Month: May 2014
Building a spaceplane in KSP isn’t easy, it takes a whole different approach and skillset to building rockets. I’ve never built one before so this is my attempt. My objective is to make a SSTO spaceplane that can dock at the KSS and then return to the landing strip at KSC.
Rather than go straight for it, I decided to get the basics of flight ironed out with a simple little plane:
Flight 10: Basic Jet
The first plane was simply a couple of jet fuel tanks with a basic jet engine on the back and a couple of wings for lift.
The first flight was a sucess so far! It got itself up into the air without a problem and was very stable in flight. There was only one real problem with it…
After a quick flight around the KSC I decided to try and land. And this I simply could not do. I could line up to the runway and with some trial and error (and many dead Kerbals, no ejector seat on this baby!) I could get it to touch down at a reasonable angle. But as soon as I applied the brakes or it slowed down to some critical speed, the nose would pitch downwards and slam itself into the ground. At the time I couldn’t figure out what was wrong but in hindsight I found that the front landing gear has to be placed on the capsule itself, not just behind it as I had done. I fiddled around with some other none-spaceworthy designs for a while to get a better feel for things….
Over time I learnt what worked and what made stuff crash or fail in other unspeakable ways. I learnt that:
The centre of lift needs to be behind the centre of mass.
There needs to be enough of it to lift the weight of the craft.
You need enough control surfaces to be able to force the nose to point up when in thick atmosphere (it tends to point towards the direction of travel which is straight ahead just after takeoff).
Basic jet engines have waaaaay more thrust than turbo jets at low altitudes.
You need enough thrust to gain speed but too much will make you flip.
The plane needs to be slightly back-heavy or the nose will tend to pull downwards.
But if it is too back heavy the plane will flip.
Flipping is both hilarious and frustrating.
No matter how many Kerbals die, more will always want their chance to get into space.
So, after all that messing around with basic flight, it was time to get into space!
Flight 11: Spaceplanes in space!
My first attempt at this used rocket fuel for the central fuselage and two jet fuel fuselages on the wings, equipped with turbo jets. Two more basic jet engines and a LV-T45 rocket engine on the back provide extra thrust at low altitudes and non-atmospheric propulsion respectively.
The plane was able to get to space but not establish orbit. One of the main problems was a lack of air from the intakes. Jet engines need atmospheric oxygen to run and all 4 of mine had their own air intakes for this purpose. However, once it got to around 17000m, the basic jet engines were almost useless (their thrust plummets at high altitudes) and the intakes weren’t pulling enough air in to run the ramjets efficiently. That meant I had to start the rocket engine earlier than I would have liked and it used up it’s fuel before it could get into orbit. So, modifications were made…
This time, more control surfaces were added and ram air intakes were added to the turbo jets. These are far more effective at grabbing air at high velocities and altitudes. It still retained the basic jets for thrust at low altitudes. However, the plane wasn’t able to gain any altitude.
No matter what I did with this plane the nose just refused to rise and I couldn’t get above 1000m. Luckily, I had by this time learnt how to land!
The problem this time was that the control surfaces at the front weren’t providing much lift so the centre of lift was too close to the rear of the plane.
So, more trial and error time!
After an hour or so of re-jiggering spaceplanes I finally came up with a design that worked:
The basic jets were scrapped, I found that the turbo jets produced enough thrust as long as there were enough lift surfaces. The turbo’s managed to stay on up to 26000m and kicked the plane up to a speed of 1100m/s. The aerospike engine then fired and carried the plane into orbit.
Jeb was so excited and confident about this one that he even did an EVA selfie once orbit was achieved.
Once orbit was achieved, another burn took the spaceplane straight to the KSS for a docking maneuver.
After swapping some science and admiring the RIS docked to the other end, Jeb undocks and begins his return journey, aiming for the KSC.
A quick burn of the jets brought the plane on a course for the KSC. A few kilometres away the engines were cut and the plane glided towards the runway for a smooth nightime landing.
A very proud moment for me! Not only had I created an SSTO plane, I had also learned to fly it, docked with a spacestation and returned for a textbook landing on the runway. Happy days!
Flight 10 – Dres
Jeb, of course, volunteered and his lander was prepared for him.
The lander is launched into orbit and the RIS is undocked from the KSS. The two meet above Kerbin.
So Jeb got himself to Dres. With just one minor problem. Although the lander still had a full tank of fuel, the RIS was running very low! The orange tank was completely empty and even the four side tanks over the nukes were slightly depleted. I had to hope that the lander would have some fuel left over after the landing and that the lighter payload for the return journey wouldn’t guzzle so much fuel.
