Planes Above 10 KM??

[DaveBowman]

Okay, I MUST be doing something wrong. I've always played KSP for rockets -- just getting into planes! 

Every time I get to 10 KM, I can't seem to climb any higher. My top speed is about 300 m/s, and as soon as my vertical speed is over 1 m/s my horizontal starts going down.

Whether I climb at 10 degrees or 45 to get to 10 KM, the problem is always the same. I'm getting this with every plane that I build, even stock planes! What could I be doing wrong? 

[FancyMouse]

You're probably just using the wrong jet engine. Basic jets can't produce much thrust above that altitude or above certain speed. You'll need ramjets like Whiplash or even Rapier.

[Snark]

Welcome to the forums!  Moving gameplay question over to Gameplay Questions.

Could you post a screenshot of your attempt?  There are a lot of possible things that could be wrong, it's really hard to give specific advice without seeing the ship.

[DaveBowman]

1 hour ago, FancyMouse said:

You're probably just using the wrong jet engine. Basic jets can't produce much thrust above that altitude or above certain speed. You'll need ramjets like Whiplash or even Rapier.

Hahaha ya I figured that out after trying the Rapier like 5 minutes after writing this post. That always seems to be the case  

Thanks for the response!!

[AeroGav]

Troubleshooting help - press f12 for aerodynamic forces display.  Look for the red arrows - drag - which is bad.

also right click on your engine you can see it's thrust tail off with altitude.

In Kerbal,  jet engines have two modifier curves to their basic power level.    Increasing altitude always results in less thrust, but the table in the config file determines what % of thrust it looses with each altitude.      The other modifier is speed.  Generally, thrust goes up with increasing speed, to a certain point, then tails off again.    

If you're new to aeroplanes it might be worth hitting google for "angle of attack",  "lift:drag ratio",   "parasite drag" and "lift induced drag",   things that will help you eke the most performance from your plane.

Generally

• plenty of wing area, if altitude is your goal.  best lift : drag occurs at 2 degrees AoA, which requires lots of wing 
• minimise frontal area, and the amount of radially attached parts
• there should be something pointy at the front and back end of your fuselages and nacelles - flat plate drag is awful, even on the back end !
• tail planes or canards are just like wings.   they too make a lot of drag at large deflection angles.  I'm a fan of spamming Advanced Canards, because their max deflection angle is only 10 degrees instead of 30.   You may need more than one pair to get enough control authority however.  If your plane has centre of mass way too far forward this can also cause excessive drag from these surfaces.

[RocketBlam]

The Panther is the first engine you get that is useful for higher altitudes, above 10k, and even then you need it in afterburner mode. Make sure you use the newest intake you can also, one per engine. The whiplash is even better, and can go higher and faster. The Wheesley is not suitable for above 10k, and that beginner, tiny engine can't even get above about 6k.

Edited March 25, 2016 by RocketBlam

[AeroGav]

20 hours ago, RocketBlam said:

 The Wheesley is not suitable for above 10k, and that beginner, tiny engine can't even get above about 6k.

Actually that "beginner, tiny" engine, aka. Juno is better for speed and altitude than the Wheesley and Goliath.   The first jet engines were pure turbojets,  the  Wheesley and Goliath are types of high bypass civil turbofans,  which trade some of the turbojet's fast and high capability for better efficiency and static thrust. 

As you point out, the Juno IS tiny, so you need at least 10 to see what even a mark 1 cockpit vehicle can do.     The Juno produces max thrust at mach 1.3,  which coincides nicely with the fact this is where supersonic drag coefficient is at its lowest too.    0.85 to 1.2 mach is the high drag transonic region,  and above mach 1.3  drag starts to go up again as you go faster and faster.  Obviously subsonic has lowest drag of all, but that's not what we're about is it?

I have built low tech spaceplanes with 12 Junos and 1 Terrier, for the lulz.   Could generally get up to 1.3 mach and 12km on the jets before firing the rocket.  Without the weight of the rocket and its fuel, you could probably fly a little higher on just the junos.  Not high enough for any of the high altitude research missions unfortunately.

**pps. these "spaceplanes" had no cargo and only barely made it to orbit.   they also jettison their landing gear and dump the jet engine pods when they loose power, so not the most practical or re-usable.

 

Agreed though, the Panther is streets ahead of anything you've seen before when you finally unlock it.    If you're not making sustained flights at 18km and Mach 2.5, you're doing something wrong.