Clockwork Gremlin plays Kerbal Space Program Part 4: The Last Horizon

Kerbal Space Program 0.23 is set for release TOMORROW(Tuesday, December 17), and it’s going to completely overhaul a few things, like how SCIENCE! works.  This will be the last update for my 0.22 LP.  Maybe the next one will go better.

Anyway, when we last left our heroes, they had accumulated this much SCIENCE!

Filling out the tech tree rather nicely.

Filling out the tech tree rather nicely.

There are a couple of things that I just unlocked, which are REALLY COOL!

First, there’s external fuel ducts.

As the rocket burns, a tank which is above another will naturally feed fuel to it, to simplify…several things, actually.  The net result of this is that two smaller tanks stacked on top of each other are functionally the same as one tank which is twice the height.  At least, as far as fuel transfer.  They’re more fragile and, because of how KSP calculates drag, they have more drag, but that’s actually fairly negligible unless you end up stacking a lot of parts on top of each other.

What this doesn’t allow you to do is transfer fuel between two adjacent tanks.  If you want to do that without the ducts, you have to do it manually.

Aside from the inherent balance issues caused by the transfer delay, there’s a neat trick that you just can’t do manually: Asparagus-style booster staging.

Named because you attach boosters like the leaves on the head of an asparagus plant, Asparagus staging works by evening out your thrust/weight curve.  You have the most thrust early on, when you need it to get through the thick atmospheric soup, and as you go higher, you shed boosters as the atmosphere falls off.

So is all of this really that efficient?  I tried to ballpark the math in my head, and didn’t really get a whole lot of anywhere.  Besides which, the math can lie to you really easily, or you can mess something up without realizing it.  Instead, you want to test it.

Default fuel flow and thrust curve

Default fuel flow and thrust curve

That’s a rocket with no staging whatosever, Asparagus or otherwise.  It can shed the engines once all the fuel runs out to reduce its aerodynamic profile, but by the time the fuel’s all gone, the air is so thin there’s not much benefit to that.

Though 7 boosters does get you going pretty fast, as indicated by the Vapor Cone.  Unfortunately, our accelleration curve is rather flat, and even if I modulated the thrust to save fuel at higher altitudes, we’re still hauling around 6 engines that we really only need for that first kick.  The result is fairly unimpressive.

Orbits that pass this close to a planet in KSP are automatically captured and removed from the simulation.

Orbits that pass this close to a planet in KSP are automatically captured and removed from the simulation.

Well that was pathetic.  I can actually do almost that well if I throw away the outer ring of engines before I even launch.  Hey, here’s an idea! Why don’t we apply some fuel ducts, siphon the fuel from the ring of engines around the outside, so we can shed them once they empty out, and the main engine will still have plenty!

Same engines, same amount of fuel.  You can see in the sidebar that the middle tank is emptying more slowly than the external ones.  It is actually, in fact, still full.

Same engines, same amount of fuel. You can see in the sidebar that the middle tank is emptying more slowly than the external ones. It is actually, in fact, still full.

Outer ring of fuel tanks runs dry, the 6 outer engines sputter and die.  They’re no use to us anymore, so we shed them.

 

You can actually get pretty far if you launch with just one of these.  Imagine how far you can get with a 14km and 500m/s head start.

You can actually get pretty far if you launch with just one of these. Imagine how far you can get with a 10km and 600m/s head start.

If that looks like an improvement, it’s because it is.

Hey look at that!  Just by messing around with gas flow, we were able to send the exact same rocket 30x as high!

Hey look at that! Just by messing around with gas flow, we were able to send the exact same rocket 30x as high!

Building an Asparagus-staged craft is a bit more complex than building a normal ring-stage one.  You have to either pluck the individual decouplers out of a mass collection, or you have to add the pods in the right order in the first place.  Then you have to make sure you’ve got all of your stages in order, so that when you jetisson a pair of pods, your center of gravity doesn’t end up all wonked-out, and you don’t accidentally chuck something that still had fuel in it.

Same rocket, modified fuel flow AND staging.

Same rocket, modified fuel flow AND staging.

Two things should stand out immediately in that picture.  The first is that you can actually see the fuel consumption curve!  For the first leg of the journey, only two tanks are feeding SEVEN engines!  Naturally, this causes them to drain seven times as fast as they would normally, but it turns out that’s enough to get through the thickest parts of the atmosphere.

