[0.23.5] Realism Overhaul: ROv5.2 + Modlist for RSS 6/30/14

[Scripto23]

Oh so it is part of RO and not a separate patch?

Right. If you've go the newest version you can see a config in that folder named SolarPanels_NFPP

[dlrk]

I don't know if this was intended, but in the RFTS engines, gimble appears to have been removed.

EDIT: I just cghecked the CFG, and module gimbal is still there, but it isn't showing or working in KSP anymore.

[dlrk]

never mind, didn't realize I needed tweakable gimbal

[dlrk]

And, now I've got a different problem:Engine state is showing as INVALID, autoignite is ?/800, ignitions is showing as infinite. That's on all the engines, it seems

I did update Exsurgent Engineering

Edited January 26, 2014 by dlrk

[NathanKell]

Which engine configs are you using? I assume by needing Exsurgent Engineering you're using RftSEngines?

Did you delete the CFGs in the Engine Ignitor folder after installing Engine Ignitor?

Did you grab Exsurgent Engineering from the link in the OP?

Did you delete any RftsEngines.cfg in the RealismOverhaul folder before installing the RftS Pack?

[dlrk]

Yes to all

[dlrk]

It works normally if I remove tweakable gimbal.

[dlrk]

I removed tweakable gimbal, and now the previous problem that led me to believe I needed tweakable gimbal has been resolved, apparently accidentally fixed in the process of attempting to fix the second problem. So, all is well now, but tweakable gimbal is evidently incompatible

[Andrezado]

Anyways, It's working now, somehow, sorry for the waste of time...

[dlrk]

I do have a suggestion: For the LR-42R, the Aerozine/N2O4 Config should have ullage simulation false.

[NathanKell]

Andrezado: what changed?

dlrk: that's a turbopump-fed engine, not pressure fed, and therefore you have to worry about ullage. Also: no idea why tweakable gimbals would interfere with a non-ModuleGimbal module, unless assumes a regular ModuleGimbal is present and has trouble if it's not?

[Andrezado]

The engine nodes came back to normal, I don't know what was causing them to be weird before, TBH. I had removed the other engine packs, and I only had FASA/RealFuels installed to see if they were conflicting with other mods.. turns out they werent, it was something else.. no idea on what it could have been.

[Agathorn]

Yep i've fixed it.

I don't understand why the attachment points were changed from the original part, but setting the bottom point back to the same value as the original part fixes it.

@PART[galaxvr2]
{
    %title = Aestus
    %manufacturer = EADS Astrium
    description = Upper stage engine of the Ariane 5ES vehicle that launches the ATV to ISS. Burns hypergolic propellants.
    !MODEL {}
    !MODEL {}
    MODEL
    {
        model = AIES_Aerospace/Engine/AIESenginegalaxvr2/model
        scale = 0.307, 0.307, 0.307
    }
    %rescaleFactor = 3.25
    %node_stack_top = 0.0, 6.38, 0.0, 0.0, 1.0, 0.0, 2
    %node_attach = 0.0, 6.38, 0.0, 0.0, 1.0, 0.0, 2
    %node_stack_bottom = 0.0, -48, 0.0, 0.0, 1.0, 0.0, 2
    %attachRules = 1,1,1,0,0
}

I only fixed node_stack_bottom. I left the others alone, even though they were changed from the base part, since only the bottom was broken.

I just did a full re-install of everything and noticed this engine appears to still be incorrect. Or I messed up my install

[eggrobin]

[...] not pressure fed, and therefore you have to worry about ullage.

I'm confused by this part of the statement (and previous ones regarding pressure-feeding).

Pressure-feeding shouldn't remove the need for ullage: if your pressurised gas ends up below the propellant in the tank, opening the valve will just throw helium into space, depressurising the tank, the propellants will not reach the combustion chamber, and you will not return from space today.

As an example of a real-life pressure-fed engine which required ullage, take the TRW Descent Propulsion System (hypergolic pressure-fed).

The DPS burn was preceded by a two-jet +X LM Reaction Control System

(RCS) ullage maneuver of 7 seconds to settle propellants.

Note that +X is upwards here, just to confuse everyone.

The same considerations hold for the SPS (AJ-10).

EDIT:

The RCS doesn't require ullage because its propellants are stored in a bladder which sits inside a tank of pressurised gas. This can only be done for small volumes though. Here is an example of a hydrazine bladder manufactured by Astrium EADS (wait, now it's Airbus Defence & Space) for the Ariane 5 ACS (picture with humans for scale. They don't make bladder tanks for more than 39 L of hydrazine.).

EDIT2: Of course, the LM RCS used bipropellants, each in its own bladder. The schematics can be seen on page 4 of this document. It seems the tanks are larger than on Ariane 5, but they're still below 100 L.