Jeb was confident enough to go ahead and land on Dres in any case, how bad could being stranded in interplanetary space be anyway? So he detached from the RIS and burned retrograde to land. Dres is a small world with a gravity similar to the Mun. In that sense, landing here was easier than landing on Duna although there was no atmosphere to slow descent.
Not at all distracted by the way the world below him was giving his skin a grayish tinge, Jeb expertly piloted the lander to the surface without incident.
Jeb found he could jump just as high here as he could on the Mun but without the glorious view of Kerbin to keep him company. He had a look around for the famous Dres Canyon that had been spotted by astronomers from Kerbin but it didn’t seem to be anywhere nearby.
All in all Dres seems… pretty dull. After doing some science and posing for a selfie…
Jeb does some science things with Goo and samples but swiftly runs out of things to do. He blasts off from Dres, happy to have expanded the borders of Kerbally exploration but a bit jaded that the surface wasnt covered in awesome gray…somethings. What’s awesome and gray? Chicken walkers from star wars perhaps? On reflection Jeb decides that most things that are awesome aren’t gray and decides that the next place he visits should be a different colour.
The lander still had about 150 units of fuel left inside. Jeb transferred this to the RIS and ejected the empty lander cans. It’s still looking extremely tight for fuel however, getting back to Kerbin is going to take quite a lot of detla-V and at this point I wasn’t sure if the craft would make it.
And sure enough, after escaping Dres’ orbit, burning to an encounter with Kerbin and arriving in Kerbin’s sphere of influence, the RIS ran out of fuel… at this point…
No chance of even so much as an aerobrake, the craft was going to head straight back out into Kerbol orbit. I only really had a couple of options at that point, either give up and terminate the mission, starting all over again, or attempting a rescue. I really don’t like the idea of ‘terminating’ Jeb after all he’s done for the KSP so I decided to try and rescue him. All he really needed was some fuel, so I simply launched a fuel tank into orbit.
The fuel tank docked with the RIS and gave it enough delta V for a proper Kerbin encounter. I put both on a suicide burn for Kerbin, undocked the lander then used the RIS’s engines to push it’s periapsis higher, going for an aerobrake rather than a suicide burn.
So the rescue worked! This wasn’t a particularly smooth mission however, I have learned a few things from it.
My main change for future is realising that the current RIS does not have enough fuel for taking landers beyond Duna/Eve. Luckily, it’s design included a nice big docking port Sr. to attach extra fuel tanks in just such a situation (which is how the refueling tank was able to dock). So I sent another gray fuel tank to increase the range of the RIS.
At least this mission did show that the RIS concept could work, even if it didn’t go quite as planned!
Flight 9 – Icarus
How close can you get to the sun before you burn up?
I have absolutely no idea, but I did find out how close you can get to Kerbol.
A small rocket was all that was needed to take the small payload into orbit. I included a second stage of small oscar B fuel tanks with a little rockomax 48-7S engine. I originally wanted to make the entire rocket out of ‘tiny’ sized parts. This proved a bit awkward, as the oscar B’s have a lot of weight in them that isn’t fuel, so they weigh the craft down even when emptied. I was however impressed with the 48-7S which put out quite a lot of power when the rocket is so little! Anyway, the tiny parts were enough to get the probe out of Kerbin’s SoI and begin the de-orbit around Kerbol (once the ‘small’ sized parts lifted the rocket into Kerbin orbit). I do want to do something more in the future with tiny parts, maybe an SSTO rocket or a Mun landing but that’s for another time.
Annnnnyway back to the Icarus mission. The idea is to see what it it’s like to get damn close to Kerbol and see how far it’s atmosphere extends and at what point a ship will blow up (I’ve read that they DO blow up, you can’t land but I don’t know at what point that happens). No Kerbals were to be risked for this mission so all I really needed was a way to get any probe body close enough. I decided to use the most efficient engine in the game – the PB-ION electric propulsion system. This engine uses xenon as fuel and can make use of tiny amounts to push along the ship. The problem is that it produces barely any thrust. Since I only need to shove a tiny probe body around, that shouldn’t be a problem. I stuck on plenty of solar panels (six of the smaller panels ended up weighing quite a bit less than the two gigantor arrays I would need for balance) and a little battery and it was good to go. The whole thing weighed 1.47 tons, 1.05 of which was solar panels!
* After I did this mission someone pointed out that I could have gotten with just using one gigantor array if I put it on the very top of the probe, that would way much less and would get around the need to balance it. Doh!
