Probe to Europa low orbit under 80t

[Darthan]

The challenge is to send a probe to Europa low orbit (whatever SFS considers to be a low orbit, I used 20km) using a launcher of under 80t.

Single launch, the launcher must be under 80t.
Gravity assists allowed
Normal difficulty, default solar system only.
No ions
No acarii drives
No cheats
'Non-cheaty' BP editing allowed - no engine resizing (any dimension), no tank overfilling, no engine heat disable
No custom parts
Any custom textures
Mods allowed as per the Team Challenges rules i.e most of them apart from the teleporting mods.

I originally planned to use aerobreaking for the Jupiter capture. However, although it is possible, when testing I found out that it is more efficient to use the would be heatshield's weight in fuel instead.

My first atttempt was for a 100t launcher and ended up with 1343m/s dV left in Europa orbit. This attempt was for 80t and I still ended up with 1093m/s dV in Europa orbit, so there is scope for improvement!

The flight plan I used was:
Gravity assists from Venus and Earth. Only only needed one of each.
Jovian capture from the Jovian periapsis at 110km altitude, aiming to be just within Jupiter's SOI.
Target Europa's orbit at the apoapsis of the capture orbit.
Then target Europa low orbit.

Design screen and launchpad


Launch to LEO


Venus flyby


Earth flyby


Jupiter flyby and capture


Europa transfer orbit, capture and low orbit

 

[SpaceExplorer2008]

I managed it with a 77 ton launcher (total weight including the probe). I sent it on a direct trajectory to Jupiter and used gravity assists from Callisto, Ganymede and Europa itself. When was about to do the Europa orbital insertion burn, realized that wouldn't have enough fuel for low orbit. As I included solar panels on the probe for visual purposes, decided to place the probe on a collision course with Europa, so that one of the panels served as a "shield". The impact caused the probe to lose more than 300 meters of delta-V, thus being captured by Europa. It only took a few additional small/medium burns to enter a low 20 km orbit. In the end, the probe had 7.2% fuel remaining.
In total, I needed 10 gravitational assists from the Galilean moons. And the sacrifice of a solar panel was the salvation lmao

 

[Darthan]

That was a close one - and you managed it on mobile! I tried various gravity assist techniques when attempting this. I didn't have much success with the Jovian moons from a high eccentricity orbit. For my first attempt I used gravity assists from the Earth alone. That took a long time (both game time and real time) but was useful to practice gravity assists using the ANAIS mod to plan them. For that attempt the final gravity assist went too high so the aerobreak attempt wasn't enough to capture. As a result I attempted a powered deceleration while still close to Jupiter an found that not much delta-v was needed. That attempt needed a 100t launcher and ended up with 784m/s left at Europa LO.

The second test was Jupiter direct with aero breaking at Jupiter that resulted in 528m/s left at Europa LO. The third test was Jupiter direct without the aerobrake and taking the heatshields weight in fuel instead - 805.9m/s at Europa LO. Then I tried it with the classic Venus-Earth-Earth GA - 1343 m/s at Europa LO. All these were done with a 100t launcher.

Finally I tried reducing the mass of the launcher (and the probe carrier). I thought that 80t would only leave a very small margin. However, that resulted in 1093m/s at Europa LO. Rather that continue expermenting I decided to post the last attempt to give a challenge that should be beatable.

 

[SpaceExplorer2008]

Yes, I usually play on mobile (rarely on PC).
Next time I'll try with the Frontier engine, which is much more efficient in terms of fuel consumption. Will also try to use just an Earth assist, which only requires a burn at aphelion.

 

[Mario Hobbs]

Now I don't wan to sound vain, but I think I win. I didn't use any gravity assists, just a direct burn to jupiter and the oberth effect (and ANAIS), My rocket is 76.74 tons in total. Though mind you my probe was rather simple, and I may have saved weight by using fairings instead of separators but I've yet to check. My first and second stages are meant to get the rocket into orbit then the final stage pushes it to jupiter and europa orbit (Kolibri is the best engine) Rocket Link

 

[Darthan]

Now I don't wan to sound vain, but I think I win. I didn't use any gravity assists, just a direct burn to jupiter and the oberth effect (and ANAIS), My rocket is 76.74 tons in total.

