Jupiter's Moons Challenge (in 1.4)

[Asgad]

Well done! I always enjoy how seemingly effortless you use the swing-bys (or Altaïr-swing, as we should call them).

 

[Altaïr]

Haha, thanks!
But I didn't invent that technique, I just copied it
Actually, this requires a lot of practice and precision. A small error can lead to a totally different trajectory. But that's how I like spaceflight: being precise, smart, and letting the gravity work for me instead of brute-forcing

 

[Asgad]

Well, you may say it's not rocket science... but it is!

 

[TtTOtW]

Well done! It is amazing how the gravity that's supposed to pull you in actually makes inward movement harder. @Altaïr does only Europa have an atmosphere? And is it useful for parachutes?

 

[Altaïr]

Well done! It is amazing how the gravity that's supposed to pull you in actually makes inward movement harder. @Altaïr does only Europa have an atmosphere? And is it useful for parachutes?

No, the atmosphere on Europa is only a visual effect, it generates no drag. Actually Europa is famous for its cryovolcanoes, that eject thin ice particles in suspension around it. That's not technically an atmosphere, but this is what generates that glowing effect.

 

[Aiden]

Yes, I thought about the ion engines, and I will surely use them in a first time, but I'm pretty sure this won't be difficult indeed. The real challenge is to do it with combustion engines only

You can do it

 

[Altaïr]

You can do it

Haha, I'll try but this will be hard.
Even landing on a single moon and coming back is not that easy. So, all 4 moons in a single launch... Ouch

 

[s.victor.q]

And if you are interested, some shots during the mission.

Good job. But the designs wasn't realistic.

 

[TtTOtW]

You could replace the unrealistic parts by using pad assembly

@s.victor.q he knows

 

[Altaïr]

I finally found a way to complete that challenge with combustion engines only!
Of course, as the rocket will have a limited capacity, that implies that I'll have to make a lot of maneuvers to save as much fuel as possible. But with an optimized design and a good trajectory, this is... surprisingly easy in practice
I also played with an additional constraint, which is not to left any debris in space. All debris shall at least be put on a reentry trajectory so that drag deorbits them.

@8bitCosmonaut if you want to do that mission with a realistic design, you can use this as a basis and improve the launcher so that it has a better look

So here we go:

After the booster phase, the ship quickly reaches LEO:

The main stage used a lot of fuel for this, as expected. That's why I made a separate fuel reserve. Now it's empty, I separate it, put it on a reentry trajectory, and redock the propeller with the payload:

Much better now: space is kept clean, but above that, I won't have to propell that dead weight further.
Now, time to aim for Venus for a few gravity assists:

Now the main stage is empty. It's separated and its trajectory slightly modified so that it crashes on Venus. I won't need such power from now on. I've still not left the Earth's SOI, but the lander with its cargo is now on its own.

The rest of the trajectory is precalculated and only need a few adjustments:


I finally enter Jupiter's SOI. Time to satellize:


That small ship can hardly brake with all that mass attached to it, but because of the massive Oberth effect from Jupiter it's far enough. My intention is only to left my ship on a very elongated ellipse, so this doesn't require so much delta-V.

To be continued...

 

[8BitCosmonaut]

I finally found a way to complete that challenge with combustion engines only!
Of course, as the rocket will have a limited capacity, that implies that I'll have to make a lot of maneuvers to save as much fuel as possible. But with an optimized design and a good trajectory, this is... surprisingly easy in practice
I also played with an additional constraint, which is not to left any debris in space. All debris shall at least be put on a reentry trajectory so that drag deorbits them.

@8bitCosmonaut if you want to do that mission with a realistic design, you can use this as a basis and improve the launcher so that it has a better look

So here we go:
View attachment 7752
After the booster phase, the ship quickly reaches LEO:
View attachment 7753
The main stage used a lot of fuel for this, as expected. That's why I made a separate fuel reserve. Now it's empty, I separate it, put it on a reentry trajectory, and redock the propeller with the payload:
View attachment 7754
Much better now: space is kept clean, but above that, I won't have to propell that dead weight further.
Now, time to aim for Venus for a few gravity assists:
View attachment 7756 View attachment 7755
Now the main stage is empty. It's separated and its trajectory slightly modified so that it crashes on Venus. I won't need such power from now on. I've still not left the Earth's SOI, but the lander with its cargo is now on its own.

The rest of the trajectory is precalculated and only need a few adjustments:
View attachment 7757 View attachment 7758 View attachment 7759

I finally enter Jupiter's SOI. Time to satellize:
View attachment 7760 View attachment 7761

That small ship can hardly brake with all that mass attached to it, but because of the massive Oberth effect from Jupiter it's far enough. My intention is only to left my ship on a very elongated ellipse, so this doesn't require so much delta-V.

To be continued...

Damn your gravity assist is much more efficient than mine. I used 3 times Mars gravity assist, and 3 times callisto gravity assist.

 

[8BitCosmonaut]

How exactly do you calculate the trajectory?

 

[TtTOtW]

Very exciting journey! I'm nervous about the fuel though.

 

[8BitCosmonaut]

I finally found a way to complete that challenge with combustion engines only!
Of course, as the rocket will have a limited capacity, that implies that I'll have to make a lot of maneuvers to save as much fuel as possible. But with an optimized design and a good trajectory, this is... surprisingly easy in practice
I also played with an additional constraint, which is not to left any debris in space. All debris shall at least be put on a reentry trajectory so that drag deorbits them.

