Laythe Orbit velocity, NEAR/FAR turbotjet limit

[KerikBalm]

So, basically, I'm planning my long term laythe mission, and wondering what sort of landers I should build, and what sort of orbital fuel depot I should deploy.

I'm wondering if I can get away with just liquid fuel and xenon gas....

One question thats been bugging me for a long time:

What exactly does FAR/NEAR do to airbreathing engines? I can't seem to get them much above 1700 m/s (still, its plenty for SSTO purposes).

I'd like to know how it adjust the thrust and velocity curves.

But that's sort of an aside from the main question:

The orbital velocity of low Laythe orbit....

Gravity: 4/5ths that of Kerbin

Radius: 5/6ths that of Kerbin

Its obviously going to be less than that of Kerbin, but not that far off...

a = v^2/r?

0.8 = v^2/ (5/6) -> 2/3 = v^2... v = 81.65%

Assuming Kerbin's orbit velocity is 2,300 m/s for low orbit (70 km), then Laythe's would be: 1877?

Did I do that right?

I guess it will be a little lower because the gravity will be a little weaker in laythe orbit vs Kerbin orbit (since as a ratio of height of atmosphere to the radius of the planet is a bit higher for Laythe)

So.. In stock, where you can easily exceed 2,000 m/s on jets alone, a laythe lander could have just jets, and either an ion engine for circularization, or even just some scoops that are shut and full of air?

80% atmosphere and 80% gravity should mean that landing speeds are the same, no? but given the lower orbital velocity, the AoA needed to climb will be lower.

For stock, this is even more important due to linear vs squared lift/drag equations

*80% lower speed needed to supply the needed lift for a given air density

*Less needed lift as you get even closer to orbital velocity

So, if I wanted a reusable(SSTO) lander for laythe, I should be able to get away with no oxidizer at all, right? Jets-> above orbital velocity.

Effective ISPs in the range of 1200*16 to 2500*16 = 19,200 to 40,000

Stored air or ions for circularization.... seems pretty sweet.

For NEAR.. I don't know if I can get away with no rockets...

Maybe with the reduced lift requirement, I can get to 1750?

Ions were buffed... maybe with the reduced thrust requirement, I can accelerate that last 150 m/s needed to get to orbit?

[Rocket Farmer]

I have never used near/far (as i play totally stock) and it's been too long since my last jet mission to Laythe to comment on the exact math although 1,870 seems about right.

The biggest issue I had was landing. I am a decent lander (can land on the runway with no issue) but I found the uneven terrain on Laythe very tricky to touch down on. Even picking a teasonably flat plain I found lots of humps and bumps that made it very tricky. Go try landing 5-6 times in the wilderness away from the flat space center to see if your SSTO can accommodate rough landing situations.

For my new Laythe mission om about to launch my SSTO has vertical landing capabilities. Basically after much testing the best method I have found are little engines midship pointed about 30 degrees down from forward (pointed down my usual glide path). As I am landing I can nose up to slow horizontal speed more or trim down to take out vertical. With a little practice and the brakes locked you can stick a landing without even rolling. 2 small tanks hold enough fuel for 3-4 landings as well so it doesn't add much to weight.

Best of luck.

[Kryxal]

The orbital speed for an object of relatively negligible mass is (GM/r)^.5

Note that r is from the center of the object the orbit is centered upon, and the value of GM is given in the wiki for all planets/moon.

Also note that you'll need to go FASTER than orbital velocity within atmosphere to exit it.

Edited September 20, 2014 by Kryxal

[Claw]

I believe FAR specifically reduces the stock jets capabilities. The basic jet and TurboJet are overpowered for what they are, so ferram reduced their capabilities. I don't know if NEAR followed suit.

The problem with that (in my opinion) is that the game does not come with a scramjet or ramjet part. So for now I'm happy to have an overpowered jet that fills that gap.

If you are using FAR, you simply aren't going to get the same performance out of then as you did in stock. Which is fine, but you'll have to design the rocket portion to match up with that.

Cheers,

-Claw

Edited September 20, 2014 by Claw

[KerikBalm]

Rocket Farmer: My previous missions on old KSP versions took this into account.. they weren't space planes, they were basically like my duna landers, except with a pair of turbojets. Land under parachutes, do a vertical takeoff and pitch over like a standard rocket ascent, but pitch over a bit more (relying not on lift, but thrust angled slightly down + being near orbital velocity).

I've been having good results with carefully placed parachutes to allow my smaller SSTOs to just pop chutes and land anywhere.

I'm still having trouble deciding if I'll do a conventional VTOL lander (as you'd use on the mun, except with parachutes and turbojets), or a spaceplane

Kryxal: Yea, I suppose I should just use those formulas, KSP doesn't mess up gravity the way it does light... solar panels produce too much energy, relatively speaking, at Jool, for instance

Stricktly speaking ,you don't need to go faster than orbital velocity to get out of the atmosphere, its easy enough to get a suborbital trajectory out of the atmosphere... but I get your point, but I don't need to go much faster in horizontal flight to pop out of the atmosphere (while having a PE that is above the ground, but still in the atmosphere)

Claw: Does it speciically nerf those specific parts (also, rapier) - or if I make any engine that uses intake air (ie, text editing of part files), will it be affected?

Or is it just an adjustment to parts that use the velocity curve?

I'm not complaining, even a scramjet IRL won't get a craft to even half of orbital velocity... whereas even with NEAR/FAR, we can still get over 70% of the way there (and still with ridiculous ISPs)

I just want to know precisely what it does "under the hood"

:/ I don't know if I should try to make a craft that can accelerate with ions through the last part, or to just stick a LV-N on it