I think I beat that one. This one is under 50t (49.63t) and used Kolibris as boosters!

The flight plan was:

1. A gravity assist from the Moon.
2. Two gravity assists from Earth.
3. An Oberth manouver just outside Jupiter's atmosphere to capture just inside Jupiter's SOI, resulting in the first half of a bi-elliptic to Europa.
4. The second half of a bi-ellipitic to Europa.
5. And finally a capture into Europa LO.

I ended up with 7.43% of fuel or 187.1 m/s dv remaining.

It could be possible to go lower. The Europa capture was somewhat expensive - there might be a way to use gravity assists from one or more Jovian moons after the Jupiter capture to slow the craft down before Europa capture.

Design screen and launchpad


Launch to LEO


Lunar gravity assist


Earth gravity assists and Jupiter encounter setup


Jupiter capture orbit to Europa

 

[floatingfuel]

I thought this one gonna be easy, turned out I was wrong.

Rocket, launchpad, and LEO. Decided to go direct to Jupiter. Devided the burn into two parts, so the 2nd stage could be dumped to Earth's atmosphere. Then the satellite went on a long journey to Jupiter. After capture burn, a flyby path to Callisto was set.

After several Callisto flybys, the satellite went further lowering its orbit to Europa level through Ganymede flybys.

The last Ganymede assist set the trajectory to Europa. Sequences of Europa flybys and raising the perijove was done, and finally, an opportunity to capture appeared.

The craft satellized in Low Europa Orbit, with barely any fuel left. Heart skipped few beats when doing the capture burn, ngl. I tried several path to be captured in Europa, but only this one worked.

 

[Darthan]

Well done! Also you managed it with 'cosmetic' parts.

I think using gravity assists to reach Jupiter first helps a lot - that is how I managed the 50t attempt. I've since tried 33t (in order use a valiant without boosters) using both gravity assists to reach Jupiter and gravity assists from the Jovian moons but was 100m/s short.

 

[floatingfuel]

Well done! Also you managed it with 'cosmetic' parts.

I think using gravity assists to reach Jupiter first helps a lot - that is how I managed the 50t attempt. I've since tried 33t (in order use a valiant without boosters) using both gravity assists to reach Jupiter and gravity assists from the Jovian moons but was 100m/s short.

Thanks!

Yep, VEEGA or any assist saves dV quite a lot. If I did that, the margin would be higher.

Do you use asparagus staging for the 33T?

 

[Darthan]

Thanks!

Yep, VEEGA or any assist saves dV quite a lot. If I did that, the margin would be higher.

Do you use asparagus staging for the 33T?

"asparagus staging" ???

This is the design screen of the test:

The probe had to be off-center to line up its COM and keep the 3rd stage from spinning.

 

[floatingfuel]

From what I understand, Asparagus Staging is staging just the fuel tanks. Take a look here, courtesy of Altaïr. At the final stage, after the last Frontier Engine dropped, it's just a game of refilling the core tank after a burn and dropping the empty ones. So no extra dry mass from unused engine.

Please CMIIW if there's inaccuracy of my description on Asparagus Staging

 

[Axiom]

Take a look here, courtesy of Altaïr

Well technically that would be called breadcrumb staging, Asparagus staging is when all the boosters crossfeed into the next booster and they drop off seqentially leaving the other boosters full of fuel

 

[floatingfuel]

Well technically that would be called breadcrumb staging, Asparagus staging is when all the boosters crossfeed into the next booster and they drop off seqentially leaving the other boosters full of fuel

Thanks for the correction. So, I guess it's impossible in SFS beyond 2 booster/ stages then..

 

[Axiom]

Thanks for the correction. So, I guess it's impossible in SFS beyond 2 booster/ stages then..

Until fuel line get released

 

[Astro826]

Thanks for the correction. So, I guess it's impossible in SFS beyond 2 booster/ stages then..

I've done it with three stages at once, by juggling between fueling the second stage and the third stage in my 199 ton Voyager Quest. It did complicate an already precise ascent. Theoretically it could be done with as many stages as you want if their total fuel consumption is lower than the fuel transfer speed, but this would get very difficult with more than a couple and more fuel consumption. On very large rockets, you can try to work in the Mercury Atlas engine base which is fuel lines. I did this on my max payload Atlas/kiloton challenge.

