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Why do recoverable parts need a pod/probe?


Sigma117
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As he said it and i understood it, this is only for debris near KSC. For simple drops on chutes while already in your gravity turn you should be able to recover the debris if you follow them down.

It's said its for performance wich makes sense because you wont clutter your launch side up with junk and have better performance launching.

And things, which you actually will fly back to KSC for 100% refund, will have a probe body for control anyway.

So only restriction i see is: Dont drop anything down while still heading strait up! But you won't anyway because it would delete it after passing 2.5 km, unless you follow it down, which deletes your ship, unless your high enough and inserted an orbit, whereas you wouldn't land near KSC anyway with your uncontrolled debris unless you have a probe body attached anyway.

So if you understand this pretty long sentence you see there is practically no problem, unless you test this system on purpose, like in Scotts Video ;)

Jeb: I can't see any problem whatsoever ;)

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Seems to me landing near KSC happens to delete debris, but isn't the only reason you need a probe core or pod on your recovered ship. I'm guessing the current gameplay mechanic only lets you recover funds from "piloted" craft. That means probe core or pods.

I'm not sure, but I believe currently (0.23.5) the recovery button is only available for those piloted parts. Guessing they didn't change it for 0.24.

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Is that a technical, or design choice?

Only just learnt about the restriction by watching Scott Manley's latest video.

Without a probe core or pod, parts are considered "debris" instead of a vessel, and can be removed automatically. This is probably a combination of technical limitations (current debris removal algorithms) and conscious design choice.

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Right now there's not a good way to tell what was jettisoned and what "fell off" due to any number of "mishaps". It's a design choice to not recover things that "fell off" due to "mishaps" because those parts should be damaged... beyond repair. But it's a technical limitation that there's no distinction between these two types of "debris".

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I am of the opinion that any "debris" should have a value if only as scrap metal. That said there should be some logic to the staging that would allow an object that was "properly released as part of a stage" to maintain a small bubble of existence allowing it to land if the player designs it to do such. So a booster with chutes could be a simple example. They are something that should be recoverable as long as they have a parachute that would reduce their velocity to below the impact tolerance.

Though...may be this entire discussion is a little off just because the contract rewards look to be enough to account for the wasted parts. So if this a difficulty thing? Or is it a mental glitch that we do not like the idea of waste in a game where waste is irreverent?

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I cannot see how a rocket body, empty and under parachute, could possibly survive a landing on hard ground. These things are like paper machete or thin-walled coke cans. Drop them even at 0.5 m/s on one corner and the entire thing will bend out of wack. Ever notice how fast the shuttle moved on that crawler? They are meant to take force in one direction and that direction only.

And after watching the vids, the stock contracts seem to give an inordinate amount of 'funds'. I don't think anyone who has played KSP for more than a week will have any problem maintaining a positive bank balance regardless of recovery rates.

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The wonderful thing about a game is that it is not reality. So while in reality some parts would not be recoverable (Remember shuttle SRB's were recoverable) we do not need to worry about that when the numbers are all that count. So if an object has a crash tolerance of 4m/s then darn it, all you need are enough chutes on it to get it below that critical threshold.

I do agree that people will not need to build 100% recoverable things. But at the same time being able to recover bits and bobs and get some amount of refund is also not much to request.

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I cannot see how a rocket body, empty and under parachute, could possibly survive a landing on hard ground. These things are like paper machete or thin-walled coke cans. Drop them even at 0.5 m/s on one corner and the entire thing will bend out of wack. Ever notice how fast the shuttle moved on that crawler? They are meant to take force in one direction and that direction only.

And after watching the vids, the stock contracts seem to give an inordinate amount of 'funds'. I don't think anyone who has played KSP for more than a week will have any problem maintaining a positive bank balance.

The shuttle crawler moves that slowly, because of balance issues, its not like some 92 tons sticking up like a pencil on its end or anything o.O. That and in reality they aren't in a hurry, its soon to go so fast it gets into orbit. Also the "Shuttle" crawler, was designed for the Satarn rockets, which where literately pencils standing on its end. So 'going fast' is not something you wanna do when your transporting a table with a pencil standing up on its end.

