No flying conditions

[scarpelius]

Let's say we have this planet which is atmosphere-less due to the fact it is tidally locked.
I would like to make the flight at the planet surface expensive in terms of fuel or even prohibited by particular conditions of the planet.
Up until now I come up with just one idea:

• gravity is higher than Earth, not much, maybe 1.2 times, which will increase the fuel consumption and thus making it impractical for commercial use;

P.S.
Tidally locked means that the rotational period is equal to the orbital period. So point A is ALWAYS facing the Sun, no matter where the planet is on its orbit (found this explanation on internet)

 

[Brian G Turner]

atmosphere-less due to the fact it is tidally locked.

This doesn't make any sense to me - the presence of an atmosphere will depend upon the composition of the planet, not whether it is tidally locked or not.

If you mean no weather, again, it would make no sense - it's basic physics that warm gases on the side facing the sun will become energetic and rise, forcing cooler air from the dark side to be drawn in - creating impressive wind speeds.

Also, "expensive" relates to economic principles, not technological ones - and that political interests can work against economical ones (cf the Apollo missions in the 1960's). Again, it's nothing to do with gravity.

In which case, it may be better to look for political or even cultural/religious reasons rather than scientific ones for restrictions on atmospheric flight. After all, if you're on a completely different world to Earth, its principles are not going to be developed relative to Earth but in spite of it.

2c.

 

[Biskit]

atmosphere-less due to the fact it is tidally locked.

This puzzled me. As @Brian G Turner pointed out, I don't think a lack of atmosphere is necessarily a consequence of tidal locking.

 

[Phyrebrat]

And wouldn't technology like an ekranoplan make the issue somewhat redundant?

Edit: sorry, misread the OP.

pH

 

[Ursa major]

I would like to make the flight at the planet surface expensive in terms of fuel or even prohibited by particular conditions of the planet.

The absence of an atmosphere would make flight difficult: without an atmosphere, wings wouldn't be of any use, so you'd need the engine(s) to provide vertical, as well as horizontal, thrust (not to mention thrust to allow one to steer the craft).

 

[Venusian Broon]

Now I could imagine a situation where a tidally locked planet has no atmosphere - a planet is more likely to be tidally locked to it's star the closer it is. At an orbit of, say Mercury's or less, the sun would probably quite effectively strip a rocky planet of it's atmosphere (see Mercury!)

However as others have hinted at, the main determiner of atmosphere should be the mass of the planet. Even Mercury can hold onto some gases in the face of the intense solar weather. A more massive planet will probably have even more (quite heavy) gases.

Oh, and flight kinda suggests you will be flying. i.e. using an atmosphere. I guess you mean ballistic/rocket transport?

Of course this also depends on the type of star you are orbiting. Orbiting a sun-type star at 'reasonable' distance for tidal locking will probably mean that one side of the planet will molten metal, the other a freezing wasteland....however if you are orbiting a much more feeble red dwarf then the star's output could be much less and will not make the planet a hellish dual world. (But also therefore more likely to retain an atmosphere...)

Yeah, having a massive Earth-type planet with a higher than 1g gravity will up the cost of transport for getting into orbit - but will also make life for any humans quite brutal as we're adapted for a 1g planet

 

[Ihe]

As someone pointed out, you cannot have atmospheric flight if there's no atmosphere to push off of. So, if the planet had an atmosphere, maybe the heated gases in the planet's sunside could ruin a spaceship's integrity, so you're only allowed to fly on its darkside? Although making it a political/religious no-go zone, as @Brian G Turner suggested, is a great idea, and is what I would do--it'd also give you an excuse to do some world-building about the sacred/forbidden planet's history.

 

[scarpelius]

I need to explain more of my story setting:
Because the planet is tidally locked most of its atmosphere had frozen over time in the dark side or simply was stripped by its sun. Also, in my mind, not sure is true or not, a tidally locked planet might have lost is inner core rotation, thus no magnetic field to protect its atmosphere from the solar wind.
As @Venusian Broon mentioned, I choose a planet whit metal liquid on hot side and nitrogen liquid on cold side. It might exists or might be impossible, but for my story it is imperative to be this way. There is no life as we know it on this planet and no human colonies, except for a mining town. This only settlement is under a big dome which is protected against asteroids and particular disruptive conditions of the planet. The colony is set on the twilight zone where the sun is just but a dim line at the horizon, on the single flat surface existent. The rest of the planet surface is very fractured making the land exploration to very difficult to impossible.
Due to the fact it is a mining colony resources are scarce. For a jet engine flying machine to work, you will need a lot of fuel. But the stakes are high and this is no longer an obstacle. People could jump into a flying machine and start surveying the fractured zone to find more mining pockets.

So, considering the above, I need to limit peoples ability to fly over the planet surface.

 

[Ursa major]

For a jet engine flying machine to work

For a jet engine flying machine, you would need an atmosphere: jet engines don't work in a vaccuum, as the fuel needs something to react with (on Earth, it's oxygen) and the jet engine gets this from the atmosphere.

The only difference between

• "flying" above the landscape on a planet with no atmosphere, and
• travelling in space

is that the landscape is a lot closer to the vehicle when one is "flying".

 

[scarpelius]

True, jet engines need air. Then we are talking about some sort of rocket type propulsion.
And i think this solves the problem, because a rocket engine will require massive reservoirs, which is impractical to use in an exploration vehicle.
Thanks guys.

 

[Plucky Novice]

If my science is right, the need for a reservoir of fuel isn't the only problem. Rocket engines need oxygen, normally in the form of highly explosive liquid oxygen. You therefore need a source of oxygen. Are there frozen water sources on your planet? If not, where does the oxygen come from?

Of course with this problem, staying alive will be a bigger issue than flying about.

 

[Plucky Novice]

Actually, now I come to think about it, where's the rocket fuel going to come from?

Or food for the settlers? Resources will be almost non-existent in such a harsh environment. I'm sure you've got this covered, the dome is a great idea but don't forget to put a floor on it. If the planet is in a vacuum any gas or liquid will disappear through the ground. Not sure what happens on rock?

Sorry I've gone completely off topic...

 

[scarpelius]

@Plucky Novice This is a mining colony. Every resource they need, they get it from outside the planet. For the water and gases, they could mine the dark side. The dome has its flooring, but that is beside my interest. Only the begining of the story take place under the dome and it doesn't require to describe the environment too much.
Anyway, I don't need to build a full featured universe. I had a dilemma over why the main protagonist wouldn't use a flying vehicle, rather than crawl for days in a ground vehicle.

 

[Ihe]

Concerning tidally locked sun and darkside gases/liquids, I thought that those sort of planets still had atmospheric currents because of the heat diferential, at least where light and dark meet on the surface, as one heats up enough to rush towards the cold and viceversa. Don't quote me on this; I might be far off, but I'd think that would give you some more options if it's true.

 

[scarpelius]

@Ihe I had thought of that, burst of gases traveling through the twilight zone, posing problem for inhabitants.
It suit my story better to have near absolute zero temperatures on dark side and above 500 degree Celsius on light side. Our Mercury have -180 Celsius and +427 Celsius and is not completely tidal locked (1 year is 88 earth days and rotation period around its axis is 58 earth days).
Anyway, thanks for your comment, it gave me a great idea.