Cheap rocket to Moho and Eeloo

[camacju]

So I'm trying to practice abuse of gravity assists and to do that I want to send a Kerbal to Eeloo and Moho for under 10000 funds.

The general plan:
-Have a solid fueled booster stage and a Terrier powered upper stage to send the spacecraft to orbit
-Have a Moho fuel tank, an Eeloo tank, and an Ant powered lander
-Use the booster to do most of a Mun transfer and use the Eeloo tanker's Spark engine to finish it (higher Isp than the Ant engine on the lander)

From here until Eve it's a pretty standard low energy Mun assist route.

-Mun assist to raise orbit into a resonance
-Second Mun assist to eject into a 6:5 resonance
-Six years later, encounter Kerbin and Mun again to get a 7:11 resonance, dropping orbit to Eve
-Seven years later, encounter Kerbin and Mun a third time, getting a plane change and fine tuning Eve encounter
-Eeloo tanker separates from the craft here
-Eeloo tank passes behind Eve, throwing it onto a Kerbin intercept
-Moho lander passes in front of Eve, lowering periapsis to Moho
-Moho lander gets Moho and Eve assists until its orbit is lower than Eve's orbit. At this point it performs a series of MESSENGER-style Moho assists to reduce its capture burn
-Eeloo tank gets Kerbin assists to Jool and captures around Jool using Tylo, waiting for a transfer window
-Eeloo tank transfers to Eeloo with a Tylo assist
-Moho lander lands on Moho and returns. It then performs another series of MESSENGER style assists for an Eve transfer
-Moho lander grabs assists from Eve and Kerbin to get to Jool, where it follows the same path to Eeloo
-Jeb lands on Eeloo and performs a Jool transfer
-After Kerbin, Eve, and Mun assists, Jeb splashes down at KSC

Part 1: Launch until Eeloo tank separation

Rocket is 9995 funds

I slightly stagger the solid rocket motors. If I fire them all at the same time, I reach too much speed in the lower atmosphere and things start burning. If I wait to fire the sustainer until the boosters are empty, I lose energy to gravity and drag. I end up firing the sustainer when the boosters are half empty, for a good balance between these two.

Gravity turn

I coast to the upper layers of the atmosphere to reduce drag and heat.

Circularization

Mun assists plotted

I already have the Kerbin-Mun assist plotted before my second Mun assist

This will bend my trajectory around retrograde while also giving a boost from Mun

Finally, I get a plane change off Kerbin and Mun, and plot my Eve encounter

Eeloo probe plots Kerbin encounters

Separation

 

Next: Eeloo probe goes to Jool, Moho lander tries to imitate MESSENGER

Edited February 9, 2021 by camacju

[camacju]

The Moho lander sets up another Eve encounter at the descending node between Eve and Moho for a plane change and to lower the orbit until it's just below Moho's orbit at this point

The two crafts swing around Eve in opposite directions

Eve assist - plane change and lowering orbit

Jool encounter after a couple of Kerbin assists

Capturing around Jool, plan is to use the moons of Jool to get into a good loitering orbit to wait for the Eeloo transfer window

Moho assists 2 and 3 plotted

Next: Waiting for Eeloo transfer and more Moho assists

Edited February 7, 2021 by camacju

[camacju]

Moho assists 4 and 5

Moho assist 6

Moho assists 7 and 8

Eeloo transfer

Eeloo capture

Moho assists 9 and 10. Now the orbit is really close to Moho's orbit, so I can capture on the next intersect.

450 m/s to capture, instead of 2000+ from a direct transfer. Much more efficient!

Moho capture

In Moho orbit with half the tanker's fuel left.

Landed on Moho. The lander was designed to land and return, but only with a jetpack-less Kerbal. So I had to get out and push for my deorbit burn, and my margin was much smaller than I had anticipated.

Moho ascent

Barely had enough fuel to get back to the fuel tank

Taking stock of fuel remaining. I have a lot more fuel than I expected from the Moho assists so I can do a direct Eve transfer. The FL-T200 will run out during the correction burns but I'll keep it since it has a solar panel on it.

Eve assist puts me onto another Eve intersect two years later, and gives a plane change also

Substantial correction burn so I intersect Kerbin's orbit at the descending node, where I'll do another plane change

Second Kerbin assist will put me onto an intercept with Jool

 

Next: Jool->Eeloo, rendezvous, landing

 

[camacju]

By the way, the route I took to Moho was based on something discovered by Chen-wan Yen in 1985. Yen used two Venus gravity assists, one to lower the orbit and one to get a plane change, followed by several Mercury assists and deep space maneuvers on the opposite side of the orbit. In this manner, the delta-v needed to capture around Mercury was substantially lessened. In effect, this technique multiplies the effectiveness of your deep space maneuvers while also splitting the long burn up to reduce gravity losses.

[camacju]

Using Tylo and Vall to capture around Jool

Tylo assist

Eeloo intercept

Rendezvous with tanker

In low Eeloo orbit

Descent

Landed on Eeloo!

Ascent

In orbit around Eeloo

Docked with fuel tanker

I got a very low cost Jool transfer but I had to wait 40 years. But what's 40 years in a >210 year mission?

Using Tylo to swing around retrograde and also get a plane change

I need to use almost all of my gravity assist from Tylo in order to do the plane change, so I can't go to Kerbin directly. Even if I could, I wouldn't, since the reentry is far too fast for the unshielded kerbal to survive. So I bleed off speed using an Ike assist followed by a Duna aerobrake - Duna's cold atmosphere is much easier to scrub velocity.

Surprisingly enough, there aren't any temperature gauges showing up.

Transfer from Duna to Kerbin

Reducing fuel consumption or speed is entirely unnecessary at this point - I have enough fuel for a propulsive capture. However, it can't hurt to do more gravity assists. A Mun assist reduces my velocity relative to Kerbin.

This means that I can capture purely through aerobraking, even if the Spark engine did get a little toasty.

Second aerobrake - still getting a bit hot. I'm pointing normal to scrub off velocity faster in the upper atmosphere. Pointing prograde will shield the kerbal behind the large fuel tank so I don't have to worry about heat here.

I attempt to land on the VAB but the lander is simply too heavy for just a kerbal parachute. Plus it's extremely hard to control.

In the end, I simply bail out and land on the KSC grounds.

 

We have landed on Moho, and then landed on Eeloo, and then come back to Kerbin, all with a rocket that costs less than 10000 funds. The mission used 42 gravity assists and took over 210 years. Good thing kerbals don't age

[Daedalus3000]

These orbital acrobatics are... impressive ... you could maybe even make a challenge to see if anyone can beat this (which would be difficult with the 42 gravity assists and all...).

[camacju]

Oh, I'm sure someone can beat this. I left a lot of room for error on this mission - I just packed in as much fuel as possible into the 10000 funds available.

[Daedalus3000]

Still... it’s impressive, it would also be fun to see this being done on other “courses” (like a grand tour or something). It’s just mind boggling to me that you can do a moho and eeloo mission in a single launch with only R&D level 1 tech.

[camacju]

??? This isn't level 1 tech. There's no tech restriction at all - only the funds restriction. With only level 1 tech and a 10000 fund limit? I don't think that's possible

[Daedalus3000]

I meant no R and D upgrade (like the building) sorry for the confusion.  Yeah doing it with just fleas though... Now that’s a challenge