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I cannot see how a rocket body, empty and under parachute, could possibly survive a landing on hard ground. These things are like paper machete or thin-walled coke cans. Drop them even at 0.5 m/s on one corner and the entire thing will bend out of wack. Ever notice how fast the shuttle moved on that crawler? They are meant to take force in one direction and that direction only.

And after watching the vids, the stock contracts seem to give an inordinate amount of 'funds'. I don't think anyone who has played KSP for more than a week will have any problem maintaining a positive bank balance regardless of recovery rates.

I'm guessing there'll be something in the configs, a simple contract reward multiplier or something, so we can change that pretty easily if we want more of a challenge.

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I cannot see how a rocket body, empty and under parachute, could possibly survive a landing on hard ground. These things are like paper machete or thin-walled coke cans. Drop them even at 0.5 m/s on one corner and the entire thing will bend out of wack. Ever notice how fast the shuttle moved on that crawler? They are meant to take force in one direction and that direction only.

And after watching the vids, the stock contracts seem to give an inordinate amount of 'funds'. I don't think anyone who has played KSP for more than a week will have any problem maintaining a positive bank balance regardless of recovery rates.

If it won't take a landing at a certain speed, its crash tolerance should be reduced. As it is, we know exactly what speed it'll take a landing at.

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The wonderful thing about a game is that it is not reality. So while in reality some parts would not be recoverable (Remember shuttle SRB's were recoverable) we do not need to worry about that when the numbers are all that count. So if an object has a crash tolerance of 4m/s then darn it, all you need are enough chutes on it to get it below that critical threshold.

I do agree that people will not need to build 100% recoverable things. But at the same time being able to recover bits and bobs and get some amount of refund is also not much to request.

Not necessarily. Remember, a stage could quite easily be (and likely would be) made of different parts, with different impact tolerances. Also, the terrain it lands on is quite important as well - land on a slope, and it's entirely possible that the whole stage would fall over, if physics was still being simulated on it, destroying some of the parts on the top, perhaps. Similarly, landing in water is a very different experience to landing on dry land, as the effects of lithobreaking are no longer a thing. The actual landing site of the stage is also somewhat required - distance from KSC determines recover value. Without fully simulating physics, the stock game has no way of getting all the data it needs to generate an accurate recovery value, making this less trivial than it seems.

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The shuttle crawler moves that slowly, because of balance issues, its not like some 92 tons sticking up like a pencil on its end or anything o.O. That and in reality they aren't in a hurry, its soon to go so fast it gets into orbit. Also the "Shuttle" crawler, was designed for the Satarn rockets, which where literately pencils standing on its end. So 'going fast' is not something you wanna do when your transporting a table with a pencil standing up on its end.

Also you gotta think about inertia. If you could get the CT (crawler/transporter) to move at 30mph, then the shuttle stack would be moving at 30mph, and then you'd have to be able to stop, but the upper part would keep going (although it's not like the crawler could stop all that fast anyway).

Like you mentioned balance was the biggest problem, as the ground isn't exactly flat, plus it has to go up hill to get the MLP to the tower, so it had hydrolics that adjusted to keep the MLP level as it went up the hill, and hydraulics take a little bit of time to actuate.

As far as KSP goes, I mentioned in another post that I remember seeing a mod that allowed you to customize the distance at which things unload/physics stops/starts. I don't remember the name of it, but it could come in handy now IF you wanted to recover everything you dropped. You could set the unload distance to 70k(plus some for curvature) or whatever so boosters, and other spent stages wouldn't unload and would be recoverable if they survived.

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And i think you'll be fine recovering any debris far away from KSC. It works through the Tracking Station right know, so it should in 0.24. Only deleted on the Ground of KSC;)

While this is true, there is one important thing to note. Debris that you jettison, i.e. stages, disappear after 2.5km, because they are still in motion. If you were sitting still/crashed/landed and THEN dropped your stages, they would stay as debris. This rule changes when you reach orbit.... anything you jettison in orbit technically is still moving when you go 2.5km away from it, however there are no physics to track other than position at that point, since it's not interacting with an atmosphere. Much easier and CPU friendly to track, therefore it is. I think the devs also knew that people would want to see their debris cluttering orbit, because it's realistic. Sources: Tons of experimentation. And, I slept at a Holiday Inn last night.

