The Retro Solar Rescue

[linuxgurugamer]

Have to go to work, but it looks like this first sim got me an intercept in about 80 days.  Its a looooong burn, about 5 1/2 hours.  I cant timewarp because of physics issues.  As the vessel gets smaller i will be able to increase the timewarp

[herbal space program]

A quick question for @Physics Student: Is the use of one tank of EVA propellant by Burbarry allowed, ala The Martian? That could obviously save me a fair bit of deltaV in my rendezvous. My apologies if one of the other entrants has done this already, but I'm not looking at what anybody else did until I've completed my run.....

[Human Person]

35 minutes ago, herbal space program said:

A quick question for @Physics Student: Is the use of one tank of EVA propellant by Burbarry allowed, ala The Martian? That could obviously save me a fair bit of deltaV in my rendezvous. My apologies if one of the other entrants has done this already, but I'm not looking at what anybody else did until I've completed my run.....

It's allowed and it has beed done already.

[linuxgurugamer]

1 hour ago, herbal space program said:

A quick question for @Physics Student: Is the use of one tank of EVA propellant by Burbarry allowed, ala The Martian? That could obviously save me a fair bit of deltaV in my rendezvous. My apologies if one of the other entrants has done this already, but I'm not looking at what anybody else did until I've completed my run.....

It's needed so that if nothing else Burberry can Eva over to the rescue ship. However, keep in mind that Eva tank has at most 2 2 to 5 meters per second I believe that's get exactly but it's not a lot. Your best bet would be to get close to within a couple of kilometers of Burberry and then Eva over from there.

Edited August 9, 2017 by linuxgurugamer

[tseitsei89]

2 hours ago, linuxgurugamer said:

It's needed so that if nothing else Burberry can Eva over to the rescue ship. However, keep in mind that Eva tank has at most 2 2 to 5 meters per second I believe that's get exactly but it's not a lot. Your best bet would be to get close to within a couple of kilometers of Burberry and then Eva over from there.

Actually EVA packs have some hundreds of m/s worth of deltav and if the dv for whole mission is 2.xy km/s that extra dv from EVA pack is very significant...

[herbal space program]

9 hours ago, Physics Student said:

It's allowed and it has beed done already.

Awesome, thanks!

5 hours ago, tseitsei89 said:

Actually EVA packs have some hundreds of m/s worth of deltav and if the dv for whole mission is 2.xy km/s that extra dv from EVA pack is very significant...

Indeed, according to the Wiki it's actually around 650m/s, which is over 10% of my dV budget for the whole mission! And that amount basically counts double, because whatever dV Burbarry can use to bring his orbit closer to Valentina's represents dV she would otherwise have to expend going in both directions. Of course the lack of a navball in the EVA interface will make actually boosting in the right direction pretty challenging, but it could be well worth it....

[septemberWaves]

I might give this a try. In 4x scale. Where delta-v requirements are approximately doubled. Maybe.

[linuxgurugamer]

43 minutes ago, herbal space program said:

Awesome, thanks!

Indeed, according to the Wiki it's actually around 650m/s, which is over 10% of my dV budget for the whole mission! And that amount basically counts double, because whatever dV Burbarry can use to bring his orbit closer to Valentina's represents dV she would otherwise have to expend going in both directions. Of course the lack of a navball in the EVA interface will make actually boosting in the right direction pretty challenging, but it could be well worth it....

personally, I consider that a cheat, although I'm not going to knock you if you use it.  I'd rather get my ship to 100m away and then do a simple eva transfer

[herbal space program]

21 minutes ago, linuxgurugamer said:

personally, I consider that a cheat, although I'm not going to knock you if you use it.  I'd rather get my ship to 100m away and then do a simple eva transfer

 For the way you're doing it, it hardly makes any difference, so that's easy for you to say. For the way I'm doing it OTOH, it could make as much as 1,200m/s difference in a contest where the benchmark score is 5200m/s all told. I'd be plain dumb not to do it if OP sez it's OK, unless of course it proves too difficult...

Edited August 10, 2017 by herbal space program

[linuxgurugamer]

When I said personally, I was meaning for myself. The OP says it's OK so it's fine. Go for it, I look forward to seeing the results of your rescue.

[tseitsei89]

1 hour ago, herbal space program said:

 Of course the lack of a navball in the EVA interface will make actually boosting in the right direction pretty challenging, but it could be well worth it....

