Refueling without docking

[guituga---]

I went on a flyby to Eve and then came back to SOI of Kerbin but i just had Delta-v to orbit around Kerbin and i need to get the vessel back to Kerbin for the contract to complete.  Is there any way for me to refuel the vessel without docking and get back to Kerbin or do i need to flyby Eve again?

Edited June 28, 2021 by guituga---

[Caerfinon]

If you don't want to plan a rendezvous refuel mission your could always edit the persistent.sfs file from your saved game, find your ship, locate the empty fuel tank part, change the numbers so the tanks is full again.

The section with the active vessels is FLIGHTSTATE

Look for your vessel's name; it will look like this;

		VESSEL
		{
			pid = 1e9af2d3ef3d465ab364c1a2436ce57b
			persistentId = 1529596895
			name = Scan Sat 1 RA

Then search for resources in the ship. The fuel tanks look like this. Change the amount to the same number as the max amount

				RESOURCE
				{
					name = LiquidFuel
					amount = 6.6646537167559128
					maxAmount = 18
					flowState = True
					isTweakable = True
					hideFlow = False
					isVisible = True
					flowMode = Both
				}
				RESOURCE
				{
					name = Oxidizer
					amount = 8.1456872087368488
					maxAmount = 22
					flowState = True
					isTweakable = True
					hideFlow = False
					isVisible = True
					flowMode = Both
				}

Save the persistent.sfs file and restart your game

NOTE: FIRST MAKE A COPY OF YOUR PERSISTENT.SFS FILE IN A SAFE LOCATION.  (to avoid loosing your whole game)

[Streetwind]

The Advanced Grabbing Unit (also called "the klaw") is a part that can latch onto another ship and establish a docking connection without the need for a docking port on the target ship. Though, note, I'm not sure if certain difficulty settings might not interfere with fuel transfer across the klaw. Even in that case, though, you can still use the engines on the ship with the klaw to pull your Eve return craft's orbit down to intersect with the atmosphere. After that, it's just a question of aerobraking until you reenter.

[guituga---]

Quote

6 minutes ago, Caerfinon said:

If you don't want to plan a rendezvous refuel mission your could always edit the persistent.sfs file from your saved game, find your ship, locate the empty fuel tank part, change the numbers so the tanks is full again.

The section with the active vessels is FLIGHTSTATE

Look for your vessel's name; it will look like this;

		VESSEL
		{
			pid = 1e9af2d3ef3d465ab364c1a2436ce57b
			persistentId = 1529596895
			name = Scan Sat 1 RA

Then search for resources in the ship. The fuel tanks look like this. Change the amount to the same number as the max amount

				RESOURCE
				{
					name = LiquidFuel
					amount = 6.6646537167559128
					maxAmount = 18
					flowState = True
					isTweakable = True
					hideFlow = False
					isVisible = True
					flowMode = Both
				}
				RESOURCE
				{
					name = Oxidizer
					amount = 8.1456872087368488
					maxAmount = 22
					flowState = True
					isTweakable = True
					hideFlow = False
					isVisible = True
					flowMode = Both
				}

Save the persistent.sfs file and restart your game

NOTE: FIRST MAKE A COPY OF YOUR PERSISTENT.SFS FILE IN A SAFE LOCATION.  (to avoid loosing your whole game)

 

I dont want to cheat, but thanks for answering!

[guituga---]

8 minutes ago, Streetwind said:

The Advanced Grabbing Unit (also called "the klaw") is a part that can latch onto another ship and establish a docking connection without the need for a docking port on the target ship. Though, note, I'm not sure if certain difficulty settings might not interfere with fuel transfer across the klaw. Even in that case, though, you can still use the engines on the ship with the klaw to pull your Eve return craft's orbit down to intersect with the atmosphere. After that, it's just a question of aerobraking until you reenter.

Okay, i will do that, thanks for the answer!

[18Watt]

@Streetwind’s suggestion of using the Klaw, or Grabbing Unit is probably your best bet.   However, now that Kerbals can add parts to vessels in flight there are a few more possibilities.

• If you can’t dock because your ship doesn’t have a docking port, you can add one using the new EVA construction tools.  I know this works with the Docking Port Jr. (the small one), and also the Inflatable Docking Port.  Not sure if the regular one is too big or not.  But it is now possible to add docking ports to vessels after launch.
• I don’t recommend doing this, but you could also attach a small fuel tank.   By repeatedly switching which ship the tank is attached to, you could eventually transfer however much fuel you need to your ship.  That would be a painfully tedious process however.

In the end, the best solution is likely going to be using the Klaw to dock the two vessels.   Most players don’t use this setting, but it is possible to have a setting prevent fuel transfer through the Klaw.  If your game is set up that way, here’s two ways to get around it.

• Change the setting back to allow fuel transfer through the Klaw.   I think the setting is called something like ‘fuel transfer obeys cross feed rules’.  You want that box unchecked.
• Or, you could bring a fuel hose (the yellow ones) and connect the two ships using the EVA construction tools, to add the fuel line- bypassing the Klaw.

