The Retro Solar Rescue

[Spricigo]

13 hours ago, ManEatingApe said:

So long probe core

there is a saying "the Devil is in the details"...

Congratulation on a devilish rescue.

[Cpt Kerbalkrunch]

On 5/6/2017 at 4:45 PM, MarvinKitFox said:

Conceptually, reasonably easy.

 

A 3.6 ton ion drive rescue ship (that's mass in high Kerbin orbit, about 1000km!)

Burn prograde with kerbin orbit, head out to the deeeeeeep reaches of space:  3600 m/s

Wait 9 years to get to apogee.

U-turn, 1830 m/s

9 years later, intercept Res-Q vehicle.

Intercept requires 4200 m/s

 

To return, you basically reverse the procedures..

4200 m/s prograde burn.

1830 u-turn at distant apogee

this bring you to an atmospheric meeting with Kerbin at mission time ~ 36 years, and a velocity of some 5.5km/s

As my vehicle is nothing more than a command chair on an octo, on an Ion Drive, I chose to use propulsive braking rather than aerodynamic breaking.

a messy 6000m/s of burn later, my pilot is safe in a 100x100 orbit around Kerbin.

 

I'm not sure I follow. Did your ship make it and you rescued Burbarry? If so, congrats. You'd definitely take the low-cost prize.

[Cpt Kerbalkrunch]

@Aetharan, go big or go home. I love it. Awesome ship. And a pretty sweet mission profile. Burbarry didn't even have a chance to lose weight before you got to him (on the contrary, he was probably stark raving mad by the time I got there). The little lander instead of a typical touchdown/splashdown was a nice touch. Overall, great mission. Membership in the Retro Rescuers Club is highly coveted. Welcome aboard.

[Spricigo]

6 minutes ago, Cpt Kerbalkrunch said:

I'm not sure I follow. Did your ship make it and you rescued Burbarry? If so, congrats. You'd definitely take the low-cost prize.

Since he started the post  with the word " Conceptually" I suspect may be just theory. Maybe he is working to bring this theory in practice.

But  a TWR around 0,1 will result in the long burns even longer. Something much easier to endure in theory than in practice. And there is the case of thing tha in practice dont follow the theory.  In result I want to see someone trying it even more.

 

[Aetharan]

@Cpt Kerbalkrunch Thanks for the praise, but I wasn't done yet!

@Physics Student  You think the Olympia was ginormous?  Behold...  the Kilamanjaro!

http://imgur.com/a/HuCK7

 

I managed to come within one day of cutting my mission time in half with this mission profile, and could probably have done better still if I'd actually been calculating more than eyeballing.  Still, I'm happy with this one, so don't expect a third entry from me today.

 

TL:DR version of the mission profile for those who don't want to go through the story in the album: Launch an oversized ship into LKO, lower orbit to intercept with the Goliath, reverse direction there instead of in orbit around Kerbin, pick Burberry up, turn around a second time at that lower altitude, lift back up to meet Kerbin, circularize, then deorbit and land wherever.  Mission ends at UT 159d 2:31.

Edited July 21, 2017 by Aetharan

[Clancy]

Rescue Complete!

I made a pretty simple attempt. Kind of a minimalist brute force method. No fancy gravity assists, just a chair, an Ion drive, lots of Xe and lots of patience.

I launched the whole thing into orbit on a Skipper and two Thumpers with a Poodle on the second stage. The ship itself has a command chair, a probe core, and an Ion Engine with the requisite batteries and solar panels to make it run. It carries enough Xe to make about 46,000m/s. Which was more than enough.

Once in orbit I set up a 10 hour (!) Ion burn to go into a retro solar orbit. I start with a Sun Pe of 600,000km (so nothing melts) Then adjust the Ap to intersect Burberry’s orbit. Once back at Ap, burn prograde to set up an intercept on the next pass. Once Burberry is safely in his seat, make another loooong burn to get back to and elliptical prograde orbit, make another sun dive to get back to Kerbin orbit, set up intercept on next pass. I didn’t do any crazy aerobraking except de-orbiting, I had plenty of fuel to slow down using the engine. Finally I detached the chair and dropped Burberry into the atmosphere with a heatshield and a parachute on his back. He landed pretty hard, but he survived, so I’ll take it.

