Jumping on fumes

iain666

iain666
I'm sure someone's done this experiment so I don't have to...

You've got your big tank that you jump with, and you've got your little tank that the ship runs off.

Does the level in the little tank have any effect on jump range? For a given mass of fuel in the main tank can I jump further if the little tank is nearly empty than if it's just refilled?
 

Sapyx

Sapyx
Interesting question. Does the game calculate "actual" mass of the ship in fractions of a tonne, or does it round all masses to the nearest tonne for jump range purposes?

I would assume the answer is "no", the 1-tonne-capacity so-called "reserve fuel tank" (I prefer the term "active fuel tank" or even something like "fuel cell", as "reserve tank" implies it's available to use in an emergency, when it actually isn't) would be considered part of the ship's mass, and thus constant.
 

Straha Yeagar

S
Interesting question, and as it turns out, I have an answer :)

I did not set out to specifically experiment with this, but rather observed the answer while doing some precision fume jumping. Short answer is yes, the fuel in the reserve tank does minimally affect jump range as if it were in the main tank. It does not just all of a sudden turn massless when it moves from the main tank into the reserve tank. I discovered this by looking at my jump range, then stepping away from the flight controls for an hour or so, and coming back and noticing my range has slightly increased by .01 ly. My reserve tank had gone from almost full to half full.
 

CMDR Eryn Liamson

CMDR Eryn Liamson
iain666 said:
For a given mass of fuel in the main tank can I jump further if the little tank is nearly empty than if it's just refilled?
Click to expand...

No. I've tried this recently when out on the edge of the galaxy using a plasma slug accelerator to dump fuel. The ships range doesn't increase until the reserve tank empties and refills from the main tank.
 

Straha Yeagar

S
Supermoose said:
No. I've tried this recently when out on the edge of the galaxy using a plasma slug accelerator to dump fuel. The ships range doesn't increase until the reserve tank empties and refills from the main tank.
Click to expand...

Interesting, because that is different from my experience simply sitting and idling fuel out of the reserve tank. I did gain range as it decreased. That was a while ago, well before plasma slugs were in the game, so perhaps it has changed.
 

Major Klutz

Major Klutz
It might depend on the mass of the ship. Whether a half ton or 0.9 t of fuel can affect the jump range by 0.01ly, enough to be observable.
It would have more of an effect on a smaller ship I think.

Personally, on distant stars I had to wait a to burn off fuel to make the big neutron jump to M67. In my engineered and stripped down Asp Explorer, I did not see any change in jump range whatsoever until my "power plant tank" completely emptied and refilled.
IIRC, I had to burn off about three tons before I could make the jump.
 
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CMDR Eryn Liamson

CMDR Eryn Liamson
straha20 said:
Interesting, because that is different from my experience simply sitting and idling fuel out of the reserve tank. I did gain range as it decreased. That was a while ago, well before plasma slugs were in the game, so perhaps it has changed.
Click to expand...

Hmmm.... I'll try it again. May be the ship type too. Small drops in fuel for a very light ship can show up, but it's too small a change in a 600T Anaconda. What ship did you try this in?
 

Straha Yeagar

S
Supermoose said:
Hmmm.... I'll try it again. May be the ship type too. Small drops in fuel for a very light ship can show up, but it's too small a change in a 600T Anaconda. What ship did you try this in?
Click to expand...

That is quite possible, and would explain our seemingly different observations. I am in a lightweight engineered AspX, and with rounding when it comes to mass and range, if your rounding flip coincided with the full amount of fuel in the reserve tank, it could flip for you as the tank fills and my lower mass, the rounding would flip with a partial tank.
 

Shinji Ikari

Shinji Ikari
Maybe a Hauler would help testing this idea.

Either way, I crunched the numbers based on this reddit post https://www.reddit.com/r/EliteDangerous/comments/30nx4u/the_hyperspace_fuel_equation_documented/

Here are the results:

asfOpZs.jpg


So the reserve fuel should make a noticeable change.
 

Allitnil

Allitnil
Here's what I've found:

1) The jump range as displayed in the right hand panel functions tab fully takes into account the fuel in the reserve tank. Specifically, it includes both the weight of the fuel and assumes that you could use it as part of the jump. The functions tab range will increase as the reserve tank runs down (as long as you have more than one jump of fuel in the main tank) although you might need to relog to see the displayed range increase.

2) When actually attempting to make a jump, the reserve tank level is completely ignored with all the fuel in it being treated as though it were massless.

This can be tested in a couple of ways:

a) With more than one jump of fuel in the main tank and the reserve tank nearly empty empty look at right hand panel range and find a system fractionally under that distance away. Select the system in the galmap and attempt the jump - you should get the max distance exceeded message. Wait until the reserve tank empties and refills and you will now be able to do the jump.

b) Run down your main tank and jump to a (scoopable!) star such that you arrive with a nearly empty main tank and the reserve tank as near full as possible. Select a system close to your normal max jump range away. Now slowly scoop fuel until the right hand panel just shows you have just enough jump range (*) and attempt the jump - you will get the insufficient fuel message. Scoop a reserve tank of fuel (**) more and you can now make the jump.

* - my technique for this is to first go to the right hand panel modules tab and select the fuel scoop. Then sit in the edge of the corona slowly scooping whilst watching the functions tab. As soon as the desired jump range is about to be reached turn off the fuel scoop (like this it's just a quick pressing of the right UI tab control twice followed by select twice). Check range and if not quite achieved, back to the modules tab and quickly turn the scoop on and back off again, recheck level & repeat as necessary. With care you can precisely set your fuel level like this.

