Arugela

Spaceplane off EVE!!??

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Posted (edited)

Something crazy just dawned on me... I can get a space plane off Kerbal with only 1900 DV easy. So, space planes by nature reduce delta v requirements for vehicles on planets with atmospheres. Has everyone been trying to do eve wrong this whole time. It's one characteristic is it has the thickest atmosphere in the game(for a landable planet). Is this a big sign saying use a space plane on me instead of a rocket. If you designed a space plane correctly could you reduce delta V enough to actually start getting loads off EVE and explore it like other planets. It would almost make sense. Space planes are more advanced. Why would you not make the hardest planet for the hardest vehicle to design?!!! It, so, coincidentally has the best atmosphere to do it!

1900/3200=0.59375*6000=3562.5DV

How is that not doable with sufficient thrust, even on a potential SSTO to get off EVE?! Is it not doable if you think of maximizing use of the atmosphere and wing surfaces? Has anyone tried this? Has some obvious potential for this been overlooked or not explored completely? I would imagine the best type would be high thrust to weight to get out of the thickest parts as quick as possible. But not enough to overheat and die. You can reduce fuel and or drop engines as you go if you don't want to do a pure SSTO. You would probably want something like the Vector engines to start moving forward. and then go to smaller or more efficient(like poodle?!) as you get up until nukes for deep space.

Sorry for not demonstrating first:

I would test this in game but I have computer problems ATM and can't... But this is the first thing I'm trying when I get it fixed. That might be while though. But I thought this might be interesting and crazy enough to be worth it. I have a hunch this might be more correct than people will think at first glance. I've played lots of space planes. And as unlikely as it seems to work I have a feeling I'm hitting on something people may have missed. I wonder if it was intended to work this way...

Does the atmosphere on Eve and space plane design potentially start to allow bigger loads off eve if designed correctly? I've tried this in the past but I may not have done it well enough. I usually dropped stuff not worrying much about thrust and getting back. But it's just nagging me how easily this could be missed given how little people understand space planes and how much Delta V you can really skim off with a space plane if you actually do the calculations. If you do sufficient wing load and sufficient thrust to weight especially.

Edited by Arugela

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One, how would you get a fully assembled Space Shuttle to Eve without Hyperedit, filled to the brim with fuel? Two, it is too challenging because of the greater SURFACE GRAVITY and higher Karman Line.

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Posted (edited)

You would have to put on a minimal mining rig. And that is why you might do lower levels with better fuel efficient but high thrust items like the Vector.

Edited by Arugela

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Posted (edited)

I've seen people build EVE SSTO's. They shown this to be possible with Mammoth engines and a very high landing spot. 

However, not a challenge for me as I am terrible with planes.

What ur up to to is just crazy, look here:

 

 

Edited by Physics Student
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Does your space plane for Kerbin by any chance use airbreathing engines? These cannot be used on eve. A jettisonable stock prop could be used to get to altitude and maybe 200m/s so that a rocket with more efficient engines could continue. The other advantage of a thick atmosphere is that by using a plane you don't need as much thrust because your wings provide lift

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2 hours ago, Arugela said:

. I can get a space plane off Kerbal with only 1900 DV easy.

You start with a completely, utterly false premise, and go off over the horizon from that.

(in effect, you are saying that you can reach a speed of 2350, by only speeding up to 1900)

And no, the 175m/s of the surface rotation helps, but not that much.

 

Good luck, 'cause you are stuck in a fantasy land.

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Posted (edited)

No, I'm saying I can use 1900 delta V to go 3200 delta V! 8p >< And that is fairly easy on kerbin with jets and nukes. I'm proposing it might be possible with good wing design and thrust to do something similar on EVE. And wondering if it can be taken further than normal with a correct approach potentially. Not that others haven't tried. Maybe if you focus on it enough you can do something like 50 tones off Eve or something. I assume less though.

