Grogs

One of my Mun Buses hauled a load of tourists into Minimus orbit. Nobody was landing so I pulled it into a polar orbit where it collected gravioli scans from the poles before returning to Kerbin. I have a contract to mine 150 units of ore on Minimus so I sent a scanner probe. It first fulfilled another contract to place a satellite in a retrograde orbit before going polar for the scan. I also included relay antennas so it can function as another relay after the scan is complete. The scan revealed a high concentration of ore underneath my Minimus surface base so I'll place the mining rig near the base. I launched another probe, the Kerbsat LR-1. I put the LR-1 (LR = long range) in orbit to fulfill a satellite contract, but its main purpose was to test the design for future interplanetary missions. This has enough range to visit most of the planets without the EC headaches of a xenon-powered engine. Finally, I launched a crew shuttle with 14 kerbals onboard, almost my entire space program. The main ship is the orbital shuttle seen earlier, but with full fuel tanks on the upper stage to give it 3000 m/s dV once in orbit. Once in orbit, the shuttle will pick up a 15th kerbal stranded there, then visit the Mun, Minimus, and finally make a quick trip out of Kerbin's SOI so that the crew can get promoted to three stars. After they return, I'll have to figure out what I want to do next with this career. The next world-firsts contract is to orbit Eve, but the launch window isn't for over a year. I'll probably start setting up a refueling infrastructure around Minimus to support kerbed missions to other planets.

Two stars is the best you can do in the Kerbin system. You'll need to visit both moons. Plant the flag on one and flyby the other will be enough. To reach three stars, you'll need to briefly pop out of Kerbin's SOI so that you're in orbit around the sun in addition to visiting both moons.

I tested out a new design for a crew-launch vehicle to get lots of kerbals up to orbit and back. I don't have the tech level to build a proper space plane SSTO, but I took advantage of the Mk3 passenger module to give a total of 19 seats. The upper tank is empty to keep the COM low for re-entry. Here's the orbital shuttle docked at Kerbin Station. The ship to the left is the Mun Bus bringing a load of kerbonauts and tourists back from the Mun. The design is getting long in the tooth and I'll probably retire it soon and replace it with something more up to date. Bringing the orbital shuttle back to the KSP. With the shape and fuel at the bottom, it holds rock steady on re-entry. I don't think I can land it reliably on land so I have to bring it in to overshoot and then fire the engines to get it close to the coast. It's also a little too aerodynamic and without the airbrakes it would smash into the ocean before chutes deployed. Coming in safely just a few km offshore from KSC. Over at Minimus, the fuel tanker arrived. Jeb flew the lander up and then left on one of the Mun Buses seen earlier. When the next group comes they can use it for further exploration of the surface.

I took a group of five tourists to the Mun as part of a contract. I landed two of them to the surface and returned them to the station. Pretty routine by now. The others only paid for an orbit. I'll send them back to Kerbin tomorrow on the Mun Bus. Over at Minimus, things are beginning to get going. First, I landed a rover on the surface to complete a contract to scan an Olivine formation. I was going to detach the skycrane after landing, but I realized I could keep it attached and drive around with just the two rear wheels. I was able to cruise around at 12 m/s and the skycrane actually made for a decent roll cage. After the scan was complete, I put the vehicle on it's rear to recharge the batteries so I would have enough juice to transmit the data home. Over on the other side of Minimus, I landed a kerbed mission. I had a dedicated lander, but I realized contract also wanted me to return a vehicle from the surface. Since the lander had no parachutes I decided to just land the whole crew shuttle instead. I had to disable the gimbal on the Poodle because it kept leaping off the ground otherwise. After leveling up some of the crew in the nearby science lab the ship headed back up and prepared to return to Kerbin.

I've got three in my current career save. One around Kerbin, another around the Mun, and a third on the surface of Minimus. All were built/expanded as part of a contract. Stations are convenient, so if someone is going to pay me to build one, why not? I actually have a Rockomax Jumbo-64 tank on the way to Minimus that will become a new station in orbit there. The contract said it had to have a probe core, generate power, and have an antenna. I think I had to add a thermometer to meet the terms of the contract. Once it's in orbit for 10 seconds and the satellite contract is complete I'll move it to the final orbit. Details below

I think my biggest one was the mother ship for my Jool-5 mission. It weighed in at 1414 tons. The lifter mass was 11,354 tons. It had all the aerodynamics of a brick and I had to fly it like an Eve ascent - straight up until 20,000 meters before starting a gradual gravity turn. Because of the steep ascent profile and low TWR of the Nerv engines, I put it into a 500x500 km orbit. The central booster had about half its fuel left (which I used for the first periapsis kick). Counting that, the total payload to orbit was 1586 tons.

