Posts tagged ‘kerbal space program’

Bop Transfer

JE1 Tylo to BopOver the weekend I returned to my Jool exploration mission and got the Explorer transferred from Tylo to Bop.

It took about two hours of real time and required three burns. A 10 minute burn to leave Tylo, a 6 minute burn to match inclination with Bop’s orbit and get an intercept, and a final 6 minute burn to get into orbit around Bop. Docking turned out to be easier than I expected but was quite slow.

Overall I’m pretty disappointed with the VASIMR engine on the ship. I tried an alternate design in the VAB with two reactors and engines which did help with the TWR of the craft but not enough to offset the hit to the available deltaV. Instead, I’ve started looking at a new version of the Explorer that uses nuclear engines. The current design looks very promising. It has better TWR and roughly the same deltaV. The ship is smaller because nuclear engines run on liquid fuel not hydrogen which takes more volume, and there’s no nuclear reactor required which saves a lot of mass as well.

Speaking of mass, I drastically overestimated the amount of supplies I would need for the crew. Or really I under estimated how well the hydroponics modules would do at recycling waste. Three years into the mission, and the crew still has a full set of supplies. The next mission should easily be able to get away with half the number of supply containers or more.

So now that the Explorer is docked at the refinery I have to make a decision about whether to cut the mission short and return to Kerbin or continue on to Pol, Laythe, and Vall. I’m leaning to cutting things short and coming back to Jool with a redesigned Explorer with better TWR. Either way, I can send Jeb down to the surface as planned and then leave the lander at the refinery.

Bop Refinery Approach Bop Refinery

Tylo Landing

Continuing my extended weekend in KSP, I left off yesterday with the crew of the Jool Explorer 1 starting their two year journey to the outer edges of the Kerbol system. I time warped the game through most of that journey, slowing down to complete a few research missions and check in on a science lab in orbit around Kerbin’s second moon, Minmus. I use a mod called Kerbal Alarm Clock which is invaluable when running multiple missions at once. It does just what it sounds like it does. I can set alarms for various events like a ship is coming up on a sphere of influence change or a maneuver node. In this case I had an alarm set to remind me when the JE1 was getting close to Jool’s gravity well.

Tylo gravity breaking

Getting to your destination is only half of the challenge for interplanetary travel. You also have to slow down somehow to get into orbit. In the above picture the solid blue line shows the trajectory of the JE1 coming into the Jool system and then escaping. Not only that, but the ship would have picked up a little velocity because of how it was passing Jool. In previous versions of KSP, the easiest way to get into orbit of Jool was called aerobraking, and involved dipping into the upper layer of Jool’s atmosphere and using that to slow down. In the current version that just causes you ship to overheat and explode. Instead of using atmosphere, it’s possible to use gravity. Jool has three decent sized moons with nearly Kerbin levels of gravity, which makes them excellent candidates for this.

In the map screenshot above there’s a maneuver node at the top left of the blue orbit which creates the new dotted orange orbit. That orbit intersects with Jool’s third moon Tylo (which is highlighted in a peach color). Because the JE1 comes in on the backside of Tylo’s orbit, instead of picking up speed the craft instead sheds it, and after exiting Tylo’s gravity well the JE1 will be in the third green dotted orbit. This let’s me get the JE1 into an elliptical Jool orbit for only 73 m/s, compared to spending 250 or more burning on the periapsis marker of the blue orbit.

This kinds of stuff is very cool to me and one of the reasons why I enjoy KSP so much. Of course it’s fun to launch rockets, fly planes, and blow stuff up, but I have really enjoyed learning about orbital mechanics and getting a deeper appreciation for the science and work involved in space navigation.

Finally at Jool

Tylo Rendezvous ManeuversFinally in orbit of the Jool system, it was time to transfer to the moon Tylo and the initial moon landing. The Tylo rendezvous wasn’t difficult, but it was pretty tedious. First I had to push JE1’s periapsis out to intersect with Tylo’s orbit for 418 meters per second delta V which was about an 8 minutes and 30 second burn. Second, I needed to match inclination with Tylo, so we were orbiting at the same angle, which was another 192 m/s and 4 minutes. It’s not strictly necessary to match inclination but it makes rendezvous far easier to do and I’ve never had any luck without doing it. Lastly I needed to wait two orbits and then burn to bring down my apoapsis (point an orbit furthest from the center) to match Tylo’s orbit, which required 183 m/s and a 3 minutes 47 seconds burn. Again, time warp can’t be used while the ship is under acceleration, so I had about 16 minutes of real time waiting to sit through.