Edited by Arugela

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Posted (edited)

Spaceplanes don't reduce the delta-v requirements, they actually increase them a lot for a normal spaceplane ascent because you stay in the atmosphere a lot longer, causing lots of drag losses. The reason spaceplanes are efficient is because they normally use jet engines to gain a lot of their speed, and jet engines are a LOT more fuel efficient than rocket engines.

Edited by Michaelo90
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3 hours ago, Arugela said:

I can get a space plane off Kerbal with only 1900 DV easy.

To put it a little more diplomatically: there is no free ride in physics. To reach orbital speed you need to put in the required energy, regardless of *how* you do it.

Orbital speed being 2296m/s at 70km, and your plane starting at 175m/s (assuming you launch eastwards taking full advantage of the planet rotation), you still need an absolute minimum of 2296-175=2121m/s dV (because that is what delta-V basically means: the difference between initial and target velocity). And that doesn't even account for the vertical acceleration needed to get you to orbital altitude, or the losses to drag and steering errors.

Lift is not 'free energy', if that is what you are thinking: lift is generated as a factor of the speed you push the wings through the air, and the energy required to push them through the air... is all on you.

 

That out of the way, the problems with making an spaceplane work on Eve:

  • No fuel-efficient airbreathing jet engines at your disposal, which is a huge factor of why spaceplanes work on Kerbin. You have to use rockets all the way, which need oxidizer, which without even considering anything else means more than twice the mass in fuel load is required.
  • Much higher atmosphere pressure than on Kerbin, which affects almost all engines negatively, leaving them with less thrust during a significant part of the ascent (resulting again in more fuel mass required).
  • Much higher atmosphere = longer ascent = exposed longer to drag = more fuel.
  • Much higher orbital speed, about 40% more to make low orbit. Yep... more fuel again.
  • And last but not least (this is actually pretty much the killer): much denser atmosphere, which makes drag and heating on the way up a huge problem compared to Kerbin. On Kerbin, just about when you start getting into problematic heating, you're already at the edge of the atmosphere. On Eve, you pretty much just got off the ground. Usually this is dealt with by going almost straight up for a significant part of the ascent, to minimize how much time you are in the thickest parts... but with a spaceplane, by design you are looking at an almost horizontal ascent, maximizing the time spent in the thicker atmosphere.

An Eve spaceplane would need to go almost painfully slow for a loooong part of the initial ascent to not kill itself in a ball of fire. Combined with no airbreathing engines, this means burning a LOT of fuel, just to even get to the part of the atmosphere that will allow you to safely start accelerating to orbital speeds... and then you still have to make it to 3216m/s before dropping back down into the atmosphere.

 

4 hours ago, Arugela said:

It's one characteristic is it has the thickest atmosphere in the game(for a landable planet). Is this a big sign saying use a space plane on me instead of a rocket.

In short: no, it's a big sign saying 'you need to minimize drag to the absolute minimum or you dead'. Wings add drag instead of reducing it, so you would basically be trying the exact opposite of what this type of atmosphere requires.

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Posted (edited)

But the wings help keep the nose up and make more use of any thrust, saving fuel. It could aid in a fairly fast higher thrust plane. The faster SSTO's usually get better mileage after hitting orbit. So it uses less delta V on the way up effectively. Especially if you consider getting away from the worst gravity faster and utilizing the fuel/thrust more efficiently in a flight. You would still want the best lift and thrust possible for the design.

Can't you reduce drag with wing shape and still get good lift and better heat. There are some pretty heat tolerant parts to use for wings too.

Edited by Arugela

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1 minute ago, Arugela said:

So it uses less delta V on the way up effectively.

Delta V is the difference between initial and target velocity. You cannot 'use less' than what you need... the difference is the difference.

How many kg of oranges will you need to balance a scale with 80kg on the other side? Now... how many kg of watermelons? You need 80kg of them in either case, the size of the individual fruits doesn't change that. The same happens with the energy needed to achieve a certain change in velocity: it doesn't matter HOW you do it, it will still require (at least) that same amount of energy.