 

[Darthan]

Under 33t to Europa LO: Part 1

I managed it! Using 'breadcrumb' stageing to provide a little extra fuel and using gravity assists from Callisto and Ganymede rather than only Europa I managed it with 173m/s of fuel remaining. The trajectory involved:

1. A gravity assist from the Moon.
2. 5 gravity assists from Earth (plus one lucky gravity assist from the Moon)
3. Jupiter capture from a close Jupiter flyby.
4. 4 Gravity assists from Callisto
5. 2 Gravity assists from Ganymede
6. Europa capture.

If I had followed ANAIS's plan for a Europa capture into a retrograde orbit I might have made it with 295m/s of fuel remaining, but I adjusted the trajectory for a prograde Europa orbit instead.

Lets see if Astro826 can beat that!

Design Screen and Launchpad


Launch and LEO


Moon GA


Earth GAs


Jupiter Capture


Callisto GAs

 

[Darthan]

Under 33t to Europa LO: Part 2

Ganymede GAs
21..22

To Europa
23..25

--------

Well technically that would be called breadcrumb staging, Asparagus staging is when all the boosters crossfeed into the next booster and they drop off seqentially leaving the other boosters full of fuel

Thanks for the correction. So, I guess it's impossible in SFS beyond 2 booster/ stages then..

Until fuel line get released

There is a 'Fuel Port' in PicoSpace Industries' Utility Pack that can balance fuel between two tanks. With multiple fuel ports it might be possible to work out how to do 'asparagus' staging.

 

[floatingfuel]

Amazing! The record is now far below the original requirement .

 

[Altaïr]

It's been a long time I haven't been to Jupiter, so I decided to give it a go. Actually I'm not even sure I already used ANAIS in the Jovian system...
I was too lazy to try making an optimal rocket, so I made a quick one:

Reaching orbit is a formality...


Of course, the next step is following the VEEGA path... I COULD aim for the Moon and chain 8 LEGA (Lunar Earth Gravity Assist) to make it more efficient. I could TOTALLY do it. But I preferred to keep things simple.


After a little patience, I finally encounter Jupiter:


Then the plan is the following: chain several Callisto gravity assists to lower my orbit to Europa level:


Then after my last Callisto assist, the first encounter with Europa is planned:


Nice view...

Honestly I could easily satellize myself directly, given my current speed and my delta-V.

After a few V-leveraging passes...


Europa orbit is reached!

That was easy to be honest. Let's land Snoot!

To be honest, with all that delta-V remaining I could bring back to Earth... Better like that, the last time I sent Snoot on another planet without planning to bring him back there were some riots...

 

[floatingfuel]

Snooty is back! It's interesting that you didn't use Ganymede for assists.

Also, I like the decoration. Is it another fairing trick?

 

[Altaïr]

Snooty is back! It's interesting that you didn't use Ganymede for assists.

Also, I like the decoration. Is it another fairing trick?

My reasoning was that using Ganymede would have lowered my orbit too much, so it was more interesting to use Callisto.
The decoration are made through a texture pack, that was me playing with Gimp once ago

 

[Darthan]

That was easy to be honest. Let's land Snoot!
View attachment 122527 View attachment 122528
To be honest, with all that delta-V remaining I could bring back to Earth... Better like that, the last time I sent Snoot on another planet without planning to bring him back there were some riots...

Well done! You had more delta v at Europa LO than my original mission and used a heavier capsule rather than a probe as well.

I think I made the original challenge a bit too easy. My best attempt so far was with a 33t launcher.

 

[ilikespace]

My reasoning was that using Ganymede would have lowered my orbit too much, so it was more interesting to use Callisto.
The decoration are made through a texture pack, that was me playing with Gimp once ago

You know what to do...

 

[Altaïr]

Well done! You had more delta v at Europa LO than my original mission and used a heavier capsule rather than a probe as well.

I think I made the original challenge a bit too easy. My best attempt so far was with a 33t launcher.

Thanks. Honestly I was too lazy to design an optimal launcher, I just built the biggest I could (Though it's probably not optimal in terms of design either, it proved to be very draggy).
33 tons will be hard to beat though...

You know what to do...
View attachment 122580

It's ok, we're still far from Christmas. And he can come back by himself this time