I would say that 8 minutes is really pushing it in an 80x80 orbit. A rule of thumb I've seen about long burns is to not exceed 1/6 of an orbit, i.e., 60 degrees. At 80 km your period is around 35 minutes so you're well over that. It's probably doable, but it's going to be a less efficient burn. If I were planning the mission from scratch I would either aim for a higher starting orbit or else try to divide up the burn over multiple orbits (periapsis kicking). From an 80x80 orbit you could preburn around 900 m/s, leaving you a bit over 1100 to finish. Unfortunately the orbit would take you well over a month to return to periapsis so you'd have to plan ahead. One thing you can do if your first stage has a higher TWR is to lower the thrust of the engines so that they match. This gives you a continuous thrust over the whole burn, but unfortunately in your case it would make it a good bit longer. For a more reasonable length of burn I'll often do that to keep the burn balanced. As for your specific questions: 1. The maneuver nodes assume an instantaneous burn right at the node. The best way to approximate that is to start the burn when the time to the node is half the burn time, i.e., half the burn before the node and half after. 2. What I usually do is switch back and forth. Start burning towards the maneuver node and watch your periapsis. When it starts getting too low (say 71 km), switch to prograde. Once you pass the periapsis you can safely switch back to the maneuver node. Anyway, Eeloo is a tough target. If you can pull off an encounter with the initial burn you're doing really well. I think I had to do two correction burns before I finally got an intercept. With this long burn it's going to be even harder. You need to allow a decent margin of extra fuel (10-20%) to make up for the inefficiencies. I use MechJeb to do most of my interplanetary transfers. It seems to do a pretty good job most of the time. I also make frequent use of the info windows which display things like degrees to prograde and relative inclination with the target.

It's not all that uncommon unfortunately. I see it a lot with complex staging like asparagus setups. I usually keep the MechJeb Delta V stats up and it's not uncommon when it disagrees with the stock numbers. But sometimes both of them are wrong. In your case, I think it's the fact you're using crossfeed through the decouplers. It sees that there's no fuel in the outer tanks where the engines are and reports 0 dV remaining. If the fuel was in the outer tanks, or if there were actual hoses then I think the game would pick up on it.

I ran into this today trying to refuel my lander from the space station around the Mun. I refilled the center tank fine, but then nothing when I tried to refill the six external tanks. When I went to the tracking station and back I was at least able to highlight all six external tanks and the refill tank at the same time and finish the refueling using the OUT button on the refuel tank. Since I'll probably change focus between lander refills anyway it's makes this annoying, but not completely game-breaking to me. I just have to remember to refill all the tanks at once and not try to do them one at a time.

Ouch. Eve is really good at tearing up parachutes like that. I've learned the hard way to use drogues and not deploy the main chutes until the drogues are fully opened.

Heh, I just did something similar in my career game, and I should know better. I had a contract to put a base on the Mun and another to land 4 tourists on the Mun. I figured I would just kill two birds with one stone and land the tourists with the base. Since the base was meant to be 'permanent' I only sent enough fuel to get it down, planning to just send a regular lander down to collect everyone and take them home. Only problem - tourists can't EVA. Oops. Now I have to build something that can land next to the base, roll over, dock, and then reorbit. Those are the kind of things that make KSP what it is. It's frustrating at times, but still fun to try and fix your mistakes.

This tutorial has the parachute math that you can use to calculate landing speed. I used it in 1.7, and it was pretty accurate. As far as I know, they haven't changed anything in the model since then.

