Eve flyby and return

[Chequers]

Hi all,

Thanks for all of your help so far in my career - I'm really coming along in my ability to 'do stuff' in the Kerbin system. I've made eight return trips to various Mun biomes, and a few to Minmus.

But I've just received my first contract to visit another planet. Very exciting times. I'm to do a flyby of Eve, gather science, and return to Kerbin.

I'm confident I can use a transfer planner to figure out how to get an encounter with Eve... but I'm not sure what to think about in regards to returning - do I fling myself back into an orbit of Kerbol and work it out from there?

This will be a tiny unmanned probe - I have no quicksave or reverts enabled, so I can't trial and error. What is the general process of planning this mission? The contract requires the probe to return, so I can't just beam back the science data - although if all goes wrong, that will be the alternative.

[Superfluous J]

While you can't trial-and-error, you can fly by the seat of your pants.

Your Eve flyby, if close, will likely change your Sun orbit. if it's far out (past Gilly's orbit) then it won't alter it too much. The important thing to remember though is YOU get to decide how it alters your Sun orbit and by how much.

About halfway to Eve, the maneuver planner will likely place a maneuver node (or have you place one) to actually encounter Eve. Once you have that in place, fiddle with it, either with Precise Node or with the stock maneuver node widget, whichever you prefer (I've moved to using the latter exclusively). Use it to make tiny changes in the maneuver node to modify how you pass by Eve, and then zoom out and look at what your resultant Sun orbit does. Keep fiddling until you can see what passing by in different ways does, and then keep fiddling until you have a resultant Sun orbit that is similar to your current one in one important way: It passes really close to Kerbin's orbit, hopefully just touching it near Apoapsis before heading back down toward Eve's orbit.

Then after your flyby, you'll be in an orbit that goes up to Kerbin's orbit. Kerbin won't be there (unless you're ridiculously lucky) but now you can kind of pretend Kerbin is a space ship, the Sun is Kerbin, and your ship needs to do a typical rendezvous. Set up a maneuver node just past your encounter with Kerbin and see if burning prograde gets you an encounter on the next orbit. If you must, jump forward an orbit and check again.

It may take years to get back but what's time to a Kerbal?

[Vanamonde]

Why return at all? Just transmit the science and wave goodbye to the probe. It's what NASA does. 

[Superfluous J]

14 minutes ago, Vanamonde said:

Why return at all? Just transmit the science and wave goodbye to the probe. It's what NASA does. 

I assumed it was because the Explore contract tacked "Recover a vessel from a flyby of Eve" to the end, but it's by no means guaranteed.

That's the only reason I ever come back to Kerbin anymore.

[Vanamonde]

I don't recall getting a contract which called for a return from a fly-by. Interesting. 

[Chequers]

Thanks for the solid advice @5thHorseman; I'm going to spend some time in the VAB to see what I can pull together for this mission. Might share my design to get your thoughts, and I'll definitely take your recommendations on board

And phew.. skipping years is going to be interesting. So far, I've been maximising my use of time... rather than time-warping entire weeks, I'll spend the time it takes a ship to arrive at Minmus doing local missions, like surveys of Kerbin etc. Looks like I'll be getting really friendly with the time-warp hotkey.

Also, I'm not using any mods at all for this playthrough, so I'll only be using the manoeuvre planning nodes that come with vanilla. They've not let me down yet!

2 hours ago, Vanamonde said:

Why return at all? Just transmit the science and wave goodbye to the probe. It's what NASA does. 

I have to return to Kerbin as part of the contract, otherwise that's exactly what I'd have done. This really feels like a dramatic step in difficulty; it went from 'dock two vessels in orbit of Minmus' to 'go interplanetary' really fast. Still, nothing like a challenge to rise to, hey?

1 hour ago, Vanamonde said:

I don't recall getting a contract which called for a return from a fly-by. Interesting. 

Unless I'm misunderstanding it? *crosses fingers*

Edited March 31, 2020 by Chequers

[Chequers]

Alright, presenting the Leviticus I - the pioneer of interplanatary missions! 

The design is incredibly simple; according to my calculations, the first stage, powered by a RE-I5 Skipper should get me the majority of the way into a Kerbin orbit (rated @ 3,727m/s dV ASL), the second LV-909 'Terrier' stage will do the trans-Eve burn (rated @ 1,392m/s dV VAC), leaving the probe, powered by a Spark to carry out correction burns, and the trans-Kerbin burn after passing by Eve (rated @ 1,946m/s dV VAC). The probe core detaches from the main body, re-enters with heat-shield and parachute. In theory. On paper. 

