and I didn't notice until the new rocket was rolled out on the pad, so that cost me another six months of construction time, because a vessel on the pad doesn't count as a "new vessel" for contract purposes -- taking the next contract would give a launch that would never close the contract. Grrr.

I'm playing 1.6.1, RSS, RO, and RP-1 (installed recently, within the past couple months). After making two successful Lunar flyby missions, I accepted the first (of three available) Lunar impact missions. These require that a craft of at least 40 kg, with at least one unit (W*s?) of Electrical Charge, impact the Moon. My vessel was 350 kg in final configuration (give or take some nitrous oxide monopropellant for the RCS -- I'd burned about half of that adjusting orbit), and the batteries were full, more than 6500 units of EC (40 tiny solar panels produce more power than the avionics and helical omni antenna consume). However, my impact was beyond the Moon's limb, several minutes after losing contact with Mission Control because the Moon itself was in the way. Apparently, this doesn't count to close the contract. Would have been handy if they'd specified that I needed to hit the visible hemisphere of the Moon in the contract wording -- if they had, I'd have had plenty of time and dV to adjust my orbit (a couple m/s just after transfer insertion would have done the job -- a couple dozen as a mid-course correction). Now I have to build and launch another entire craft (okay, it only costs about 6500, but it takes about six months to build and roll out), and make sure I impact the near side...

If the fire had occurred at a significantly higher altitude, even a few hundred meters (as opposed to mooring height, with the gondola only about twenty meters above ground level, so that it was still mostly floating when the disintegrating frame and envelope lowered it to the ground) there would have been no survivors, instead of only a couple dozen fatalities. As it was, the last survivor among the passengers and crew (a child of about eight years on that day) just died this past week, aged 90.

Might have, on either the S1-C or the SIV-B (second stage). There was a serious proposal at one point to build a 1 1/2 stage version of an uprated booster, the S1-D, that would have shed the four outboard engines like an Atlas dropping its boosters to continue on the core engine -- and put a bunch of tonnage into LEO with 80% reuse of the engines, or even recovery and reuse of the entire booster (how to recover an assembly of four uprated F-1 engines with thrust structure and fairing, ejected at 60-100 km and Mach 2-3 is left as an exercise).

You do realize you're talking about a million volt static generator full of hydrogen, right? Hindenburg would have been much worse if it hadn't happened almost at ground level...

This is actually pretty normal in RO. Most engines before the post-Apollo era (and many after) were either on or off, no throttling. Launch at TWR of 1.25 (still faster than the Saturn V), and by the time you've burned the fuel in your stage, the rocket (including all the following stages!) will be in the range from about 3.5 to 6G. An A-4 (commonly known as V-2), carrying three quarters of a tonne of "payload", would top out around 7G. One of the design issues with the Saturn family was keeping the peak G load of each stage low enough that the astronauts aboard could remain functional throughout launch. Shuttle used throttling, both to limit dynamic pressure (hence the "go at throttle-up" call just past one minute) and to limit G load on the crew when that big External Tank was down to its last few seconds of propellants. The only throttled engine on a Saturn stack was the LEM descent engine, which could be reined in to 50% thrust.

Okay, next best: install a real-scale Kerbin mod, along with an Outer Planets mod. Those shouldn't create much if any lag, but still increase the challenge level significantly. Of course, you may find that stock engines won't do the job at all, but I'm pretty sure others have done this mod set and kept engines stock. You just have to upscale a bit -- more engines, more stages -- when lifting from planets and moons.

KSP is too easy? Install Realism Overhaul (which includes Kerbal Construction Time) -- merely getting a Kerbal or two to the Moon and back will be a huge challenge again. Doing it before 1970, in Hard difficulty (no reverts, no quick saves, starting with only 20,000)? Probably out of the question, but if you manage it, you probably won't be bored getting there. FWIW, my current career is on the (recommended for "new" RO players) "easy" difficulty; with multiple reverts and quick-saves, I've just completed my first uncrewed Lunar flyby -- in early 1967 (real world, those were accomplished in 1959 by both USA and USSR, leading up to Apollo flights around the moon in 1968 and landings in 1969). Between engine failures (managed by Test Flight based on real test and flight data for the engines modeled) and my own mistakes, and occasionally just not knowing something I need to know, my prior RO careers (in an older version of RO and KSP) have all gone bankrupt, only a couple managing orbit missions, only one before today succeeding in even a Lunar flyby. Rocket science is hard -- and that's what makes KSP with RO fun!