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Posted (edited)

Yes, but you can still use less fuel if you have lift aiding in plane flight. If it aids in upward descent you take less time to get out of heavy gravity or use less fuel and you can use fuel more efficiency. So, no. If you can use fuel less efficiently you can use it more efficiently. lift can help in this.

Either way, the point is to try.

Edited by Arugela

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1 minute ago, Arugela said:

Yes, but you can still use less fuel if you have lift aiding in plane flight. If it aids in upward descent you take longer to get out of heavy gravity and you can use fuel more efficiency. So, no. If you can use fuel less efficiently you can use it more efficiently. lift can help in this.

You are viewing lift as free energy; it isn't. Your wings only generate lift because of the speed by which you push your craft through the air. This is why you need to accelerate before it takes off the runway: a certain percentage of the horizontal push of your engines gets translated into vertical push by the air 'bumping' against the wings. The plane does not get magically pulled up into the air from standing still. To reach and maintain the speed that generates that lift, you have to keep pushing = engine thrust, which expends fuel. Lift does not make it require less fuel, it spends fuel.

Make yourself a paper plane. Hold it up in your hand, and just let go without moving your arm. What do you expect to happen? (*) Now try again, but this time throw the plane: do you expect the same result? Unless you put the energy of your throw into it to give it a minimum speed, it won't 'lift' by itself out of your hand, just because it has wings: you have to put energy into it to push it through the air FIRST, and then some of that speed is translated into lift.

(*) yes, it might actually pitch up and fly a bit before hitting the ground, but that is gravity doing what you didn't do with your arm - adding speed to the plane. Note that it still needs to speed up before it will generate lift.

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Personally, I think spaceplanes on eve is not a feasible option. You can't make a pure stock eve SSTO. Mainly because of these factors:

1. Eve has higher upper atmosphere altitude (90km), which means your craft is going to spend it's time inside atmosphere longer than on kerbin (70km) and that means, your craft will be exposed to drag forces longer than on kerbin

2. Eve has thick atmosphere that kills your engine efficiency, and there's no oxygen there, so jet engines is useless. The only engines that efficiently operates on eve is aerospike, mammoth and vector, all of these are rocket engines, they need oxidizers to operate, which means higher fuel onboard, not to mention rocket engines have lower fuel efficiency than jet engines

3. Eve has high gravity, which means higher Dv required to get off of it, however, with thick atmosphere, your craft is going to burn up while it's still on the lower altitude than what you did on kerbin, which means, your craft is subjected on atmospheric heating longer and risk being destroyed

4. Wings do not generate lift by itself. It needs a pushing force against atmosphere from engines to generate and maintain lift

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All vehicles have a "lift to drag" ratio. The L/D ratio says how much upward force the wings and body generate for a given amount of parasitic drag. For example, a glider with very long wings may have an L/D ratio of 50, meaning the upward lift produced by the wings is fifty times greater than the backward drag of air over the wings. In contrast, a Boeing 747 may have an L/D ratio of 17, meaning the upward lift produced by the wings is seventeen times greater than the drag on those wings.

Importantly, the L/D ratio tells you how much engine thrust you need in order to maintain level flight at constant speed. A 747's engines need to produce 1/17th of its weight in thrust just to fight the drag produced by the wings. A high-performance fighter, like an F22, has a much lower L/D ratio and so its engines must be much more powerful (in proportion to its weight) to maintain cruise. 

But when you're talking about spaceplanes, things get messy. L/D ratio is dependent on air density, airspeed, and angle of attack. As you climb, the air gets thinner and your L/D ratio drops. As you accelerate, drag forces increase quadratically and your L/D ratio drops. If you pitch up, your wings become less efficient and your L/D ratio drops. So you need ridiculously powerful, ridiculously efficient engines to continue thrusting harder so you can counteract drag AND have enough thrust left over to continue accelerating into orbit. The RAPIER is good for this because it has good specific impulse at all speeds and its thrust skyrockets once you are high-supersonic, which is precisely where you need thrust the most.

