[0.25] Engine Ignitor (Workaround for some bugs V3.4.1: Aug.31)

[tygoo7]

Is there a tutorial on how to use this? I can't figure out how to.

[HoneyFox]

Is there a tutorial on how to use this? I can't figure out how to.

First, make sure you have Module Manager installed.

Second, make sure the plugin is installed.

If you are not using RealFuel mod, things are rather simple:

1. To ignite you may need certain resources. Normally you don't need to worry about it because either they are same as main propellants (to emulate hypergolic fuel) or they are carried with the engine itself already.

2. Some big engines like Mainsail or some KW/NP's heavy engines need external ignitor (you can check in part information panel to see if the ignitor type is "External"). The external ignitor is now integrated into the launch clamp. You just need to install the clamp as close as possible (or surface-attach if possible) to that engine. Such engine obviously can only be ignited when launched from pad and cannot be restarted.

3. Most engines (except those very small ones) need some acceleration to make fuel stably flow into pipes and pumps before they are to be ignited. You can use various ways to achieve that: RCS thrusters, small solid boosters, small auxiliary liquid engines that don't simulate ullage (as they are supposed to be pressure-fed) ...

4. Rocket's acceleration and rotate rates will affect fuel stability. e.g. Don't roll the rocket fast before a burn. Don't either roll it too fast during a burn (thrust can generate some acceleration which can compensate the centrifugal effect by the roll rate a bit), or you might get an ignition failure / a flame-out.

If you are using RealFuel, things might become a bit complicated.

You might find that some engines requires LiquidFuel+Oxidizer as ignitor resources (by mouse hovering on the engine in VAB/SPH) while using MMH+N2O4, LiquidFuel+LiquidOxygen or LiquidH2+LiquidOxygen as propellants. You need to add some small volume for LiquidFuel+Oxidizer using MFS' customize fuel tank capability to make it work.

Edited January 3, 2014 by HoneyFox

[J_Davis]

You need to add some small volume for LiquidFuel+Oxidizer using MFS' customize fuel tank capability to make it work.

The more daring can change the configurations for ignition to use realfuels.

[HoneyFox]

The more daring can change the configurations for ignition to use realfuels.

That's right. Though that will take quite a while... There're quite a lot of engine configs in RealFuels. I've just finished about three engines of them, each has 2~3 configs.

[J_Davis]

That's right. Though that will take quite a while... There're quite a lot of engine configs in RealFuels. I've just finished about three engines of them, each has 2~3 configs.

Yeah. It's quite 'fun'. I'm trying to rewrite the stockalikes for it atm.

BTW, Do you think it would be possible/fair to implement an alternative to ullaging, something akin to stirring the tanks to force the pressure up and get fuel into the line? Accidents during stirring not required.

[HoneyFox]

Yeah. It's quite 'fun'. I'm trying to rewrite the stockalikes for it atm.

You mean the RLA stockalikes or the engine config from MFS 3.3? Hope that you're working on the latter one, which i'm very looking forward to.

BTW, Do you think it would be possible/fair to implement an alternative to ullaging, something akin to stirring the tanks to force the pressure up and get fuel into the line? Accidents during stirring not required.

I don't get it. What do you mean by "stirring the tanks to force the pressure up"?

[J_Davis]

You mean the RLA stockalikes or the engine config from MFS 3.3? Hope that you're working on the latter one, which i'm very looking forward to.

The latter. I like things KSP sized, but with realistic problems. I'm a math major, I'm not afraid of some equations, but I'm also not an engineer, keep them small! XD

I don't get it. What do you mean by "stirring the tanks to force the pressure up"?

It was something done on Apollo until 14, to make H2 and O2 - cryogenic - flow better. They had heating elements and stirring fans in the tanks to warm and mix the stuff, which forced the gas out of the tank for use. That way, the H2 and O2 could essentially be their own ullage gasses and the need for ullaging was reduced. My thought was that it could be an option. We could 'stir the tanks' when in space to stabilize the fuel flow, as an alternative to the other ullage methods.

(As for the comment about accidents during stirring, they stopped doing this with Apollo 14 because they had a bit of trouble with it during the previous mission.)

[xZise]

Hi, I have two questions. First what is this auto-ignite? As this seems to be the same value as the temperature reading from the reentry mod I guess it is the temperature and if it is above the second I don't need an igniter?