There is a navball in the EVA view nowadays isnt there? Or am I remembering everything completely wrong?

Edited August 10, 2017 by tseitsei89

[herbal space program]

30 minutes ago, tseitsei89 said:

There is a navball in the EVA view nowadays isnt there? Or am I remembering everything completely wrong?

I stand corrected, there is one! So this won't be difficult at all....

[Laie]

On 8/8/2017 at 8:56 PM, Aetharan said:

@linuxgurugamer A bit of advice for my direct competition:  Your best bet, with enough delta-V available, is to push yourself into a prograde orbit with PE closer to Kerbol than the Goliath's.  You'll burn a lot of delta-V there, and your encounter will be well over the usual 20 km/s relative velocity, but it's possible to get the encounter in under 70 days.  If you can get the timing right so you actually pull up alongside him instead of missing by thousands of kilometers like I did, then I'd assume that a return to Kerbin thereafter should be doable in under 20 days after that.

And I though I was smart to think of this approach....

With a high-TWR test vessel and infinite fuel, starting on day 1, I got ~1km/s from Kerbin to encounter after about 80 days; slightly more than 20km/s to match, and another 15km/s for a 30-day return trip that should be stoppable by heatshield alone.

The good news (if you want to call it that) is that almost all of the dV has to spent in a situation where TWR barely matters.

[jonny]

4 hours ago, herbal space program said:

it could make as much as 1,200m/s difference in a contest where the benchmark score is 5200m/s all told.

I just want to clarify: the difference in the final score should be 600m/s, because the 600m/s spent in EVA should Count. Of course the difference for the rescue vehicle itself is 1200m/s. If you don't count the dV in EVA you would look at a benchmark score of ~4800 m/s from my second entry.

Quote

The Kerbals can navigate outside their spacecraft by climbing ladders, walking, or using their personal RCS jetpacks, which have a Δv of 600 m/s RCS fuel that is completely restored upon entering a command pod.

http://wiki.kerbalspaceprogram.com/wiki/Extra-Vehicular_Activity

 

[Human Person]

1 hour ago, jonny said:

Quote

The Kerbals can navigate outside their spacecraft by climbing ladders, walking, or using their personal RCSjetpacks, which have a Δv of 600 m/s RCS fuel that is completely restored upon entering a command pod.

http://wiki.kerbalspaceprogram.com/wiki/Extra-Vehicular_Activity

 

I'm waiting for the guy who pushes Burbarrys Capsule home on EVA. It will be even more tedious than

20 hours ago, linuxgurugamer said:

a looooong burn, about 5 1/2 hours.  I cant timewarp

Seriously, if you make TWR a bIt lower, you can do the burn overnight or while you're working.

@herbal space program:

1 hour ago, jonny said:

I just want to clarify: the difference in the final score should be 600m/s, because the 600m/s spent in EVA should Count. Of course the difference for the rescue vehicle itself is 1200m/s. If you don't count the dV in EVA you would look at a benchmark score of ~4800 m/s from my second entry.

He's right, we did count the Delta v spent by Burbarry on EVA. The delta v record might be the toughest to beat, but a successful SSTB (Singl Stage To Burbarry) Spaceplane will most certainly beat the cost record and get you an award for the first one to do such a thing.

 

7 hours ago, eloquentJane said:

I might give this a try. In 4x scale. Where delta-v requirements are approximately doubled. Maybe.

Brave. I'd recommend using Tweakscale and/or procedural parts to keep partcount low as you're going to need a huge rocket.

Edited August 10, 2017 by Physics Student

[Human Person]

On 4.5.2017 at 3:57 AM, Starman4308 said:

For you, 8 km/sec was the fastest, most hair-raising reentry you've ever performed.

For me, it was Tuesday*.

*8 km/sec is a bit less than lunar reentry speed at 6.4x scale, which is what I've mostly played at. For the RSS players, it's LEO reentry speed.

I'm not sure I'll take this challenge on, but there are multiple ways to do it.

#1: Bi-elliptic transfer. Eject straight from Kerbin orbit out to a very elliptical heliocentric orbit: then, at apohelion (Sun apoapsis), reverse your course, and you've done the plane change. Granted, you're going to have Fun (tm) at your new perihelion, bringing your apohelion down to something that you can reasonably use to rendezvous with Burbarry, and then Fun (tm) again going for another bi-elliptic back into prograde solar orbit.

