[1.8+] Real Fuels

[DracovaXIV]

Very good information, thank you! This was actually very well thought-out, I see.

It would be terrific if resource changes, as well as mixtures of resources could somehow be implemented. That would be a huge boon to all the life support mods out there. I always thought it was strange how ECLSS had huge CO2 capacities, for instance; and of course the biggest element for game mechanics would be the ability to mix your own fuels, and get resources out of fuels, like with the peroxide example. From all I've read - liquid oxygen in fuel tanks doesn't actually boil away somewhere; the tank is hermetically sealed, of course. Instead, liquid oxygen undergoes a state change into gaseous oxygen (which is much less reactive). If GOX is placed in an environment cold enough to get it to condense, it would turn back into LOX. So, there isn't actually supposed to be any loss of mass, and the fuel should be able to be recouped once the tank gets cold from radiating heat away into space...

[Starwaster]

Very good information, thank you! This was actually very well thought-out, I see.

It would be terrific if resource changes, as well as mixtures of resources could somehow be implemented. That would be a huge boon to all the life support mods out there. I always thought it was strange how ECLSS had huge CO2 capacities, for instance; and of course the biggest element for game mechanics would be the ability to mix your own fuels, and get resources out of fuels, like with the peroxide example. From all I've read - liquid oxygen in fuel tanks doesn't actually boil away somewhere; the tank is hermetically sealed, of course. Instead, liquid oxygen undergoes a state change into gaseous oxygen (which is much less reactive). If GOX is placed in an environment cold enough to get it to condense, it would turn back into LOX. So, there isn't actually supposed to be any loss of mass, and the fuel should be able to be recouped once the tank gets cold from radiating heat away into space...

Here's the deal on boiloff: As liquid oxygen (or any cryogenic fuel) starts boiling off, the gas produced will increase pressure to the point that the tank will BURST. That part will happen pretty definitely unless steps are taken to correct the problem. Right now that means deliberately venting the gas off before the pressure buildup becomes a problem. Refrigeration has been talked about a lot (such as 'zero boil off' or ZBO) but to my knowledge no ZBO systems have ever actually flown. Another solution that has been discussed is enclosing a LOX tank inside of an H2 tank. As the H2 tank boils off it carries away enough heat to prevent the LOX tank from heating above its boiling point.

[DracovaXIV]

Interesting. I figured there'd be additional complications in using LHO in the real world, but tanks bursting is a new one. I figure, the problem is further exacerbated by the pressure difference between the tank's interior and the vacuum of space.

[Starwaster]

Interesting. I figured there'd be additional complications in using LHO in the real world, but tanks bursting is a new one. I figure, the problem is further exacerbated by the pressure difference between the tank's interior and the vacuum of space.

Possibly, but it's even a problem here on Earth with things like liquid propane or liquid oxygen (for medical purposes) or liquid methane. They have to have pressure relief valves fitted to handle the boil off.

[kuruma]

I've searched and searched, and I cant find the answer to this:

my RCS thrusters are attached to throttle control. So if I throttle up so does the rcs unless I have them turned off.

Can anyone assist me or tell me what I need to change in order for it to be unlinked?

[panarchist]

Possibly, but it's even a problem here on Earth with things like liquid propane or liquid oxygen (for medical purposes) or liquid methane. They have to have pressure relief valves fitted to handle the boil off.

It also depends on factors like tank volume - the larger the tank, the lower the maximum pressure it can withstand. With large tanks like the shuttle ET, which relieves pressure above 44.1 PSI, atmospheric pressure is a significant factor. On the other end of the spectrum, the shuttle's helium tanks can withstand 4,700+ PSI, and atmospheric pressure is comparatively irrelevant.

[NathanKell]

kuruma: that's Mechjeb.

DracovaXIV, Starwaster: a practical example is the S-IVB, where the insulation between the LOX and LH2 tanks was carefully designed such that the heat input to the LOX tank from the stage structure was perfectly balanced by the heat outflow across the LOX/LH2 barrier. They exchanged slightly higher LH2 boiloff for near-zero LOX boiloff.

[Konrad9]

Please help! I've got all of the required, suggested, and other recommended mods installed.

While I'm in assembly my top stage has fuel, but when I launch, it's empty! I've tried replacing the part, using different tanks, using different fuels, different levels of fuels.

I have no idea what I'm doing wrong and have tried searching for other people having the same problem but I can't find any info. Any help would be greatly appreciated.

http://i.imgur.com/XbMKeMd.jpg (fuel in top stage)

http://i.imgur.com/vBrnouz.jpg (no fuel in top stage)

[Starwaster]

Please help! I've got all of the required, suggested, and other recommended mods installed.

While I'm in assembly my top stage has fuel, but when I launch, it's empty! I've tried replacing the part, using different tanks, using different fuels, different levels of fuels.

I have no idea what I'm doing wrong and have tried searching for other people having the same problem but I can't find any info. Any help would be greatly appreciated.

http://i.imgur.com/XbMKeMd.jpg (fuel in top stage)

http://i.imgur.com/vBrnouz.jpg (no fuel in top stage)

The first picture you linked to does not show fuel in the top stage.