After 1.5 years of waiting, 1.5 years in a spacesuit, getting irradiated by the sun, almost roasted to death twice, and landing with a 15 m/s face-plant in the middle of the desert, Burberry Kerman is home safe!

 

 

The Stats:

 

Total Mass: 57.6t

Total Cost: 216,352

Total Dv:  ~45,000 m/s

Total Time: 3 years, 59 days, 1 hour, 40 minutes

 

P.S. Now I’m kicking myself, if I had left out just a few grams of Xenon, I could have beaten @ManEatingApe‘s cost record!

[Cpt Kerbalkrunch]

14 hours ago, Aetharan said:

I managed to come within one day of cutting my mission time in half with this mission profile, and could probably have done better still if I'd actually been calculating more than eyeballing.  Still, I'm happy with this one, so don't expect a third entry from me today.

No third mission? I was sure if you made your ship a little bigger you could pick up Burbarry before he even left. 

Seriously, though, that was fantastic. Great mission.

[Cpt Kerbalkrunch]

9 hours ago, Clancy said:

Rescue Complete!

I made a pretty simple attempt. Kind of a minimalist brute force method. No fancy gravity assists, just a chair, an Ion drive, lots of Xe and lots of patience.

 

The Stats:

 

Total Mass: 57.6t

Total Cost: 216,352

Total Dv:  ~45,000 m/s

Total Time: 3 years, 59 days, 1 hour, 40 minutes

 

P.S. Now I’m kicking myself, if I had left out just a few grams of Xenon, I could have beaten @ManEatingApe‘s cost record!

Fantastic. Those solar pics you had were extremely cool (though not for Burbarry ). I especially loved the reentry. Evidently, Burbarry Kerman is the baddest Kerbal who ever lived. The guy survives years on end floating through space, a close flyby of the sun, and atmospheric reentry without a capsule. I've got my badge, but when does Burbarry get his Bad S?

Great mission, though. How you had the patience for those Ion burns is beyond me.

[jonny]

Burberry Kerman splashed down in the ocean tonight!!

After mastering the art of gravity assists, KSC was able to pull off a 103 years and 294 day long mission to rescue him. They even could have left a entire stage with a Kerbodyne S3-7200 tank (2944 m/s) at home.

The short story:

dV: 5219 m/s
Mission time: 103y 294d 05:36
Route: LKO - Eve - 2x Kerbin - Jool - 2x Eve - Jool - Retrosolar - 2x Eve - 9x Kerbin - Rendezvous - 4x Kerbin - 7x Eve - Jool - Prograde - Kerbin (Aerobraking) - Kerbin

The long story:  I will post the pictures tomorrow. Done

Spoiler

 

The first maneuver is finished, and the Eve flyby already fine tuned to intercept Kerbin.

2 Kerbin flyby's and 1 orbit later the Jool flyby was fine tuned to intercept Eve again.

It was very important to set up the the Eve flyby to miss Jool 1.5 orbits later, but intercept Eve 1 again.

Eve flyby #3 --> high velocity Jool intercept.

Jool will flip the solar orbit to retrograde.

after a ~300m/s push at Ap I got Eve flyby #4

a very standard maneuver to lower the Ap an rise the Pe

finally the Pe has the same hight as Butbarry's orbit.

~2950m/s after LKO

How hard can the trip back be?

Ok, same procedure but in reverse.

Many gravity assists later.

What the f....??? How can Jool give me that much energy? Didn't I came from a retrograde orbit? Okay, after a second thought, it is somehow logic. But what shall i do with all that energy? Didn't I challenge myself to use minimum delta-V?

Okay, do it Kerbal style!!

Sorry Burbarry, but this will save some years.

luckily the RCS thrusters survived.

 

 

Edited May 11, 2017 by jonny

[Human Person]

@jonny wow, I didn't believe it until I saw the detailed report.

you truly are a master of gravity assists. 

The second Jool-flip got you as well, huh? I'm starting to wonder if there is a good way of doing it at all! Maybe you need a higher velocity just like the first flip? Maybe that would make things worse.

The reentry was erpeccially interesting, it's like getting the Idea of a skip-reentry to the next level. How to call that? Aerobreak-Assisted-Gravity-Assist?

[jonny]

5 minutes ago, Physics Student said:

The second Jool-flip got you as well, huh? I'm starting to wonder if there is a good way of doing it at all!