#2: Bi-elliptic transfer with gravity assists. Ignoring the fact that you're leaving poor Burbarry alone in a capsule for years, this would be how I'd approach the problem, probably trying something like Kerbin->Eve->Kerbin->Jool->apohelion reversal->Jool->Eve (with a braking maneuver at Eve) -> Burbarry -> Eve -> Kerbin -> Jool -> apohelion reversal -> Jool -> Kerbin/Eve braking -> Kerbin return. Doing the big burns in the SOIs of Eve and Kerbin gives you some benefit from Mr. Oberth, because X velocity added or removed inside their SOIs can translate to more than X added or removed once you escape their SOIs.

Granted, that's a vastly more ambitious set of slingshots than I've ever actually pulled off.

#3: Massively staged nuke/ion spam: a brute force approach.

#4: Playing a fun game of gravitational ping-pong inside the bounds of the Kerbol system, which is most of Cpt Kerbalcrunch's strategy.

Reading through the thread again, I found this pretty good. All of these strategies have been realized so far. 

Edited August 10, 2017 by Physics Student

[septemberWaves]

2 hours ago, Physics Student said:

Brave. I'd recommend using Tweakscale and/or procedural parts to keep partcount low as you're going to need a huge rocket.

No tweakscale or procedural parts. SpaceY is pretty good for gargantuan rockets. I have a lot of options with the mod set I'm using, so I should be fine. And anyway, I'm very used to getting payloads into orbit at this scale. I know how to do it fairly well by now.

I do have a couple of questions regarding balance. Most of the mods I have installed are reasonably close to stock-balance because I feel like that's about the right level of balance for a 4x rescale. However, there's a few things I'm not sure would be allowed:

• Is it acceptable to use hydrogen-fueled cryogenic engines with I_sp usually in the 400s (keeping in mind that the hydrogen tanks require power)?
• Is it okay to use nuclear engines even though the stock nuclear engine has been rebalanced to run on hydrogen (again with tanks which require energy) and now have an I_sp of 900s instead of 800s?
• I have Near Future Propulsion installed, which adds a lot of electric engines with varying balance. Is it fine to use ion engines with slightly better I_sp than the stock ones due to the high requirements of this rescale, or should I stick with just the stock ions if I go that route?
• Is it okay to use MechJeb for a) everything or b) only information? I can fly manually if I have to but generally large vehicles are painfully laggy (less than 1fps with a few hundred parts sometimes) so I prefer not to if I can avoid it. And if autopilots aren't okay I would at least like the ability to use the information readouts. It strikes me that this is more of an engineering challenge than a piloting challenge so I assume MechJeb is fine, but I'd like to clarify that rather than do the challenge only to discover that it wasn't okay to use the mod.

Edited August 10, 2017 by eloquentJane

[tseitsei89]

3 hours ago, Physics Student said:

@herbal space program:

He's right, we did count the Delta v spent by Burbarry on EVA. The delta v record might be the toughest to beat, but a successful SSTB (Singl Stage To Burbarry) Spaceplane will most certainly beat the cost record and get you an award for the first one to do such a thing.

Regardless it is still worth using as much of Burbarrys dv as possible since, as @herbal space program already mentioned above, it is effectively "double effective dv"

[Human Person]

2 hours ago, eloquentJane said:

I do have a couple of questions regarding balance. Most of the mods I have installed are reasonably close to stock-balance because I feel like that's about the right level of balance for a 4x rescale. However, there's a few things I'm not sure would be allowed:

• Is it acceptable to use hydrogen-fueled cryogenic engines with I_sp usually in the 400s (keeping in mind that the hydrogen tanks require power)?
• Is it okay to use nuclear engines even though the stock nuclear engine has been rebalanced to run on hydrogen (again with tanks which require energy) and now have an I_sp of 900s instead of 800s?
• I have Near Future Propulsion installed, which adds a lot of electric engines with varying balance. Is it fine to use ion engines with slightly better I_sp than the stock ones due to the high requirements of this rescale, or should I stick with just the stock ions if I go that route?
• Is it okay to use MechJeb for a) everything or b) only information? I can fly manually if I have to but generally large vehicles are painfully laggy (less than 1fps with a few hundred parts sometimes) so I prefer not to if I can avoid it. And if autopilots aren't okay I would at least like the ability to use the information readouts. It strikes me that this is more of an engineering challenge than a piloting challenge so I assume MechJeb is fine, but I'd like to clarify that rather than do the challenge only to discover that it wasn't okay to use the mod.