Before I launch, is there anything I'm missing about interplanetary missions? Do I have enough antennas? Solar panels? Delta-V?

Apologies if I'm a bit excited for what might be a really bread-and-butter mission for you... reaching milestones for the first time in KSP is the biggest buzz for me!!

[Space Nerd]

The 2G antenna isn't quite enough to reach Kerbin from the other side of the sun, and the probe might not be controllable after main body separation because I don't think that probe core have enough stored EC.

Also the dv might be enough to capture into Kerbin orbit after returning.

Edited March 31, 2020 by Space Nerd

[Chequers]

24 minutes ago, Space Nerd said:

The 2G antenna isn't quite enough to reach Kerbin from the other side of the sun, and the probe might not be controllable after main body separation because I don't think that probe core have enough stored EC.

Also the dv might be enough to capture into Kerbin orbit after returning.

Great - so bigger antenna and more delta-v.

Back to the VAB!

[Space Nerd]

I mean your probe probably have enough dv to return to kerbin orbit after flyby, so you can have less dv and the mission still works.

[Chequers]

12 minutes ago, Space Nerd said:

I mean your probe probably have enough dv to return to kerbin orbit after flyby, so you can have less dv and the mission still works.

Ah, good to know. I'm happy to take the extra, in case I have to strong-arm a manoeuvre. This is my first time outside of Kerbin's SOI, so I want to have a little dV insurance.

[Superfluous J]

2 hours ago, Chequers said:

And phew.. skipping years is going to be interesting. So far, I've been maximising my use of time... rather than time-warping entire weeks, I'll spend the time it takes a ship to arrive at Minmus doing local missions, like surveys of Kerbin etc. Looks like I'll be getting really friendly with the time-warp hotkey.

You basically have 2 options when it comes to interplanetary missions.

1. Do things in between and never get there.
2. Time warp no matter how hard it hurts and explore the system.

[Chequers]

Just now, 5thHorseman said:

You basically have 2 options when it comes to interplanetary missions.

1. Do things in between and never get there.
2. Time warp no matter how hard it hurts and explore the system.

Absolutely!! If I have dreams of exploring other planets, that's the price! Especially as time doesn't really affect anything in game. 

[Superfluous J]

1 minute ago, Chequers said:

Especially as time doesn't really affect anything in game. 

It doesn't. The ONLY thing that really matters with time is transfer windows and the timings of encounters and burns. The rest is really skippable and there is no penalty in game. I agree though that it's hard to do.

I think that probe is usable though I agree it could use a bigger antenna. I'd suggest the HG55 and a level 2 tracking station (you probably have that already, as going interplanetary without patched conics and maneuver nodes is crazy hard), though I bet 2 DTS-M1s would do you fine in a pinch. Also note, with the HECS probe core you can still aim prograde and retrograde, and fire the engines full blast, without communications so not having connection isn't a death sentence.

As for returning, use up all your fuel slowing down so that when you run out, your periapsis is around 30-40km and your orbit is under Mun's, and you should be fine. If you trigger the parachute early (in space even), running out of charge isn't a big deal with the probe as it should be heavy on the side of the heat shield. One thing you could do, upgrade that heat shield to the next size up, and be 100% sure that not only will it be the heavy side, but it'll also protect the probe core from heat even if it's a bit wobbly coming down through the thicker atmosphere at high speed.

[Chequers]

I did a test flight today, to confirm my delta-v numbers, and ensure re-entry would work with the probe core and heat-shield.

• First stage got me to a 100km circularised orbit, with 853m/s to spare. I might switch the X200-32, for a X200-16. 
• I had ~ 1,300m/s in the second stage - is this enough, or too much for Eve transit? I used it to push my orbit right to the edge of Kerbin's SOI, and had about 450m/s dV remaining.
• The actual probe has 1,912m/s dV. Which seems a lot just to get back to Kerbin from a flyby of Eve - or is it? If I remove fuel there, I actually run out of surface space for experiments and the antenna!

Unfortunately, the probe did burn up on re-entry, so I'll take your advice on a bigger heat-shield. My latest Mun mission yielded enough science to unlock the QBE Probe Core... will its smaller profile might help keep everything tucked behind the heat shield.

Just waiting on a mission to return from Minmus - then I'll timewarp to a good transfer window... and it's go time!