I think the key is not the velocity but the vector. if you intercept Jool exactly at Ap you would have to flip your vector 180°. But if you intercept Jool before or after Ap you don't have to change your vector that much. --> higher Jool Pe --> less energy to kill later.

I didn't find a way to get a second flip without a hyperbolic Kerbol trajectory, and the timing for the Kerbin "Aerobreak-Assisted-Gravity-Assist" (I did try to compose a German word, but i can only think in english about space stuff.) was pure luck.

I think it was the best solution. Okay, I could have burned the 3000m/s left in the tank.

[Human Person]

1 hour ago, jonny said:

Aerobreak-Assisted-Gravity-Assist

Luftbremsungsunterstützte Gravitationsunterstützung.

I added you to the leaderboard btw. Please check on the little summary I wrote there.

Edited May 11, 2017 by Physics Student

[Cpt Kerbalkrunch]

@jonny 

I have a crappy phone, so I couldn't see your pics very well. Had to wait 'til I got home to get a good look. Just went through them and, man, that was fantastic. I had read your earlier post on page 2 when you said your first attempt had failed. I saw all the gravity assists and just shook my head. I seriously thought you were nuts. I know it took a century, but that was some unbelievable maneuvering. What is it with Germans and rockets? 

I don't expect you to spill your trade secrets, but I'm definitely curious; did you begin with a general outline of what you wanted to do and then take each encounter one at a time while plotting the next one (thinking a couple moves ahead like chess), or do you actually own a supercomputer or two and plotted the whole thing out like the freakin' Voyager probes? Either way is actually just as impressive to me. The reason I'm asking is because I would love to be that good at gravity assists. I feel like I've learned a lot, and gotten better, but I know there's a ton more to learn.

Anyway, absolutely superb mission. Congrats to you. How you survived that aerobrake dipping that deep is beyond me. I'm gonna take a guess and say you had to try it more than once. Still just as cool, though.

 

P.S. I'd of burned what was left in the tank. Some guys like to show off, I guess. 

[jonny]

On 7.5.2017 at 4:20 PM, ManEatingApe said:

Burbarry has enough dV in his jetpack to make a Kerbin intercept - I found this made it easier to rendezvous and saved about 2000 m/s dv as I was able to use my LKO velocity.

Why didn't I read your entry carefully? Great idea!! I think I have to do the mission again, and save some time and fuel while performing EVA gravity assists in parallel to the rescue vehicle.

I wonder if I can pull this off.

3 hours ago, Cpt Kerbalkrunch said:

did you begin with a general outline of what you wanted to do and then take each encounter one at a time while plotting the next one

Yes, pretty much like that. The biggest problem is that the close approach marker sometimes don't appear. Placing some more maneuver nodes can help.
You always want to check, that you don't mess up your inclination, and to get the timing right. Precise Node is a must have, as you have to account for every mm/s. I sometimes place a maneuver with 0.001m/s --> make sure to set the thrust limiter to 0.5 and, as always: mod+F5 is your best friend.

[ManEatingApe]

@jonny Fantastic rescue, wonderful use of gravity assists and a truly Kerbal aerobrake into Kerbol capture!

35 minutes ago, jonny said:

I think I have to do the mission again, and save some time and fuel while performing EVA gravity assists in parallel to the rescue vehicle.

I had a crazy dream that just using EVA it might be possible to go Eve -> Eve ... -> Eve -> Jool and flip Burberry's orbit without needing any vehicle at all 

Probably not enough precision in the jetpack, but I really like your idea of bumping up Burberry's orbit as much as possible.

Edited May 12, 2017 by ManEatingApe

[Human Person]

12 hours ago, jonny said:

Great idea!! I think I have to do the mission again, and save some time and fuel while performing EVA gravity assists in parallel to the rescue vehicle.

In theory, one could use Burbarrys EVA-Pack to push his pod back home, but I don't even try to imagine how tedious that would be.

Edited May 12, 2017 by Physics Student

[Human Person]

Hey Hey, Ladies and Gentlemen! I hereby proudly announce that Marcus House himself participated in the Challenge

@marcushouse sorry to leapfrog you here, but I was just too excited.

Edited May 13, 2017 by Physics Student

[marcushouse]

No problems mate. Thanks for posting for me. Yes it was a fun challenge and I couldn't help myself trying to make it even more troublesome with the low tech parts requirement. Thanks for starting this thread. I think everyone has had a lot of fun.

