sevenperforce

Looks like all systems go! Liftoff!!!!!

Yeah, that's just the screenshot of the failed SSTO attempt. I'm going with something closer to an SLS now.

@Nucleartaxi I've got my lander and my transfer vehicle worked up. Was going to build an Oscar-B-fueled RAPIER-based SSTO to get the thing into orbit, but after repeated attempts I haven't been able to get it off the ground, so I'll just go for Level 2 and drop a regular LV underneath it. My current attempt: The actual ascent vehicle was pretty easy, honestly.

Thanks for the interesting challenge! @ManEatingApe almost always beats me at challenges like this, though whether due to patience or genius, I'm not sure.

In which case they could well have pumped down the surroundings to near-vacuum and then pumped up the inside of the suit to two atmospheres.

All it would take is an updated cfg -- changing the values for allowed attach points, crossfeed, etc. No new part.

Shouldn't be.

Precisely.

After I finally figured out exactly what North/South orientation my Kerbal was holding, I was able to make it work:

It probably means they tested it to three atmospheres of internal pressure. The stress on a pressure vessel (or, in this case, a pressure suit) is a function of differential pressure, not absolute pressure. In other words, if the inside has one atmosphere of pressure and the outside has zero atmospheres of pressure, that's one atmosphere of differential pressure. If the inside has two atmospheres of pressure and the outside has one atmosphere of pressure, that's still just one atmosphere of differential pressure. Elon meant that the difference between the internal and external pressure, during the test, was twice as much of a pressure differential as being in a hard vacuum. So they probably just pumped up the inside of the suit to three atmospheres; that's the easiest way to do it. Of course, they could have pumped the inside to 2.5 atmospheres and then pumped the outside down to 0.5 atmospheres. Same difference.

Here you go. Here's the cost, by the way:

