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I’m currently working on a scene for a book where the heroes stumble across a seemingly abandoned Age of sail airship. After a brief investigation they find that the entire crew seems to have mysteriously dropped dead. How and why I am keeping close to the vest, but what I want to know is, if all the crew are dead, how long could such a ship remain airborne? I want to know weather or not the ship will be flying or crashed by the time my heroes stumble across it.

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    $\begingroup$ The Age of Sail was circa 1600-1850 and the first practical airship flight wasn't until 1852. (By definition, airships have an engine and balloons do not.) So it is unclear what this question is even asking. Moreover, the nature of the airship is unspecified, e.g. type of lift (hot air or lifting gas) and propulsion. $\endgroup$ Aug 24 at 2:21
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    $\begingroup$ Hi OP - no airships existed in Age of Sail. There were balloons, very limited in size with a crew of not more than 1 or 2, but no 'ship'. These came later and divided into blimps (soft controllable balloons) or airships (rigid, or semi-rigid, controllable 'airships'). You might want to clarify which one you are referring to. $\endgroup$
    – flox
    Aug 24 at 5:45
  • $\begingroup$ It's WBSE guys, we're filled with anomalous tech (for the real world at various times in history) type questions so I don't think the lack of the airships during the age of sail is a question killer by itself though it deserves a nod & maybe a suggestion the OP gives attention (perhaps a question) to how that tech can plausibly develop (or not) within the environment of the prevailing tech level of course. $\endgroup$
    – Pelinore
    Aug 24 at 9:46
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    $\begingroup$ @flox -- and other commenters: keep in mind that in the world the OP is presenting to us, Age of Sail airships EXIST. It's not our job to carp about their world or complain that it wasn't like that on Earth or that it's scientifically impossible, but rather to work with the world the querent gives us. $\endgroup$
    – elemtilas
    Aug 24 at 14:30
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    $\begingroup$ @elemtilas The question still remains: what kind of airship is it? If the querent is asking for something anachronistic, they need to provide the specific details of the anachronism in order for the question to be answerable. $\endgroup$ Aug 24 at 14:47
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Rigid Airships require constant adjustment - ie. likely not very long at all (minutes only)

Unfortunately, rigid airships ('Airships' implies rigid, which are motored and different from 'blimps') require constant operator input to stay afloat. This is because rigid airships can only have one 'buoyancy setting', the gas inside the gas bags are inflated, and lift is altered only by:

  • adjusting ballast
  • adjusting pitch of propellers
  • adjusting pitch and speed of airship as a function of wind over control surfaces

Initial buoyancy settings are set to allow the airship to be controlled in normal flight and allow it to land (landing being one of the most dangerous requirements of airship flight).

Unless the initial buoyancy setting is quite high, by the release of all ballast, the airship will succumb to either:

  • common downdrafts forcing the airship to lose altitude (faster than you may think, this was the cause of many airship crashes)
  • pitch adrift, causing loss of control and propellers to orient in a way that could cause the airship to pitch down
  • wind movement over incorrect control surface settings, causing pitch down and loss of altitude

As they require constant adjustment, an estimate of time with a complete loss of control would mean the airship really only has minutes to survive, maximum perhaps an hour, unless all ballast is released suddenly, causing lift upwards.

However even if this happened the airship is still susceptible to downdrafts or wind which can only be countered by pitch up propellers and elevators in normal flight, so in these events no control would still cause an imminent crash and loss of the airship.

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  • $\begingroup$ Sorry - didn't get the 'Age of Sail' on first pass - there were no airships in the 'Age of Sail' so frame challenge would be that question is not answerable. My answer here is using 'Airship' reference and not 'Age of Sail' reference. $\endgroup$
    – flox
    Aug 24 at 5:43
  • $\begingroup$ "minutes" You sure about that? the specific airship design is important I'm sure not to mention the situation at the time everyone dies & loss of control' isn't the same as 'it drops out of the sky' // it's basically a balloon, with the cells fully filled & all ballast jettisoned for maximum altitude, depending on the exact design could potentially stay up for hours, maybe even days in unlikely ideal conditions. $\endgroup$
    – Pelinore
    Aug 24 at 9:18
  • $\begingroup$ OK you have covered all that ^ answer could benefit from an estimate under ideal conditions to go with the worst case scenario, how about if they all drop dead in the middle of a long flight with higher altitude settings, something like a transatlantic flight with calm skies perhaps? $\endgroup$
    – Pelinore
    Aug 24 at 9:35
  • $\begingroup$ @Pelinore It's basically an aircraft where instead of a lift being supplied via airspeed over the wings, it is supplied via bouyancy, however control, direction and altitude are all controlled through finely tuned, constant inputs on control surfaces and propeller orientation - in this manner it acts like a slow moving aircraft. I did some flying lessons and as an experiment, let the stick not have my input. The aircraft (slowly at first) started to drift and I realised without inputs the aircraft would quickly be unrecoverable within seconds. An airship would take longer, but not much longer. $\endgroup$
    – flox
    Aug 24 at 9:41
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    $\begingroup$ An airship that loses engine power can be (and in a number of cases has been) flown as a free balloon, balancing venting of lifting gas against dropping of ballast. atlasobscura.com/places/crash-site-of-the-uss-shenandoah After a squall broke the ship's back, the nose half was flown as a free balloon by the surviving crew aboard that section as they sought a survivable landing. $\endgroup$
    – Zeiss Ikon
    Aug 25 at 16:51
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It seriously depends on the airship. For example some airships blimps can stay up for as little as 24 hours. Some may stay up for a few days to a week. Basically until the lifting gas escapes, which depends on the gas. But lets assume the lifting gas does not escape, then until the first storm comes and breaks the airship, since they are quite fragile (Most airship disasters were because of this. Such as the USS Shenandoah) But if it was made with age of sail manufacturing, I'd give it a week at most, since the would gas to escape, but certainly not over a hundred, since the fabric of the shell would rot assuming the airship magically avoided all storms.

