The Retro Solar Rescue

[Human Person]

@jonny You're correct, but What I have in mind are not ideal gravity assists without any propulsion or moons involved. I don't habe time now, PM me for further discussion if you like.

[ManEatingApe]

14 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?

That made me laugh out loud - I got some strange looks from people nearby!

12 hours ago, Physics Student said:

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

I love the idea of anti-records to inspire creativity. There's so many different great approaches in this thread.

I'm also pretty sure we can improve on the normal records too - a low mass mission < 30 tons should be doable. Also by using only 5219 m/s @jonny showed that an SSTBAB (Single Stage to Burbarry and Back) is within the realms of possibility for anyone crazy enough to try.

5 hours ago, jonny said:

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.

Thanks for the tip! Just to check you mean go K-E-K-K-J-E -> To infinity and beyond?

(I'm also following your gravity assist conversation with interest)

Edited May 16, 2017 by ManEatingApe

[jonny]

2 minutes ago, ManEatingApe said:

Thanks for the tip! Just to check you mean go K-E-K-K-J -> To infinity and beyond?

nope, K-E-K-K-J-E -> To infinity. Okay, you don't want to go to Infinity, but you have the possibility. Which means you can set up the last Eve assist, however you like, to get a Ap which suits your need. The big advantage is the low Pe. (below Eve) that means you don't need a very high Ap to flip the Orbit.

[Bubbadevlin]

Dang this looks hard.. but also really fun, might do this challenge

[Cpt Kerbalkrunch]

1 hour ago, Bubbadevlin said:

Dang this looks hard.. but also really fun, might do this challenge

Give it a shot. Even my first try, when I failed miserably, was a lot of fun.

[Aetharan]

1 hour ago, Bubbadevlin said:

Dang this looks hard.. but also really fun, might do this challenge

The level of difficulty isn't actually all that high.  A big, dumb rocket can do it (as I've shown), and a little, smart one can do it too if you're more careful with how you spend your fuel.  What difficulty there is in the challenge comes from figuring out exactly what mission profile you're going to aim for, then constructing a ship capable of pulling it off.

Of course, I've had about a dozen failures for each of the two successes that I've posted, and am still having more as I work for a third (and faster) one.  Take the Dwarf Fortress mental approach to it: "Losing is fun!"

[Human Person]

4 hours ago, ManEatingApe said:

I'm also pretty sure we can improve on the normal records too - a low mass mission < 30 tons should be doable.

Considering the current launch mass record was a brute force mission, yes.

4 hours ago, ManEatingApe said:

Also by using only 5219 m/s @jonny showed that an SSTBAB (Single Stage to Burbarry and Back) is within the realms of possibility for anyone crazy enough to try.

Dang it! I wanted to create a challenge that cannot be done with an SSTO! That was my initial goal with this whole thing. I have a feeling, the delta v record will last a while, it's pretty solid.

3 hours ago, Bubbadevlin said:

Dang this looks hard.. but also really fun, might do this challenge

It's hard, yes but it's less effort than a Jool 5 or an Eve return mission. I made it on my 2nd try and I was pretty surprised when I realized it's gonna work out. Just pack a crapload of delta v into a rocket and off you go!

Edited May 16, 2017 by Physics Student

[marcushouse]

If anyone is interested in my brute force attempt at this... say hello to my little friend.

 

[cratercracker]

It feels weird that there is my art in tons and tons of signatures, it is like..hmm. You are taking over the forum and this is your army...

[Human Person]

@marcushouse very nice, you make this look so easy. I guess, with raw delta v, anything can be done.

 

It's heartwarming to see that you guys like the challenge so much, you even participate multiple times. I'm going to do it again too. 

[Laie]

Ahem. Is there a solution to atmospheric entry @20km/s?

Too lazy to check all the entries, and the ones I did check appear to have flipped their orbit twice. Anything I missed?

[Starman4308]

3 hours ago, Laie said:

Ahem. Is there a solution to atmospheric entry @20km/s?

Either use RO-rated heatshields (and even those might need buffing), expend 15-17 km/sec of delta-V to bring your reentry velocity down, or use similar techniques as you used to get to Burbarry to flip your orbit again (i.e: gravitational assists, bi-elliptic transfers, etc).

It's all just part of the challenge: not only do you need to make incredible velocity changes on the way to Burbarry, you also need to make incredible velocity changes on the way back.

[Cpt Kerbalkrunch]

3 hours ago, Laie said:

Ahem. Is there a solution to atmospheric entry @20km/s?

Yes. Don't. 

