In Progress Let's go to the Moon and do the other things (Kerbal Space)

[Burning Bridges]

10,178 m/s? That's a lot, think you could get to Moho with it without a gravity slingshot of Eve? I was honestly shocked when I saw how much delta-v my Moho probe needed to change inclination, not to mention the final transfer burn. And I did save like 1k or 2k delta-v by doing a tight slingshot around eve.

Anyway, to my surprise, it turned out that my Duna Rover now burns through RCS a lot faster than it did. It seems it benefited from the old buggy RCS usage a lot but 0.18.2. kind of changed that. However it turned out that the lander pod can easily turn left and right using E/Q with no RCS. So now I'm making an improved version with 4 ion engines.

After more testing, I think there is a LOT more potential for the NERVA. I think I could get close to 15,000 m/s with a NERVA quite soon.

My last test reached 12,730 m/s on a vertical takeoff / acceleration test. An improvement of 2,500 m/s over the previous design.

Total burn time was 31 minutes, how does that sound compared to Ion drives?

Optimizing deltaV in Excel absolutely pays off now - I can see the influence of a few kilograms, and I also learned that a lot of stuff goes against intuition.

For this test I optimized weight and staging (asspergers staging for the interplanetary burn). I increased fuel somewhat to take full advantage of the saved weight (total mass at takeoff is now ~158 tons). I also used a weight reduced probe (absolute minimum is stable energy supply, a basic propulsion system and all 4 scientific instruments). The biggest weight reduction was achieved by stripping the probe completely of RCS, that stuff really adds too much weight. This scientific interplanetary probe weighs ca 0.48t, and could be turned into a simple lander with only a little extra weight. It can achieve ca 12-13 km/s after a vertical takeoff, and a lot more with a proper gravity turn.

An attempt at 15,000 m/s is planned. So far the result is quite satisfactory.

 

[Hellraiser]

31 minutes of burn to reach total delta-v is quite good actually, single ion engine probes can "burn" all the xenon in 2 hours I believe? Well the NERVA is by far the most practical engine for interplanetary shenanigans currently. It's only weaknesses are somewhat meh thrust and high mass of the engine. You can get more raw delta-v out of an ion engine probe, but who is willing to have the thing accelerate for 8 hours straight to reach top speed?

Anyway, about that slingshot:

Basically you aim for the most fuel efficient rendezvous, with the periapsis as close to eve as you can. If it's right you get something like that, a trajectory that bends backwards sending you deeper into the inner system for free. The new Kerbol Periapsis should be about half-way between Eve and Moho. Either way it's free delta-v and quite a substantial bit.

When they add more outer planets doing Jool slingshots will probably be a good idea. The damn thing has such a large SoI that regardless where you want to go it will probably be conveniently somewhere along the way.

BTW an image somebody found on the KSP forums, a soviet NERVA prototype:

That thing looks so eldritch that I bet the engineers working on it went insane from looking at it too much.

 

[Burning Bridges]

Thanks a lot, the image tells more than 100 words!!

I think I know how to build a 15,000 m/s ship. It would basically be a NERVA, plus an additional push with the LVT-1 engine, with an absolutely weight balanced probe.

Surprisingly, a LVT-1 is good for a deltaV of up to 5000m/s if used right! The problem is that the total burn time would be 30-60 minutes, I think that's getting too too long now. Instead, I should rather try to optimize speed vs burn time and weight now.

It's also interesting that an LVT-1 can no longer benefit from asspergers staging. That's simply because the saved weight is already less than the weight of the fuel line and separator! If these parts were weightless, deltaV would double up to 10,000 m/s for a LVT-1 alone. That means, in addition to what can be achieved with the NERVA already! Such a ship could reach 20,000 m/s. But as I said I think it's not possible because of the minimal weight of the parts (1 fuel line + separator).

 

[Burning Bridges]

Looks gorgeous. I'm totally in love with soviet hardware, and would die to have them in the default parts.

Just look at this beauty.

 

[Hellraiser]

Yeah, all those spacecraft they built looked quite unique. They've got that retro-vibe that NASA's gear lacked, Sputnik? Vostok? Lunokhod? They looked out right alien in a way.