Doesn't look like much of a head-start, does it?  It's worth more than you think.

Doesn’t look like much of a head-start, does it? It’s worth more than you think.

Now the two empty tanks have been dumped, alongside the incredibly heavy rocket engines that they’re no longer providing any fuel for, and the next two are being spent to feed only 5 engines.  We’ve effectively started our journey 2km up, already traveling over 250 meters per second.

Why yes, I did just trigger re-entry effects while leaving the atmosphere.  The last rocket actually did this too, but it was out of fuel by the time it happened.

Why yes, I did just trigger re-entry effects while leaving the atmosphere. The last rocket actually did this too, but it was out of fuel by the time it happened.

Did you know that 5 rocket engines put out an AWFUL lot of thrust?  Even the smaller ones we’re using here.  You may also have noticed that we’re 5 km higher than when the last rocket dumped its outer ring, and there’s STILL fuel in those tanks.

We are twice as high and going twice as fast as we were at this point with the previous rocket.

We are twice as high and going twice as fast as we were at this point with the previous rocket.

This high up, going this fast, you could practically nudge yourself into orbit using the aftermath of a chili-eating competition.  I could have cut the engine here and I’d still have left atmosphere.

But I didn’t.

I hope you weren't planning on being back by dinner.

I hope you weren’t planning on being back by dinner.

Going… going… OUT OF HERE!  That’s one rocket that will never see planet Kerbin again.  The orbit actually goes from just inside Kerbin to slightly outside Duna.

Asparagus staging.  SUPER EFFECTIVE!

Mission Eight

After the flyby last time, Vincent just would NOT shut up about the Mun.  I finally told him “Hey, you know what?  If you want to keep an eye on the Mun so badly, why don’t you just GO THERE YOURSELF!”

This is Vincent's Price.

This is Vincent’s Price.

Perhaps I shouldn’t have said anything.

Remember that thing about stacking parts on top of each other?  Yeah, it turns out that I didn’t have enough SCIENCE! to unlock the Rockomax Jumbo-64 orange tanks, so I had to make-do by bolting together 4 X200-16 tanks each.  Also, I only had the least powerful 2.5-meter engine available, and THAT wasn’t going to get me off the ground, so I had to use trios of 1-meter engines instead.  Vincent’s Price barely got off the ground.  In fact before I added the launch supports, it DIDN’T get off the ground.  The engines got crushed under the weight of the rocket!

But it did get off the ground.

We're going to the Mun, we're going to the Mun.

We’re going to the Mun, we’re going to the Mun.

See that, children?  The engine on the back of that craft is the anemic Rockomax “Poodle” liquid engine, the least-powerful 2.5-meter engine IN THE GAME.  It’s barely more powerful than any 1 of the 21 engines I put on the first stage.  So why did I use it?

Because it’s also the most EFFICIENT 2.5-meter engine, and about 5% more fuel-efficient in a vacuum than any of the 21 engines I put on the first stage.  Once you’ve gotten into a stable orbit, how hard your fuel can push you doesn’t matter NEARLY as much as how far it can take you, and this baby, coupled with the two x200-16 tanks on top of it, could have taken me to the Mun and back again.

It didn’t, but it could have.

Going from low-Kerbin orbit to an encounter with the Mun took barely more than half of my remaining fuel.

Going from low-Kerbin orbit to an encounter with the Mun took barely more than half of my remaining fuel.

It also took about 3x as long to make orbital changes as anything I did in the 7th mission.  But that’s a Mun encounter.

This shot doesn't show it, but I actually had a very pretty double-orbit spiral going around the Mun.

This shot doesn’t show it, but I actually had a very pretty double-orbit spiral going around the Mun.

That’s a pretty solid Mun encounter, actually.

Love them orbital splines!

Love them orbital splines!

Now if you wanted to re-create what the Apollo missions did, you would have the lander docked with a return vehicle, which would enter orbit around the Mun.  I don’t have docking rings or multi-Kerbal command pods, and Jeb and Bill said they didn’t want to be stuck in a tin can with Vincent for 3 days anyway.

Orbital capture complete

Orbital capture complete

So instead, I noticed that the stable capture orbit gave me a PERFECT spot to make a bid for the daylight side of the Mun, AND there was a nice, wide area clear of craters right under the… excuse me.