The second question is how ullage exactly works. I'm using RealFuels with the stock alike preview by J_Davis which might make this more complicated. But once for example my main engine (while running at "full" throttle: thrust limiter to about 40%) cut of after I ditched the SRBs. So I guess the thrust wasn't enough so that the fuel was faster than the rocket which was slowing down due to atmospheric drag? I increased the thrust limiter and the subsequent starts were fine. But the weird part is the last stage: Over the course of the mission it was never unstable (luckily because if it would there was no ullage motor to fix that). Are some tanks "special" and which prevent them from becoming unstable? I guess some tanks must be like that because for example the ullage motors of Saturn V's third stage were powered by RCS which "should" have the same problem with any other liquid fuelled engine to get the fuel to the nozzle (SRB ullage motors have this problem obviously not).

But apart from that (and that J_Davis configuration doesn't support all features of your plugin yet (really looking forward to it)) it is a nice mod. For example the last stage has 24 ignitions and while I was doing the mission I almost used all of them. I really should have used RCS. What would really cool if there is a part which sprays sparks like they did for the Space Shuttle so you first start that and then your engines with it.

Fabian

[HoneyFox]

Hi, I have two questions. First what is this auto-ignite? As this seems to be the same value as the temperature reading from the reentry mod I guess it is the temperature and if it is above the second I don't need an igniter?

The second question is how ullage exactly works. I'm using RealFuels with the stock alike preview by J_Davis which might make this more complicated. But once for example my main engine (while running at "full" throttle: thrust limiter to about 40%) cut of after I ditched the SRBs. So I guess the thrust wasn't enough so that the fuel was faster than the rocket which was slowing down due to atmospheric drag? I increased the thrust limiter and the subsequent starts were fine. But the weird part is the last stage: Over the course of the mission it was never unstable (luckily because if it would there was no ullage motor to fix that). Are some tanks "special" and which prevent them from becoming unstable? I guess some tanks must be like that because for example the ullage motors of Saturn V's third stage were powered by RCS which "should" have the same problem with any other liquid fuelled engine to get the fuel to the nozzle (SRB ullage motors have this problem obviously not).

But apart from that (and that J_Davis configuration doesn't support all features of your plugin yet (really looking forward to it)) it is a nice mod. For example the last stage has 24 ignitions and while I was doing the mission I almost used all of them. I really should have used RCS. What would really cool if there is a part which sprays sparks like they did for the Space Shuttle so you first start that and then your engines with it.

Fabian

Hi.

1) yes. if the temperature is higher than that and you cutoff the engine, it will be in HIGH_TEMP state, before the temperature drops you can reignite without consuming ignitor / resources.

2) it will somehow simulate gas pocket distrubution in the tank. acceleration & rotate rates will affect it. So yes, if you are deaccelerating with prograde attitude due to aerodrag, it will spoil the fuel flow (they might stick to the top).

In next release, MFS + EI integration might give you pressurized tanks & pressure-fed engines. In current version, several engines (e.g. these stock small radial engines) are made to ignore ullage issue. they are best choices for multi-restart ullage motors. (RCS thrust might not be enough, and solid boosters can only work once obviously )

3) Umm, I'm not good at modeling at all. so for that eye-candy sparks-sprayer... well. plus that might be just fuel burner to burn these vented gasous fuel before launch instead of ignitor.

Edited January 10, 2014 by HoneyFox

[J_Davis]

So I guess the thrust wasn't enough so that the fuel was faster than the rocket which was slowing down due to atmospheric drag?

Yeah, that happens to me constantly too. DSG for sepratrons and the KW ullage motor.

HoneyFox, I was reading that a mere .0001g of acceleration for a second or two is enough to ullage a tank, how demanding is your simulation?

[xZise]

[...]HoneyFox, I was reading that a mere .0001g of acceleration for a second or two is enough to ullage a tank, how demanding is your simulation?

This may allow the usage of RCS to ullage a tank (which would be nice as you could ignore setting it to false).

By the way what is DSG?

[...]In current version, several engines (e.g. these stock small radial engines) are made to ignore ullage issue. they are best choices for multi-restart ullage motors. (RCS thrust might not be enough, and solid boosters can only work once obviously )[...]

Okay I was using the LV-909 and interestingly there was no "useUllageSimulation" set to false. Buuut in J_Davis setting it is false.

[...]3) Umm, I'm not good at modeling at all. so for that eye-candy sparks-sprayer... well. plus that might be just fuel burner to burn these vented gasous fuel before launch instead of ignitor.

Oh that might be, after I read yesterday that they flooded the engine bell of the Antares launch with nitrogen.

Fabian

Edited January 10, 2014 by xZise
fix quote tag

[TomatoSoup]

Weirdly, most of my rockets immediately get stuck at a ridiculously low thrust (~0.8kn for a mainsail, basically) when I max the throttle and then activate them. Shutting down and starting again, of course, makes them fail to ignite.

[xZise]

Okay I checked it ingame: Can you maybe show which engines don't simulate ullage?

