Titan ascent profile

[RedKraken]

http://imgur.com/a/vN9UM

(Realism Overhaul, KSP v1.1.3)

An ascent from Titans surface to a 650 km orbit (~1660 m/s)
This profile uses about 3520m/s with a liftoff twr 1.57
Yes the dv maps suggest a solid 7600m/s. 

The vehicle is 42t powered by a 100kN methalox engine with isp 320s (sl) , 360s (vac)
It takes about 25 minutes real time.

The first 40km is soup : 
at surface 1.45atmos. density 5.52 kg/m3 
at 40k     0.18atmos. density 0.86 kg/m3 
at 100k    0.01atmos. density 0.03 kg/m3 
Gravity is very low 0.14g. or 1.356 m/s2
ie the moon with an earth-style atmosphere (of extremely cold nitrogen).

Go vertical, and stay vertical until the turn.
Off-vertical prograde produces a lot of drag.
100% thrust at liftoff to 120m/s.
Hold velocity at ~120m/s for a while.
Drag losses are reported by FAR.
Atmospheric pressure and density reported by MJ/KER.

Keep drag (in kN) about 10% of gravity losses (craft mass * 1.356)
I used MJ to limit acceleration to ~1.4 m/s2 to keep from speeding up.

You can slowly increase velocity to keep the drag losses constant at 10%

At 70km, grav turn east to gain orbital velocity.
Stay prograde on the remainder of your turn using throttle. 
Burn an ap up to 630km
Any angle of attack will drag at higher speeds.
Circularise at ap. You should only need about 800 m/s.

Your stage should be built tall and thin like an atmospheric rocket.
You should use fairings.
You need fins at the base to prevent fliping out.
Jettison landing legs and any draggy bits (isru) at launch.
RCS made is not very effective down low, but very handy for the turn and the coast to ap.

You dont need more than twr 1.5 for your ascent stage.
Most of the ascent (15minutes) you will be throttled back to keep your drag constant.
 

Edited October 25, 2016 by RedKraken

[UnusualAttitude]

Very interesting. Thanks for posting this.

Now I'll have to run a simulation with my Mars shuttle to see if it could be re-used on Titan (it has more than enough delta-v, but it is much less aerodynamic). 

[RedKraken]

heh ... my first ITS model ( the "Eva Green" )  was flipping off the deck at titan.

Going too fast. Lots of drag. Not enough fins.

A 2100t ITS needs only ~400t of thrust to ascend titan. The three sl raptors throttled 40-50%

Edited October 24, 2016 by RedKraken

[RedKraken]

Aerobraking into Titan is a real treat. So soft and friendly even at 7km/s. Pe 150km for 2t or 200t. Its like the softest glove in the system.

Edited October 24, 2016 by RedKraken

[RedKraken]

ITS ascent from Titan.

http://imgur.com/a/NOKG9

2200t at liftoff. 3444m/s to orbit

[Nuke]

make the first stage a prop job.

[RedKraken]

A mothership ascent?......sure give it a try.

I've seen a balloon launch suggested for Titan.

KerikBalm suggested air-augumented rockets in KAL9000's titan sample return thread.

http://forum.kerbalspaceprogram.com/index.php?/topic/150231-titan-sample-return-concept/

 

We are down to minimising 1500-2000 m/s required for the soup part of the ascent up to 70km. (For me ~90% gravity losses, 10% drag)

At 70km,  we have to pay the 2000 m/s to orbit price regardless of what technique we use.

This second part is roughly the same as a Ganymede ascent....(pointed out by KerikBalm).

[Nuke]

i was thinking something like the roton. seems a direct rocket would be rather inefficient in that soupy atmo. instead do a slow controlled climb out to where atmospheric pressure is more earth like. eject your rotor, and continue on rocket power from that point.

Edited October 27, 2016 by Nuke

[RedKraken]

On an 9.8m/s^2 planet, 50km of soup would be a massive problem. Venus?

On a 1.35m/s^2 moon, its not.

You can take your time. You can pack a tiny engine, and idle for a good 30% of the ascent dv cost. 

Once u are siting just under the terminal velocity, u are barely siping the gas.

I'm using barely 800 m/s to get up to 70km. Out of a total of 3500.

Then a stock standard grav turn for about 2700. 2200 may be the limit here.

Low grav plus atmos is so good for areocapture, its a shame there are not more moons like titan.

Edited October 27, 2016 by RedKraken

[RedKraken]

Huygens EDL makes for interesting reading : http://www.nature.com/nature/journal/v438/n7069/pdf/nature04347.pdf

Wind sheer (100m/s) at 60-80km from a big thermal gradient. Just at the end of the soup.

These will incur some extra drag/steering losses....not modelled in RSS.

The temp goes from 140K (80km) down to 74K (60km). And back up to 90K at the surface.

West to east winds (130m/s) above 120km for a slight assist to orbit.

More detail and nicer graphs : http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.458.108&rep=rep1&type=pdf