sevenperforce

When career mode starts, all you have is the parachute, the basic command module, and the RT-5 SRB. Your launch pad also has a 30-part, 18-tonne limit. However, you have full access to staging, and explosive decoupling is always a possibility. You can also set the individual fuel and thrust levels of each RT-5 during assembly. With a few tricks, it might be possible to squeeze quite a bit of dV out of an appropriately-designed vehicle within those limitations. Who wants to give it a go? EDIT: At Ultimate Steve's suggestion, I'm making two leaderboards: one for maximum altitude, one for maximum velocity. SPEEDSTERS: 1. Ultimate Steve (1.891 km/s) 2. 3. SOARERS: 1. Ultimate Steve (338.14 km) 2. 3.

All right, my entry! I did this in Stock Demo, almost; the only non-stock change I made was setting the SRB's .cfg to allow engine restarts, because the rockets on John Glenn's LV had multiple firings and Demo doesn't really have a better way of doing that. Some clipping just for aesthetic purposes. The tanks feeding the engines on the side are crossfed to the central column. Launch and orbital album below: All done! Godspeed, Colonel Glenn. You were the first of the greatest of us.

Hmm, I think I can do this in Demo.

Cosmonaut means "universe sailor"; astronaut means "star sailor". Not really much of a difference, except that IIRC the Russians were trying to convey a sense of conquest while the Americans were trying to convey a sense of exploration.

Ooh, thought of a potentially simple(ish) way to do this. What about using an asymmetric "flying saucer" ship with vertically-oriented airbreathing engines in the center, horizontally-oriented rocket engines on one side with poor SL Isp and high vacuum Isp, and an opposite-facing ion engine on the other side? The airbreathing engines would lift the craft straight up, with the effective thrust of the rocket engines being fairly low at the start but increasing as the craft gained altitude. Fuel would be routed so that all but one of the airbreathing engines would flameout due to fuel loss in the upper atmosphere as the rocket engines pushed it into orbit. Once the rocket engines flame out, the ion engine would burn retrograde until orbit decayed. On re-entry, the whole craft would passively re-orient and the airbreathing engine would automatically come back on since it had oxygen again, gaining thrust as it descended, and coming to a survivable terminal velocity at sea level.

A few thoughts: Staging (of sorts) is entirely possible using carefully timed explosive stack decoupling. Lithobraking and orbit-to-surface suicide burns are individually impossible, but a suicide-burn-assisted lithobrake should be doable enough. Using timed burnouts (due to fuel) and a changing COM should permit aerodynamic stabilization of the craft during re-entry and the suicide burn. You don't need a true suicide burn; you just need enough thrust to lower terminal velocity to something survivable. Someone who isn't me should try each component individually as proof of concept.