This is why spaceplanes won't work on Eve. The air is thick, so you can get a good L/D ratio at low speeds...but once you start accelerating and climbing, the quadratic increase in drag robs you of your L/D ratio and you need exponentially increasing thrust just to stay aloft, let alone continue accelerating. Meanwhile, airbreathing engines don't work on Eve, so you have no engines efficient enough to do the job. It just doesn't work.

A glider would work very very well on Eve...but not for getting into orbit.

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2 hours ago, Arugela said:

... getting away from the worst gravity faster ...

 

2 hours ago, Arugela said:

... to get out of heavy gravity ...

Might be nitpicking, but I feel like mentioning this here still:

To clarify, gravity itself will change much less on your way to orbit than you might think. In orbit you only have the "illusion" of zero g because you are falling sideways so fast that you keep missing the planet. Lose any horizontal velocity and you will drop down pretty quick indeed. Think about it this way, if gravity goes away when you go up, what is keeping the moon from flying away?

IRL, gravity at 400km altitude is still 90% as experienced on the surface IIRC.

This adds nothing (or not much) to the discussion at hand, just wanted to clarify. It is a very common misconception too. Like, why do the astronauts in the ISS float? Because there is no gravity of course. But thats not true.

https://en.wikipedia.org/wiki/Gravity_of_Earth#Altitude

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I've been trying to do this on GregroxMun's Eve Space Program. Even made an engine mod to do the attempt. Managed to barely get sub-orbital in a variant of the LTS Kestrel-FC, with the biggest problem being overheating nose parts on the way up. If I cheat the thing into orbit I can descend and land the thing if I'm gentle on re-entry. Dynamic pressure below 10 km is fun. :sticktongue:

Remember that this is in a craft with modded parts, notably a 'jet' engine that breathes atmospheric hydrocarbons and burns oxidizer. The dynamics are rather different, but at that point an Eve SSTO is 'just' an engineering problem.

--

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Posted (edited)

6 hours ago, Arugela said:

But the wings help keep the nose up and make more use of any thrust, saving fuel. It could aid in a fairly fast higher thrust plane. The faster SSTO's usually get better mileage after hitting orbit. So it uses less delta V on the way up effectively. Especially if you consider getting away from the worst gravity faster and utilizing the fuel/thrust more efficiently in a flight. You would still want the best lift and thrust possible for the design.

Can't you reduce drag with wing shape and still get good lift and better heat. There are some pretty heat tolerant parts to use for wings too.

First I want you to prove you can make a more efficient rocket-only SSTO on Kerbin, with stats and pictures

The one advantage a plane may have, which is a lower required TWR, is nothing compared to the:

  • Drag from wings and longer time spent in atmosphere
  • Lower engine efficiency and longer time spent with lower engine efficiency

On Kerbin jet engines can be used, giving more than 10 times the efficiency of the rocket engines. On eve you must use rocket engines, and they are less efficient because of the atmospheric pressure being higher at sea level on eve. And the only reason it is worth launching horizontally on Kerbin  is because spaceplanes can get up to speed using the oxygen in the air, and this makes it worth having a lower TWR which requires horizontal launch

Edited by Skylon
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Posted (edited)

What about more outside the box. What if you can get one space plane with 1-5 tons into Eve orbit. If that is possible. would it not lend itself more than a rocket to paralleling it slapping multiple together and doing the same with 10? At which point you can customize the engines more for better weight to thrust and remove mining gear from all but one of them. And you have potentially the ability to get off eve and get back to kerbin given relative amounts of fuel after getting into orbit.. If that is possible should you not be able to use one no matter what to get a full trip. As long as you can manage to land it refuel and takeoff without introducing too much lag(I meant drag but both apply) and keep it together on the way up. Assuming you can get a connector that can take the heat etc. I haven't played in a while, so I don't remember heat tolerances of connecting parts. I know struts are decent in practice but it would be fun flying it obviously.

Edited by Arugela

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2 minutes ago, Arugela said:

What if you can get one space plane with 1-5 tons into Eve orbit. If that is possible.