[jonny]

I was very busy the last weeks. Working hard to get my dV requirement down. But unfortunately I was not patient enough. I ended up using 203 m/s more dV than last time (including 600 m/s EVA propellant). But I made major changes to my rocket. I got the cost down to 15,780 Founds and the mass down to 39.846 t.

The short Story:

LKO -> Eve -> 2x Kerbin -> Jool -> 2x Eve -> Jool -> Rerosolar -> 4x Eve -> Separation between "Chair on Engine" and capsule -> 7x Kerbin -> Burberry going EVA -> rendezvous between "Chair on Engine" and Burberry -> 5x Kerbin -> rendezvous between Burberry and capsule -> 3x Eve -> Jool -> Kerbin Aerobraking and splashdown

dV from LKO: 1326 m/s -> Separation between "Chair on Engine" and capsule ->  1324 m/s + 600 m/s EVA -> rendezvous between "Chair on Engine" and Burberry -> 1435 m/s -> rendezvous between Burberry and capsule -> 737 m/s -> splashdown

The Long Story:

Spoiler

The very long story is at Imgur: http://imgur.com/a/V7bEc but here are the important steps. The route is similar to my last entry.

I left LKO at Y2 D160 heading for the standard K-E-K-K-J route.

Jool will send me back to Eve, where I tune my orbital periode for a high velocity Jool intercept.

The second Jool flyby is set up to flip my orbit around Kerbol, as well as bringing me back to Eve.

Some Eve flyby's later

many Kerbin flyby's later Burberry is heading for a rendezvous with his new chair

Burberry had not enough propellant but no worries, the chair has plenty.

I had to maneuver very carefully because Burberry used 100% of his EVA propellant.

many Kerbin flyby's later Burberry was on his way to rendezvous with his new home.

Again, I had to orient the spacecraft properly and approach the hatch very slowly due to the lack of EVA propellant.

After some Eve flybys I planned the whole route home.

@Physics Student I did try a lot, but there seems to be no way to use Tylo for the second orbital flip. However, if you manage to get the timing right and intercept Kerbin tangential to its orbit the velocity difference is not that bad and with ~6000m/s very survivable.

This picture is somewhat counterintuitive. There is a second maneuver with 300m/s retrograde at Jool Pe. I am not sure how much that subtract from my intercept velocity with Kerbin. But more important it makes for the right timing, to intercept Kerbin in a tangential direction.

 

 

 

 

[ManEatingApe]

@jonny Nice work, cost and mass records in a single mission! 

[Human Person]

On 16.6.2017 at 10:02 PM, Laie said:

 

Ahem. Is there a solution to atmospheric entry @20km/s?

 

This is absolutely impossible. The maximum velocity seems to be at around 8 km/s.

But reading through all th entries is quite fun, they're all awesome. You should do it.

 

@jonny wow, 2 new records, yet again you amaze me. 

[Human Person]

I'm posting this here, because it's a really nice Video. I'm a huge fan of The Gamer Alchemist.

However, I don't agree with the reentry at over 60 km/s. Is that possible in RSS?

I'll put him in the Category 2

 

Edited June 26, 2017 by Physics Student

[Cpt Kerbalkrunch]

On 6/24/2017 at 10:03 AM, Physics Student said:

I'm posting this here, because it's a really nice Video. I'm a huge fan of The Gamer Alchemist.

However, I don't agree with the reentry at over 60 km/s. Is that possible in RSS?

 

Really cool video. I especially like the close flyby of Jupiter. However, I'm with you on the reentry. I don't know enough about RSS to say it can't be done, so I can just compare it to what I do know. On my first attempt to rescue Burbarry, I tried a direct return at 18km/s. I set Pe at 60km, figuring I'd go for the "dip a toe" method. At that altitude, Kerbin's atmosphere is so thin, I figured I'd be safe and, even though it wouldn't slow me down a whole lot, it would at least slow me down a bit. I was dead wrong. I don't think I even hit 65km. About 2 seconds after entry, my ship just completely exploded. I know he basically had nothing but a heat-shield and a Kerbal, but I'm not sure that's survivable. Still looked cool, though.

Edited June 25, 2017 by Cpt Kerbalkrunch

[wibou7]

On 2017-06-18 at 1:48 AM, Physics Student said:

This is absolutely impossible. The maximum velocity seems to be at around 8 km/s.

I seem to burn in flame whenever I go above ~5.5km/s.

I'm pretty sure I am doing-it-wrong (tm), but still, 8km/s looks rather high.
Has that ever been mathemetically calculated? Or tested practically in a challenge of some sort?