EDIT3: With surface tension tanks, you can remove the need for ullage (as in, at low accelerations or in zero-g, the fuel will eventually settle where you need it), but it doesn't work under significant accelerations (in a way, the ullage works backwards for them).

Edited January 28, 2014 by eggrobin

[HoneyFox]

I'm confused by this part of the statement (and previous ones regarding pressure-feeding).

Pressure-feeding shouldn't remove the need for ullage: if your pressurised gas ends up below the propellant in the tank, opening the valve will just throw helium into space, depressurising the tank, the propellants will not reach the combustion chamber, and you will not return from space today.

As an example of a real-life pressure-fed engine which required ullage, take the TRW Descent Propulsion System (hypergolic pressure-fed).

Note that +X is upwards here, just to confuse everyone.

The same considerations hold for the SPS (AJ-10).

EDIT:

The RCS doesn't require ullage because its propellants are stored in a bladder which sits inside a tank of pressurised gas. This can only be done for small volumes though. Here is an example of a hydrazine bladder manufactured by Astrium EADS (wait, now it's Airbus Defence & Space) for the Ariane 5 ACS (picture with humans for scale. They don't make bladder tanks for more than 39 L of hydrazine.).

EDIT2: Of course, the LM RCS used bipropellants, each in its own bladder. The schematics can be seen on page 4 of this document. It seems the tanks are larger than on Ariane 5, but they're still below 100 L.

EDIT3: With surface tension tanks, you can remove the need for ullage (as in, at low accelerations or in zero-g, the fuel will eventually settle where you need it), but it doesn't work under significant accelerations (in a way, the ullage works backwards for them).

TBH I was not convinced that pressurizing can eliminate the need of ullage (see this thread), but NK and some othey guys told me about the bladder thing... I still asked them if it's only suitable for small sized tank...

[eggrobin]

TBH I was not convinced that pressurizing can eliminate the need of ullage (see this thread), but NK and some othey guys told me about the bladder thing... I still asked them if it's only suitable for small sized tank...

It seems you got it right originally: you *need* ullage thrust for anything other than small-capacity tanks (the propellant is in a bladder by the way, not the other way around). It's a good thing you don't need ullage thrust for RCS, otherwise you'd need to light an SRB in order to to enable fine attitude control...

The exception is low-thrust stuff, where you can use surface tension tanks. You'd have to tweak the ullage simulation for those though, as they settle in zero g but are messed up by any acceleration. Apparently, these are widely used. The Astrium site seems to confirm they're used in quite a few spacecraft: Astra 1K, Insat-SE, Astra 1M, Amazonas 2, Arabsat 5B, Astra 1N, Astra 2E-F, Astra 5B, Artemis, Arabsat 2, Cesasat, Eutelsat W24, Arabsat BSS, Thaicom 3, Sinosat, Sirius, GEII, HotBird, Sircal, Globalstar, Theos, Pleiades, RocSat, Cosmo/SkyMed, Aeolus, BepiColombo, AMOS-3, TV-Sat, TDF, Tele-X, Italsat, DFS Kopernikus, Eutelsat-2, Turksat, Nahuel, Insat-2A to 2D, the ATV...

EDIT: for surface tension tanks, I guess you want to check that the radial and vertical ranges of the bubble are mostly in the middle, in which case you can feed from tanks marked as surface tension (the surface tension flag needs to be implemented on the MFS/RF side, like the current pressurised one of course).

EDIT2: This stuff is pretty reliable...

Nahuel 1A was a Spacebus 2000NG satellite manufactured by Aérospatiale in Cannes-Mandelieu and launched on January 30, 1997 [...] It was successfully reorbited in June 2010, when most of the on-board propellant depleted, using the remaining propellant and blowdown helium still stored in the propellant tanks.

EDIT3: Actually, I'm not sure pressurised fuel tanks are interesting to model (you *need* a pressurised tank for a pressure-fed engine, but since it's an engine property, maybe we can just abstract it out of the tank, much like we ignore the helium used to fill the ullage space in non-pressurised tanks, e.g., on Saturn V), perhaps the following classification might make sense;

- bladder (no ullage constraints to feed from it, max. volume a few 100 L)

- surface tension (can only feed from it at very low accelerations)

- normal (can feed from it under the current ullage conditions)

Where only pressure-fed engines can feed from bladder and surface tension tanks.

EDIT4: Of course things would have to be tuned so that starting an AJ-10 from a bladder or a surface tension tank and then feeding from a normal tank isn't practical. Perhaps only RCS thrusters should be able to feed from the bladder and surface tension tanks. In any case, there should be some ullage simulation in RCS thrusters in case they feed from surface tension tanks (which they often do).

Edited January 28, 2014 by eggrobin

[Agathorn]

So what is a typical ascent profile for a heavy launch vehicle designed to put a payload directly into GTO? Is it more vertical, to a higher altitude before going horizontal?