[guituga---]

Quote

2 hours ago, 18Watt said:

@Streetwind’s suggestion of using the Klaw, or Grabbing Unit is probably your best bet.   However, now that Kerbals can add parts to vessels in flight there are a few more possibilities.

• If you can’t dock because your ship doesn’t have a docking port, you can add one using the new EVA construction tools.  I know this works with the Docking Port Jr. (the small one), and also the Inflatable Docking Port.  Not sure if the regular one is too big or not.  But it is now possible to add docking ports to vessels after launch.
• I don’t recommend doing this, but you could also attach a small fuel tank.   By repeatedly switching which ship the tank is attached to, you could eventually transfer however much fuel you need to your ship.  That would be a painfully tedious process however.

In the end, the best solution is likely going to be using the Klaw to dock the two vessels.   Most players don’t use this setting, but it is possible to have a setting prevent fuel transfer through the Klaw.  If your game is set up that way, here’s two ways to get around it.

• Change the setting back to allow fuel transfer through the Klaw.   I think the setting is called something like ‘fuel transfer obeys cross feed rules’.  You want that box unchecked.
• Or, you could bring a fuel hose (the yellow ones) and connect the two ships using the EVA construction tools, to add the fuel line- bypassing the Klaw.

 

Thanks for saying other alternatives, but i think i will use the Klaw.

[herbal space program]

On 6/28/2021 at 8:46 PM, 18Watt said:

  Most players don’t use this setting, but it is possible to have a setting prevent fuel transfer through the Klaw.  

I'm playing a hard* career game, and that seems to be the default setting. I don't know where in lower difficulty levels that changes.

*except with quicksave enabled

[herbal space program]

On 6/28/2021 at 1:36 PM, guituga--- said:

... but i just had Delta-v to orbit around Kerbin and i need to get the vessel back to Kerbin for the contract to complete....

I don't know if you have a quicksave that you could go back to, but how did you determine that you had just enough dV to get to Kerbin orbit but not to land?  Specifically, how did you set up your transfer? From an optimal Eve-Kerbin transfer, most craft can enter Kerbin's SOI with a low enough velocity that they can aerobrake all the way to the ground. I think an initial  PE of 52-55km should be about right to get you aerocaptured on your first pass, but you may have to fiddle a bit. Once you're in some kind of high-AP orbit, you can adjust your PE as needed from that AP for next to nothing, keeping it at a height that slows you down significantly on each pass but doesn't make you burn up. If you can't quite get captured without boosting, then you should do so as close to your PE as possible and stop as soon as you see yourself no longer escaping Kerbin.

[Cavscout74]

19 minutes ago, herbal space program said:

I'm playing a hard* career game, and that seems to be the default setting. I don't know where in lower difficulty levels that changes.

Not on my game computer right now, but if I remember correctly - hit Esc, click settings, at the bottom is a button marked "advanced settings" or something like that.  Click that & it will take you to the same settings windows you had when creating the save.  One of those tabs has the "Fuel Transfer obeys crossfeed rules" option, near the bottom left on whichever tab it's on.

[guituga---]

42 minutes ago, herbal space program said:

I don't know if you have a quicksave that you could go back to, but how did you determine that you had just enough dV to get to Kerbin orbit but not to land?  Specifically, how did you set up your transfer? From an optimal Eve-Kerbin transfer, most craft can enter Kerbin's SOI with a low enough velocity that they can aerobrake all the way to the ground. I think an initial  PE of 52-55km should be about right to get you aerocaptured on your first pass, but you may have to fiddle a bit. Once you're in some kind of high-AP orbit, you can adjust your PE as needed from that AP for next to nothing, keeping it at a height that slows you down significantly on each pass but doesn't make you burn up. If you can't quite get captured without boosting, then you should do so as close to your PE as possible and stop as soon as you see yourself no longer escaping Kerbin.

Yes i have a quicksave when i was next to Eve. I will play KSP in a few minutes but i remember my PE is at least +250km. 

Edit: The vessel where i went has 7868 delta-v and the delta-v i had after the Eve flyby was 1448 delta-v. The AP of the Kerbin orbit is 7441km and the PE is 2358km.

Edited June 30, 2021 by guituga---
Added Information

[herbal space program]

29 minutes ago, guituga--- said:

Yes i have a quicksave when i was next to Eve. I will play KSP in a few minutes but i remember my PE is at least +250km. 

If you are near Eve with Kerbin encounter that has a 250km PE already dialed in, then it should take just a tiny amount of dV to lower that to just inside Kerbin's atmosphere. In fact, you may want to warp forward until you're about halfway there so you'll have better control.  Did you do a plane change burn anywhere? That would be a good spot to do this.  Either way, place a maneuver node just in front of your vessel and twiddle the handles until you see a PE of say 60km. Then advance the game to where you're just outside of Kerbin's SOI and quicksave  (or alt-quicksave) again. From there, you can adjust your PE up or down as needed to get a safe aerocapture, starting at ~55km.  Even if you can't  get to Kerbin orbit purely by aerobraking, any retrograde boosting you do  from that lower PE will be significantly more efficient than trying to slow down into orbit from 250km, and will be added to whatever slowing you can get from drag.  Those two things combined should leave you plenty of dV when you first make orbit to manage your subsequent aerobraking passes and safely lower your AP until you're in low orbit.

