XrayLima

Hulk Recovery - "Nonsense", "Total Nonsense" or "Hmmmm, maybe?"

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Posted (edited)

So, after something like 2000 play hours (yes I know, I could have learnt to fly a real spaceship in that time....)  I finally tried out a hulk recovery mission.  No real bother, Tug Probe with claw and plenty of parachutes, very shallow Pe and Bob's your uncle.  Nearly perfect, just a shame I landed just short, on the plane West of the Westward Mountains.

This got me thinking, apart from the prohibitive cost of launching a rocket to attempt to recover junk worth 1/1000 the value of the recovery craft, what would actually happen if you were to attempt an 'open' recovery of a man rated capsule with a Tug rather than in a cargo bay of another ship? Assuming it's unmanned, would the heat soak likely raise the internal temperature of the hulk to equipment damaging levels?  Is a burn up inevitable?  Could a shallow enough descent work?  Would it likely spin so fast it would rip itself to pieces?  Has any research been done into this?  Why does my brain ask annoying questions at 3am? etc etc.

Just something I'm thinking about and wonder what others think?

 

XrayLima

Edited by XrayLima
Coz I got East and West confused.....

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It's definitely be possible with a heatshield, and more practical with parts with heat tolerance over 2000K -without heatshield this time. Shallow reentry is forgiving for the latter case.

Also mk3 spaceplane can be excellent for recovery of small parts, as it can get to orbit for nearly nothing and grants 100% recovery.

But even with rockets, lifting 350/t is possible. As the hulk will cost more than 300 and recovery equipment don't cost much, there should be net gain in funds if you aim it right.

 

The real question is: Is it worth the real time spent for the mission?

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Posted (edited)

That makes sense, but I was rather asking the question "If I tried my recovery parachute tug design in real life, what would happen?"  Large space junk can survive re-entry but usually cooked to a crisp, and flattened by hitting the ground at terminal velocity.  But if cost was no object, in real life, could an unprotected unmanned capsule, be de-orbited and landed in such a way as for it not to be a steaming slag pile?

Part of the reason for asking, apart from curiosity, is that most other missions seem viable and feasable.  The recover junk missions tend to push my limits of belief, hence my usually not taking them.  But if it might be viable, even remotely, then...... more contracts!

Edited by XrayLima
Addition of final paragraph

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This is my option, I collected several parts near of Kerbin, not only the contract parts, also old stages. 

uUzDvEb.png

eyAdhtd.png

I can manage more than 15tn, but the reentry is tricky.

But is worth recovering that parts?

-> with an space plane (SSTO)? yes, the only expenses is the fuel.

-> In real life? that is more tricky.

Sorry, in Spanish http://elpais.com/diario/1994/07/06/sociedad/773445601_850215.html 

This is the news of 1994, a meteorite impact a moving car near of madrid. Years later the researchers found that the meteorite was an old part of the space shuttle. 

Several of the man-made objects survives the re-entry, nobody knows how is possible but we have several photographs. 

worth the risk? 

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Great question @XrayLima, got me thinking:).

What conditions would have to occur before such a mission need be taken? I can think of only two.

1. Capsule is out of fuel and cannot return from orbit

2. Capsule is damaged (i.e. Heat shield or parachute) and would not survive reentry. 

 

In in either case, the safest solution would be to send a replacement rescue capsule and abandon the damaged one. This assumes crew could actually transfer between vessels, I don't know if that is possible with current crew vehicles.

For the first case, an automated probe that could attach to the "hulk" and deorbit it and then detach would be best. 

For the second case, I really doubt any hastily assembled in space construction would survive a Kerbin Earth reentry intact.

so no, it does not seem plausible to do it this way in reality. But Kerbin is a special place with an easy road to and from space, so they obviously have a different evaluation. 

 

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Posted (edited)

We could make a challenge of this.

 

  • Savefile with several hulks in orbit. More expensive hulks farther from Kerbin.
  • You don't have to recover all the hulks
  • Savefile is in science mode with basically-unlimited funds (say, ten million :funds:)
  • No ISRU
  • When you're finished, your score = 10,000,000 - {:funds:-when-done}
  • Lowest score wins - and negative scores are (theoretically) possible.
Edited by icantmakemodels
No ISRU

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Posted (edited)

@Nightside I was beginning to think the same thing.  I've been looking at the Skylab re-entry and it started to degrade from an almost circular orbit, which in a perfect world would mean that both Ap and Pe would degrade similarly. (This is an assumption I've made, no idea if it's true)  This would lead to the lowest velocity entry possible (I think?).  It broke up at about 10 miles (16km) which suggests that unless high altitude braking, either by retrofiring or some form of supersonic parachute was used, the hulk would be ripped apart by high forces before the typical parachutes modelled in KSP would be useful.