 

[Burning Bridges]

Konald Reagan declares that the "Manhattan" project to study nuclear propulsion has reached it's goals. The Jool-2 launch vehicle has completed its first successful test, and could become the future backbone of Kamerican interplanetary travel.

Jool-2F

weight: 183.5 tons.

first stage: LVT30 (8 + 4), 90t fuel, deltaV 2082 m/s
second stage LVT30 (4), 58.5t fuel, deltaV 3895 m/s
third stage NERVA (1), 10.125 t fuel in 3 asperger stages, deltaV 12988 m/s
lander engine LVT-1 (1), 0.4t fuel, deltaV 2262/s
scientific probe ca 0.5 tons

calculated deltaV total: 18.900 m/s

deltaV reached 13.500 m/s (vertical takeoff)
burn time: ca 39 minutes

JOOL-2F.craft

The first assembled unit of the multi million $$ rocket

12 chambers in the first stage, for a total thrust of 2580, looks like it can deliver some push.

Liftoff.

Separation of the booster rockets. Fortunately they don't hit the rocket, engines or something.

The second stage burns out at close 2600 m/s. That means this stage can reach Kerbin orbit and a bit more.

From here on it's going to be one long, boring burn through the fuel in the interplanetary stages.

The nuclear engine fires at ca 5:55

19:22, the first assperger stage is out of fuel

the stage is separated

it has propelled the rocket by another 3550 m/s, to 6146m/s

24:38, the second assperger stage is out of fuel at 9096m/s

separation is tricky, because

the spaceship must be carefully maneuvred around the stage

27:59, the NERVA has used up the last container of fuel, speed is now 11,323m/s

For the rest of the acceleration the tiny LVT-1 engine is used. Altough in practical situation this stage is supposed to be used to land, this serves just as a test to show the capabilites of the rocket.

Owing to the extreme lightness of the stage, the tiny engine reaches a maximum acceleration of 0.54g, and propels the probe to

13,506 m/s, after 0:39 minutes

 

[Burning Bridges]

Meanwhile, the Koviets may or may not be testing their nuclear rocket.

They seem to have had some problems, perhaps they wanted too much, again.

The design looks to be in the same class as the Jool - 2, 160 - 170 tons

Secret photo of their nuclear assperger unit.

 

[Hellraiser]

Wouldn't side facing seperatrons be good to seperate the assperger stages? Unless you don't like the idea of having that much more mass.

 

[Burning Bridges]

Well of course. The thing is just that I like to have the stages in different sizes, that is getting smaller towards the end (as you can see in the screen first was 3 tanks, second 1 tank and last 1/2 tank) and that would mess up balance.

I think these asymetric sizes are better because dry weight becomes more important at the end of the acceleration, with a tiny package at the end.

Also you need less separators and fuel lines that way, and save some weight.

But it would probably not be much difference.

P.S. I also adopted the idea of top mounted assberger stages (first saw the idea first in Hellraisers thread), because they seem to fly better.

 

[Ulminati]

P.S. I also adopted the idea of top mounted assberger stages (first saw the idea first in Hellraisers thread)

As with our cars, it is in the nature of a Polant to steal credit for our revolutionary ideas.

 

[Hellraiser]

Well you did post it in my topic

 

[Hellraiser]

Anyway I've been screwing around with this lately:

A shuttlecraft that travels up and down Kerbin's gravity well (or rather SoI) between space stations, ferries 3 cosmonauts around and has two mini-landers to bring kerbals down to the Minmus surface base. Also comes with 2 free small docking ports for 2 more landers. The landers have 2 small rockomax 24/77 radial engines, a small RCS tank and small docking ports on the top and bottom. You can use those to dock with small ports if you can't use the main ones.

A trip down to LKO with a munar gravity slingshot uses up 75% of its fuel (unless you plan the slingshot wrongly and the Mun hurls you onto an escape trajectory). I need to test if it can get back to Minmus from LKO, it was originally launched from a higher orbit. Also I need to add flags and a probe pod (landers have those though). But I also need sleep.