While it was really nice to have a design that included so much delta V, it hasn’t really been offset by a much lower TWR, which is why all of these maneuvers were taking so long. I’ll probably not be using this same design on my next big ship. Despite the slight frustration over waiting, I was finally in orbit around Tylo. The first really exciting part of the mission was about to begin.

KSP 2015-09-07 21-20-47-14

Jeb transferred over to the lander and undocked from the Jool Explorer. After making a save point, because nothing ever goes right the first time, Jeb made a small burn to bring his orbit down close to the planet above a landing site that  I selected semi-randomly. My only criteria was to get a different biome than an earlier probe mission so that I could run a full set of science experiments. After passing around the far side of the moon and making a second burn, I create a maneuver for the deorbit burn and waited as the Jool 5 Lander came back around to the daytime side of Tylo.

Tylo Deorbit

The deorbit burn was 1,495 meters per second, which was 67% of what I had in the descent stage. My plan had been to use that stage for most of the descent and jettison it just before landing. I had a minor moment of panic though because I wasn’t sure how much I would need before actually touching down. In the end I had almost a perfect amount. The remaining 33% was enough to keep my speed down for most of the descent after the deorbit burn finished. I ended up jettisoning the main descent stage and using about 460 m/s of my ascent stage touching down on the surface. But I had budgeted a few hundred extra meters per second on my ascent stage just for that reason. I thought it might be close, but I was pretty confident Jeb wouldn’t be stuck on the surface.

This Tylo landing was one of the more intense things I’ve done in KSP recently. It reminded me quite a bit of when I was first learning to do Mun landings and orbital docking. Trying to keep track of remaining fuel, heading, and descent velocity all while the surface is rushing up to meet you. These are some of the most exhilarating and rewarding activities I’ve ever done in gaming.

Jeb on Tylo

After planting a flag and running some experiments, I was a little anxious to get Jeb back into space and see if I could get him docked up with the JE1. Taking off from a moon with no atmosphere is pretty straight forward. You throttle up and point the craft to the east at a 45° pitch. East because then you get to add the rotational velocity of the body you’re on to your orbital velocity, and 45° is a good rule of thumb although you can always go lower or higher depending on the terrain.

It turned out that my fuel situation was a lot tighter than I realized. The Jool 5 Lander ended up in a 53.5 km by 17.5 km orbit with only 34 m/s fuel remaining. That’s not much, but this was after I had already gotten an intersect of 2.9 km with the Jool Explorer, so all I really needed was for my relative velocity to not be too much over 34 m/s when I got to my rendezvous point. I still have a bunch of monopropellant for RCS thrusters, but those aren’t create for slowing down more than 10 m/s or so.

Tylo with Jool, Vall, and Laythe

Tylo with Jool and it’s moons Vall (left) and Laythe (right)

After a last orbit of Tylo, Jeb’s Lander intercepted the Explorer and had a relative velocity of 45 m/s. Ideally it would have been 34 or less, but the remaining 11 m/s after I exhausted the lander’s fuel was easy to take care of with RCS. Docking went smoothly and then Jeb transferred back to the Explorer’s crew module bringing along all of the science he’d collected on the surface.

The next stage of the mission was to head to Laythe and land, but I ended up using more hydrogen than I expected getting from Kerbin to Tylo. So instead the crew of the JE1 will make for Bop which is where the orbital refinery that I had previously sent out is located. Bop is inclined and the fourth moon in the system, but it has very little gravity which made more sense for mining operations.

Journey to Jool

My intentions going into the weekend were to launch my Jool exploration expedition, meet up with my local Golem Arcana group, and restart on my multi-tasking experiment. Two out of three isn’t bad right? I ended up playing two Golem Arcana matches using my Dread Vanguard army, winning both so my Ashmogh remains undefeated, and playing a lot of Kerbal Space Program. A lot. Maybe 20 hours worth? I wish Steam showed detailed play statistics. Raptr kind of does, but it’s not as good at that as it used to be. As a matter of fact, if I think about it Raptr is past the point where its usefulness to me outweighs its memory footprint. I should probably find an alternative that just tracks gaming time.