The little blue glow from the silent ion engine told me it was on and the orbit speed around kerbol started to slowly go down. Even with such an insanely light payload, this wasn’t going to be a fast mission. The burn for my first taget (500million metres) was going to take 17 minutes. Nothing much exciting was going to happen in that time so I got some housework done, made some tea and waited for my little burn to be done.
For reference, Kerbin has an apoapsis of 13 billion metres and an orbital speed around Kerbol of around 9200m/s.
So what does the sun look like from 500 million metres away?
Fine so far, but it still doesn’t really feel like I’m close to the sun. Time for another burn then! This time to bring me to within 100 million metres of Kerbol.
Getting pretty close! Certainly looks a bit more impressive than 500Mmetres. But we can do better! MOAR xenon burn!
Gah! Now the sun takes up nearly the entire screen! Lets get another point of view…
Still no burning up though, the paint the Kerbals put on those solar panels must be pretty epic. This close to Kerbol, the speed at periapsis was a whopping 80000m/s!
But enough of these fly-by’s. I set out to see how close I could get before blowing up and there’s only one real way to do that.
The Icarus was never meant to be recovered and it got it’s name for a reason. Down it goes!
Thankfully, the corona-like glare disappears around this point, otherwise I think it might burn out my computer screen! I assume the cameras on my little probe have adaptive filters or somesuch.
Shortly before this picture was taken I lost the ability to timewarp (except for forcing physical warp). However, I figured this wasnt a problem as I was goint the insane speed of 84000m/s! Soon my main problem was to be missing screenshot milestones! I assumed this might mean I was inside the ‘atmosphere’ of Kerbol. However, usually that would slow the craft down, at the very least decreasing my apoapsis. However, the ship wasn’t slowing and a check of the apoapsis actually showed it to be slowly increasing which was weird…. does that happen on other orbital bodies near periapsis? If so I’ve never noticed it.
It’s hard to get a sense of scale in still pictures but that’s not the only problem. Things didn’t actually look very different in the last few hundred thousand miles ingame.
Having said that…. you can now see what look like indentations in the surface. I assume these are sunspots and I didn’t really expect to find details like that on Kerbol so I’m suitably impressed!
Now remember, although this would still be quite high on a planet, I’m still going well over 85000m/s here so I was getting pretty trigger happy with the F2 key (for screenshots).
But even so I almost missed it! Poof! At exactly 1379m the probe just disintegrates without warning. Well…. unless you count the rapidly decreasing altimeter and the fact that it was pointed straight at a star as warning. Also the fact that it was called icarus which was never going to end well for the poor probe.
Note that that does NOT look like I’m actually 1300m or so from the surface. The graphic for Kerbol seems to stop quite some way below what the altimeter counts as the surface, which would explain some of the lack of perspective changes below a million metres.
So there you have it! How close can you get to Kerbol?
Somehow I doubt NASA has enough aerogel to get that close to our star.
KSP 1 Reality 0
After their first trip to another world, penny pinchers at the KSC wanted a cheaper way of performing future missions. They came up with the idea of a re-useable interplanetary ship, the RIS. They would use a ship that could attach to a lander in low orbit, take it to another planet, let it do it’s stuff then take it back to Kerbin. The lander could then return to the ground while the RIS would be refueled ready for another mission.
To refuel something however, you need fuel. Therefore….
The Kerbal Space Station in it’s first iteration is purely going to be a fuel depot for the RIS. There will be 5 components in total, a central hub and 4 fuel tanks.
The Hub has 6 spokes to attach other modules (I’m only adding four at this point though) and two docking ports on either end for the RIS to dock. Ive put parachutes on the boosters and the middle stage of the launcher in the spirit of re-useability.
I decided to personally take the mid-stage booster back down to Kerbin (it has a probe core on it for that purpose)
The fuel tanks are launched and shoved into position in a very similar way to the Hub.
Although this time the mid-stage had landing legs!
Piece by piece, the KSS was assembled in orbit.
But finally the station is complete! Its not the most pretty or complex station out there, but its mine! Plus it can always be added to later.
So now to make use of it…
As shown above, the RIS is very similar to the ship that took Jeb to Duna last week. The docking port on the top can be used to attach a lander and four nuclear engines can propel it to other worlds.
On the other side is another, large docking port. My thinking it that if a particular mission needs more fuel than the current RIS, I can stick another tank on here. Or even a larger lander if required.
The RIS is a bit wide so I decide to see if I can fit it into one of the central docking ports of the KSS…
The RIS and KSS are now ready to help Kerbals get further afield and re-use a good chunk of the hardware needed to do it.