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Absolute maximum: half a day

The buoyancy of an airship changed constantly from many factors, but the greatest of these is the simple thermal heating of the gas from sunlight warming. Both direct (on the surface of the blimp) and via atmosphere heating in the daylight.

As the air around the blimp warm or cools, and as the gas in the blimp warms and cools at different rates, the buoyancy of the blimp gets upset.
Unattended, it will either sink down until it hits the unforgiving surface of the Earth, or worse it will rise up unchecked until it hits the even less forgiving limit of altitude where the pressure safety valves of the gas bladders are forced to vent gas to prevent rupturing.
Once vented, and especially with no crew to replenish (if there even is a way to replenish, which is very uncommon!!) the airship will start descending very rapidly, and is due for another meeting with the hard surface of the Earth.

Some blimps, and all dirigible airships like Zeppelins, controlled their altitude dynamically, by literally "flying" up or down using control surfaces. They could also drop ballast to lighten themselves, or vent gas to make themselves heavier, but these were undesirable as they consumed very limited resources, whereas steering via control surfaces just required a tiny amount of fuel to keep the dirigible moving to enable the control surfaces.

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Like the ocean, the atmosphere can have temperature and density layering. If it happens that the ship's buoyancy was trimmed correctly to float on a denser air layer (cold air trapped in a valley or canyon, for instance) the ship might remain aloft until leakage of the lifting gas brings it down.

Alternatively, if the ship happens to be trimmed "light" when control is lost (or close to neutral with engines running, which will make the ship light as fuel burns off), it will climb, ultimately to "pressure altitude" where the gas in the lift cells cannot expand further (because of limited space or elasticity in the cell material); if the cells are strong enough, an airship might remain at that altitude (much too high for crew survival without oxygen) until, once again, lifting gas leakage brings it down. In fact, if control of the gas vents was lost, this might be what killed the crew -- a combination of hypoxia and hypothermia as the ship ascends uncontrollably to the tropopause.

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Mysterious boy.

Aside from the ships cat, there is a survivor on this age of sail airship - a boy. He is a foreigner of some sort - and a deaf mute and possibly a simpleton. But he has kept the boilers fired on the ship and kept other things running. He cannot steer the ship or land it and he does not know how to signal for help, but he knows enough to keep the ship aloft and he knows he does not want to crash.

He has covered the bodies of the dead with sails but otherwise left them alone. He probably saw what happened. Or so one would think.

The cat will have nothing to do with this boy.

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  • $\begingroup$ Hmm, I like the idea of a traumatized survivor, thank you very much. $\endgroup$ Aug 25 at 2:43
  • $\begingroup$ Re: "boilers fired", fuel is heavy and an airship wouldn't carry much excess beyond what is necessary to get to the intended destination. Perhaps the survivor is burning the cargo but the cargo capacity wouldn't be all that high and much of it would likely be things that either aren't burnable or lower energy density than fuel. And if the airship uses liquid or gaseous fuel, the cargo wouldn't even be usable to replace fuel at all. $\endgroup$ Aug 25 at 3:31
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    $\begingroup$ "I like the idea of a traumatized survivor" the cat? $\endgroup$
    – Pelinore
    Aug 25 at 9:41
  • $\begingroup$ @GrumpyYoungMan - acknowledged; boilers seem to violate "age of sail". But the OP does not give us much to work with and mechanics are not the question here. There are airships and they are vehicles and must be tended. If you like, in your head you may replace "boilers" with "tanks containing 8th Barsoomian Ray". $\endgroup$
    – Willk
    Aug 25 at 12:14

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