Tips for my ascent profile

[leocrumb]

I was wondering about the markers people tend to use for their ascent which helps them hit a good profile

At the moment I am using a few which really help and the second part of my ascent to orbit is now really good. I want to improve the first part of my ascent tho ie when to start my gravity turn (altitude, speed etc).

The ones im using at the moment which work really well are

1. keep speed under 200 m/s under 10,000 alt

2. keep speed under 500 m/s under 30,000 alt

3. make sure I'm on a 45 degree angle by 20,000 (and time to apoapsis around 50s)

4. get horizontal around 50,000.

These work well but I'm wondering when u start the turn and at what rate (if I pitch too early, stability can be an issue, but too late and I lose a lot of DeltaV by being inefficient)

[heng]

not driving anything close to optimal myself, so no protips from me...

but you could just grab KER (it's a mod displaying a lot of useful infos) and try to be as close to 100% atmospheric efficiency as possible as soon as you can. that should work for the optimal speed values. since this value is drag dependent it differs from ship to ship.

rest sounds fine, but as i said, not a pro here

Edited May 29, 2015 by heng
typo

[leocrumb]

One thing that really helped is a Scott Manley tip to get that 50s to apoapse time at 45 degrees (absolute gold) (I have Kerbal engineer so I can watch this) then you can use pitch to get either side of the prograde marker to get it there. But my pre 20,000 ascent is not efficient enough.

[rkman]

~250m/s @ 5,000m

~350m/s @ 10,000m

~600m/s @ 20,000m

~1000m/s @ 30,000m (@ ~30 angle from horizon)

gravity turn @ ~85m/s (usually @ <1000m)

[cybersol]

For me, throttle is always max. After all, I put the engines on the rocket to USE them. Plus my starting TWR is 1.7-2.1 because time is not your friend when you are fighting gravity. Does that mean I have to build better rockets? Sure, but the main concepts are simple enough: more control, less drag.

With those TWR ratios and the ability to maintain control, I find the optimal ascent profile is something close to this:

Start turn around 1 km or 100 m/s

Aim for 45* mark at about 12.5 km

Aim for 22.5* mark at about 25 km

Horizontal by 50 km

[Ferdoni]

The KSP wiki gave this ascent profile (works fine for me)

[TABLE=class: wikitable]

[TR]

[TD]500 [/TD]

[TD] 105 [/TD]

[/TR]

[TR]

[TD] 1,000 [/TD]

[TD] 110 [/TD]

[/TR]

[TR]

[TD] 2,000 [/TD]

[TD] 120 [/TD]

[/TR]

[TR]

[TD] 3,000 [/TD]

[TD] 130 [/TD]

[/TR]

[TR]

[TD] 5,000 [/TD]

[TD] 160 [/TD]

[/TR]

[TR]

[TD] 6,000 [/TD]

[TD] 180 [/TD]

[/TR]

[TR]

[TD] 7,000 [/TD]

[TD] 200 [/TD]

[/TR]

[TR]

[TD] 8,000 [/TD]

[TD] 220 [/TD]

[/TR]

[TR]

[TD] 10,000 [/TD]

[TD] 260 (remember to start your turn!) [/TD]

[/TR]

[TR]

[TD] 13,000 [/TD]

[TD] 350 [/TD]

[/TR]

[TR]

[TD] 15,000 [/TD]

[TD] 425 [/TD]

[/TR]

[TR]

[TD] 16,000 [/TD]

[TD] 470 [/TD]

[/TR]

[TR]

[TD] 32,000 [/TD]

[TD] 2250 [/TD]

[/TR]

[/TABLE]

[cybersol]

Ferdoni, that is great information for version 0.90 or before, but it has absolutely nothing to do with 1.0+. Terminal velocity is much higher now. Indeed it so high that it's hard to hit it, and if you do then you will likely overheat very quickly.

[Ferdoni]

Ferdoni, that is great information for version 0.90 or before, but it has absolutely nothing to do with 1.0+. Terminal velocity is much higher now. Indeed it so high that it's hard to hit it, and if you do then you will likely overheat very quickly.

Mmmm you have a point there, seems I have to change my ascent profile than...

[eddiew]

I'm an SSTO person so I'll suggest something from that perspective. The below works fantastically for spaceplanes, and there seems to be no reason why rockets should fear going fast by 20km either...

1) get to 10km any way you like that doesn't involve orange flames happening.

2) point at 8-10 degrees and go full throttle.

3) reach 1300m/s or higher by 20km.

On a good day, you'll pass 18km before you overheat; above this altitude you'll start cooling off whatever speed you're at.

Drag is very high below 10km, and spaceplanes won't get much thrust beyond 20km, so that 10-20 band is where they have to do all their serious acceleration. While that's not the case for rockets, it gives some clue as to the thermal problems involved with speed at this altitude; namely they aren't that bad, and a steeper rocket ascent will give you even less time at this altitude.

(Steep angles of ascent are horribly inefficient for SSTOs and means you're either wasting air-breathing mode, or using more engines than you need, so resist the urge to do them even if they are fun. You want shallow ascents to get the absolute most out of your air breathing engines. A 5-10 degree pitch can get over 1400m/s out of rapiers on-air; don't waste that )

Edited May 29, 2015 by eddiew

[leocrumb]

~250m/s @ 5,000m

~350m/s @ 10,000m

~600m/s @ 20,000m

~1000m/s @ 30,000m (@ ~30 angle from horizon)

gravity turn @ ~85m/s (usually @ <1000m)

I like your numbers the 250 and 350 limit for 5 and 10k works better. Just tried them, still under atmospheric drag but keeps much more stable after the turn. Thanks

What kind of DV do u need. Im getting about 3900 to get to a 80km orbit.

Edited May 29, 2015 by leocrumb

[cybersol]

The way I posted above routinely gets 3300-3450 vacuum dV to orbit, because I pay less gravity tax. Plus each launch is quicker for my time.

Edited May 30, 2015 by cybersol

[Superfluous J]

I tip over around 50m/s, less than 5 degrees. I ignore my altitude and pay attention to 2 numbers from here on out Apoapsis and angle tilted over east. 90 is straight up, 0 is horizontal on the due east spot on the ball.

When I hit 2000m Ap, I go to 85 degrees. From there to Ap of 20, I go 5 degrees every 2000m. When my Ap is at 20km, I'll be pointing at the 40 degree mark on the navball.

Then I just slowly bring it down with the goal of hitting 30 degrees when my apoapsis is 30km, 20 degrees when it's 40km, 10 degrees when it's 45km, and dead horizontal from 50km onward.

Depending on the aerodynamics and TWR curve of my rocket, I usually get less than 3500m/s of vaccuum dV to orbit and that's good enough for me.

[Wakaleo]

That is a cool-looking craft, eddiew! And it's a great name for a craft that resembles the fearsome predator of the Cambrian seas.

[Pecan]

... The below works fantastically for ...

AIR BREATHING ENGINES.

Say it slowly: Spaceplane, rocket, Single Stage To Orbit, air breathing engine. They're all different, overlapping concepts. Saying SSTO=>Spaceplane=>Jets is just mashing so many different things together your advice doesn't even mean enough to be wrong.