Bumping this with my entry. Two LV-T30s parallel to a single RT-10, with a small inline reaction wheel just above each engine. I've set up the fuel to flow up into the central stack of fuel tanks in order to keep the COM as far forward as possible during ascent. I've used just two struts to tie the parallel tanks to the SRB. I even drained the command module of monopropellant in order to save weight. Going to rely on the engines to keep the command module's battery charged to run its reaction wheel. The fuel tank clipping at the top and bottom is an attempt to help maintain aerodynamic stability. Sunrise...and...launch! GLOW of 38.2 tonnes and a SL thrust of 556.8 kN gives it a spry T/W ratio of 1.49. My initial attempts focused on stacking as much fuel as I possibly could, but I've gotten better performance using high initial thrust to get the LV-T30s up into the atmosphere as fast as possible to improve their Isp. The dry mass of the RT-10 is low enough that there isn't much of a loss from bringing it along for the ride. At SRB burnout, I've just broken 100 m/s and I've gained about 3% in specific impulse on the two remaining engines. It's enough to overcome drag and maintain a T/W ratio of around 1.15, enough to start edging into an early gravity turn. Just past Mach 1, thirteen kilometers high, and well into the gravity turn. As with virtually any SSTO, I have ample T/W, so I'm taking advantage of that by not using a lofted trajectory. Apoapse is just under thirty kilometers at this point. Notice that I've already almost maxed out the specific impulse of my engines. You can see how flat the ascent trajectory is. Outside the bulk of the atmosphere. I'm aiming for a 70x70 orbit, so I've throttled way down and trying to build up to it gradually rather than worrying with a restart at apogee. Orbit achieved! 70x72 km, with 2.73 tonnes of fuel remaining. Given the specific impulse of my engines, that gives me up to 881 m/s of dV. My electric charge is lower than I'd like, but I should still be able to pull off the deorbit burn, and aerodynamics will take care of the rest. The trick here is going to be selecting the right deorbit point so I end up coming down in the water or on land near sea level, during the daytime. A 40 m/s deorbit burn, and I'm all set. Taking a shallow re-entry that hopefully will put me down in the ocean; I'm still a little shaky on planning deorbit trajectories. By my calculations, I'll have about 770 m/s of dV at sea level. Re-entry! With a trajectory this shallow, heating is minor and comes after I've already dropped pretty far, since the upper atmosphere slowed me down a bit already without heating. Aerodynamics holding me close to retrograde with a little residual wobble. Unfortunately, it looks like I'll be coming down over land close to sunset, which makes the suicide burn doubly dicey since I don't know my true altitude and shadows will be deceptive. Made it through re-entry and I'm already nearing the thickest part of the atmosphere, so my terminal velocity should be low. Just going to have to wing the suicide burn; that 770 m/s will go fast and I'm coming down in the mountains. My max T/W ratio is right around 3.5 which is good for a hoverslam. Acceleratometer is down to just about 1 gee, so I know I'm close to terminal velocity. I've got more than twice the dV I need, though, so I'll break it into two burns. A back-of-the-envelope estimate tells me I'll need to start my preliminary suicide burn around 1100 meters above the ground, but I'm not sure where the ground is. These mountain ranges average around 1 km so I'll start a preliminary burn around 2.2 km. Uh oh. I hate mountains. 2,043 meters? Are you kidding me!? Still, if I had started that burn just three seconds earlier, I would have zeroed out with almost 400 m/s of dV remaining, which would have been more than enough for a feather-light landing. Catastrophic failure, yes...but it's clearly possible. So surely someone can do it.

I come out of orbit with about 800 m/s of dV remaining...that's with two liquid engines and a single solid booster. Should definitely be enough for a hoverslam with corrections if a better pilot than I was at the wheel, so to speak. EDIT: And now that I recall, terminal velocity is closer to 250 m/s anyway. So yeah, that should definitely be enough. I've air-launched several times while trying to hoverslam so I know I have enough fuel. Given the usefulness of SRBs for their high TWR and relatively low dry mass, I think there could be numerous ways to squeeze a little extra fuel onboard and really maximize delta-v. I'm also hoping to see some unique designs, for ships that maintain a forward COM on the way up and then a rearward COM on the way down. The aerodynamic fins in the Demo are very heat-sensitive and fixed, but giving the ship a bit of crossrange (to get it back to the launch pad) or using aerodynamics to slow it down more before the suicide burn would be neat to see.

Well, maybe the standard game is a lot harder than the demo, because I've come awfully close numerous times. Terminal velocity for my SSTO after a tail-first re-entry is around 320 m/s, which really isn't much dV. The times that I've judged the suicide burn properly, I've usually been within 50 m/s of success. My biggest trouble is a landing target... somehow I always end up landing in the dark in the middle of the ocean.