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If it won't take a landing at a certain speed, its crash tolerance should be reduced. As it is, we know exactly what speed it'll take a landing at.

Except that KSP doesn't do crash tolerance in particular directions. It just takes the impact and checks against the part's crash tolerance. It doesn't say that the part is good for impacts in one direction or another. SRBs, particularly shuttle's as they were build in segments so they could transported by train (insert politics) are tough because they are one giant combustion chamber. Liquid fuel tanks are more like tinfoil balloons. Has a liquid fuel tank ever been recovered and reused?

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Except that KSP doesn't do crash tolerance in particular directions. It just takes the impact and checks against the part's crash tolerance. It doesn't say that the part is good for impacts in one direction or another. SRBs, particularly shuttle's as they were build in segments so they could transported by train (insert politics) are tough because they are one giant combustion chamber. Liquid fuel tanks are more like tinfoil balloons. Has a liquid fuel tank ever been recovered and reused?

Well, technically Shuttle had liquid (monopropellant) fuel tanks and they were recovered every time, so yes. But in terms of large, cryogenic boost-phase tanks where the tank represents the major structural element, I don't know of any successful recoveries thus far.

But it's not impossible, or at least SpaceX doesn't think so, as they have outfitted their Falcon 9 first stages with landing legs and intend to attempt to recover them in the future. The first attempt managed a water landing, but I don't think the stage was in condition for reuse. Maybe next time. (http://www.nasaspaceflight.com/2014/02/spacex-crs-3-landing-legs-plan-first-stage-recovery-ambitions/).

This would make a great high-tree technical ability: "Recovery and Re-usability".

The way I see it, it would work like this:

1. All jettisoned debris without a control function is 100% lost, as it is currently (I think), until the Recovery tech is researched.

2. Once the tech is researched, two things happen: i) you get a new part, the "auto chute" which can be used to slow the decent of jettisoned parts, and ii) the acceleration survival rating of all parts in the tree are increased by, let's say, 20%, due to better hardening and engineering. If the number of chutes installed is sufficient to get the jettisoned assembly under the lowest acceleration rating in the jettisoned part list, the part is automatically salvaged. Penalties for distance from KSC remain. In addition:

a. Any part whose acceleration rating is violated is destroyed 100% and the remainder are penalized 15% each for collateral damage due to the failed part (you get a report explaining what happened).

b. Part trajectories during reentry are estimated based on an assumed wind resistance acting as a gravity vector, so they don't drain processor (is this possible? I don't know, maybe). The intent would be to realistically estimate the reentry location without having to do a full physics simulation.

c. Parts landing in water get no landing damage penalty. Parts landing on plains get a 10% landing damage penalty. Parts landing on desert, ice, or mountains get a 20% landing damage penalty. Parts landing on rugged mountains get a 50% landing damage penalty. Landing physics are thus handled procedurally, not through physics simulation.

d. The difficulty of recovering thin liquid fuel tanks would be handled by giving them very unforgiving g-force survival ratings. Solid boosters, struts and frames, and other gear would have more robust ratings and so the auto-chute would work very well for them.

3. There could be a "Recovery and Reusibility II" tech, that would i) boost your part acceleration rating further and ii) give you a new module, similar to a control pod, but radially attachable and very light. It would automatically cause jettisoned liquid tanks/rockets to attempt a restart/landing, let's say with 75% success. But you'd have to jettison them with at least 5% fuel remaining, and the tank would have to have landing legs installed unless the landing was in water. That would close the loop and allow the player to attempt to reproduce SpaceX's feat. Again, the landing location estimate would be procedural, not physics based, and the damage/recovery value would be computed statistically per the overview above.

In reality, managing hardware costs are a huge part of running a space program, so this would allow/encourage realistically low contract payouts and would force the player to spend a considerable amount of forethought planning her reuse and recovery opportunities, which is very true-to-life. Because the recovery value/survivability percentages are quite adjustable as I've laid them out, this scheme could be play tested against several possible difficulty metrics, and could be adjusted for novices and experts in future releases.