Originally I wanted to also try to rescue from a retro orbit between Eve and Moho but the exta DV requirement made it pretty impractical with low tech. I wouldn't mind doing a brute force method as well (burning right from kerbin to retro orbit and back again) but the DV needed would be massive (like 45k crazy or something).

Edited May 13, 2017 by marcushouse

[Aetharan]

22 minutes ago, marcushouse said:

[snip] but the DV needed would be massive (like 45k crazy or something).

Yeah, brute-force methods require a ton of delta-V, and the faster you want to get it done, the more you need (as my own attempts have shown).  I'm still looking for ways to pull off a rescue that would bring Burberry home (using the save file in the first post, modified to fill up the entire Community Tech Tree) in less than the time that it takes for the first orbital alignment between Kerbin and the Goliath.  So far, the best I've managed was an intersect before Day 70, and that burned over 7 km/s of delta-V just getting the intersect, with a relative velocity of somewhere around 23 km/s at closest approach.  If you assume that a quick return would require similar delta-V, then we're talking a required ship capability of some 60+ km/s after making orbit.

Edit: With that initial phase angle of roughly 180º on Day 1, we hit an angle of 360º on Day 97 during the 1:00 hour.  Thus, my ultimate goal is to get Burberry home before this mark.

Edited May 13, 2017 by Aetharan

[ManEatingApe]

Here's the promised primitive penny-pinching entry suitable for even the most cost conscious of space programs - a mere 16,917 funds. None of yer fancy nuclear or ion engines, just good 'ol fashioned chemical engines.

Now it may have taken a teensy little bit longer than some other entries, some 23 years erm...I mean centuries, but who's in a hurry right? 

 

Outbound journey used the standard Kerbin -> Eve -> Kerbin -> Kerbin -> Jool route culminating in an AP a millennia away!

A modest 82 m/s burn then flipped our orbit retro-solar and gave a Jool intercept dropping our PE to the same as Burbarry's.

Now for the tricky part. The relative velocities of the Goliath and Against the Grain were still over 3,400 m/s. Normally you could use Kerbin or Eve gravity assists to slow down, but when you're going the wrong way these are much less effective - it would take dozens to slow down enough.

Instead a lightweight barebones rescue tug (no reaction wheel, batteries or antenna) packing 7 km/s dV rendezvoused with Burbarry and then caught up again with the Against the Grain

It was barely enough, still had to use all the Jetpack propellant

A 3rd Jool assist kicked us into a wonderfully eccentric Kerbol orbit. It's only barely the right way around. Left alone we'll plunge into the sun but our orbit is so wonky that it's cheap to fix that.

From there it was straightforward to use a Kerbin assist to drop our PE

A relatively tame aerobrake at 4.2 km/s

Hey, anyone visit Dres while we were gone?

 

Summary: Cost 16,917 funds, mass 70 tons, 8 gravity assists, mission duration 2,304 years.

Craft was completely stock but I used Precise Maneuver and Better Time Warp mods (for obvious reasons )

Route Details:

1. Outbound Kerbin -> Eve -> Kerbin -> Kerbin -> Jool (1078 + 20 + 4 + 117 = 1219 m/s)
2. Retro-solar burn at AP then reverse Jool and Kerbin assists (82 + 20 = 102 m/s)
3. Rendezvous with Burbarry (7,600 m/s total including jetpack)
4. Inbound Jool -> Kerbin -> Kerbin (99 + 159 + 11 = 269 m/s)

Full Mission Album

Download Craft File

Edited May 16, 2017 by ManEatingApe

[Cpt Kerbalkrunch]

Just out of curiosity, after having been gone for so many centuries, did your Kerbals return home to find it had become a Planet of the @ManEatingApe s?

[Human Person]

6 hours ago, Cpt Kerbalkrunch said:

Just out of curiosity, after having been gone for so many centuries, did your Kerbals return home to find it had become a Planet of the @ManEatingApe s?

Nothing to worry, @ManEatingApes eat Man, not Kerbals.

Also, they go absolutely nuts with this challenge. You just took a few records (edit: I thought you took the lowes launch mass as well, but that isn't the case) there and beat the longest mission time by a factor of 23. Since your entry wasn't just an improvement of your first one but a completely new one, I put you on the leaderboard twice.

