Orbital propellant depot

[Temstar]

With docking and fuel transfer coming, orbital propellant depots are going to be all the rage soon. So gentlemen, in what ways do you think your game will change with the introduction of propellant depots?

Me I think I\'ll be designing and launching a lot fewer giant boosters to loft spacecraft full of fuel into orbit. Once depot is in I see myself building spacecraft in a way so they use up most of their own fuel to reach orbit. Then they will refuel from depot before going about their mission to Mars or something. The fact that boosters + spacecraft\'s own engine now only have to lift an empty spacecraft into orbit as opposed to one with full load of fuel means a dramatic reduction in size of rockets needed for the same mission at the cost of more launches to refill depots. On that note I would like to see parts like 'FL-T500 fuel tank (empty)' in the VAS.

Other than that I think Spacecraft Exchange is going to be full of people show casing efficient and reliable tanker designs since they will become an integral part of any long range missions.

[Stevenator1]

This also means that something like mechjeb would have to be implemented. It is INCREDIBLY challenging to manually rendevouz with anything in space, much less get it at the perfect spot to dock up with more fuel.

[xclusiv8]

That would be awesome! A question though. What would one do with the fueling stations once they are empty?

[Temstar]

I don\'t think an official mechjeb is required, wouldn\'t want to make this game too easy. AFAIK all of NASA\'s docking are all done manually too since NASA never had a unmanned resupply spacecraft.

Getting close to another craft is not that hard even in the current game, what is hard is to get both ships\'s docking interface to line up properly since currently any spacecraft not in focus will have its ASAS offline causing it to slowly rotation in random directions. To implement docking they at least need to have a way for ship to remember ASAS status when not being controlled. Ideally there should also be a docking helper module that knows how to rotate the ship one revolution per orbit so it always keeps one orientation relative to the body the ship is orbiting.

A docking cam with a crosshair and showing distance and speed of approach would be pretty important too, other than that I don\'t think any other aids are needed.

That would be awesome! A question though. What would one do with the fueling stations once they are empty?

Well two ways:

Method 1: The propellant depot stays exactly where it is and you send up tankers to dock with the depot and refill it. Afterwards the tanker is deorbited.

Method 2: The tanker itself is the propellant depot, once it\'s empty you just deorbit it and launch another one.

Both require expandable tankers, I don\'t think SSTO reusable tankers would be a good idea given their much smaller payload - you\'ll go crazy from all the rendezvous you have to make if you use SSTO reusable tankers. Method 1 is for those who like to build up a big permanent station in orbit and will be worth it if we get a lot of space station stuff like canadarms where you probably don\'t want to throw away. Method 2 needs less rendezvous but also results in less sophisticated depots.

Fun fact: NASA and ULA are working on method 2 style missions using half empty Centaur upper stages

[Stevenator1]

That would be awesome! A question though. What would one do with the fueling stations once they are empty?

Well you could push them out of orbit (if you set them up correctly at 70km orbit, only a little tap would airbrake them back down to earth), or use a large 'tanker' to bring fuel back up to them and refuel them.

[Temstar]

a large 'tanker'

Oh yes

27.5 tanks of fuel to bring 23.5 tanks to orbit, 46% payload fraction.

I\'ll put this up in the exchange tomorrow once I get some better pictures

[mrdest21]

An official Mechjeb would be necessary, I think. While some players claim that it\'s easy to rendezvous, I think the majority have never done it and an even greater number could never do it consistently. (I\'m not ragging on people, I\'ve never succeeded myself). Some people just want to fly spaceships, not make orbital charts and figure out optimal maneuvers for every little thing they do, especially when they have no clue how that stuff is even figured out.

As for a fuel depot, I wonder if we\'ll be able to 'attach' rocket parts with docking. The current fuel depot designs aren\'t so useful because the fuel depot itself has the fuel and possibly the engines to complete the mission. If Fuel Depot A has 100 units of fuel and you build a ship B to come and take the fuel and launch its mission, why not just stick some engines on fuel depot A and bypass having a Ship B?

[Oggula]

Perhaps an official mechjeb could be unlocked in stages by manually completing its component modules (e.g. Ascent, transfer, rendezvous, landing)- that way, the challenge would still remain, but you wouldn\'t waste time completing the same operations manually.