What asparagus staging (or any staging really) allows you to do is "cheat" the tyranny of the rocket equation a bit. The equation is dV = g0 * ISP * LN(m_wet / m_dry), where g0 is the standard gravity (~9.81 m/s), m_wet is the mass of the ship with fuel, and m_dry is the mass of the ship with no fuel. In KSP, most of the tanks are 8/9 fuel and 1/9 tank by mass. That means that even at the most extreme case where the mass of the engines and payload are negligible compared to the fuel tanks, the best you can do is ISP * 9.81 * LN(9) = 21.55 * ISP. For chemical engines, the Wolfhound has an ISP of 380 s => dV = 21.55 * 380 = 8188 m/s. With the asparagus staging, you reduce the dry mass part of the way through. For example, let's say you have three tanks - a central core with the engines, and two side boosters. For the first stage (i.e., until the side tanks are empty), the rocket equation looks like this: dV = g0 * ISP * LN(27 / 11) = 8.81 * ISP, or for a Wolfhound 3346 m/s. So you've added about 40% to your dV to get it up to 11,534, but you've also tripled you starting mass. If you added another pair of tanks, it would only increase dV by another 1637 m/s, or about 14% over a single pair of drop tanks. A third pair of drop tanks would only give 1092 m/s extra, and so on. I don't know what the infinite sum ultimately converges to, but as a practical matter it's hard to do much better than doubling the single tank dV without an obscene number of radial tanks.

Awww I mean, yay! Thanks for the cool challenge. It was a lot of fun and it gave me a reason to visit some places I've never been to like Eeloo, the Mohole, the Dead Space Kraken, and Vallhenge.

Well, in fairness you did ask for the most efficient engine. The price for bleeding-edge efficiency is, yeah, low TWR. I did a mockup of something similar to what you have with a probe core and 4 S3-14400 tanks plus and ADPT 2-3 adapter on top. (EDIT: Now that I'm looking at your total mass, maybe those are S3-7200s you have? Still, same principle should apply). So with a single Wolfhound, you get 7900 m/s. That's pretty extreme for a single stage, but your vacuum TWR is only 0.11. You could use an engine plate and stack 3 Wolfhounds. It would almost triple your TWR - so burn time down to 6 minutes or so. The trade off is your dV is down to 7384 m/s. Or use a Rhino. Still pretty efficient at 340 ISP and gives 2000 kN vs. the Wolfhound's 375. dV is down to 6700, but the TWR is 0.58. That should get you down to about a 3.5 minute burn, which is pretty manageable IMO. BTW, I've read that a good rule of thumb is that a burn should be less than 1/6 of an orbit to avoid big cosine losses. In your screenshot you're in about a 52 minute orbit so anything less than about 8 minutes should be OK.

@Superfluous J, I'm happy to report that Joolollo is now complete. You can find the details over at my mission report here: I finished it up today before 1.10 came out so I could check it out. No worries if it takes you a while to review it. I've got a comet to visit! Maybe I'll pull Bob, Jeb, and Val out of retirement for a manned mission there after I send a probe.

I've found that flashing markers usually indicate it's on a later orbit. So you've probably plotted a course that will take you between Kerbin and Duna orbit, but won't actually get you near the planet until the 2nd (or more) pass of Duna's orbit. Hope you packed a lot of snacks!

Chapter 11: Victory over Vall; Homecoming FROM: KSC Mission Control TO: Bob Kerman, KSS Victory Prime DTG: 27:279:03:00 -------------------------MESSAGE FOLLOWS Understand you've reunited at Jool Station and are now preparing for mission to Vall. KAS has detected another anamoly on the surface of Vall at 60° 5′ 10″ S 83° 46′ 48″ E. Please investigate if possible. Good luck on your final moon. -------------------------END MESSAGE

I did a quick test and I'm going to have to admit that I'm wrong on this one, at least in a specific case like Moho. I chose a scenario where we're inbound to Moho with a target orbit of 1 million meters (1 Mm). I launched from Kerbin, then had to make a correction burn to get a Moho intercept. I chose 2 different Pe's: 15 km and 1 Mm. In both cases, the capture was set for an Ap of 9 Mm, which is close to the Moho SOI. For the 15 km case, I then added a burn at Ap to raise the Pe up to 1 Mm. At that point, both orbits are equal and any subsequent maneuvering would be, too. Case 1: Inital Pe @ 15 km: Capture burn is 3004.3 m/s. The burn to raise Pe to 1 Mm is 34.0 m/s. Total dV = 3038.3 m/s. Case 2: Initial Pe is 1 Mm. Capture burn (and total) is 3504.2 m/s. This is about 466 m/s more than case 1. Some caveats: - This is a pretty extreme case dealing with such a fast approach speed and a very high target orbit. I suspect it does get into the gate orbit concept @OHara mentioned and that there's a cutoff Pe where it's more efficient to burn at the target Pe instead of as low as possible. I recall a really old thread where someone had calculated these orbits for each pair of bodies, but I can't find it now. - In practical terms, you also have to consider that the maneuver calculator assumes an instantaneous burn. Coming in hot to Moho a lot of the burn will be far from Pe unless you have a very high TWR. Still, we're talking a savings of 13% of dV so even a fairly long burn should realize significant savings.

