Rocket only SSTO to Eeloo and back

[camacju]

The challenge was to make an entirely rocket based SSTO that launches vertically. I added another element of challenge which is that I only used 1.25m parts. This means that I can't get the same performance as if I used a Mammoth and a cluster of nuclear rockets, but this approach keeps part count and mass down.

The rocket consists of a Vector engine for Kerbin takeoff and landing, and two Nerv engines for everything else. Inside the fairing are a command seat, reaction wheel, battery, and a bunch of Mk 0 fuel tanks.

This rocket is very aerodynamic so I take a shallow ascent profile.

At 1500 m/s I shut off the Vector engine and let the Nervs continue. I'm not using all the oxidizer here because I need it for the landing back on Kerbin.

In Kerbin orbit

I use the same sequence of Mun assists that I always use for an Eve transfer. Mun assist brings me into an orbital resonance that gives me a better assist three orbits later, which brings me into an orbit that gives me a final assist 3/4 of an orbit later.

This flings me onto a 6:5 resonance with Kerbin, where I intersect Kerbin for another Mun assist, which drops my orbit down and gives me a plane change, where I get an intersection with Eve's orbit.

I don't have enough Eve relative velocity to do a Kerbin-Eve-Kerbin-Kerbin-Jool route. So I do a Kerbin assist, followed by another Eve assist, to get greater Kerbin relative velocity. This gives me a Kerbin assist that puts me onto an orbit intersecting Jool's orbit.

I need to intersect with Jool's orbit at the ascending node of Eeloo with Jool, but Jool is in the wrong place. So I swing by Kerbin one more time to adjust my orbital period.

My problem now is not too little energy, but too much energy. I have to eject from Jool in a nearly prograde direction in order to reduce my Eeloo relative velocity, but that would put me on an escape trajectory. Instead, I use a Laythe assist to bleed off velocity relative to Jool and also do a plane change to line up my descending node with Eeloo's apoapsis. Doing this reduces the capture burn significantly.

Laythe assist

Only 35 m/s to capture around Eeloo. That's quite good

In low Eeloo orbit, and I've got plenty of fuel to land and take off again.

This rocket is tall so landing was a bit of a challenge. I had to quickload a bunch of times.

Eventually, I found a flat enough place to touch down. The question is, is 1403 m/s enough to get home?

Eeloo ascent

In Eeloo orbit with 820 m/s remaining. This should be enough, as long as I remember to save enough liquid fuel for the powered landing on Kerbin.

Jool transfer. As you can see, I can't get a Kerbin transfer orbit directly from a Jool transfer. Instead, I use a Tylo assist to build up relative velocity to Jool. The problem with this is that I can't eject from Jool at the right angle.

Closeup of Tylo assist. 570 m/s left. I definitely have enough to make it home at this point so I accept a less than optimal correction burn.

I solve the problem of ejection angle by setting up a second Jool assist at a better angle.

Kerbin encounter plotted. I use Kerbin and Eve to slow down, and thanks to the double Jool assist I have more than enough energy to do so.

Using the body lift of the near empty fuel tanks to slow down

Terminal descent using the last of the oxidizer.

Landed back on Kerbin.

 

 

Edited March 5, 2021 by camacju