[sgtblazing]

If there is an R&D system like I believe has been mentioned, flight computers and planning can be researched but take time to get to which is the best of both worlds. You don\'t start with one, but you get one later on (and of course each mechanic is an individual piece of work). Personally I want to see the money / RnD put in asap as we are so accustomed to getting as much as you want with no limitations at all. The game will be better when it happens as it will turn into more of a game, but the sudden lack of anything you want will be aggravating.

[Phoxtane]

I\'ve always thought that a fuel depot should always be a WIP; that is, you should always be adding tanks to it. I like the idea of just docking tankers end-to-end and decoupling a tiny deorbit stage to bring the kerbonauts back.

[Bluejayek]

An official Mechjeb would be necessary, I think. While some players claim that it\'s easy to rendezvous, I think the majority have never done it and an even greater number could never do it consistently. (I\'m not ragging on people, I\'ve never succeeded myself). Some people just want to fly spaceships, not make orbital charts and figure out optimal maneuvers for every little thing they do, especially when they have no clue how that stuff is even figured out.

As for a fuel depot, I wonder if we\'ll be able to 'attach' rocket parts with docking. The current fuel depot designs aren\'t so useful because the fuel depot itself has the fuel and possibly the engines to complete the mission. If Fuel Depot A has 100 units of fuel and you build a ship B to come and take the fuel and launch its mission, why not just stick some engines on fuel depot A and bypass having a Ship B?

Constructing ships in space should definately be added. That being said, if we can launch \'empty\' tanks, the fuel depot thing can still be useful without construction in space. You launch a ship with empty tanks into orbit, use other smaller ships to fuel it. Then, you can use ships that don\'t have the engine power to take off with full tanks, launch them with empties, fill up at the fuel depot, and continue on.

[Nomad]

I am pretty sure something is being added to 0.16 to make rendezvous easier.

[Bluejayek]

I am pretty sure something is being added to 0.16 to make rendezvous easier.

Some sort of docking UI I believe. Distance and relative velocity (with direction). The velocity in particular will be awesome. It can acually be fairly hard to tell what direction something is moving in 3d on a 2d screen...

On a related note, when does KSP add support for 3d monitors?

[Temstar]

Constructing ships in space should definately be added. That being said, if we can launch \'empty\' tanks, the fuel depot thing can still be useful without construction in space. You launch a ship with empty tanks into orbit, use other smaller ships to fuel it. Then, you can use ships that don\'t have the engine power to take off with full tanks, launch them with empties, fill up at the fuel depot, and continue on.

This, it also allows construction of ships with structures that will only survive intact fully fuelled in microgravity. For example a large 100 FL-T500 capacity propellant depot when fully fuelled will be 250kg + depot hardware. To lift this propellant depot fully fuelled into orbit will require a colossal booster like http://kerbalspaceprogram.com/forum/index.php?topic=10468.0, three times the size of the depot and impose very strict requirements on the geometry of the depot or it will simply crush the booster underneath with its sheer mass. On the otherhand launching this depot empty will only result in a payload of 30kg + depot hardware, easily within the reach of your average heavy lifter and allowing more varied shapes like long docking arms more suited for a depot.

[samstarman5]

To those who are such proponents of a mechjeb, I want to remind them that many players here have achieved stable orbit, performed a trans-munar burn and injection, and landed on the mun all by the seat of their pants.

I don\'t see why a little docking maneuver makes an interface that takes so much out of their hands and makes the point of the game pointless necessary.

Mechjeb is nice as a modded option, but it shouldn\'t be necessary in KSP.

Remember we learn by failure here at the KSC. It is an option and it is to be expected. Once success is achieved then it is time to step up the game to the next rung and crash all over again.

Cave Johnson would be ashamed of you.

If you want a better example, check the threads that were posted once persistence was implemented, on all the bumps in space people submitted. Harv has already stated there will be a kerbal way to dock easing the process somewhat. That is good enough for me. Getting there is the best part of the challenge and I am not about to hand it over to some calculator.