Can you get a surface sample from Minmus, with a command pod, with a launch vehicle less than 10 tons, shorter than 6 meters, with less than 13 parts, and cheaper than 10,000 credits? I daresay I can. Done for this challenge: I present: the Magnificent Micro Minmus Munchmobile! Weighing in at only...wait for it...5.815 tonnes! No part clipping (although the ROUND-8 tanks place very closely, which helped). As you'll see, I didn't use any decouplers; this saved me weight, part count, cost, and height. I plan to use explosive decoupling to get rid of the booster, and hopefully I can blow off the tanks on a re-entry just steep enough to overheat them but not so steep that the pod can't survive. All the ROUND-8 tanks, as well as the Mk0 LF tank, are full. I drained the command pod of monoprop, and I only filled the lower FL-T100 about half full of oxidizer to give myself a bit more LF right before the RAPIER loses its airbreathing thrust. Speaking of which, I disabled manual mode switching and programmed an action group to close the intake when I switch modes, to cut drag. I toyed with drop tanks, but the part count, cost, and drag losses were prohibitive. Lifting off! I'm monitoring a lot throughout the flight so I locked a bunch of the windows open. This takes a very specific pitch curve. It'll make orbit without trouble, thanks to plenty of thrust on the Spark, but making orbit with enough dV is the tricky bit. I'm keeping an eye on the RAPIER's thrust as well as the lower fuel tank. It's set to drain after the Mk0 tank so I'll know when I'm almost out of LF. This ascent was tough, because if I did the gravity turn early, I burned through all my LF waaaay too low in the atmosphere; if I did the gravity turn late, I would be going too fast to turn efficiently. I didn't want to throttle down, though. So I tipped my nose over early and then pitched up hard, so that once I needed to turn I could just drop from SAS-hold to prograde and take off. Supersonic and rolling over. This places the differential drag from the intake on the top of the craft, helping me to keep my nose up during the early acceleration phase. Starting to drain LF from the FL-T100, so I don't have much airbreathing time left. As planned, excess LF is bingo just as the RAPIER thrust starts to drop precipitously. Now, things start happening FAST. I can tell I'm almost out of fuel on my booster. Explosive decoupling is always hairy... And I'm starting to lose fuel in my top tank (see top left), so it's time to blow the fairing and ignite the Spark to decouple! Bam. There goes the booster. Jenton looks appropriately horrified. Thankfully, I've already got a good ascent. I tried doing this with the Ant, but the thrust just isn't enough, and the isp losses make it barely worthwhile anyway. Not at full thrust...I don't want to push my Ap too high. The numbers on that resource tab are awfully low! It'll take about half a minute to circularize. Almost there.... And I made orbit! With quite a bit of dV. Is it enough to go as far as I need to go? Well, we'll see. To save propellant on the Minmus injection burn, I'm going to take a loop around the Mun. Gotta wait for it to line up, though. Ignore all the tracked objects on the left; this is my challenges save that I'm also using for the Orion Style challenge. Setting up the slingshot. And here's my slingshot into Minmus's SOI! This burn is going to use almost all of my fuel. And there you have it! Looks like I'll need to make a correction burn during the Mun swingby. Set up the swingby. Burning gingerly. I'll take that! Coming up on Minmus... Uh oh. Did I really send an engineer on this mission? Crumbs. Oh well, gotta wing it. Capture burn. That'll do it! So...it looks like I have enough fuel to get home, but not enough to make the landing on Minmus. What to do? Well, I'll just lower my apoapsis to around 240 km... ...and hop out! Just a tiny, miniscule RCS puff to lower my periapse below the Minmusian mountaintops. Warping down. This will be touch-and-go. Starting the RCS braking burn. Still braking hard. Timing has to be perfect. If I'm right, I think I can hit the surface with quite a bit of residual velocity and let friction bleed it off. Not this much velocity, though. Steady as she goes... I think 20 m/s is just about the cutoff. Ouch! But hey, I made it! Nommmmmmmmmmmmmmm! No time to waste. Without the ability to set nodes (or even thrust prograde, really), I have to use the ship's velocity vector as my guide. Can't afford to wait for another orbit, either, because I'll be out of the path. Set up the target. Liftoff! Burning up and forward. I just wanna barely clear these mountains. Aiming to have my Ap just reach the ship's Pe. Really disorienting when I reach "orbit" and it switches targeting modes. Closing as carefully as I can. And there's my orbit! I didn't expect to get a rendezvous on my first go-round, but at least I got a nice coelliptic orbit. Figuring out exactly how much of a burn I'll need to line up for an intercept. Fuel is going to be very, very close. Made the burn...I have less than 1 unit of monoprop remaining for the rendezvous. Matched speed! Looks like a good intercept. And here we go! Of course, I managed to come in on the wrong side and had to swing around. Aaaaaand I got the ladder! With 0.04 units of monoprop remaining. You better believe I've got that surface sample added. Burning at Pe would send me out of Kerbin's SOI, so I'm swinging around to Ap. Escape reached! Will I have enough prop to lower my Pe into Kerbin's atmosphere? Once-more-around and finding out. If I have to, I can use a Mun assist to get back home. Nah! Here we go! No turning back now. Here's where things get REALLY dicey. If I come in too hot, I'll burn up the engine, the tanks, AND the capsule. Too cool, and the tanks and engine will survive. Which will throw off my CoL/CoM balance and turn me into a lawn dart, making my chute useless. Getting an overheat indicator; that's good. Transferring fuel to my lowest tank in an attempt to keep my CoM forward. Definitely past the point of no return now. Overheat indicator dropping. I'm a little worried. Going to burn retrograde to make my entry steeper. That should be enough! This'll be hotter. Aaaand there's the tumble! Perfect! The tumble ripped off the engine and tanks. How's that for cheap decoupling? Capture complete. On my way home! Made it through re-entry. Down to chute-safe speed, so I'll waste no time. Away goes the chute! It's opened up fully now. Aaaaand... Splashdown! We made it.

How can I thrust prograde from EVA, when my thrust vectors are all plane-dependent?

Wow, I completely messed up what I meant to say. I said prograde, but I meant pro-heading. Like, if I want to match orbital velocity with my target, I'll line up the navball heading indicator with the target-retrograde marker. But what do I do then? If I press W, the target-relative speed starts to drop, but then the marker starts wandering. I think I'm thrusting off-axis...maybe because I can't control pitch?

So Jeb's on the surface of Minmus, and his capsule is in an eccentric orbit, about to pass directly over his head. The capsule has no probe core, so it's up to Jeb to make the rendezvous on his own. He should definitely have enough RCS monopropellant to get back to it, since he deorbited and landed using less than half of his RCS propellant. I can get Jeb into orbit easily enough, but I'm having a lot of trouble with the controls. I can't seem to get him to thrust prograde in the same direction as the navball marker. I can set the capsule as target and (apparently) line it up, but I always end up thrusting slightly off-angle, and by the time I make the corrections I'm out of propellant. What am I missing? Is this doable? (edited)

omigod omigod yessssssssssssss

Lifetime considerations drive up the cost of commercial jet engines, but the performance is still a factor of raw physics (with a little chemistry thrown in for gits and shiggles). Allowing a lower lifetime doesn't make the rocket equation any less punishing. Thinking about the inlet is the right track. The problem with airbreathing launch is known as "the air-breather's burden". If you want to continue accelerating (which is pretty darn important if you want to go to space today), you have to have net-positive thrust. If you want to have net-positive thrust, you want your exhaust to have more momentum per second than your intake. And here's the problem. Even if you had NO parasitic drag or compression drag from your intake (not to mention your vehicle body), your thrust is only the difference between your intake momentum and your exhaust momentum. If you're gulping one ton of air per second to burn with your fuel, your net thrust is your actual exhaust velocity times one ton per second plus your fuel consumption, minus your airspeed times one ton per second. The closer your airspeed gets to your exhaust velocity, the closer your net thrust gets to zero. That's the problem with trying to get up to a significant fraction of orbital speeds with an airbreather.