I dug through the forums and couldn't find anything quite like this. It promises to be a pretty kerbal sort of challenge, so hopefully we will get some interesting entries. Building an SSTO seems to be pretty popular for early players. Airbreathing spaceplanes are the most common, though pure-rocket and VTOL SSTOs are typical too. Building a reusable SSTO in Demo Mode, on the other hand...that's a bit of a challenge. It's easy enough to stack stages in Demo to achieve pretty much anything you want, but with only a single liquid-fueled engine, what you can do in a single stage is limited. The LV-T30 (at least, the one in the Demo) has a sea level TWR of 14.8, which isn't exactly ideal for an SSTO. With an ISP maxing out at 305 s and the demo's maximum tankage ratio of 9:1, the theoretical maximum delta-v of an LV-T30-based SSTO is 5.47 km/s with a launch TWR of exactly 1:1. This is more than enough to reach orbit, of course, but when you factor in decreased atmospheric specific impulse, aerodynamic drag, a reasonable launch TWR, and a host of other considerations, you end up cutting it pretty close. And getting back down to the atmosphere, surviving re-entry without heat shields, and still having enough fuel to land without parachutes...that's tough. So that's the challenge! Build a single-stage rocket using only Demo parts that can take off, reach a stable orbit, re-enter, and land propulsively without a parachute. A list of demo parts is available here. However, this list includes the TVR-1180C Mk1 Stack Tri-Coupler, the AV-R8 Winglet, and the Telus Mobility Enhancer, none of which are present in the demo I have, so they aren't allowed for the purposes of this challenge. Anything else on that list is fine. To qualify as a single-stage rocket, the entire rocket (minus launch clamps) must reach orbit and return to land without any loss of parts. A stable orbit is an orbit greater than 70x70 km. Water landings are permitted as long as you touch down under rocket propulsion and no parts break. No autopilot mods, but anything else is fine. Control is going to be a challenge; without a vectorable engine or control surfaces (and minimal mass budget for reaction wheels or RCS), a lot is going to depend on aerodynamics and your center of mass. For that reason, some part clipping is fine. Scoring of qualified entries is based on extra points, available as follows: Playing in the actual demo: +200 points Reaching an orbit of at least 100x100 km: +500 points Retrograde orbit rather than prograde orbit: +300 points Using a single re-entry rather than multiple aerobraking passes: +100 points Landing on the daylight side of Kerbin: +50 points Landing on land rather than on water: +75 points Landing in sight of the VAB: +200 points Landing on the actual launch pad: +100 points Landing on deployed landing legs: +25 points Ties will be decided by whichever entry has a lower launch mass. Good luck to all!

Final update: Even though you can make multiple copies of a given part show up in the VAB, the game will default to one of the cfg files (seemingly at random) when you actually go to launch. Too bad. You can still modify all three engines present in the demo, so you could edit the cfg for the RT-10 to make it a heavier, beefier launch SRB, then stick with a standard or slightly modified LV-T30, then edit the RT-5 to make it a restartable vacuum-optimized hybrid-fueled kick motor. But no multiple copies of the same engine. There are multiple tanks, though, so you can change the dry mass and increase the fuel capacity of the T100 or the T200 independently. You can also set the launch fuel of each tank independently in the VAB.

UPDATE -- turns out it's quite simple to duplicate parts in the demo. You just have to duplicate the cfg file in the same directory and rename it (to anything) and then change parameters, keeping the same part name. The game will see multiple cfg files for the same item and so it will put both into the VAB.

Hey, thanks for the answer. Sorry about the confusion; the build id is listed as "00813" but the readme says "Version 0.90.0 Beta", so I wasn't sure what to put. If duplicating parts simply isn't possible in the demo then I'll just mess around with the cfg for the one liquid engine I have.

I've searched, didn't find the answer to this. Pretty sure it's one of those "oh you're missing this basic critical element" problems. Running the 0.90.0 Beta Demo. I know how to edit the cfg files for existing parts, but I'm trying to duplicate the LV-T30 engine so that I can make a separate vacuum-optimized upper-stage version. However, even though I know I can successfully modify existing parts, including the standard LV-T30, I can't seem to get duplicated versions to show up in the VAB when I actually go to build it. So far I've tried duplicating and renaming the cfg file, duplicating and renaming the entire LV-T30 directory in GameData/Parts/Engines, and making the associated changes in the PartsDatabase.cfg file, but nothing I do produces an additional engine in the VAB. Is there something obvious I'm missing?