@8bitCosmonaut if you want to do that mission with a realistic design, you can use this as a basis and improve the launcher so that it has a better look

So here we go:
View attachment 7752
After the booster phase, the ship quickly reaches LEO:
View attachment 7753
The main stage used a lot of fuel for this, as expected. That's why I made a separate fuel reserve. Now it's empty, I separate it, put it on a reentry trajectory, and redock the propeller with the payload:
View attachment 7754
Much better now: space is kept clean, but above that, I won't have to propell that dead weight further.
Now, time to aim for Venus for a few gravity assists:
View attachment 7756 View attachment 7755
Now the main stage is empty. It's separated and its trajectory slightly modified so that it crashes on Venus. I won't need such power from now on. I've still not left the Earth's SOI, but the lander with its cargo is now on its own.

The rest of the trajectory is precalculated and only need a few adjustments:
View attachment 7757 View attachment 7758 View attachment 7759

I finally enter Jupiter's SOI. Time to satellize:
View attachment 7760 View attachment 7761

That small ship can hardly brake with all that mass attached to it, but because of the massive Oberth effect from Jupiter it's far enough. My intention is only to left my ship on a very elongated ellipse, so this doesn't require so much delta-V.

To be continued...

For the part where you burn to enter jupiter's orbit, you should have used one of the moons' gravity to slow down, I saved a lot of fuel with that maneuver.

 

[8BitCosmonaut]

Before you ask, I haven't succeeded yet, my gravity assists to get to Jupiter are terrible, and ended up burning fuel to correct my trajectory to get into an encounter, probably because I eyeballed everything.

 

[Altaïr]

Ok, now I just let my ship reach the apoapsis, and it's time to unpack that cargo. Let's see what we have...

The cargo is compound of a reserve that will stay attached to the lander, and there are 2 refuellers which destination are Ganymede and Callisto. The refueller for Callisto also carries the parachute with it.
The lander with the reserve will first go to Io, which is the most demanding destination.
By the way, the fairings have been released after a slight trajectory modification so that they fall into Jupiter. Now, each module is on its trajectory:

This is a pretty cool scene
Each module will use its moon to reduce its orbit thanks to gravity assistance:

Those fly-by above Io are really amazing.

All at the same time, this is quickly a big mess
But I finally bring each module to its destination:

Now the mission can begin! First destination: Io, obviously.

Ok, now I lift off and join the reserve left in orbit. I transfer the remaining fuel into the lander and deorbits the reserve (no debris!).

The following part will be tricky: the closest refueller is on Ganymede, but I have to visit Europa first. Actually Europa is a light moon so it doesn't require so much delta-V. That's why I didn't put any refueller around Europa, and why I made the lander as light as possible (without separator/parachute) so that it has a chance.

So now, my destination is Europa:


To be continued...

 

[8BitCosmonaut]

I spoke too soon.

 

[TtTOtW]

I haven't been to Europa... Sounds nice

 

[8BitCosmonaut]

Altair probably won the challenge since his work is better than mine, mine didn't even work. I guess I will use his concept in my next large project which is to land on every planet, Venus, Mercury, Jupiter's moons, Mars and his moons.

 

[Altaïr]

Ok, now, with what's left of fuel, I have to encounter the refueler on Ganymede
This is doable, but I'm extremely short on fuel in the end!


Now, I can breathe and refill the lander at full capacity. I'll need this to handle Ganimede's high gravity.

Now I go back onto orbit, refill the lander with what's left of fuel (I just let 1% into the lander so that I can deorbit it), and let's go to my last destination:

Ok, I've finished, I just have to lift off and join the refueller. I can refill my ship a last time, and take the parachute with me. Again, the refueller is deorbited. That was the last debris, so I've complied with the "no debris" rule.
Well, unless I fail to come back to Earth and I become myself a debris

The return part is done with an Oberth maneuver:

Burning at the perijove allows to come back to Earth with very little fuel.
Finally...

Mission accomplished

 

[8BitCosmonaut]

 

[Danny Batten]

View attachment 7789 View attachment 7790 View attachment 7791

Hahaha XD

 

[Altaïr]

Damn your gravity assist is much more efficient than mine. I used 3 times Mars gravity assist, and 3 times callisto gravity assist.

This is probably more tedious with Mars indeed, as this planet is lighter, it won't be as efficient. The advantage is that Mars is slightly closer than Venus in terms of energy, but the difference is not huge at that point.
To establish a gravity assist path I use synchronized orbits to make sure I encounter a planet again. For example, the trajectory I have after the first Earth slingshot has a period such that my ship orbits twice when the Earth orbits 5 times. Those orbits are determined using the 3rd Kepler law. If you are interested I made a chart to calculate automatically all orbits with an integer ratio like this one.

 

[Altaïr]

For the part where you burn to enter jupiter's orbit, you should have used one of the moons' gravity to slow down, I saved a lot of fuel with that maneuver.

Oh, I'll have to try, thanks for the tip
Actually it doesn't cost much (I could also aerobrake either), around 100 m/s I believe.
I prefer to keep my apoapsis high because at this stage it's easy to raise the periapsis. Otherwise, exiting that gravity well is incredibly painful
Then the successive fly-by allow to do the rest

 

[Altaïr]

View attachment 7789 View attachment 7790 View attachment 7791

Lol, that's so true
That part was extremely short in fuel, but actually if I ran out of fuel I wasn't stuck: the refueller could still travel by itself to the lander.

Very exciting journey! I'm nervous about the fuel though.

Thank you
I've been nervous about that too, but the lander was as light as possible to maximize its capacity. I also tried to optimize that part as much as possible, because 1 more ton on Jupiter also means x more tons on the initial launcher, with x... not negligible

At least that leaves way to improve the launcher and make it bigger if necessary