As for orbiting depots, I am all for that. Using jets for boosters, you already have a more fuel-economical way to get payloads into orbit. It is worth trying out. I have already had a ball discovering what one can do with jet engines on a ballistic transport.

[rkman]

To those who are such proponents of a mechjeb, I want to remind them that many players here have achieved stable orbit, performed a trans-munar burn and injection, and landed on the mun all by the seat of their pants.

I don\'t see why a little docking maneuver makes an interface that takes so much out of their hands and makes the point of the game pointless necessary.

I agree there should not be (at least not early in the game) a one key 'rendevous-and-dock' function. Mechjeb currently does not have such a function, most people use mechjeb\'s rendevous module only to kill relative velocity and to aim at target. The rendevous function that people ask for isn\'t all that different from what mechjeb currently offers.

Let\'s be fair though, 'a little docking maneuver' (especially the orbital alignment and final approach) is quite a bit more difficult than landing on the Mun.

[Awaras]

An official Mechjeb would be necessary, I think. While some players claim that it\'s easy to rendezvous, I think the majority have never done it and an even greater number could never do it consistently. (I\'m not ragging on people, I\'ve never succeeded myself). Some people just want to fly spaceships, not make orbital charts and figure out optimal maneuvers for every little thing they do, especially when they have no clue how that stuff is even figured out.

As for a fuel depot, I wonder if we\'ll be able to 'attach' rocket parts with docking. The current fuel depot designs aren\'t so useful because the fuel depot itself has the fuel and possibly the engines to complete the mission. If Fuel Depot A has 100 units of fuel and you build a ship B to come and take the fuel and launch its mission, why not just stick some engines on fuel depot A and bypass having a Ship B?

Rendezvous is a piece of cake once you understand the basic principles. You need \'orbital charts and optimal maneuvers\' if you want to go for a direct, least time approach. I am quite happy \'eyeballing it\' - yes, it might take me 2-6 full orbits to make a rendezvous, but it is not that difficult.

[Steve5451]

It\'s quite easy to rendezvous once you get the hang of it. I\'ve done it several times just because I had nothing better to do.

A couple times I\'ve gone up just to blow up debris with the sunbeam laser.

[flaillomanz]

If there is an R&D system like I believe has been mentioned, flight computers and planning can be researched but take time to get to which is the best of both worlds. You don\'t start with one, but you get one later on (and of course each mechanic is an individual piece of work). Personally I want to see the money / RnD put in asap as we are so accustomed to getting as much as you want with no limitations at all. The game will be better when it happens as it will turn into more of a game, but the sudden lack of anything you want will be aggravating.

Just so long as they keep a sandbox mode open (Yes, with everything unlocked - I play this game solely because it is currently a sandbox) I\'m in agreement. I hope that Harvester and the other devs don\'t take half the fun out of the game by making everything cost 'money' or have to be 'unlocked' before it can be used in said sandbox.

[samstarman5]

Just so long as they keep a sandbox mode open (Yes, with everything unlocked - I play this game solely because it is currently a sandbox) I\'m in agreement. I hope that Harvester and the other devs don\'t take half the fun out of the game by making everything cost 'money' or have to be 'unlocked' before it can be used in said sandbox.

Harv has stated that sandbox is here to stay. Campaign will pretty much be a step up in the difficulty factor, when you consider the risk of losing kerbals you\'ve put a lot of training into, as well as watching a pile of cash you spent several missions building up disappear in a puff of smoke and dust on the Mun because of a failed landing.

Much as it may cost me a cordless mouse or two after a disastrous mission, I eagerly await the added challenges of campaign. Sandbox can easily be considered a training simulator, only without the added benefits of experienced crews and other features you should be able to acquire in Campaign.

[Awaras]

Just so long as they keep a sandbox mode open (Yes, with everything unlocked - I play this game solely because it is currently a sandbox) I\'m in agreement. I hope that Harvester and the other devs don\'t take half the fun out of the game by making everything cost 'money' or have to be 'unlocked' before it can be used in said sandbox.

I have played TogFox\'s and DonLorenzo\'s excellent forum campaigns, and I have to say that the addition of a budget and having to pay for each part you put on your rocket forces you to think harder about your designs and makes you build things more efficiently. It\'s great fun. A different kind of fun but still fun.