Thanks!

Well, it could happen, but that's part of why IRL rockets don't do the full gravity turn too soon, preferring instead to climb above the majority of the atmosphere.

Looks like a homework problem because it's a very specific question, but it isn't actually homework. I graduated college a long time ago. Trying to estimate specific impulse of different solid fuels, but I can't get specific impulse without specific energy, and I can't get specific energy unless I know the equation products so I can balance it and calculate bond energies.

I can balance equations but only if I already know both sides. Trying to find the following products: Na2S2O5 + O2 = ? Na2S2O5 + KNO3 = ? Na2S2O5 + KNO3 + Fe2O3 = ? Na2S2O5 + KNO3 + C12H22O11 = ? KNO3 + C12H22O11 = ? KNO3 + C12H22O11 + Fe2O3 = ? Thanks!

Wait, that doesn't make any sense to me at all. Why would the fuel break apart and come out in chunks? It would be just like any solid or hybrid rocket: there's a burn layer which deflagrates into a gas, and that gas comes out the back end of the rocket. In this case, you'd have a very hot fuel-rich pressurized gas coming into one side of the chamber and a very hot fuel-lean pressurized gas coming into the other side of the chamber. They would react, combust, and shoot out the back end of the rocket.

A perhaps-odd but suddenly burning question (no pun intended): Would it be possible to have a staged-combustion dual-hybrid rocket? Basically, you'd have two solid-fueled rockets, one which was exceedingly fuel-rich and one which was exceedingly lean. Neither would be particularly dangerous or explosive on their own. But their exhausts would feed a central reaction chamber where secondary combustion would take place essentially like a liquid-fueled rocket engine. Might be good for amateur rocketeers to achieve greater engine sizes without as much risk of blowing themselves to bits. Each of the rich/lean solid rockets would be much more forgiving and have a much lower burn rate than a typical stoichiometric solid rocket.

Thinking about making my own rocket motors for hobby rockets. However, my chemistry is not nearly as good as my physics, so I'm a touch uncertain as to what fuel+oxidizer combinations would be best. I can get finely powdered potassium nitrate easily enough for the oxidizer. Mixing it with confectioner's sugar would make classic R-candy. But what about making a paste out of the potassium nitrate and something like mineral oil? Would it not produce a good burn surface? What about a mixture of sugar, mineral oil, and the K nitrate? Interested in specific impulse, probable TWR ratios, general safety, and ease of handling.

Yeah, I saw that. Can't really disguise them as grid fins, though. You could do a combination landing, where the grid fin rotors and the landing motor each provide a TWR of 0.7 or so and are used in sync for a soft landing.

The thickness of air has a lot to do with it. At small engine sizes, the air is comparatively thick enough to damp destructive resonance and vibrations. Not so much with orbital-class SRBs or hybrids. That being said, you can look at Sugar Shot to Space for a Karman Line version.

Lemme think about this. Each of the Falcon 9 grid fins have a surface area of 20 square feet, for a combined surface area of 80 square feet or 7.43 square meters. The Falcon 9 masses 22 tonnes dry. Electrical induction motors wouldn't mass too much; the power output of the Merlin turbopumps should be enough to hover it. You'd want to launch in an unpopulated area after a rain. Then you just need a servo for pop-out shock-absorbing landing legs.

That would be...awesome. Assuming, of course, that you can engineer a foldaway design. Put the rotors in a square cowling and you'd never know. As an added bonus, the rotors will function as true grid fins while extended even without being powered. You could even use a ninth central motor with a TWR << 1 to give the appearance of retropropulsive landing. You know, come to think of it, that might actually work for orbital-class rockets.