I'm very curious what's the ultimate velocity limit to survivable kerbin re-entry... I wonder what kind of shenigan craft could survive at 8km/s (or above!).
...an idea for a challenge maybe..?

 

[Starman4308]

60 km per sec is quite steep. The Galileo probe hit Jupiter at a mere 48 km/sec, and would have liquefied any human onboard. From what I've gathered, ordinary LEO rated shields would have just exploded on contact, and I'm not sure any RO part would've sufficed, nevermind liquidating the Kerbal cargo.

[Cpt Kerbalkrunch]

52 minutes ago, wibou7 said:

I seem to burn in flame whenever I go above ~5.5km/s.

I'm pretty sure I am doing-it-wrong (tm), but still, 8km/s looks rather high.
Has that ever been mathemetically calculated? Or tested practically in a challenge of some sort?

I'm very curious what's the ultimate velocity limit to survivable kerbin re-entry... I wonder what kind of shenigan craft could survive at 8km/s (or above!).
...an idea for a challenge maybe..?

 

If you check my mission report on page 1, my reentry was at just under 8km/s. I got the distinct impression that I would not have survived if I'd been going much faster. In fact, I didn't think I'd make it at all. Had to try 3 times. I set Pe at 45km and then 40km the first 2 times. Skipped through the atmosphere and kept going. And that was after burning the last of my fuel at 300km to slow down enough to survive. The last time I set Pe at 35km (which I was afraid was too steep), burned retrograde at 300km, and (somehow) survived. I play strictly vanilla stock, so this was all legit. I even still have the quicksaves from the game, as well. I believe (before slowing down a bit) that I was coming in a little over 8km/s. I could reload it tonight and see if I survive without the retro-burn before reentry. I'm dubious if I'll make it, but I'll give it a shot and let ya know.

[Human Person]

2 hours ago, wibou7 said:

I'm very curious what's the ultimate velocity limit to survivable kerbin re-entry... I wonder what kind of shenigan craft could survive at 8km/s (or above!).
...an idea for a challenge maybe..?

I'm sure having seen Scott Manley doing such a thing in a live stream. I'm searching for the video but can't find it.

Sounds like a great challenge! Go ahead and start one before I do so!

2 hours ago, wibou7 said:

I seem to burn in flame whenever I go above ~5.5km/s.

What reentry vessel are you using? It's not only atmospheric shock heating that kills you, parts can also be destroyed by heat transmission from the heatshield. Make sure the part directly attached to the heatshield has a high heat tolerance itself.

Edit: Also, don't use the inflatable heat shield. It hasn't got ablator on it wich makes it explode at more than 5 km/s.

Edited June 27, 2017 by Physics Student

[jonny]

On 11.5.2017 at 0:20 AM, jonny said:

Okay, do it Kerbal style!!

well, that was not a reentry, as i left Kerbin SOI again. but i think that is pretty much the limit. I will see if I can find the save somewhere.

Edit:

I found the save should work with stock KSP1.2.2:
https://www.dropbox.com/s/w2nahhz1mww7f1t/quicksave %232.sfs?dl=0

Pe of 37Km seems to be the limit with the engine and everything attached and 36Km if you decouple the engine section prior to reentry.
I experience a Bug where the RCS thrusters don't explode if reenter with the engine section attached, but the certainly explode if I decouple. That actually means I was able to do my first Entry to the challenge because of this bug .

 

Edited June 27, 2017 by jonny

[Cpt Kerbalkrunch]

1 hour ago, Physics Student said:

Also, don't use the inflatable heat shield. It hasn't got ablator on it wich makes it explode at more than 5 km/s.

I think another reason the inflatable is no good in a situation like this is because of the huge area it takes up. Not sure what to call it. Area of exposure? I think that that, mass, and angle of approach all make a huge difference in whether or not you survive such a high-speed reentry. An inflatable in that situation would be the equivalent of a high-speed belly flop into a lake of lava. Sounds painful.

I'll reload that Retro Rescue save tonight. Instead of slowing down, I'll use the fuel I had left to speed up and see if I can make it. Should be interesting.

 

One more thought: I wonder if even an Mk1-2 could survive? With it's larger width and higher mass, I'm not sure.

Edited June 27, 2017 by Cpt Kerbalkrunch

[Spricigo]

26 minutes ago, Cpt Kerbalkrunch said:

 An inflatable in that situation would be the equivalent of a high-speed belly flop into a lake of lava.

Nice metaphor and sound reasoning. 

Drag depends, among other things in exposed area, with means stronger forces acting in a big parts like the inflated heatshield. I'm not saying that heat will necessarily build up faster(there are other factor to be considered) but mechanical stress for sure will be stronger.