 

Edited April 1, 2020 by Chequers

[Regor]

43 minutes ago, Chequers said:

I did a test flight today, to confirm my delta-v numbers, and ensure re-entry would work with the probe core and heat-shield.

• First stage got me to a 100km circularised orbit, with 853m/s to spare. I might switch the X200-32, for a X200-16. 
• I had ~ 1,300m/s in the second stage - is this enough, or too much for Eve transit? I used it to push my orbit right to the edge of Kerbin's SOI, and had about 450m/s dV remaining.
• The actual probe has 1,912m/s dV. Which seems a lot just to get back to Kerbin from a flyby of Eve - or is it? If I remove fuel there, I actually run out of surface space for experiments and the antenna!

Unfortunately, the probe did burn up on re-entry, so I'll take your advice on a bigger heat-shield. My latest Mun mission yielded enough science to unlock the QBE Probe Core... will its smaller profile might help keep everything tucked behind the heat shield.

Just waiting on a mission to return from Minmus - then I'll timewarp to a good transfer window... and it's go time!

 

1300 is good, because you might need to make a correction burn. AFAIK, an eve transfer (to the right periapsis) takes around 1020 m/s, but you may need to adjust your inclination. This might take 400m/s. So maybe 1500m/s for a bad eve transfer if you are unlucky. However, you have lots of fuel in the probe, so that's probably fine.

[Chequers]

2 hours ago, mabdi36 said:

1300 is good, because you might need to make a correction burn. AFAIK, an eve transfer (to the right periapsis) takes around 1020 m/s, but you may need to adjust your inclination. This might take 400m/s. So maybe 1500m/s for a bad eve transfer if you are unlucky. However, you have lots of fuel in the probe, so that's probably fine.

Thanks for the additional information - just redesigning the probe to feature a 1.25m heat-shield, then it's go time.

[Regor]

46 minutes ago, Chequers said:

Thanks for the additional information - just redesigning the probe to feature a 1.25m heat-shield, then it's go time.

Do keep us updated!

[Chequers]

Mission Accomplished!

What a rush! Thanks all for your help. Everything went smoothly and as planned; and I just had enough dV in the probe to capture at Kerbin.

The most challenging part was definitely setting up the trans-Kerbin burn after the Eve flyby - had to spend quite a lot of time playing with the manouvere node to get a Kerbin encounter - managed to get it within a single orbit of the Sun though.

Then it was hoping that the probe core didn't burn up on re-entry. No quicksaves or reverts - but @5thHorseman's idea to use a larger heat-shield worked wonderfully and I touched down on Kerbin soil, 1 year 355 days after I left... and now have a contract to orbit Eve. Typical!

Eve looks beautiful! Passing by at 5,000km - my first view of another planet.

My thoughts exactly!

Edited April 3, 2020 by Chequers

[Superfluous J]

2 hours ago, Chequers said:

my first view of another planet.

I love this. I know exactly how you feel.

I saw Jool in the tracking station many times. I saw pictures of it on the Internet. but for some reason when I was *actually there* the images my screen was showing me were special because I was *actually there*.

Edited April 3, 2020 by 5thHorseman

[Chequers]

1 minute ago, 5thHorseman said:

I love this. I know exactly how you feel.

I saw Jool in the tracking station many times. I saw pictures of it on the Internet. but for some reason when I was *actually there* the image my screen was showing me were special because I was *actually there*.

Totally. I didn't time-warp for a long time during the fly-by. I went and did a few other missions, just so I could keep coming back to just look at it.

Pretty strange that some of my favourite moments in this game are when I'm not actually doing anything. Just... watching.

 

[Superfluous J]

Oops dup post.

Edited April 3, 2020 by 5thHorseman

[Hotel26]

On 3/31/2020 at 5:44 PM, Superfluous J said:

You basically have 2 options when it comes to interplanetary missions.

1. Do things in between and never get there.
2. Time warp no matter how hard it hurts and explore the system.

I've thought a lot about a hybrid of the two.  Run multiple interplanetary missions simultaneously and multi-task, warping out all the dead time.  Interplanetary missions aren't 'incompatible' with each other the way that local 'crawl time' is.

I've also thought about having a 'save', Terra, for local SOI exploration and an Astra for interplanetary -- then applying a gene-splicing technique I've invented to copy Astra assets back into Terra to continue exploration all over the system simultaneously in 'crawl time'.

Might sound like a krakpot idea, I'm vaguely aware...

Edited April 25, 2020 by Hotel26