Talking about scoring, the record-system works better than I thought, I'm gonna introduce some ani-records as well.

Consider the non-record prizes special as they are only given to those who are first to come up with some crazy ideas.

Edited May 16, 2017 by Physics Student

[jonny]

@ManEatingApe Congratulations! That was a very interesting Mission Profile.

12 hours ago, ManEatingApe said:

Outbound journey used the standard Kerbin -> Eve -> Kerbin -> Kerbin -> Jool route culminating in an AP a millennia away!

one small suggestion, how you could cut the Mission time in half, (or just double it): go from Jool back to Eve. the gravity assist is very easy to set up, because Eve has a very short orbital period. Eve is capable to kick out your Ap to infinity, but your Pe will always stay below Eve.

On 11.5.2017 at 10:07 PM, Physics Student said:

you truly are a master of gravity assists.

How could I’ve been, I did never really understand why and how gravity-assists work.

I just had the “aha! moment” when I thought about @ManEatingApe's last entry, and why nobody is able to get a “good” second orbital flip at Jool. The answer is very simpel: it is Impossible.

So let’s start with a very simple and obvious fact which I never considered: the velocity in reference to the celestial body which you use for the assist. Is at SOI entry and exit equal. This is because you spend the same time before and after Pe. But the celestial body will change the direction of this velocity. In theory, If the orbital velocity of the celestial body is zero, you could think of the gravity assist as an engine burn in any perpendicular direction to your velocity vector (in reference to Kerbol). Okay, the velocity of a celestial body is obviously never 0. That means you will almost ever increase or reduce your orbital velocity (in reference to Kerbol). To be precise you will add velocity in the prograde direction of the celestial body if your Pe is above the retrograde facing hemisphere.

Enough theory, let’s think about the first orbital flip at Jool. The target is a Retrosolar orbit that means we have to leave Jool SOI in a retrograde direction (in reference to Kerbol) with a velocity higher than Jool’s orbital velocity (~4000m/s). --> We have to enter Jool SOI with a velocity > 4000m/s. Coming from Kerbin that is straight out to infinity. Now we have to change the direction of that velocity --> we have to place the Pe somewhere above the Prograde facing hemisphere. As we are outwards bound that would be somewhere between prograde and radial out (from jool's point of view).

For the second flip we will always enter Jool SOI with >4000m/s --> if we leave Jool SOI in Prograde direction, that would add ~4000m/s (Jool's orbital velocity) --> more than 8000m/s at Pe at a hight of Jool... I think everybody can imagine how that orbit would look like. Unless you encounter a moon of Jool, or you do a aerobraking maneuver, you will always end up leaving Jool SOI with >4000 m/s. Which is never a good speed to get a "good" Prograde orbit.

PS.: Please tell me if I made a mistake, because I am not the best in English and I'm not a physics Student .

Edited May 16, 2017 by jonny

[Human Person]

3 hours ago, jonny said:

Enough theory, let’s think about the first orbital flip at Jool. The target is a Retrosolar orbit that means we have to leave Jool SOI in a retrograde direction (in reference to Kerbol) with a velocity higher than Jool’s orbital velocity (~4000m/s). --> We have to enter Jool SOI with a velocity > 4000m/s.

Jupp, that's consistent with my expierience.

3 hours ago, jonny said:

For the second flip we will always enter Jool SOI with >4000m/s --> if we leave Jool SOI in Prograde direction, that would add ~4000m/s (Jool's orbital velocity) --> more than 8000m/s at Pe at a hight of Jool... I think everybody can imagine how that orbit would look like. Unless you encounter a moon of Jool, or you do a aerobraking maneuver, you will always end up leaving Jool SOI with >4000 m/s. Which is never a good speed to get a "good" Prograde orbi

Hmm, I get what you mean but I still believe there's a solution we're just unable to see. I'm not an expert on this, I just happen to be able to immagine orbits in my head (since I started playing KSP)

[jonny]

3 hours ago, jonny said:

the velocity in reference to the celestial body which you use for the assist. Is at SOI entry and exit equal.

@Physics Student do you agree with this?

go ahead and cheat a vessel in low Jool orbit. now try to create a maneuver which ejects you to a "good" orbit with >4000m/s (I think 4800m/s is realistic) at SOI exit.