Crew Transfer

The last phase of preparation for my Kerballed Jool exploration mission was to send up the crew and perform some minor structural maintenance.

Jool Explorer Crew Launch

The transfer vehicle was designed to send up a three Kerbal crew, the standard pilot, engineer, and scientist complement. It also had a probe core so that it could be remotely piloted and set to rendezvous and dock with the space station in orbit while the Jool mission was underway, and then be reused to bring the crew back Kerbin-side when they returned.

Jool Crew Launch nighttime

 

The crew launched at night in order to have the shortest rendezvous with the Jool Explorer 1. That means most of the launch and rendezvous was in the dark so there isn’t much in the way of pictures from that part of the mission. The actual crew transfer took place in the daytime as EVA’s, since there’s only one docking port on the Explorer and it was in use by the lander.

Jool Crew EVAOur pilot, Jebediah Kerman, enjoyed the whole process a little too much.

Jool Crew EVA - JebWith the crew aboard and some struts applied to the docking connection between the crew and engine modules by the ship’s engineer, Bill Kerman, it was finally time to deploy the habitat ring, heat radiators, and fire up the nuclear reactor.

Jool Explorer Ready to DepartThis was my first time using such a large ship as well as a VASIMR engine. With a TWR (thrust to weight ratio) of 0.10 I was expecting it to be slow to get underway, but I wasn’t really prepared for how slow. I was also surprised that the Kerbal Engineer Redux (KER) mod that I use to provide flight details wasn’t working correctly with the VASIMR engine. After plotting a maneuver to transfer from Kerbin to Jool, the built-in numbers were telling me the burn would take 27 minutes while KER was saying 6 minutes and 28 seconds. Sadly KER was wrong. It also meant that I had to break the 27 minute burn down into 4 to 6 minute chunks, which was about the maximum length I could burn at my current altitude without causing my orbit to dip into the atmosphere.

So for about five orbits I would start burning at three minutes before the periapsis (lowest point on my orbit, and the most efficient place to burn from) and keep it up for six minutes total. KSP doesn’t allow time warping while a craft is under acceleration either, so I had to do all of the burns in real-time. Well that’s not totally true, KSP does allow for physical warping by a factor of 2, 3, or 4 times but physical time warp can do very bad things to a large craft and I didn’t want to risk it. Eventually the maneuver was completed and my Kerbals were finally on their way to Jool with the trip set to take roughly two years and 48 days.

Jool Explorer Transfer Orbit

 

 

 

Jool Five Lander Launch

Getting back to my mission preparation for my first Kerballed mission to Jool, the next piece that needed to get into orbit was the Jool 5 Lander (since it’s going to land on five different moons, not that it took five designs to get it right).

Jool 5 Lander pre-launch Jool 5 Lander mid-launch

Jool 5 Lander fairing jetison Jool 5 Lander in Orbit

The launch went well, although I had to jettison the fairings below 20 kilometers which isn’t usually a good idea, but could have been much worse. I did end up using quite a bit more fuel than I expected. I still had plenty for rendezvous, but I knew then that wouldn’t have enough on the Explorer to completely refill the lander.

So of course that mean I needed to launch a refueling ship. I do have a refinery set up in orbit around Bop in the Jool system, but my plan was to go there last to refuel the ship before returning to Kerbin. I didn’t want to have to go there first, hit the remaining moons, and then  go back again. Far easier to do the refueling in Kerbin orbit instead. I happened to have a large refueling rocket design already that was over kill for  my current needs, but that’s kind of how you’re intended to play KSP anyway.

Kerbol Explorer Refueller launch Kerbol Explorer Refueller booster separation

The refueler launch and rendezvous went off without a hitch. I always enjoy watching booster stages separate and drop away. Here’s the completed ship, fully fueled, and ready to receive crew once the transfer window arrives.