Pity you can't turn off individual SAS as they tend to wobble the thing, hopefully the devs know of that and will make a fix as it can get docked craft damaged in some cases. Also it has some problems with RCS balance, probably because the landers have thrusters.

 

[Burning Bridges]

Well you did post it in my topic

Well, actually he didn't

http://www.rpgcodex.net/forums/inde...bal-space-programme.78797/page-3#post-2410084

Like all world-changing ideas, a mystery surrounds the aspergers stack.

Many believe that it was indeed invented by the Denish genius. Personally I believe that it is a long forgotten idea, which was already tried by the Kermans a long, long time ago. It may just not have worked at the time because of differences in the fuel logic A lot of astounding imagery may come up one day when the agencies open up their archive.

I think the credit belongs to the the Denish for rediscovering the idea and introducing its potential to the scientific community. This instantly lead to advances in rocketry, for example to my nuclear ships being faster by ca 1-2 km/s.

 

[Burning Bridges]

Before someone else claims it, I want to speak of an important discovery in the field of miniaturization, which belongs to us and the Manhattan project.

It is revolutionary but we hereby make it public, because it is expected the Koviets will find out by espionage anyway.

The Micro - Propulsion Principle

The discovery belongs to Künther Wendt who often played with a model of the spacecraft while he was waiting for something to do.

The principle only applies to very small and light payloads, like the scientific probe on this photo.



This probe consists only of a core, some necessary parts like energy supply, and scientific sensors.

The weight (without propulsion) is only 145 kilogram.

Another 1.2 tons are the propulsion system, consisting of a LVT-1 and one half-size fuel container. With a total weight of ~1,300 kilogram the craft develops a deltaV of 4.171 m/s with only 1.125 tons of fuel. Thats 3708 m/s per ton. Burn time is ca 20-30 minutes. Theoretical maximum of micro propulsion is ca 5000 to 6000 m/s, but with long burn times of 60-120 minutes.

Smaller fuel tanks may be preferrable because they combine excelllent deltaV to fuel ratio with a short burn time.

The optimum deltaV to fuel ratio is an oscarB tank which would provide deltaV 822 m/s with just 79 kg of fuel, or 10451m/s per ton, in just a few minutes! An LVT-1 plus oscarB micro proulsion should become part of any probe, because it adds 800m/s deltaV for only 100 kg of extra weight. Such a small weight is negligible.

As was said the result depends very much on the probe's weight. If you use it with probes already weighing several tons, you will be dissapointed by the results. Very exact computations are required to make use of the potential of micro propulsion and at this day this is only possible in the Unites States of Kamerica.

The LVT-1 micro proculsion has several advantages over Ion driven probes, mainly that it is very easy to operate, has a much better thrust of 1.5, a reasonable burn time and weighs only 30 kilograms. Under the right conditions this can offset the disadvantages like the comparatively low Isp.

And you thought the LVT-1 was crap right?

 

[Hellraiser]

But it's an engine for ants!

 

[Burning Bridges]

We believe the Koviets are working on nuclear rocket that is supposed to exceed everything the Kamericans can build. In fact very little is known. The RD-400 could weighs almost 400 tons and with advanced NUCLEAR Asperger stacking, it could become the most powerful rocket in the world.

Gigantic structural problems must be solved before a maiden flight. Apparently the Koviets have secretly tested some of the components and a second stage reached 3.500 m/s. If everything works for them a 15.000 m/s spaceship should be within their capabilities.

 

[Burning Bridges]

Koviet spaceship operating on the limits of Nuclear propulsion

The Koviets are keeping things secret about the RD-400. But we have ample evidence that it has completed its maiden flight, with the intent of breaking the 15,000 m/s vertical challenge.

Unbelievably the launch not only broke the 15 km/s barrier, but actually surpassed it. The gigantic 400t rocket launched a probe on a vertical trajectory, reaching 16271.6 m/s after 62 minutes. (then, only 8 days later the scientifically worthless mission crashed into the sun).

With RD - 400 the Koviets currently have the fastest propulsion system for interplanetary travel, and also one of the biggest, and most expensive ones. It is astounding how far they have pushed the limits of nuclear propulsion. Unless we get convincing evidence from Polant or Kenmark, we assume that this even superior to Ion drives.