Yes to everything. "Slightly better than Stock" is fine, especially when you play in a scaled system. I plan on using similar engines for my RSS attempt.

I'm not familiar with Near Future Propulsion, so don't use totally op things. Ask specifically if you're not sure.

You will however be prohibited from certain records, eg. you have to play with stock parts only if you want to beat the cost- or the lowest mass records, but this will hardly be relevant for you.

Edited August 10, 2017 by Physics Student

[linuxgurugamer]

9 hours ago, Laie said:

With a high-TWR test vessel and infinite fuel, starting on day 1, I got ~1km/s from Kerbin to encounter after about 80 days; slightly more than 20km/s to match, and another 15km/s for a 30-day return trip that should be stoppable by heatshield alone.

That matches what I was able to do with a test launch.

I also just realized that for this attempt, I don't need to bring along the freezer, since there will be more than enough LS for a mission this short.  This will save some dV, giving me a little bit of extra margin.

5 hours ago, Physics Student said:

He's right, we did count the Delta v spent by Burbarry on EVA. The delta v record might be the toughest to beat, but a successful SSTB (Singl Stage To Burbarry) Spaceplane will most certainly beat the cost record and get you an award for the first one to do such a thing.

Might I suggest that you have two dV records, one in which Burberry uses his backpack for a significant part of the dV change, and one which he doesn't?

[herbal space program]

8 hours ago, jonny said:

I just want to clarify: the difference in the final score should be 600m/s, because the 600m/s spent in EVA should Count. Of course the difference for the rescue vehicle itself is 1200m/s. If you don't count the dV in EVA you would look at a benchmark score of ~4800 m/s from my second entry.

 

Fair enough! And on that note, to insure fairness how exactly did you go about calculating Burbarry's EVA dV? Does KER report it or did you just use the rocket equation? If it's the latter, can you tell me what ISP and dry/wet masses you used? Thanks!

 

...Also, to make it less implausible, what I'll probably have Burbarry do is abandon his ship just as I'm swinging by on a tangent orbit and use his EVA pack to match velocities with me, rather than sending him off into space without a ship for months to rendezvous with me at some distant point. While I can see how the latter might smack of cheating to some, I think the former is totally consistent with  the spirit of the challenge, especially since we'll be counting Burbarry's dV.

Edited August 10, 2017 by herbal space program

[sevenperforce]

14 minutes ago, herbal space program said:

Fair enough! And on that note, to insure fairness how exactly did you go about calculating Burbarry's EVA dV? Does KER report it or did you just use the rocket equation? If it's the latter, can you tell me what ISP and dry/wet masses you used? Thanks!

 

...Also, to make it less implausible, what I'll probably have Burbarry do is abandon his ship just as I'm swinging by on a tangent orbit and use his EVA pack to match velocities with me, rather than sending him off into space without a ship for months to rendezvous with me at some distant point. While I can see how the latter might smack of cheating to some, I think the former is totally consistent with  the spirit of the challenge.

A standard jetpack has 650 m/s of dV, per the wiki.

[herbal space program]

55 minutes ago, linuxgurugamer said:

Might I suggest that you have two dV records, one in which Burberry uses his backpack for a significant part of the dV change, and one which he doesn't?

How about if we just count Burbarry's dV expenditure and say he can't be stuck in just his suit for more than one day? 

6 minutes ago, sevenperforce said:

A standard jetpack has 650 m/s of dV, per the wiki.

Which I suspect will turn out to be pretty close to what is required for me to match velocities from the best tangent orbit I can reach through gravity assists, so I doubt there would even be much to be gained from sending Burbarry off into deep space in just his suit.

[sevenperforce]

1 hour ago, herbal space program said:

How about if we just count Burbarry's dV expenditure and say he can't be stuck in just his suit for more than one day? 

Which I suspect will turn out to be pretty close to what is required for me to match velocities from the best tangent orbit I can reach through gravity assists, so I doubt there would even be much to be gained from sending Burbarry off into deep space in just his suit.

Yeah, my thought is to set up the eccentric tangent orbit, burn target-retrograde in the rescue vehicle until relative velocity is less than 500 m/s, then switch to Burbarry and burn target-retrograde to match. 

[Human Person]

1 hour ago, herbal space program said:

how exactly did you go about calculating Burbarry's EVA dV?

I suggest to note maneuver delta v or the relative target velocity when doing a Burbarry-flyby. Is that consistent with how you did it, @jonny?