Kerbol Explorer 1 - Ready for Jool

 

 

 

 

Jool Explorer Assembly

Blaugust 2015 Day 29

I had planned to spend last night’s gaming time in Champions Online, but the patcher was running extremely slowly, so instead I tried Star Trek Online and it timed out on the character loading screen. Cryptic seemed to be having some kind of network issues, although I didn’t try Neverwinter to see. Instead I took it as a sign to go play more Kerbal Space Program.

In Kerbal, I decided I’d messed around with the planning stages of my Jool mission enough. It was time to start launching rockets. I started with the crew module for the explorer ship. I figured that way I could rendezvous with the hydrogen tanker, dock it, and then dock the engine module with out having to do and undocking and rearranging.

KSP 2015-08-28 22-46-28-01 KSP 2015-08-28 22-46-46-54 KSP 2015-08-28 23-00-09-39 KSP 2015-08-29 00-05-05-52

 

I took me three tries to get the launch right. I ended up having to go straight up more than I wanted before turning the ship, so I used more fuel getting into orbit than I planned on, but I still have enough fuel remaining to rendezvous. Docking also turned out to be quite challenging. I used more than 60% of my mono-propellant getting into position and closing the remaining distance. A lot of that was due to the mass of the vehicle compared to the reaction wheels and the fact that I didn’t include RCS at the base of the rocket. All of the thruster blocks were on the crew module. I also made the whole process harder by launching when the hydrogen tanker was on the opposite side of Kerbin, so it took quite a few orbits to catch up with it.

The engine module launch when much smoother. The total rocket mass was a bit heavier (387 tons versus 316 for the crew module launcher), but I added extra fuel and engines to the initial stage to compensate and account for a less efficient ascent path. I also saved myself a lot of headaches and waited until the hydrogen tank and crew module were nearly overhead before launching, so I wouldn’t have much work to catch up.

KSP 2015-08-29 00-25-15-56 KSP 2015-08-29 00-31-29-63

KSP 2015-08-29 00-39-25-01 KSP 2015-08-29 01-16-38-08

I only needed one try for this launch. I actually managed a better ascent path as well, although I did still end up in a high orbit than I wanted to. But it didn’t take much fuel to correct that. You can see from the third picture with the fairings off that I sent the engine module up backwards. I wanted to keep the engine and reactor weight at the top of the rocket to help with stability (think of a dart if that’s confusing), and the large docking port that would eventually couple to the crew module was a strong spot to attach to the launcher. Rendezvous was very easy this time since I’d made a better choice on launch time. Docking was also painless, especially compare to the crew module, since the engine module was empty of fuel and only 31 tons where the crew module was fully stocked with supplies and 72 tons during docking.

After completing assembly of the explorer, I transferred hydrogen from the big tank over to the ship. I was able to fully fuel the explorer and still have 66% of the big tank left. The tanker will stay in Kerbin orbit awaiting the ship’s return from Jool where it can refuel for a return voyage or a mission to one of the other planets.

My next play session, I’ll send up the lander vehicle and get it docked to the explorer. It’ll attach to the nose with the hydrogen tanker is currently docked. I’m a little concerned about the thrust-to-weight ratio of the ship once I do that. If it’s too low, I’ll have to make a different transfer vehicle attach to the lander and send it out to Jool ahead of the Kerballed mission. In testing it looked like it would be okay though. There are about 280 Kerbal days remaining before the transfer window, so I have plenty of time to finish assembly and send up the crew.

Jool Mission Planning – Engine Thermal Test

Blaugust 2015 Day 28
I played Kerbal Space Program last night and spent a couple of hours fine tuning and testing my lander and explorer ships designs as well as planning out the launch sequence and orbital construction process.

My current plan is to put the lander up one it’s own, followed by the crew and engine halves of the explorer ship. The engine module of the explorer will be empty of fuel, in fact I’ve already managed to launch a massive spherical tank of hydrogen fuel into orbit in preparation. I pretty much just threw this together and brute forced the launch, but I wanted to put something into space.

Hyodrogen Fuel Tank

Once all of the pieces are in orbit, then I’ll rendezvous the two halves of the explorer ship with the fuel tank and assemble the ship and transfer as much hydrogen as it will handle. Then, I’ll deorbit the left over launch vehicles and bring the lander craft in to rendezvous and dock nose to nose with the explorer. The last bit will be to send up a crew shuttle once the Jool transfer window gets close.