Oh, it's simple. No trouble getting a space plane of 1-5 tonnes into Eve Orbit. You just take off the wings and landing gear, since they are dead weight that you don't need. Then you use drop tanks. With engines. We can call these drop tanks plus engines "stages". Then you just drop stages as you no longer need them.

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It is impossible to use less delta-v than the theoretical minimum to reach orbit around a particular celestial body. The theoretical minimum is the absolute minimum because it is calculated as the absolute minimum change in velocity needed to ascend to orbital altitude and meet orbital speed. In practice, it is impossible to even get down to that minimum because the laws of thermodynamics guarantee that there will be some wasted energy.

What is possible is to use less fuel. Spaceplanes do this by using incredibly efficient engines that produce a greater impulse for a given mass of fuel than a conventional rocket engine, and by using the air as oxidizer for as much of the ascent as possible so that the amount of fuel spent lifting oxidizer for the engines is reduced. They do not require less delta-v to reach orbit than the absolute minimum, because that is impossible.

Another thing is lift. Lift will never decrease the required delta-v to reach orbit around a particular object because doing so is impossible. The reason heavier-than-air aircraft (which really should be termed denser-than-air) benefit from lift is because the wings cover a large enough area that the resisting force of the air on the bottom of the wings is enough to counteract gravity. This is equilibrium. It is not free energy, which would be impossible.

The only reason spaceplanes use less fuel than rockets (again, not less delta-v) is because their engines are highly efficient while in the atmosphere. The reason rockets do not use such engines is only that jet engines do not provide enough thrust for use on a rocket, and that they only function in the lower atmosphere where there is enough oxygen in the air catalyze ignition of the fuel. Jet engines rely on an oxygen-rich atmosphere, which Eve does not have. Therefore it is impossible to reduce fuel requirements with a spaceplane on Eve the same way that it can be done on Kerbin or Laythe, because it is impossible to use jet engines on Eve.

 

In short, your ideas about reducing required delta-v for orbit below the minimum will always be impossible because they break the laws of physics, and spaceplanes are only more efficient because they have more efficient engines which won't work on Eve.

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14 minutes ago, eloquentJane said:

It is impossible to use less delta-v than the theoretical minimum to reach orbit around a particular celestial body. The theoretical minimum is the absolute minimum because it is calculated as the absolute minimum change in velocity needed to ascend to orbital altitude and meet orbital speed. In practice, it is impossible to even get down to that minimum because the laws of thermodynamics guarantee that there will be some wasted energy.

What is possible is to use less fuel. Spaceplanes do this by using incredibly efficient engines that produce a greater impulse for a given mass of fuel than a conventional rocket engine, and by using the air as oxidizer for as much of the ascent as possible so that the amount of fuel spent lifting oxidizer for the engines is reduced. They do not require less delta-v to reach orbit than the absolute minimum, because that is impossible.

Another thing is lift. Lift will never decrease the required delta-v to reach orbit around a particular object because doing so is impossible. The reason heavier-than-air aircraft (which really should be termed denser-than-air) benefit from lift is because the wings cover a large enough area that the resisting force of the air on the bottom of the wings is enough to counteract gravity. This is equilibrium. It is not free energy, which would be impossible.

The only reason spaceplanes use less fuel than rockets (again, not less delta-v) is because their engines are highly efficient while in the atmosphere. The reason rockets do not use such engines is only that jet engines do not provide enough thrust for use on a rocket, and that they only function in the lower atmosphere where there is enough oxygen in the air catalyze ignition of the fuel. Jet engines rely on an oxygen-rich atmosphere, which Eve does not have. Therefore it is impossible to reduce fuel requirements with a spaceplane on Eve the same way that it can be done on Kerbin or Laythe, because it is impossible to use jet engines on Eve.

 

In short, your ideas about reducing required delta-v for orbit below the minimum will always be impossible because they break the laws of physics, and spaceplanes are only more efficient because they have more efficient engines which won't work on Eve.

Space Shuttle Atlantis

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Posted (edited)

8 hours ago, swjr-swis said:

Delta V is the difference between initial and target velocity. You cannot 'use less' than what you need... the difference is the difference.