That tank is empty.

See where it says 45% Liquid Fuel / 55% Oxidi...(BLUE BUTTON)

See that blue button? If you click the blue button it will add 45% Liquid Fuel and 55% Oxidizer to the empty tank. The tank is empty until you click that blue button or use the tank GUI (click the blue button next to show tank GUI) OR select the tank while the Action Group Editor is enabled, which will open the tank GUI and let you edit the tank.

You must do one of those three things.

Again, your first picture does not show a tank with fuel in it. It shows an empty tank.

[Konrad9]

The first picture you linked to does not show fuel in the top stage.

That tank is empty.

See where it says 45% Liquid Fuel / 55% Oxidi...(BLUE BUTTON)

See that blue button? If you click the blue button it will add 45% Liquid Fuel and 55% Oxidizer to the empty tank. The tank is empty until you click that blue button or use the tank GUI (click the blue button next to show tank GUI) OR select the tank while the Action Group Editor is enabled, which will open the tank GUI and let you edit the tank.

You must do one of those three things.

Again, your first picture does not show a tank with fuel in it. It shows an empty tank.

Blast! I thought for sure I had done that six or seven times before giving up and posting.

Thank you for reminding me

[Starwaster]

Blast! I thought for sure I had done that six or seven times before giving up and posting.

Thank you for reminding me

You're welcome

[Rollins]

Please tell me how resolve this problem with blank GUI in RF.

http://i.imgur.com/Qrb2ZWU.jpg

I tried use RF without any mods.

I love RSS and RO so much, but..

Sorry for my English.

It seems the problem lies elsewhere...

Edited August 25, 2014 by Rollins

[CSVoltage]

Bug Report.

When I place jet engines with symmetry mode, the thrust falls off in an increasing amount for engines after the parent part. This is due to the parent taking its share of intake air before the subsequent engines. I determined this with B9 engines because they show intake air flow along with fuel in the in-flight staging. The problem holds true for all jets however.

I can confirm this is not a conflict with another mod as it persisted after removing all other mods.

Happens regardless of :attachment to nodes or attached radially using editor extensions; direct connection from intake to engine with fuel lines; intake air balancing at 100x with TAC fuel balancer.

[NathanKell]

Rollins: Can you post the exact versions of all mods you have installed?

Then: cause the problem. Quit KSP (if it hasn't crashed). Upload your entire output log (NOT ksp.log) to dropbox or something.

Windows: KSP_win\KSP_Data\output_log.txt OR KSP_win64\KSP_x64_DATA\output_log.txt (depending on which used)

Mac OSX: Open Console, on the left side of the window there is a menu that says 'files'. Scroll down the list and find the Unity drop down, under Unity there will be Player.log ( Files>~/Library/Logs>Unity>Player.log )

Linux: ~/.config/unity3d/Squad/Kerbal\ Space\ Program/Player.log

CSVoltage: doesn't this occur without RF? It sounds like stock behavior. RF doesn't touch jets or IntakeAir (other than to change its density so you need a bit more of it). Add more intakes?

[CSVoltage]

thought of that. tried it. more intakes helps a little cus theres more to go around but in the end its no where near like stock. it treats the subsequent engines like they're attached to the the parent rather than them all being attached to the same part that's feeding them. i thought it might be the stock-alike real engines mod but i pulled that too and it still happened. for now ive made a workaround, a super-compressed air tank definition that i run the jets off of. but it feels cheaty cus i can go into orbit and still run jets. lol

[Starwaster]

thought of that. tried it. more intakes helps a little cus theres more to go around but in the end its no where near like stock. it treats the subsequent engines like they're attached to the the parent rather than them all being attached to the same part that's feeding them. i thought it might be the stock-alike real engines mod but i pulled that too and it still happened. for now ive made a workaround, a super-compressed air tank definition that i run the jets off of. but it feels cheaty cus i can go into orbit and still run jets. lol

I'll spare you my opinion of your air tanks because it's your sandbox.

I will will say that I don't find it necessary at all to do that sort of thing to fly my planes. Even get spaceplanes to orbit. Something is wrong with your game.

[gruneisen]

[ANSWERED] This is probably a silly question, but I am suing the Realism Overhaul w/ Real Fuels, and I am unable to get any of the upper stage mono propellant engines (like the Aerojet AJ10-118K modified from KW Rocketry), which use Aerozine / N2O4 for fuel / oxidizer. The engine will not light and, when I mouse over the engine in the VAB, it states the engine is pressure fed, and that no tank pressurized fuel tank containing the required resource(s) connected.

I understand the fuel tank I am using is not pressurized, but I cannot fill the pressurized tanks (those designed for monoprpellant) with the Aerozine / N2O4.

How are these engines used?

Edited August 29, 2014 by gruneisen

[NathanKell]

Realism Overhaul requires Procedural Parts. When you have placed a procedural RF tank, right-click and change its type to ServiceModule. Those are pressurized and will accept all fuels.