But I do like your way of thinking, the Kerbal universe is different, it has different parameters and that will mean that not only are real world possible events easier (this I have no issues with), but events impossible in real life are now possible.  This is the mental leap I need to make to enjoy recovery missions.

Edited by XrayLima
Coz I can't spell

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My rescuer SSTO design carries a KAS container with an Oscar and an Ant, a fin for drag and parachutes.  It also includes an RTG and radial attach lifesupport can for live rescues.

Huge savings could be made by just bolting on the chute (and fins if necessary), then nose-bumping the debris suborbital.  For $3000 in LF, there could be enough parachutes and fins to bump a LOT of debris into decaying orbits before landing.  The main trick would be in ensuring that you're not wasting more money on parachutes than you recover in (parachute + debris) * distance modifier.  Harder nudges to ensure the bits drop into booster bay for example.

I mostly just do it Because I Can and there was a contract for it, and I get a free kerbonaut out of the deal.

 

4 hours ago, icantmakemodels said:

We could make a challenge of this

ISRU makes for negative cost missions even without recovering orbital scrap, so be sure to disallow that.

A save file with lots of debris everywhere would also be useful for other things, such as piracy/scavenging with KAS but no new launches.

 

3 hours ago, XrayLima said:

started to degrade from an almost circular orbit, which in a perfect world would mean that both Ap and Pe would degrade similarly.

It would mean your Pe would immediately move to a bit less than 180 degrees from your current position, and the orbit would quickly become more and more elliptical.

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On 6/13/2017 at 1:54 PM, suicidejunkie said:

It would mean your Pe would immediately move to a bit less than 180 degrees from your current position, and the orbit would quickly become more and more elliptical.

I'd expect it to be fairly stable, with Ap shrinking the most thanks to Pe going the fastest through the thickest atmosphere (this should continually circularize any decaying orbit).  Once the orbit fell into "skylab is falling", things wouldn't be all that stable, but it took several years (there were plans to save it with the Shuttle) to get that far down.

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On 6/15/2017 at 0:42 PM, wumpus said:

I'd expect it to be fairly stable, with Ap shrinking the most thanks to Pe going the fastest through the thickest atmosphere (this should continually circularize any decaying orbit).  Once the orbit fell into "skylab is falling", things wouldn't be all that stable, but it took several years (there were plans to save it with the Shuttle) to get that far down.

I get the sense that the're'd be a steadilly worsening oscillation.  From a perfectly circular orbit just too low to stay an orbit, you'd immediately develop a periapse opposite your position, falling and kinda wandering in your direction as you go.  As you start to fall towards it, the drag begins to affect your apoapse more, and with more effect as you're in thicker atmosphere, and going faster.  I'd wager by the time you reach periapse, it's already your periapse, and with each half-cycle, the worsening drag would increase the amplitude of this oscilation until descent became terminal.

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20 hours ago, Archgeek said:

I get the sense that the're'd be a steadilly worsening oscillation.  From a perfectly circular orbit just too low to stay an orbit, you'd immediately develop a periapse opposite your position, falling and kinda wandering in your direction as you go.  As you start to fall towards it, the drag begins to affect your apoapse more, and with more effect as you're in thicker atmosphere, and going faster.  I'd wager by the time you reach periapse, it's already your periapse, and with each half-cycle, the worsening drag would increase the amplitude of this oscilation until descent became terminal.

Skylab spent *years* in a decaying orbit[1] that had to be roughly ~90 minutes.  Any positive feedback oscillation would be pretty unstable and crash *way* earlier.  I'm pretty sure the orbit was almost exactly circular up to the end.  This isn't Kerbin, anything in LEO is eventually coming down (anything in GSO is almost certainly batted into low PE by the Moon before it comes down and I wouldn't be surprised if something from the graveyard orbit could eventually be ejected).

[1] look up Shuttle plans to save Skylab.  They new it was decaying when they planned its orbit (ISS requires a certain amount of fuel brought up with the other supplies, or maybe just some delta-v delivered by the docking craft).

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True, but that's a 90 min cycle in a very tenuous atmosphere.  Drag is extant enough to doom anything up there, but also insanely low, enough that microsats with differential light and dark sides can use radiative pressure from the sun alone to stay up in the face of it.  I expect the oscillation'd have a fairly high exponent, which means it'd start out very, very weak, growing less than linearly at first.  There's a reasonable chance that the nasty zone of the curve doesn't come up until long after a descent would be terminal anyway.  Granted, it's possible I'm not considering the affect of the drag still experienced in the sides of the orbit, and it'd just be a gradually tightening spiral.

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