Highest jet only periapsis

[occar]

Since I was playing with the Machingbird Challenge again, I figured I'd make this slightly related challenge.

Rules:

1. Stock parts only except for as required below for control or viewing stats. (No propulsion other than air-fed jets!)

2. Mods allowed: Any auto piloting mods like Mechjeb (which also means flame-out assistance is ok) as well as informational (so that we can see your orbit stats)

3. Get in "orbit" (obviously you can't get your periapsis out of the atmosphere because jets require air)

3. Post proof of your highest periapsis.

Leaderboard

1. 62.50km - pinolallo

2. 62.00km - Kappa73

Here's an example of 49.28 km periapsis with a jet. It will go higher, but I didn't take pictures. It's a decent starting point though.

Edited May 8, 2013 by occar

[HoY]

That flight could have easily gotten into orbit with an Oscar b tank and ant engine lol. How many intakes is that for the single engine?

[occar]

That flight could have easily gotten into orbit with an Oscar b tank and ant engine lol. How many intakes is that for the single engine?

I'm not sure. I do have a variant of this design that uses two ion engines mounted mid way out the wings and it is trivial to take in to a stable orbit. You just extend the solar panels (which this model doesn't have) and fire up the ion engine each time it rises above 70km altitude. You switch back to jet the few times you dip below 69 km, and bam, orbit. The intakes mounted above and below the wings are because it isn't the most easy thing to correct the attitude of without power, and there are times that I've needed those to get the jet going again.

[HoY]

You have enough intakes to fire the jets at 69km??? That's got to be like 50-1 intakes per engine

[occar]

Fire is a relative term. The jet is providing something like 0.5kN thrust at that altitude (about like an ion engine) because the throttle is so low.

[Kerbies_are_my_Minions]

attempt #1: 131,708m

[occar]

Errr, that would be an apoapsis. Periapsis is the *lowest* point in the orbit, not the highest. You'll see in the example that the apoapsis was 285 km, so, at its highest, that ship was 285 km on jets alone, but the hard part is raising the periapsis. Taking off and going straight up like that gives you a negative periapsis.

[Kerbies_are_my_Minions]

oh. sorry. my brain isn't working today.

[Kappa73]

Here's my entry, periapsis of 62km. It was slowly going up each orbit too, but the flight already took really really long time and i got very bored heh =). Do you think it is a record of sorts, doing 240 million meters on a jet plane? =)

http://i.imgur.com/uZoWEVD.jpg"]

[occar]

Wow. 62 km....

That's impressive. I was expecting mid 50's. You also have an entry for the maching bird challenge there. (and beat my maching bird ship by 6 m/s!)

[mileshatem]

In theory, couldn't one raise his/her apoapsis enough to get a munar assist to a true orbit?

[Ninety-Three]

In theory, couldn't one raise his/her apoapsis enough to get a munar assist to a true orbit?

Without the use of infiniglide silliness, I don't think an air breathing craft can work up enough velocity in Kerbin's atmosphere to reach the Mun's SOI.

[Kappa73]

i believe that in the now lost machingbird challenge thread it was established that the max speed for jet engines was 2400 meters / second so no munar assists with jets.

[zarakon]

Turbojet engines are hard-limited to 2400 m/s I think, which is not enough to get to the Mun

[tavert]

It's in the part.cfg file under velocityCurve, the max surface speed at which the turbojet generates any thrust is 2400 m/s. If you somehow had infinite intakes with zero drag so you could get up to this speed purely on jets at the very top of the atmosphere (69078 m), your orbital speed would then be 2594.6 m/s (flying east). Using planet.determineOrbit from https://github.com/numerobis/KSP-scripts, that would give an orbit of 577738 by 69078 m. You're not escaping Kerbin or hitting the Mun's SOI with that. Would be interesting to run the numbers for Laythe though, see if getting back into a Jool orbit only on jets is possible...

[numerobis]

It's not, I checked a while ago You can't even quite escape Laythe SOI (but your orbit can be quite large!)

[occar]

It's in the part.cfg file under velocityCurve, the max surface speed at which the turbojet generates any thrust is 2400 m/s. If you somehow had infinite intakes with zero drag so you could get up to this speed purely on jets at the very top of the atmosphere (69078 m), your orbital speed would then be 2594.6 m/s (flying east). Using planet.determineOrbit from https://github.com/numerobis/KSP-scripts, that would give an orbit of 577738 by 69078 m. You're not escaping Kerbin or hitting the Mun's SOI with that. Would be interesting to run the numbers for Laythe though, see if getting back into a Jool orbit only on jets is possible...

Exactly why I think it's a neat idea for a challenge. As with Machingbird, we *know* there is a limit. The fun is getting as close as possible to it.

[mileshatem]

It's in the part.cfg file under velocityCurve, the max surface speed at which the turbojet generates any thrust is 2400 m/s. ...

Huh. Didn't realize there was a hard limit set for that. Now it all makes sense. Thanks!

[pinolallo]

Another try

62.5

click to enlarge

(I did the max speed at 5 min after takeoff)

Little more heavy bird.

Edited May 8, 2013 by pinolallo

[numerobis]

It actually would be interesting also to do the challenge on Laythe. Orbital speed is much lower, so it's hard to boost periapsis quite as much!