[NathanKell]

What's the (typical) main problem facing restartability? Cost? Fuel instability? Or are the typical turbopumps just not designed for multiple starts? Genuinely curious.

To restart an engine you need:

1. Parts that aren't broken/melted/etc.

2. A way to ignite the fuel and oxidizer (if they aren't hypergolic)

3. Propellant (not vacuum or boiloff or pressurant) in the feed lines, aka fuel stability.

If your engine is pump-fed (i.e. anything but pressure-fed), you also need a way to start the pump itself, which will have similar requirements to the above.

I mention 1 because people don't usually consider the fact that rocket engines are not designed to last all that much longer than their nominal burntime. Some have ablative combustion chambers (which will go boom if you keep firing long enough and the wall ablates away), some have ablative nozzles, and all of them will suffer component wear in the super-high-temperature, super-high-pressure environment that is the pump, the turbine, the combustion chamber, and the nozzle. If the engine is pressure-fed you can ignore the first two (which would go a long way in explaining why almost all "orbital maneuvering engines" like Transtage, SPS, the Shuttle OME, etc, are pressure-fed.*)

*And, for that matter, all derivatives of the same Aerojet engine that was designed for the Aerobee sounding rocket in the early 50s, used on Vanguard (our first launcher), and is even proposed for Orion. Note that the RL-10 is also a common "space taxi" engine, but its cycle (expander) is also a decent one for relighting.

Finally, to ensure that propellant *stays* in the feed lines and the pump doesn't have to work too hard, you need to pressurize your tanks to a higher level than you might otherwise (note that *all* tanks are pressurized, but the ones for pressure-fed engines are much, much more pressurized).

So: pressure-fed means lower performance. Reliability means lower performance and higher cost. Adding multiple uses to an ignition system lowers reliability and increases cost.

That said, there's nothing preventing many rocket engines from being ignited more than once as long as the total runtime doesn't go over-limit and the three issues are seen to: engines undergo acceptance testing (a test fire) before they're launched, generally. But that test fire is done on a test rig, where 1-3 are assured, and is short enough that there's still enough life left for the actual use.

Part of what made the Shuttle so insanely costly was the requirement to refurbish rather than replace the SSMEs (after, it must be pointed out, they were subject to an entire ascent's worth of firing, *and* a reentry).

Edited August 28, 2014 by NathanKell

[Shad0wCatcher]

Fair enough. Thanks for the explanation. I surmised the issues with the pumps / chamber / nozzle would be a fairly big chunk of the problem with the rather extreme environment they're subjected to. Did not know about ablating material in the nozzle / combustion chamber though. That's interesting. Never understood why we ever decided on re-usability on the SSMEs in the first place outside of politics or PR.

[NathanKell]

Well, the shuttle was going to make payload to orbit dollars a pound!

Actually, the absolute best resource AFAIK is The Shuttle Decision.

[Starwaster]

Well, the shuttle was going to make payload to orbit dollars a pound!

Actually, the absolute best resource AFAIK is The Shuttle Decision.

But it did make payload to orbit dollars a pound!!!

(lots and lots of them as I recall.... )

[The Pink Ranger]

Looks like the Thermal Fins are drawing too much power. I added 100+ EC/s generator modules to my nuclear engines and they sustain everything on my ships just fine except the thermal fins. Soon as I activate the fins they start draining power pretty quickly. Looked in the cfg and it says they're only supposed to draw 0.01666667 EC/s. Any idea what's going on?

Edit: I've removed the EC requirement in the cfg but I can't find anything in there relating to the activate command in the right click menu. How can I make the thing always active? I'd like to just stickem on in the VAB and forget about them.

Edited August 29, 2014 by The Pink Ranger

[Starwaster]

Looks like the Thermal Fins are drawing too much power. I added 100+ EC/s generator modules to my nuclear engines and they sustain everything on my ships just fine except the thermal fins. Soon as I activate the fins they start draining power pretty quickly. Looked in the cfg and it says they're only supposed to draw 0.01666667 EC/s. Any idea what's going on?

Edit: I've removed the EC requirement in the cfg but I can't find anything in there relating to the activate command in the right click menu. How can I make the thing always active? I'd like to just stickem on in the VAB and forget about them.

EC requirement is per unit of heat removed.

Right now I don't think they have the ability to be 'always on'

[Sandworm]

I'm running into a strange GUI conflict in the VAB. More of an annoyance, I've noticed it for a while. Today I thought I would figure things out.

Realfuels works perfectly on wholly manned craft, but whenever I either start with or add a probe core the VAB GUI becomes unresponsive. The interface does function. When I click on the fuel/tech level the change is applied to the rocket, but the display in the tooltip doesn't update. Clicking elsewhere and then returning to the part shows the new info. If I remove the probe core, the GUI returns to normal.

I'm running RemoteTech2 and I suspect that is the problem as that module is the only thing special about probe cores. Has anyone else run into this?