[Q] Jet engine efficiency

[Aphox]

I'm just wondering if anyone knows how to properly use the jet engines. Their descriptions make me feel like they can get pretty high, but it seems like after I reach a certain point in altitude, I start to drop, whether I'm using the turbo or the regular ones. My questions really come down to what is the maximum altitude for both engines, how do the nacelles work, etc.

The turbo engine's description makes me think it could go really high, because of the part that says it's better in thin air environments, but once I get around 8000 meters, I start to drop and it chokes. I'm just confused and terrible at this game. Anybody have a definition of these parts?

Another thing I've noticed is the "OptimalFlow" when I right click the engine. It says 60.00, but the higher I get, the less efficiently the engine appears to operate. I'm not a rocket scientist yet, so I'd love to have someone explain all this, or give me a link to a guide that does that.

Edited September 4, 2012 by Aphox
more confusion!

[Serratus]

There is no "maximum". It's a gradient. When You fly, right-click on the engine and look at efficiency. as long as it's over 0.2, that engine is producing more thrust than it needs to cancel its own weight (that's a presumption I'm working on). Some designs can go as hight as 10Km or even higher. My standard alt. is ~7Km.

Optimal flow is about wind speed. Don't concern Yourself with it - I never do once I go over 5Km. Keep an eye on that efficiency.

[DjVip3rStrike]

yea the MAX height i have achieved with a jet engine was 15 k but you really need to use a rocket to get any higher

[vexx32]

It is perfectly possible to get to around 20km altitude, depending on the craft.

[Fendleton]

I generally only use turbojets, and they tend to become useless at a little over 17,000-18,000m. The general "fastest/best altitude" for my aircraft is between 15,800 and 16,500 meters. At that altitude, it's possible to (more or less) level off, let the engines blast the aircraft faster and faster, and get up to 550m/s for a near fully-loaded aircraft, increasing up past 850m/s as fuel burns away and drop-tanks fall off. With enough engines or flying skill (there are tricks to milk every last bit of speed out of an aircraft), that's the altitude you want to be at to get past 1K m/s.

The main trick lies in levelling off from a climb. For a long distance cruise you want to get up to cruising height as quickly as possible....levelling out too soon means lowered fuel efficiency due to a lower speed. Levelling out too LATE means you end up on a ballistic trajectory well above where you want to be (which turns into a descent, which you then need to cancel out before climbing up to the right altitude again).

[Good_Apollo]

I haven't been able to break 18k m yet and I've been doing nothing but making jets and such for the past week. Speed seems to be a factor, I was going 580 m/s when I was reaching 18,000m. My slower craft, at 150-250 m/s, can't get past 6-8k meters.

[Aphox]

I generally only use turbojets, and they tend to become useless at a little over 17,000-18,000m. The general "fastest/best altitude" for my aircraft is between 15,800 and 16,500 meters. At that altitude, it's possible to (more or less) level off, let the engines blast the aircraft faster and faster, and get up to 550m/s for a near fully-loaded aircraft, increasing up past 850m/s as fuel burns away and drop-tanks fall off. With enough engines or flying skill (there are tricks to milk every last bit of speed out of an aircraft), that's the altitude you want to be at to get past 1K m/s.

The main trick lies in levelling off from a climb. For a long distance cruise you want to get up to cruising height as quickly as possible....levelling out too soon means lowered fuel efficiency due to a lower speed. Levelling out too LATE means you end up on a ballistic trajectory well above where you want to be (which turns into a descent, which you then need to cancel out before climbing up to the right altitude again).

Yeah, I kinda just found this out. I got my jet, which is roughly based off the design of a 747 (pretty long, 4 engines) to around 13,600 meters and it seemed to hit it's maximum thrust, giving me 200 intake power and using fuel pretty slowly. If I went higher than about 16,000m, the efficiency dropped a bit and I lost a little speed. I didn't design the craft to jettison the fuel tanks so the fastest I got going was 650 m/s, but that's still pretty fast considering my previous flights maxed around 250 because I wasn't climbing high enough.

Would still like to know if the nacelle/radial engine mounts/fans/ram scoops have any significant effect though, and on which engines each works best.

[EndlessWaves]

yeah, efficiency depends on both speed (in any direction) and altitude, if you're going up to orbit then you'll notice jet engine efficiency will often increase again when you fire the rockets because of the faster speed.

[Serratus]

And so far fans/ram have no effect as well as engines 'body'. They are just place-holders for looks.