All right, here's Falcon 9 (v1.0) with Dragon 1! I'm pretty proud of this, honestly; the Dragon 1 looks very, very close to the real thing. Dragon with omnidirectional bipropellant RCS thrusters, trunk, solar panels, and upper stage. Added four engines to the Falcon 5 configuration to make a Falcon 9; otherwise identical. Launching at night for rendezvous. Fairly slow ascent, as before. TWR is hurting with the same thrust limitation as the Falcon 5; I have almost twice as much thrust but a heavier first stage and a MUCH heavier payload. Gravity turn proceeds slowly. Trying to get a match to space station inclination early. Obligatory "almost-to-MaxQ-but-not-quite" shot. Closer to burnout. Once first-stage fuel drops below about 30%, acceleration REALLY ramps up. Here's staging! As you can see, TWR at staging is >1, which is expected. Of course, given Kerbin's precipitous drop in gravity, it's not going to hurt me here. Ascending rapidly, but I've already adjusted to continue trying to target the station. Reached apoapsis outside of the atmosphere, so that's one milestone. Blew off the "capsule" nosecone. Now it looks even more like a Dragon 1. Using my target to set up circularization. First shot of Dragon 1 and the F9 upper stage in orbit. One more intercept to match orbits. S2 ignition to match. Stage separation. Extending the solar panels on the D1. Using thrusters to match orbital speed. Continuing the approach. It's a bit rough without proper reaction wheels. Very close now. Nice clear shot of final approach. Docked! Refuelling the attitude control tanks on the station core. Separated from the station core. Everything went according to plan! Deorbit burn. This was a very narrow window to come down where I wanted to come down. Separating from the trunk. This, I think, is the biggest problem with the D1 and D2 designs from SpaceX. Solar panels are hella expensive! Why would you throw away solar panels? Re-entry impending; drag is already starting to pull the trunk away. Starting to see heat. Very hot now. I decided to turn off SAS and use RCS to send myself into a tumble, just to see whether my design is aerodynamically self-correcting. Still tumbling! Aaaaaaand success! It looks like my design is pretty good at self-orienting for re-entry. Good to know. Almost done with re-entry. Free-fall now. Drogues out. Closeup of the chute attachments. Drogues are expanded to full. Popping the mains. Keeping both the mains and the drogues attached, just to be conservative. Nearing splashdown... Aaaaaaand down! I made it! Kinda low, since I didn't burn off much of my RCS fuel, but that's ok. There's Dragon 1, back finally!

I'll give you a hint: I get into Low Kerbin orbit with 1827.41 m/s of dV.

Aaaaand got it! Cost is 9038, height is 5.9 meters, it has 13 parts, and mass is a miniscule 5.815 tonnes. No part clipping. Once I get a chance I'll do the full mission with all the screenshots.

Uh, what? All nine engines feed from the same tank.

Dammit, you beat me to it.

Not really, and here's why. About a third of the sun's incident light is scattered by Earth's atmosphere. We see this as the blue of the sky, because higher-wavelength light is scattered most sharply. If you've ever been near the bottom of a large parking garage or any other structure where a thin sliver of the sky is visible, you can sometimes see the blue skyshine coming down onto your hands independent of the redder direct sunlight. The sky acts a little like one of the big parabolic reflectors that photographers use with professional flash systems. So, even if the moon is blocking 80-90% of the sunlight directly above you, you're still able to see hundreds of miles of sky, which scatters sunlight in every direction. This scattering is one of the reasons why there's very little apparent drop in ambient light. Finally, the amount of light you see is largely dependent on the sun's interaction with our atmosphere, so there's not really a good analogue to other planets because they do not have the same atmosphere as our own. Whoa, that is fantastic! Really impressive job. I would not have thought of doing that, but the magnification is impressive. I was surprised by how clear an image I was able to get (up to 3" across) just by using my thumb and forefinger as a camera obscura. Even a single pane of glass can produce this sort of aberration, since you can have reflections internal to the piece of glass. Any place where you have a boundary between air and glass, you can have reflections.

The image bounces between the camera's lens interfaces internally, altering its apparent projected position while attenuating it enough to not wash out the CCD.