Nudge for a cleaner landing zone

Nudge for a cleaner landing zone

…RIGHT under the orbit!

Yes, we’re still running on the Poodle.

Begin final de-orbital burn

Begin final de-orbital burn

Why yes, it did take me less than 2/3 of my fuel to get here.

Unfortunately, the Poodle doesn’t put out nearly enough thrust for me to comfortably land with it.  Also, it’s around 10 meters taller than the landing legs, and there’s no way it’ll survive the impact with the ground, so as loathe as I am to watch 1/3 of a usable tank of fuel go spiralling off into space,

Where we're going, we won't need... well, we will need both engines and fuel, but not THAT engine.

Where we’re going, we won’t need… well, we will need both engines and fuel, but not THAT engine.

This is where I learned that bringing some sort of ballast to toss just before your descent burn is a REALLY good idea.  As long as it stays around, you get a little tick-mark telling you how far away it is, so when I started slowing down, I watched the tank fall.  When it was 3km away, and I was at altitude 7km, it suddenly disappeared.  Because it had crashed into the surface of the Mun.

Estimating my target altitude was always my least favorite part of powered landings, but now I know.  I need to be below the 10m/s mark by the time I reach 4km, or my pretty space ship is going to go *Splat!*

Powered descent is very nerve-wracking.  It consists of lots of waiting for your altimeter to go down, followed by slamming the thrusters to full in a panic because you're going way too fast.

Powered descent is very nerve-wracking. It consists of lots of waiting for your altimeter to go down, followed by slamming the thrusters to full in a panic because you’re going way too fast.

I can do that.

Status check.  Are all my limbs still attached?

Status check. Are all my limbs still attached?

I can do that like a BOSS!

Well, since I haven’t actually landed anything on Kerbin yet, I should do some SCIENCE!

The best part about a return vehicle is that I don't care how inefficient the transmission is.

The best part about a return vehicle is that I don’t care how inefficient the transmission is.

Vincent decides to step out, so he can keep a SUPER close eye on the Mun.  He grabs some and puts it in his pockets, and then plants a flag.

SO much SCIENCE!

SO much SCIENCE!

Vincent’s curiosity satiated, it’s time to head home.

Up up and away-web!

Up up and away-web!

Did I mention that the Mun has 1/6 Kerbin gravity?  Also, no atmosphere.  You can “orbit” at any altitude that keeps you clear of any mountains in your path.

I'M WATCHING YOU, KERBIN!

I’M WATCHING YOU, KERBIN!

Or you can launch and then burn straight at wherever you want to go.  This is probably the most wasteful way to perform an escape burn, but we’ve got plenty of fuel and very little holding us down.

Downsides to gung-ho rocketry

Downsides to gung-ho rocketry

Granted, this does put us in a rather psychotic orbit around Kerbin.  Fortunately, I’ve got 5 engines and 3 tanks worth of fuel.

Choosing a return that will drop us on Kerbin's daylight side.

Choosing a return that will drop us on Kerbin’s daylight side.

Remember what I told you about altitude?

This will drop us nicely onto the surface.

Visions of a friendly planet.

Visions of a friendly planet.

Now that everything’s in atmospheric capture, I’ll drop the lander to cut down on weight

Don't need THIS anymore, either!

Don’t need THIS anymore, either!

By a rather happy coincidence, my re-entry looked like it might drop me right on top of the Kerbal Space Center.

Then air resistance took hold.  I did manage to get the same continent, though.

When re-entering the atmosphere, you can never have too many parachutes.

When re-entering the atmosphere, you can never have too many parachutes.

On a whim, I decided to see if the SAS was capable of fighting gravity and keeping the pod upright.

Yup.

Yup.

Landing.

Landed safely.  Wait, is that what that's called!?  THIS IS UNFAMILIAR TERRITORY!

Landed safely. Wait, is that what that’s called!? THIS IS UNFAMILIAR TERRITORY!

Resulting in SO much science!

There are advantages to bringing the research back with us instead of transmitting it.

There are advantages to bringing the research back with us instead of transmitting it.

And that’s it!  Kerbal Space Program 0.23 comes out tomorrow, and I’ll be starting a brand new game(maybe even documenting my first experiences).  I sent a Kerbal to the Mun, planted a flag, and brought him back safely.

I also got some nifty wallpapers.

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