[J_Davis]

Okay I checked it ingame: Can you maybe show which engines don't simulate ullage?

https://www.dropbox.com/s/4uowuavf1kvx2p5/Combined%20Calcs.xls

Look in there at the ignition settings.

BTW, DSG = Dank sei Gott which is what my German math professor would say when something worked out nice and easy, we used it as a QED when the proof was pretty, or as an exclamation of thanks that we were able to avert a step that would otherwise be very hard.

[xZise]

https://www.dropbox.com/s/4uowuavf1kvx2p5/Combined%20Calcs.xls

That might work when the player is using your settings. But I meant in the VAB in the part properties where the other Engine Ignitor properties are like how often is it restartable. In your xls: When the type is O it doesn't simulate ullage?

BTW, DSG = Dank sei Gott[...]

o.O I only know it the other way around (and then not for proofs).

And after trying to fly to the Mun I really would like a RCS ullaged tank

Fabian

Edited January 11, 2014 by xZise
unable to write proof

[J_Davis]

In your xls: When the type is O it doesn't simulate ullage?

Fabian

O and U+. I think saying it DSG instead of GSD was some dialect thing, I forget where he was from, just that he spoke German.

HoneyFox: Can you explain the xml configuration settings? I'm finding that it can take 8 minutes to ullage a tank using RCS, only to have it go to "Very Unstable" instantly when I turn it on. I'd like to change the settings to be more forgiving than that.

[HoneyFox]

Yeah, that happens to me constantly too. DSG for sepratrons and the KW ullage motor.

HoneyFox, I was reading that a mere .0001g of acceleration for a second or two is enough to ullage a tank, how demanding is your simulation?

I've read that 0.0001g acceleration too, but EI does demand much more than that. perhaps some coefficient (stored in the config.xml) tweaks are needed.

[HoneyFox]

Okay I was using the LV-909 and interestingly there was no "useUllageSimulation" set to false. Buuut in J_Davis setting it is false.

Fabian

Ah, that one, i wouldn't call that... small

Edited January 11, 2014 by HoneyFox

[HoneyFox]

Weirdly, most of my rockets immediately get stuck at a ridiculously low thrust (~0.8kn for a mainsail, basically) when I max the throttle and then activate them. Shutting down and starting again, of course, makes them fail to ignite.

If the acceleration is too small, it might be overrun by natural diffusion rate. (perhaps the rate is not forgiving enough)

And, plus, you cannot ignite the Mainsail without assistance from an external ignitor (integrated in launch clamp).

[HoneyFox]

Okay I checked it ingame: Can you maybe show which engines don't simulate ullage?

In the next release i will add some information about it, just like the ignitor resource requirement display in the current version (V3.1).

[HoneyFox]

HoneyFox: Can you explain the xml configuration settings? I'm finding that it can take 8 minutes to ullage a tank using RCS, only to have it go to "Very Unstable" instantly when I turn it on. I'd like to change the settings to be more forgiving than that.

Ok. The first three options are quite self-explanatory.

X means radial, Y means longitudinal.

NaturalDiffusion means, the air pocket will spread naturally with time.

TranslateAxial means accelerating forward/backward. this is the main factor for simulating ullage motors, it controls how fast the air pocket will move along the longitudinal axis.

TranslateSideway means accelerating up/down/left/right. Similar to above, but is not simulated well TBH.

RotateYawPitch, controls how much the centrifugal effect will make fuel move to top&bottom part of the fuel tank.

RotateRoll, controls how much the centrifugal effect will make fuel move to the side wall of the fuel tank.

So for a more forgiving ullage simulation, you can consider increasing the TranslateAxialY, this will reduce the acceleration time you need especially when using low thrust RCSs.

[NathanKell]

Also, just O is considered pressure fed (and ullagesim set to false) in my Calcs.xls. U+ is basically the turbopump-fed version of O.

[xZise]

In the next release i will add some information about it, just like the ignitor resource requirement display in the current version (V3.1).

That was exactly what I was thinking of.

O and U+.

Hmm strange. I looked in your XLS and the condition was if the type wasn't O it would set the simulation to true, and false otherwise.

Fabian

[TomatoSoup]

If the acceleration is too small, it might be overrun by natural diffusion rate. (perhaps the rate is not forgiving enough)

And, plus, you cannot ignite the Mainsail without assistance from an external ignitor (integrated in launch clamp).

There was a launchclamp attached to the very bottom of every tank that had a first stage engine.

[J_Davis]

I looked in your XLS and the condition was if the type wasn't O it would set the simulation to true, and false otherwise.

I think you're reading it backwards. My config definitely ignores ullage for O and U+. I am a bit more forgiving with stockalikes than NK is with realistic engines, as the U+ engines make good and reasonable transmunar insertion engines.