I have the lander contained in a fairing now with enough of a launcher to get into orbit. I’ll use the lander’s existing fuel and engines to dock it with the explorer ship, which will be carrying fuel to refill the lander anyway.

Jool 5 Lander Launcher

 

Before I package up the explorer craft, I wanted to make sure I had the fission reactor and VASIMR engine set up correctly. I’ve not used either on a mission before and I didn’t want to have problems with heat before I even left the Kerbin system. So I set up a test using a stripped down version of the engine module and let it run for fifteen minutes. I’m glad I did because my original thermal system had some issues and needed tweaking.

VASIMIR Thermal Test

 

Unfortunately it turned out to be 1 am before I noticed so I had to stop there. I’m getting close though. I need to get launchers set up for the two halves of the explorer ship and then it’ll be time to start putting stuff into orbit for assembly. It’s exciting but nerve wracking as well. I keep double checking things to make sure I haven’t made any mistakes or forgotten a part. I really don’t want to have my three Kerbals arrive at Jool after a two year trip and realize I forgot something stupid.

 

Jool Mission Planning – Lander Design

Blaugust 2015 Day 23

Last night should have been my return to my multitasking experiment, and playing anything other than KSP which is what I’d played on Wednesday. But I had just watched the latest trailer for The Martian again and was in a space mood that Star Trek Online doesn’t really fulfill as it is more science fantasy and hard science.

Instead I headed back into the Vehicle Assembly Building to work on the next stage of my Jool exploration mission. My previous design work had been all about building a craft which would take three Kerbals from Kerbin to Jool and allow for refueling at an automated refinery I’d already place at one of Jool’s moons. But I still needed to build a landing craft to take along. After all it would be a waste for three Kerbalnauts to spend years traveling out to Jool and not get a chance to plant flags on at least one of the moons.

I’m actually planning something more ambitious than that, which is called a Jool 5 expedition. Basically, landing on all five moons with a single mission. Something that was much more challenging before Squad added ISRU (in-situ resource utilization) equipment to the game, so now it’s possible to set up refueling locations.

Even knowing I can refuel though, I needed to design a lander that could handle landing and taking off from all five of Jool’s moons. Some like Bop and Pol are relatively easy. Both are small, low gravity satellites, and have no atmosphere. Vall is bigger but not too difficult. Laythe is more of a challenge. Its gravity is 0.8 that of Kerbin and has an atmosphere like Kerbin does which will help with landing since I can plan to use parachutes not burn a ton of fuel to land. The real challenge of the five will be Tylo. It also has a gravity 0.8 times Kerbin, but it has no atmosphere so the entire landing will require fuel, which means twice as much as will be needed for Laythe.

I had a basic stage for the Tylo descent, but was trying to put together an ascent module that would also work for Laythe and the other moons. This is my first design. To take off from Tylo I need better than 1.0 TWR (thrust to weight ratio) and at least 3070 delta-V. The only problem is I don’t like the look of the big tank sticking out.

KSP 2015-08-23 21-01-05-75

 

I started over and played around with some other ideas. The problem was that using more smaller tanks meant more weight for basically the same amount of fuel, which meant a bigger engine or more engines. Which is not horrible, but anything that could take off from Tylo would be way over engineered for the other moons. And I’m expecting to reuse the craft for Bop quite often after completing the exploration mission. I finally settled on the following design. Not only do I like the look of this craft better, it actually has better TWR and a 1 more meters per second in delta-V.

KSP 2015-08-23 21-01-45-48

 

So now that I have my landing craft, I need to revisit my exploration ship. The current ship uses nuclear engines which run on liquid fuel only, whereas the motor on my landing craft requires LFO (liquid fuel and oxidier). So I’ll need to add a tank to the ship to allow refueling of the lander after it leaves a moon an docks. That will of course mean I need to adjust the fuel and motors on the exploration ship as well. It’s a lot of planning but that’s part of the fun of the game for me.

Here’s the completed lander with the Tylo descent module.