A scientist from East Kermany has calculated that with a extended range NERVA the RD-400 could theoretically reach a speed 18.000 m/s. But since the 1h burn was already unbearably long, it is unlikely anyone ever attempts this again. Instead the Koviets would fare better if they add scientific equipment and payload to the rocket, and simplify the ridiculously complex and impractical asperger staging.

RD-400-02.craft

Assembled RD-400 before liftiff.

Firing its 20 engines, the rocket takes into the sky.

The takeoff of the large 400 ton spaceship is an impressive sight.

The RD 400 has reached 24 km without malfunction.

At 49km and 1010 m/s, the first stage reaches its limit.

Away go the four boosters, with it hundreds of millions of rubles.

The second stage has amazing potential.

It reaches 3672 m/s at a height of 582 kilometers, while carrying 14t additional payload.

From here the nuclear engine takes over, and a 20 minute long burn begins, until 10.125t fuel is used up.

Here we see the point when the second asperger tank is used up.

The spaceship has already reached 10133 m/s.

As with the Kamerican counterpart, asperger separation is tricky, because the spaceship must be maneuvred around.

And still, the NERVA can accelerate some more with its final tank.

30:38 into the mission, the NERVA is separated. It propelled the spacecraft to 11971 m/s.

From here on the Koviets are using micro propulsion drive with 1,125 tons of fuel. It resembles almost 100% the Kamericans research.

34 min into the mission. The ship has already passed the orbit of the Mun.

1:02 After ca 30 minutes of continuous burn, the probe has reached end of its acceleration.

It easily breaks the 15km/s challenge, leaving Kerbins SOI with a velocity 16,271.6 m/s.

After just one hour flight, it has almost reached the orbit of Minmus.

 

[Burning Bridges]

Yes, I confirm that we can fly rocket at 16km/s . Rest is secret from KGB.

 

[Hellraiser]

Wouldn't the decouplers which split the rocket into half be better for assperger staging? You would have less dry-mass if you used the blue ones.

 

[Burning Bridges]

Possibly. I actually never understood what's different with the blue separators.

But to tell the truth, I think for practical use I will either give up apserger staging completely, or follow your earlier advice to arrange the tanks behind the payload. It's no fun to babysit your tanks, and the separation of the top ones is problematic.

In practice the differences between the possible setups should not be that big. But the fact remains that Asperger staging can extend the speed of a nuclear ship by 1 to 2 km/s, which is not bad.

 

[Ulminati]

Possibly. I actually never understood what's different with the blue separators.

As far as I can tell, the blue seperators push both halves apart from each other during seperation, whereas the yellow part just decouples them.

 

[Burning Bridges]

Ah, so this means the separator does not stick to one part?

This would in fact be interesting because I just recently noticed that separators stick when they are higher than the capsule (as with the asperger stacks). One can tell from the direction of the arrow where the separator will stick.

That would mean:

normal stack under capsule = normal separators
asperger stack over capsule = blue separators

Good tip. That way some kilograms could saved here and there, normally they don't matter but during the last stage (micro propulsion) they do.

 

[Hellraiser]

Yeah, I figured that out only recently as well. The blue ones don't stick although they push both parts away so you lose some delta-v, but probably not a whole lot compared to the mass savings.

 

[Burning Bridges]

I'm still waiting for your figures. How are you doing with Ion drives, compared to 16 km/s in 1 hour? As I said I think I could push a single NERVA to about 18 km/s, perhaps 20. But it becomes retarded because the burns get several hours long.

The solution would of course be to double up all engines but that would also mean larger carrier rockets etc (having two or three NERVAs instead of one does not mean more deltaV, only more acceleration).

I don't think there is a limit in the physics, but at some point the launchpad becomes too small, or the structural stress gets too large.

 

[Burning Bridges]

Yeah, I figured that out only recently as well. The blue ones don't stick although they push both parts away so you lose some delta-v, but probably not a whole lot compared to the mass savings.

Well that's certainly negligible and if it wasn't you could simply turn the ship around before separation. Of course once you are out of Kerbins athmosphere, there you have time for such maneuvres.