I think the cost of having to raise your Pe back up again is going to outweigh any savings from Oberth. I would choose a) for the first choice. For the second situation I would choose a variation of c) for the same reason. Ideally, come in on the same plane as the station and set your Pe on its orbit. Then when you do your capture burn you could set your Ap so that you intercept the station the next time you swing back down to Pe. You don't really have to calculate to pull it off, just set the station as the target and burn until the two position markers come together. There's no reason you have to do it that way, but it feels like the most elegant solution.

Chapter 10: Bob's Tale - Red Shirts; What the heck is that thing? FROM: Bob Kerman, KSS Victory Prime TO: KSC Mission Control DTG: 27:279:02:23 -------------------------MESSAGE FOLLOWS Pol and Bop missions complete. Linked up with KSS Titan and Leviathan and consolidated crew. Preparing for mission to Vall. -------------------------END MESSAGE

If you have Making History, the Wolfhound is a good long-haul vacuum engine for a fairly large craft. At 380 vacuum ISP, it's the best chemical engine I believe. I find it to be good for a transfer stage to move a relatively large payload a long way. I used 7 of them in an asparagus setup to move a 300-ton payload from low-Kerbin orbit to Jool. The stage gives about 4500 m/s dV. For something mid-sized, the Poodle is a good engine. The ISP is a little lower, but it's half the mass which makes up for it. This was my Moho return craft and it had about 3500 m/s. That's not enough to make Kerbin orbit, but plenty to get back and make a direct re-entry. If you need more dV, you can go with a Nerv setup. I think this one had about 5,000 fully fueled.

Chapter 9: Val's Tale, or Ladies' Night on Laythe. Also, Natalo gets a little hot under the collar. FROM: Valentina Kerman, KSS Leviathan TO: KSC Mission Control DTG: 27:223:03:35 -------------------------MESSAGE FOLLOWS Laythe mission complete. Linked up with KSS Titan IVO Jool Station. Awaiting return of KSS Victory from Bop. -------------------------END MESSAGE

Chapter 8: Jeb's Tale, or Tackling Tylo FROM: Jeb Kerman, KSS Titan TO: KSC Mission Control DTG: 27:214:04:00 -------------------------MESSAGE FOLLOWS Tylo mission complete. KSS Titan now in orbit with Jool Station. Awaiting return of the other ships. -------------------------END MESSAGE

CHAPTER 7: Off to the Moons, or Breaking up is hard to do FROM: KSC Mission Control TO: Bob Kerman, KSS Joolollo Victory DTG: 27:145:1:30 -------------------------MESSAGE FOLLOWS Victory crew, we're happy to hear that you arrived safely at Jool Station orbit. There are a bunch of smiling faces down here in mission control. We're sending you a small maneuver to match your inclination to the inner moons. After this burn is complete, you have the go-ahead to proceed with separation ops. We received your recommendation to move the telescope off the Leviathan over to the Victory. We agree now that you've already flown by Laythe there's no need for Leviathan to carry it. Wernher did some calculations and mounting it on the ventral docking port of the Victory should have a negligible impact on your center of gravity. That will let you get observations around Vall, Pol, and Bop. Recommend you use the Vall lander to reposition it. We're also including burns for the Victory, Titan, and Leviathan to transfer to their respective moons. Modify as necessary to meet mission objectives. BTW, Rich set up a special two-burn maneuver for the Leviathan to get a close-up look at Jool's upper atmosphere. We hope you like green because you'll be seeing a lot of it. -------------------------END MESSAGE