** - varies by ship; don't know if anyone has fully tabulated them but for the Hauler it is 0.25 T and for the Conda 1.07 T.


What this means in practice is that if you have slightly too much fuel then you need to burn off enough to get the reserve tank to refill from the main one, just running the reserve down a bit won't help. Also if you are trying to scoop to an exact amount then you can't fully trust the right hand panel figure.

PS: last time I tested this in detail was during 2.3 but I've not noticed any obvious change with 2.4
 

JonathanBurnage

JonathanBurnage
I'm rather interested to know how this works as I found myself playing fuel light bingo not too long ago. I was trying to reach a very far out system needing a really big jump, so I had to be very light on fuel. Precision scooping was required at the beginning of the run so I would have the right amount. After some calculations...

eZYrpFS.jpg


...I set off. On the way out my jump range was exactly as I predicted. For the trip back I had to make the big jump and then another one after that to reach a scoopable star. I couldn't carry much fuel across the big jump; I used Allitnil's strategy and sipped fuel whilst repeatedly hitting the hyperspace button, until the ship was too heavy to jump. I then burned off fuel in supercruise until I was at exactly the maximum weight allowed.

The right panel range indicator was indeed unreliable as the ship made the first jump whilst apparently not having quite enough range (I was about 0.2LY short when it let me go). For the second jump to the scoopable star my range was about 1LY short of what I had calculated. I've always wondered why it didn't quite match; I assumed it was the reserve tank adding weight but not contributing fuel to the jump. However, this appears to be wrong. Any ideas?

The tale had a happy ending. I was able to make the final jump to safety - just (fuel gauge below).

A3pJTP6.png
 

Shinji Ikari

Shinji Ikari
JonathanBurnage said:
I'm rather interested to know how this works as I found myself playing fuel light bingo not too long ago. I was trying to reach a very far out system needing a really big jump, so I had to be very light on fuel. Precision scooping was required at the beginning of the run so I would have the right amount. After some calculations...

https://i.imgur.com/eZYrpFS.jpg

...I set off. On the way out my jump range was exactly as I predicted. For the trip back I had to make the big jump and then another one after that to reach a scoopable star. I couldn't carry much fuel across the big jump; I used Allitnil's strategy and sipped fuel whilst repeatedly hitting the hyperspace button, until the ship was too heavy to jump. I then burned off fuel in supercruise until I was at exactly the maximum weight allowed.

The right panel range indicator was indeed unreliable as the ship made the first jump whilst apparently not having quite enough range (I was about 0.2LY short when it let me go). For the second jump to the scoopable star my range was about 1LY short of what I had calculated. I've always wondered why it didn't quite match; I assumed it was the reserve tank adding weight but not contributing fuel to the jump. However, this appears to be wrong. Any ideas?

The tale had a happy ending. I was able to make the final jump to safety - just (fuel gauge below).

https://i.imgur.com/A3pJTP6.png
Click to expand...

I'd assume so though 1 ton of weight difference is probably not very noticeable in a larger vessel.
 

jimbeau1571

J
Allitnil said:
Here's what I've found:

1) The jump range as displayed in the right hand panel functions tab fully takes into account the fuel in the reserve tank. Specifically, it includes both the weight of the fuel and assumes that you could use it as part of the jump. The functions tab range will increase as the reserve tank runs down (as long as you have more than one jump of fuel in the main tank) although you might need to relog to see the displayed range increase.

2) When actually attempting to make a jump, the reserve tank level is completely ignored with all the fuel in it being treated as though it were massless.

This can be tested in a couple of ways:

a) With more than one jump of fuel in the main tank and the reserve tank nearly empty empty look at right hand panel range and find a system fractionally under that distance away. Select the system in the galmap and attempt the jump - you should get the max distance exceeded message. Wait until the reserve tank empties and refills and you will now be able to do the jump.

b) Run down your main tank and jump to a (scoopable!) star such that you arrive with a nearly empty main tank and the reserve tank as near full as possible. Select a system close to your normal max jump range away. Now slowly scoop fuel until the right hand panel just shows you have just enough jump range (*) and attempt the jump - you will get the insufficient fuel message. Scoop a reserve tank of fuel (**) more and you can now make the jump.

* - my technique for this is to first go to the right hand panel modules tab and select the fuel scoop. Then sit in the edge of the corona slowly scooping whilst watching the functions tab. As soon as the desired jump range is about to be reached turn off the fuel scoop (like this it's just a quick pressing of the right UI tab control twice followed by select twice). Check range and if not quite achieved, back to the modules tab and quickly turn the scoop on and back off again, recheck level & repeat as necessary. With care you can precisely set your fuel level like this.

** - varies by ship; don't know if anyone has fully tabulated them but for the Hauler it is 0.25 T and for the Conda 1.07 T.


What this means in practice is that if you have slightly too much fuel then you need to burn off enough to get the reserve tank to refill from the main one, just running the reserve down a bit won't help. Also if you are trying to scoop to an exact amount then you can't fully trust the right hand panel figure.

PS: last time I tested this in detail was during 2.3 but I've not noticed any obvious change with 2.4
Click to expand...

I concur with the above. My recent Abyss crossing had me bleeding the tank to make a refill, in order for the main tank to empty a little and gain the 0.1ly I needed for the next jump. The whole crossing was done on as little of fuel as possible. The main tank was filled each jump trying to scoop no more than to gain max jump range. I was doing it by scooping at no more than 400t/s, and turning away from the star so the fuel level never went beyond the letter 'E' in the word fuel. If it got to 'L', I was begining to lose range through too much fuel on board.
 
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