(1.6.1 RSS/RO/RP-1) And success. First Lunar flyby of this career completed before expiration. Final Lunar periapsis was about 115 km (comms to Earth were blocked by the Moon at that point, but came back while still around 200 km). Between "Space High" science over every biome covered by a 28.6 degree orbit, and a fairly broad assortment of Space High over various Moon biomes (plus one set of Space Low), with telemetry, temp, pressure, ion mass spectrometer, Geiger counter, and micrometeorite impact detector (which was the most frequently polled instrument, apparently it's biome dependent in Space High over both Earth and Moon), I managed to send back just over 200 science (and that makes a bunch of KCT upgrade points at 1 per 20 science). After passing the Moon, the spacecraft then entered an Earth escape trajectory, and will become an independent satellite of the Sun (at least until Earth gets in its way again) -- but the batteries died a few days after the Lunar pass, despite the solar panels. I'll add more panels to the next spacecraft going that far out; just a few more will produce positive electrical power balance for as long as I have comms to keep orienting the spacecraft to face the Sun. Meanwhile, I need to get my whip and get over to the R&D center to make sure the big-brains over there aren't slacking off. Okay, I was lying about the whip. I'll take over an extra large urn of coffee. Started to write "box of coffee from Starbuck's", and then remembered Starbuck's didn't exist yet in 1967.

(1.6.1 RSS/RO/RP-1) I spent all my play time the last two nights fighting with MechJeb, engine failures, RemoteTech, and orbital mechanics. Just to be clear, as far as i can tell, all that stuff was working as designed, it just wasn't being any more cooperative that the laws of nature demand. My third attempt at a first Lunar flyby (first for this career, my second in RSS/RO, having done it once in 1.3.1) was launched mere days before the contract was to expire, due to rushing the build a bit. Got the spacecraft into orbit, with enough actual dV for the Lunar transfer, and every time I tried to start the burn I was out of communication (low orbit over the Pacific northeast of Australia, because that's what the Moon's position demanded). Okay, that's why MechJeb has the ability to "execute next maneuver node" (under Mission Planning). Unfortunately, this burn requires staging to ignite the engine (after settling ullage with RCS), and this MechJeb function won't do that automatically -- and did I mention my node was in a dead area for command contact? Waiting in orbit for a few days for the Moon to move resulted in dead batteries. Fortunately, I had a quick-save on the actual launch pad. Next time, I found I could push the maneuver node back two orbits (I'd tried three on the first attempt and been in another dead spot) and be able to make my burn where one station (Guam) was able to send the staging command to the spacecraft. MJ did its usual high precision job on the burn -- in other words, overburned by several meters per second, turned the entire craft and burned back with RCS (apparently MJ also doesn't know the RCS quads have a reverse). I staged away the spent engine and tank and power-hungry booster avionics, stabilized the craft with the solar panels facing the sun, and started to warp out to the Moon, on course for a flyby of a few hundred kilometers (contract required less than 4000 km). About a quarter of the way out, Science Now! notified, and I ran all the experiments on board, first time in Space High -- mass spec, Geiger counter, micrometeorite counter, temp and pressure, then started to transmit the result -- and noticed I was getting "no usable comms" messages for each experiment I tried to send. Yep, out of range. But I had a pair of helical omni antennas, for which "use case" is "the Moon!" Which work a lot better if you remember to turn them on. While you have communication via some other means. Remember that quick save? it was still on the launch pad. Spent a couple launches fighting engine failures -- the AJ10-37 has a pretty poor ignition record, it seems, and is also prone to the "loss of performance" failure that halves the delta-V for the stage. Got another launch with a good orbit, remembered to turn on the antennas, and made the insertion burn (once more, in contact with Guam only). And then it was time for bed, in order to be awake enough to drive to work this morning. Must have accidentally turned off "Hide UI" when I updated the title setting in Historian. Those first-generation solar panels generate a total of about 71 W when they have maximum sun exposure -- the avionics uses 70 W. Unfortunately, the antennas use another 5 W each, so if I remember to turn them on, I'll have dead batteries sometime after passing the Moon anyway. I may try to set up a return trajectory to bring the spacecraft back within range of the built-in antenna in the avionics; if I can do that, and turn off the helicals after transmitting the Moon data, I'll get a fully charged spacecraft back in a couple weeks.

Interesting fact I ran across relative to xenon the other day (in conjunction with a dark matter detector): refrigerated xenon liquid is so dense that granite will float in it. Its high atomic weight is responsible, which is also why it's used for ion engines -- still light enough to electrically accelerate to extreme speeds, but dense enough to produce usable levels of thrust (for values of "usable" that don't include making spilled milk hit the floor before you can grab a towel).