Edited June 30, 2021 by herbal space program

[herbal space program]

4 hours ago, guituga--- said:

Edit: The vessel where i went has 7868 delta-v and the delta-v i had after the Eve flyby was 1448 delta-v. The AP of the Kerbin orbit is 7441km and the PE is 2358km.

Not sure how you converted your Kerbin flyby into that orbit, but you definitely don't want to circularize with such a high PE if your goal is to get to the ground.  Whichever of those altitudes was the PE of your original Kerbin flyby, if you had boosted retrograde from there until you were just in orbit, i.e.  with an AP near the edge of Kerbin's SOI, you could probably have taken your ship to that high, slow spot in its orbit and from there dropped your PE inside Kerbin's atmosphere for a couple of hundred m/s at the most.

[guituga---]

32 minutes ago, herbal space program said:

Not sure how you converted your Kerbin flyby into that orbit, but you definitely don't want to circularize with such a high PE if your goal is to get to the ground.  Whichever of those altitudes was the PE of your original Kerbin flyby, if you had boosted retrograde from there until you were just in orbit, i.e.  with an AP near the edge of Kerbin's SOI, you could probably have taken your ship to that high, slow spot in its orbit and from there dropped your PE inside Kerbin's atmosphere for a couple of hundred m/s at the most.

I remember the PE was at 7000km when i did the Kerbin flyby but i was going so quick (i dont remember the speed) that the delta-v i had just wasnt enough to reenter Kerbin. I tried to lower the PE with RCS but i just could get it to 1600km before my monopropellant ended. Another thing is that the orbit is 180º, so it will be a bit hard to rendezvous.

Edited July 1, 2021 by guituga---

[herbal space program]

2 minutes ago, guituga--- said:

I remember the PE was at 7000km when i did the Kerbin flyby but i was going so quick (i dont remember the speed) that the delta-v i had just wasnt enough to reenter Kerbin. I tried to lower the PE with RCS but i just could get it to 1600km before my monopropellant ended. Another thing is that the orbit is 180º, so it will be a bit hard to rendezvous.

Based on that, I would guess that you didn't do a burn at your orbital node to change planes, which would have you coming into Kerbin's SOI either far above or far below it. WHat you need to do to fix that if you try again is to look for the little yellow marker that says "AN" or "DN", and boost either normal or anti-normal to reduce the angle between your orbit and Kerbin's. That should put your PE  much closer to Kerbin and by extension solve all your other problems. Just find that spot in your transfer orbit, place a maneuver node there, and pull on the purple N/AN handles until the two orbits are in the same plane. If you double-click on Kerbin to make it the map focus with that node open, zoom in to Kerbin, and rotate the view so you can see your node behind it, you should be able to make adjustments to the node and clearly see how that will change your Kerbin encounter.

[guituga---]

2 minutes ago, herbal space program said:

Based on that, I would guess that you didn't do a burn at your orbital node to change planes, which would have you coming into Kerbin's SOI either far above or far below it. WHat you need to do to fix that if you try again is to look for the little yellow marker that says "AN" or "DN", and boost either normal or anti-normal to reduce the angle between your orbit and Kerbin's. That should put your PE  much closer to Kerbin and by extension solve all your other problems. Just find that spot in your transfer orbit, place a maneuver node there, and pull on the purple N/AN handles until the two orbits are in the same plane. If you double-click on Kerbin to make it the map focus with that node open, zoom in to Kerbin, and rotate the view so you can see your node behind it, you should be able to make adjustments to the node and clearly see how that will change your Kerbin encounter.

Oh ok, i will try that tomorrow. Thanks for replying!

[guituga---]

7 hours ago, herbal space program said:

Not sure how you converted your Kerbin flyby into that orbit, but you definitely don't want to circularize with such a high PE if your goal is to get to the ground.  Whichever of those altitudes was the PE of your original Kerbin flyby, if you had boosted retrograde from there until you were just in orbit, i.e.  with an AP near the edge of Kerbin's SOI, you could probably have taken your ship to that high, slow spot in its orbit and from there dropped your PE inside Kerbin's atmosphere for a couple of hundred m/s at the most.

I made the Kerbin encounter again, made a orbit around Kerbin, went to the AP and burnt Retrogade until 35km and aerobraked until i landed in the sea, thanks for the help!

[herbal space program]

8 hours ago, guituga--- said:

I made the Kerbin encounter again, made a orbit around Kerbin, went to the AP and burnt Retrogade until 35km and aerobraked until i landed in the sea, thanks for the help!

No problem! I'm glad my advice was helpful.