Why is Xenon gas so expensive?

[KerikBalm]

Anyone know the balance reason they made Xenon gas so ridiculously expensive?

Lets compare them

RESOURCE_DEFINITION

{

name = LiquidFuel

density = 0.005

unitCost = 0.8

flowMode = STACK_PRIORITY_SEARCH

transfer = PUMP

isTweakable = true

}

Cost per ton = 0.8/0.005 = 160

(Oxidizer is less than 1/4th that cost)

So a ton of "jet fuel" costs 160, a ton of "liquid rocket fuel" costs about half that

RESOURCE_DEFINITION

{

name = XenonGas

density = 0.0001

unitCost = 4

flowMode = STAGE_PRIORITY_FLOW

transfer = PUMP

isTweakable = true

}

Cost per ton = 4/0.0001 = 40,000 !!!!!!!!!!

Propellant for ion engines is 250x more expensive than liquid fuel for rockets.

Sure, the ISP is higher so you use less, but its not 250x higher.

A reusable LV-N tug is much more economical than an ion tug, not to mention the TWR is much much better.

In addition, the mass ratio of the xenon tanks is pretty poor.

In real life, Xenon is fairly rare, but easy to obtain, you basically just chill air and get Xenon by fractional distillation of the liquid (since air contains a lot more krypton, you can get a lot more krypton this way, and air is chock full of argon -about 1.3%- , making argon a really cheap propellant.

Furthermore Xenon has a boiling point 75K higher than liquid O2, and is more than twice as dense. These factors combine to make it easier to make a high mass ratio Xenon tank relative to a liquid O2 tank.

So the poor mass ratios of the tanks, and the high cost of propellant for the ion engines is not really based on realism, but in most cases in a game, gamepaly trumps realism....

Is there any gameplay reason to have xenon gas so ridilously expensive (let us use krypton then), and the tanks so poor?

[Rhomphaia]

In reality a ton of xenon would cost $120,000.

Xenon is preffered because of its atomic mass, argon or krypton would make a less efficient thruster.

[Greep]

Well as far as game balance it makes perfect sense, if you're having cost proportional to how much dV you get out of it. It's not just the dV you get from that stage, it's the fact that since the top stage is lighter, the launcher and orbit stage is also lighter. Really saves on credits! (if you don't plan on landing and returning anyways)

[KerikBalm]

In reality a ton of xenon would cost $120,000.

Xenon is preffered because of its atomic mass, argon or krypton would make a less efficient thruster.

and a ton of liquid oxygen is about $25,000 - about 5:1.

In KSP, its 40,000 vs 36 (assuming oxidizer is LOX)

over 1000:1 vs 5:1....

Does not seem right

[Aragosnat]

Or it could be another element that just happens to share the same name. Also you are forgtting the cost to extract said substance. Perhaps they don't have an efficent way to do so or the subtance is a bio-hazard to dem poor Kerbals. But, yes it does seem a bit odd in pricing. Then again. We are talking about Kerbals and their universe.

[Nemrav]

Devs probably misplaced a couple 0s... suspect next patch will make it right..

[Norpo]

Gameplay balance. If you were looking for an in-universe answer, I can't provide it.

If one was completely crazy, they could propel a giant ship with a crud-ton of ion thrusters. But part count says "no" before they even get it into space.

Of course, there are those with computers that CAN handle upwards of 1000 parts. Thus, this limits them from using the most efficient thruster in the game for everything.

And besides, in some cases, a small ion probe might actually be cheaper than a larger LV-N probe. (And heck, ion probes are so small most of the time; you could put them on an LV-N ship and double your overall delta-V (provided you ditch the LV-N stage later)

[Renegrade]

The costs have a number of weird points:

- Four of the AV-R8 Winglets are almost as much as a SKIPPER??

- Ditto for a basic RCS setup

- Why is the linear RCS port more than the quad when it's less capable?

- Why are batteries on par with solar panels in terms of cost (from a gameplay perspective)?

- Why is fuel even showing up as any sort of cost at all? (real life fuel costs are usually below 1%)

If one was completely crazy, they could propel a giant ship with a crud-ton of ion thrusters. But part count says "no" before they even get it into space.

Actually the PB-ION doesn't have enough thrust to lift itself off the launchpad, and adding more of 'em doesn't help (TWR would only approach 0.815 even if you add infinite PB-IONs).