I've been trying to find examples of flight profiles on Google for different types of launches but this information is either not present, or i'm just not googling well enough.

[Scripto23]

ferram posted a pretty good reply to a similar question here . Though I generally use mechjeb for ascents and haven't really found the optimal input numbers for that yet.

[Agathorn]

It depends a lot on your vehicle's design, but here are some guidelines that I've worked with:

Initial TWR 1.2: Vertical until 100 m/s, ~2-5 degree initial pitch, follow prograde (SLS w/ Pyrios Boosters, Saturn V)

Initial TWR 1.6: Vertical until 50 m/s, 5 degree initial pitch, follow prograde (Delta II 7925)

Try to hit 1 km/s when your velocity vector is headed down the 45 degree mark, usually out of the densest part of the atmosphere (somewhere above 20 km, but below 40 km).

Don't hit 1.5 km/s until you're above ~30 km. If you do, you're probably taking too shallow a trajectory or your initial TWR is too high. This won't waste fuel, but it does risk heating melting your rocket apart.

Look to have at least 2.5 km/s of velocity and an apoapsis of >90 km at first stage burnout if your second stage has an initial TWR of 0.9 and will provide most of the dV to orbit. If you're going to need to burn a complete third stage to get to orbit, make sure that your second stage has an initial 1.2 at this velocity.

You can get away with an initial TWR for a second stage (that gets into orbit) of 0.4 if your first stage burns out at ~4.5 km/s - 5 km/s. Generally, in this case you're sending something to another planet, the moon, or to GEO.

You want an orbit of ~190 km for lunar and interplanetary missions, and ~300 - 400 km if you're sending something to LEO. The higher apoapsis gives you mroe time to circularize.

Don't be afraid to burn upwards slightly and not follow prograde once you're out of the atmosphere. It can help buy you time to get extremely heavy payloads into space. Also, don't be afraid to circularize after apoapsis; most rockets do this actually, since the lower thrust engine allows the stage to weigh less and get more dV.

If you need practice getting into orbit, build a Titan II or a Falcon 9; both have abnormally high-thrust upper stages that will make getting into orbit easier, and then you can go for the lower-thrust upper-stage rockets where piloting is more difficult.

This is nice information, but i'm still curious about my initial query. Do launch vehicles place payloads directly into GTO, and if they do then do they fly a different ascent profile? OR do they just never doe this but instead put all payloads into LEO and let them get up from there?

[NathanKell]

I stand corrected on pressurized tanks; didn't realize just how small they had to be to use the bladders. HoneyFox, my apologies for leading you astray!

Agathorn: Given that the most efficient path to GEO is usually "launch to LEO but keep burning that upper stage past circularization" the trajectory won't be *much* different. It depends on your upper stage(s)'s TWR. If you're putting a GEO payload on a LEO launcher, and getting it off the ground with thrust augmentation, odds are your upper stage will be underpowered and you'll have to fly it up much higher to have time to get to orbital velocity before hitting the atmosphere again. If it's not underpowered, you can fly a normal LEO ascent; you will have time to hit orbital velocity before reentry.

It is always most efficient (AFAIK) to (on ascent) never lift your apogee above where you want your perigee to be. So if doing a 35,786km x 185km GTO, you want your initial apogee no higher than 185km. But given the above, you may need a higher initial apogee with a low-thrust upper stage (though you will doubtless still be burning while falling after apogee, as long as your perigee eventually rises above the atmosphere you're ok).

[Agathorn]

So they actually change out to a different second or third stage if they are putting the payload higher up?

(though you will doubtless still be burning while falling after apogee, as long as your perigee eventually rises above the atmosphere you're ok).

I had one the other day that literally flew through the atmosphere at about 80k, in fire, and then came out the other side into an orbit that gave me enough time to finalize it

[NathanKell]

They generally don't, actually: that's why I mention it. Hence the upper stage being underpowered. (Not that Centaur, e.g., is *ever* overpowered, but it's even more underpowered if it's lifting a satellite and apogee kick motor into GTO).

Heh. Good show.

[eggrobin]

NathanKell: What about surface tension tanks? It seems fun (from a gameplay perspective) to have to worry about ullage on large RCS tanks (especially since the conditions for stability are somewhat backwards from normal tanks). Ullage simulation would have to be integrated into the RCS (or altogether moved to the tanks) though. They aren't exactly a niche thing either, the list I wrote above included the ATV and BepiColombo, as well as a good number of satellites (admiteddly, they're mostly used on satellites for stationkeeping, which we don't need---yet. I'm slowly working on that.---but the ATV is another story).

[NathanKell]

They do sound interesting, yes. I really do need to make that replacement ModuleRCS I guess.

Also, "I'm slowly working on that" (!) Sounds intriguing!

[tygoo7]

Is there an engine ignitor config for AIES?