Perhaps something like this will make it into the beta.

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Wonderful discussions. Personally I think it's a lot easier: because history.

Up to .24 there really was no value in any debris. With asparagus designs you'd easily be shedding hundreds of parts each launch, and littering Kerbin's surface had no real value but would slow the game down in the long run. So the obvious solution: if it's shedded during launch and doesn't have a command unit, it's debris, and you don't need it. So it gets deleted.

In-orbit debris is different because it has entertainment value (Kessler syndrome, cleanup missions) and besides that, not every command-less object in orbit is regarded "debris" by the player (think fuel tanks for refueling, etc).

I don't think it's something Squad really touched at the .24 release, not realizing that most players have spontaneously morphed into Scrooge McMizers and want to recover every last strut (god forbid you'd run out) even though you really won't run into funding problems if you don't.

Personally I just make the same launch vehicles as I did in the past, with maybe a few more SRB's instead of asparagus boosters, but I'm not trying to recover any ditched stages. And after a few days of game time I'm at $5M. Squad surely had experienced something similar when play testing so they didn't think people would be that desperate to recover everything.

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But it's not impossible, or at least SpaceX doesn't think so, as they have outfitted their Falcon 9 first stages with landing legs and intend to attempt to recover them in the future. The first attempt managed a water landing, but I don't think the stage was in condition for reuse. Maybe next time. (http://www.nasaspaceflight.com/2014/02/spacex-crs-3-landing-legs-plan-first-stage-recovery-ambitions/).

SpaceX is certainly trying to get their rocket back in one piece, but I have doubts about them reusing the entire structure. The chances of metal fatigue or any other flaw in the tank walls is too great. There are also lots of fuel lines to purge and clean. I'm betting that they will cut the engines off and reuse them separately rather than relaunch the entire stage. At a minimum they will have to disassemble lots of stuff to repeat the standard inspections that all parts go through during assembly. SpaceX has made it to orbit despite single-engine cutouts, as did Apollo 13's launch. So the insurance people will probably insist that the first "used" engines fly alongside new ones to guard against total failure.

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Long before 0.24 came along, I did experiments with recovery of launch vehicles. At the time, I was using two stage to orbit expendable rockets, consisting of a liquid fuelled core stage and solid fuelled strap-on boosters. The idea was to recover the core stage down-range by adding a large number of parachutes that would activate on separation. I would then park the payload vehicle in orbit and switch to the core stage so I could watch it re-enter the atmosphere.

The first thing I found was that I needed more parachutes that I had expected. Liquid engines and tanks have very low crash tolerances, so I added what seemed like a lot of parachutes, but as it turned out, the parachutes were frequently the only parts that survived the landing! The second problem was that a launch vehicle core stage is usually tall and thin. The first thing it wants to do after making contact with the ground or water is to tip over. Again, this does not sit well with low impact tolerances! After a lot of trial and error, I concluded that this method of recovery was unreliable and more trouble than it was worth. I switched to doing controlled landings instead, which worked much better. I eventually settled on using winged fly-back boosters that return to the runway at the KSC.

There have been a number of threads on the forums asking for a feature to be added to the stock game whereby spent stages are counted as recovered simply because the player stuck an arbitrary number of parachutes on it somewhere. As I discovered, recovering liquid fuelled stages by parachute is not a trivial matter.

At current prices, solid rockets are worth next to nothing when empty of fuel. Here are some "before" and "after" pictures of an SRB, showing how much it costs with and without fuel. As it turns out, most of the cost of the SRB is the fuel. The empty booster is worth very little.

O7BHFTL.jpg

B75dm0S.jpg

By contrast, here's a Rockomax "Oil Drum" tank shown both full and empty of fuel. As it turns out, most of the cost of liquid fuel tanks is the tank, not the fuel. In addition, the engines required to burn the fuel add additional cost, which I will want to recover if I can.

K2AgyGY.jpg

ABLkSIh.jpg

Therefore, adding a feature that automatically recovers my "trash bins full of boom" solid rockets is an irrelevance, since their recovery value is negligible. Adding a feature that automatically recovers large liquid fuelled rockets is a way of playing the game in easy mode.

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