Unless they did something insane like making it massless....

[Rhomphaia]

Devs probably misplaced a couple 0s... suspect next patch will make it right..

No i did. Xenon $1.2million/ton

And in 2001 NASA was paying $160/ton Liquid Oxygen commercial prices at that time were $210/ton

[cantab]

- Why is the linear RCS port more than the quad when it's less capable?

This one, at least, is supply and demand The 4-way blocks are made in large numbers, the linears are a specialised part.

[Kesa]

The costs have a number of weird points:

- Four of the AV-R8 Winglets are almost as much as a SKIPPER??

Plane parts seems to have higher costs, maybe to encourage/balance reusability. But I agree Tail fin and AV T1 (no control, but can put a CoL far the CoM of a rocket) should be far cheaper. What's more, one could argue that rocket boosters are simple expendables designs, therefore not that expensive.

- Ditto for a basic RCS setup

They are precision device that cost manufacturing, reguardless there wheight. And 450 is not that much. If it really matters, you're probably building a ship that does not need RCS.

- Why is the linear RCS port more than the quad when it's less capable?

Cantab answered. Gameplay-wise, they can be usefull to ballance crafts that have not the same inertia along each axis. For example a tall thin ship barely need more than reaction wheels to roll, few RCS far from COM to pitch/yaw, and more RCS to translate. As the stock RCS thruster aren't tweakable, linear port can be used to have the same sensibility along each axis, without having the same inertia.

- Why are batteries on par with solar panels in terms of cost (from a gameplay perspective)?

IIRC, solar panels are unlocked later. For big data transmission, you need both anyway.

- Why is fuel even showing up as any sort of cost at all? (real life fuel costs are usually below 1%)

You make a point. But then why the price of a rocket is the sum of its part? And why can we recover a rocket a receive it's full price? IRL raw material (including fuel) are dirty cheap, but conceiving (R&D) and assembling them is the challenge, that's why reusable launchers are not especially better than expendable ones. You can see it at as a maintenance cost.

Actually the PB-ION doesn't have enough thrust to lift itself off the launchpad, and adding more of 'em doesn't help (TWR would only approach 0.815 even if you add infinite PB-IONs).

I guess he was thinking of an interplanetary stage, no meant to land or take off.

Unless they did something insane like making it massless....

Will never happen.

[Renegrade]

This one, at least, is supply and demand The 4-way blocks are made in large numbers, the linears are a specialised part.

Yeah, the linear gets very little love... no economy of scale there. Still, I'd like to see it addressed..

Plane parts seems to have higher costs, maybe to encourage/balance reusability

Yeah, I'm totally cool with the large wing panels being costly and such for this very reason.

They are precision device that cost manufacturing, reguardless there wheight. And 450 is not that much. If it really matters, you're probably building a ship that does not need RCS.

Well, big liquid engines are precision devices too (moreso than an RCS-type thruster, as those are generally hypergolic or contact-catalyst designs that are basically a bell-shaped tube, and some valves, vs. the large scale turbopumps/ducting/cooling pipes/etc of a serious lifter engine), and it's 1800 for the RCS thrusters alone in a single ring of 4, plus another 400-800 for the tank(s).

Also from a game balance perspective, the reaction wheels (600-1200-2100 space bucks) provide unlimited (and very powerful) turning endurance once solar power is attained, for significantly less mass. Assuming you even need them, as all manned pods come with immensely powerful reaction wheels for absolutely free.

IIRC, solar panels are unlocked later. For big data transmission, you need both anyway.

That's correct, but it's a very close thing--you get batteries one tier before solar panels, and you're usually able to upgrade within one mission to solar from there.

You make a point. But then why the price of a rocket is the sum of its part? And why can we recover a rocket a receive it's full price? IRL raw material (including fuel) are dirty cheap, but conceiving (R&D) and assembling them is the challenge, that's why reusable launchers are not especially better than expendable ones. You can see it at as a maintenance cost.

Agreed, maintenance and refurbishing is completely ignored in KSP. I'd love to see the return values capped at say 80%, to represent at least some refurbishment.

Will never happen.

(regarding massless ion drives)

Thank goodness

[Bill Phil]

Because it is IRL. Xenon is rather rare in out atmosphere. And the balance reason is that Ion Engines are really good right now. Especially thanks to the buff they got in 0.23.5