How many kg of oranges will you need to balance a scale with 80kg on the other side? Now... how many kg of watermelons? You need 80kg of them in either case, the size of the individual fruits doesn't change that. The same happens with the energy needed to achieve a certain change in velocity: it doesn't matter HOW you do it, it will still require (at least) that same amount of energy.

Except with oranges you can technically change to orange juice or grind them down remove the air space and put it in a smaller lighter container effecting multiple aspects of said container. So bad analogy. Or good analogy... It's not the oranges it's the container. If you can get the slightest benefit from lift and wings you can get more. No matter how small the overall benefit. Can you squeeze a little extra from a space plane somehow?

As to physics. It doesn't work that way. the smallest thing missed or the smallest incorrect assumption and it is not true. Even if the physics theory is correct the outlining assumptions may not. And that is being generous. Nobody has fully explored the game. It's too easy to miss something. Hence the benefit of experience over theory. Theories are too easy to get wrong and when relied on push you to not try and find out(As the person who actually originally came up with the theory should have, or you should question it heavily). Experience on the other hand tends to lend itself to finding possibilities. Although not succeeding does not mean you can't. So the point of the challenge. Explore if a space plane design can be made to do better than rockets for getting off eve.

Everyone is mocking without trying it. 8p (or at least trying it again in a new way.)

What about getting enough lift to spiral up to the higher atmosphere and get off the planet with nukes or lighter engines?! Something a rocket may not be as good at. There must be some more creative approaches. What hasn't been tried.

And, BTW, I didn't say it had to be an SSTO. You can drop things! I said space plane. SSTO was just an extremity!

The emphasis is merely space plane over pure rocket. Even if it's a hybrid attempt or anything utilizing a space plane as part of the ship. Although it may be more interesting with more space plane than not. Or at least appearing as more of one.

That means you can do anything as long as part of it is a space plane. Heck even if it only space planes to land on kerbin better if you want to take it to the limit(it would technically add to the rocket on the way up potentially.). But something like lower stage rocket upper stage space plane off eve would count. It's about maximizing eve ascent to get more load no matter what! I'm just emphasizing any missing potential with space planes. Although, again, it would be more interesting with more space plane emphasis. Obviously you can't take rockets farther than rockets. So space planes is what we have left. so why not explore it. There is plenty of potential as it can be more complicated. Maybe there is an angle everyone missed.

If it adds to the ability to get off Eve, it counts!

Edited by Arugela

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12 minutes ago, Arugela said:

Except with oranges you can technically change to orange juice or grind them down remove the air space and put it in a smaller lighter container effecting multiple aspects of said container.

You will still need 80kg worth of 'orange-juice-in-a-container' to balance the scales. Which effectively will take more oranges, even if it ends up being a smaller container; not very efficient, orange-wise. :wink:

18 minutes ago, Arugela said:

the smallest thing missed or the smallest incorrect assumption and it is not true.

Good, a sign of critical thinking. How about going back to your OP and applying this? Hint: you don't need to read any further than the very first phrase...

 

Anyway, I can see you have your particular flavour of physics all worked out, so I'll stop trying to help and let you get on with providing the proof to your theory.

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Posted (edited)

80KG is 80KG if it is ground down to reduce air. It does not take more oranges(Kg is weight/mass not volume). I'm looking at 80KG of purely oranges. Not measuring a sealed air tight container.

The oranges oranges will stay exactly 80kg. But the stuff around it can be more efficient afterwords. This is a real world example. It merely needs to be applied in a kerbal way. (BTW, you can technically reduce air space effectively in KSP. You do so by looking at weight per item or fuel type.)

It's not my version of physics. It's reality... This is that real world application I'm talking about. Yes, KSP is simpler than real life. That does not exclude possibilities having been ignored or not taken far enough to reach their maximum! And, practically, Eve being difficult means lots of missed potential as it is harder to try. So, the odds are greater. Hence why it is so juicy(pun intended)!

Edited by Arugela

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