KSP 2015-08-23 21-03-18-84

 

Jool Mission Planning

Jool Explorer 1Blaugust 2015 Day 20

Rather than suffer the vagaries of a d4, I loaded up Kerbal Space Program last night. It’s kind of cheating on my multitasking experiment as KSP has basically been my primary game since October. Regardless, I spent the evening in the Vehicle Assembly Building working on my first Kerballed mission to Jool, which is the second most remote planet in the Kerbol system and the only gas giant. This isn’t my first trip to Jool, I’ve sent dozens of satellites and probes to survey Jool’s five moons, but it will be the first time I send Kerbals.

In my current career game I have a life support mod installed, so unlike in the stock game, I actually have to make sure I send enough supplies along to keep my Kerbals fed for the duration of the trip, which will take about 2 years travel out, 3 or 4 more waiting on a return windows, and another 2 back. Which is why there are four supply canisters and two greenhouses for recycling.

The current weight of the ship is nearly 100 tons, so I’ll have to send it into orbit in at least two pieces, which I don’t mind doing as I’ve practiced rendezvous and docking quite a bit. I think I’ve managed to build everything into the ship I wanted for the primary craft. The next step is to figure out a small lander so I can actually put a Kerbal on one or more of Jool’s moons.

The trick with all of this is to try and keep the part count as low as possible. Large part counts of 150 or more cause the game to lag down massively on my machine. The game is still playable, but it’s not much fun. This is my only complaint with Kerbal Space Program. I would love to be able to build and assemble large space stations and interplanetary ships, but part count lag takes a lot of the fun out of the process.

Background Noise

Blaugust 2015 Day 14

Background Noise

I am orders of magnitude more productive at work if I’m listening to music or podcasts. It provides a consistent distraction that I can then ignore while focusing on whatever programming issue I’m trying to solve, instead of all of the sporadic background conversations going on in the office. I can’t stand having music or anything else on when I’m reading though. It’s the same for TV and movies, I don’t do the whole second screen thing of live tweeting shows or looking up things. When I’m watching a show, I’m focused solely on that. Video games vary depending on what I’m doing. If I’m playing Kerbal Space Program or Minecraft, I generally always have something playing on my second monitor, often it will be a Let’s Play of the same game. With Star Trek Online, I like to watch old episodes on Netflix, but only if I’m playing combat heavy missions like patrols or queues. If I’m playing a featured episode or Foundry mission that’s story heavy, then it’s like reading or TV for me and I can’t have anything else going on.

Back in the Command Chair

Speaking of Star Trek Online, I’m coming back from a sort of break from the game. I say sort of, since I’ve still been logging in fairly regularly, but usually only for a few minutes which is long enough to complete some Duty Officer missions and queue up some new ones. But with Season 10.5 out now, regular monthly Featured Episodes being released, and Season 11 on the horizon, it felt like now was a good time to get back in. Coming back to any MMO after an absence is tough, especially if a lot of changes have been taking place in the game, so I wanted to give myself some time to get back up to speed. Hopefully the other members of my fleet will start showing up more regularly over the next few weeks as well.

 

Modded KSP

kerbalengineer02Blaugust 2015 Day 13

As much fun as stock Kerbal Space Program game is for me, it is even more fun with mods. Some of the core mods that I don’t like to play without just to give better information. The stock game expects players to experiment and play through try-fail cycles, but I’m more of a planner than a pantser.

The first mod I ever installed and still my top must have is called Kerbal Engineer Redux. It add lots of information to the Vehicle Assembly Building, the Space Plane Hangar, and to in-flight craft. The most important number is the deltaV, which is literally the amount of change in velocity a craft has. A certain amount of deltaV is required to reach orbit around Kerbin, and more is required to transfer to the moons or other planets, not to mention entering orbit and landing. Basically anytime you try to move your craft to a different orbit, land, or take-off you are spending deltaV, so knowing how much you have on a rocket is great for planning a mission.

The second mod I picked up is called Chatterer. It doesn’t affect gameplay or visuals, it adds sporadic radio chatter between the Kerbal crew on your active craft with mission control. It sounds like a small thing, but it adds quite a bit of atmosphere to missions. It’s not really a must have mod, but it’s gin nevertheless.

I keep a full list on this page, I’ll talk about a few of the parts mods soon.