Awesome, thank you!!! If we start now, the next gen might get to see alpha proxima.

But you do create a spark with the engine on. Around 1200 sparks/minute while it's idling.

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Many early cars had the gas tank right at the base of the windshield, above the engine. You can imagine the risk of fire if fuel was spilled on top of a running engine.

Cars can backfire at idle, possibly sending embers out the exhaust, a spill while filling a tank can put fuel on the ground, the fuel vapor that rapidly develops can be ignited by hot soot particles if the engine backfired.

These things are not much of an issue nowadays, but fuel spills still create a serious hazard and it's definitely safer to turn vehicles off for this reason.

For the last 40 years or so, vehicles have had sealed fuel systems for fuel vapor control. An emissions system. If the car is running while fueling, the system will detect a leak and a check engine, ses light will be illuminated.

>Spacecraft need to eject mass to move forward. Essentially they are pushing off parts of themselves, and leaving it behind.

They do not need to. Light sails exist and have been used by some satellites. So you can just let the light from the sun push you.

There is no way that filling the tank will change the output pressure of the fuel pump. I'm sorry but nothing you described here is accurate.

Do the people for whom this applies also suffer the paradoxical effect of being made sleepy by coffee?

Seems like this guy vehicles.

Rocket engines work by pushing out exhaust gases behind them at high speed. It's the same principle as the recoil on a gun.

> I’m basically asking how interstellar travel would even be possible.

Well, it would be very difficult. You would need either to wait a long time or to take a vast amount of fuel with you, bearing in mind that the more fuel you add, the heavier the rocket becomes and the more thrust is required to achieve the same acceleration.

And even if you do have a super-powerful rocket and a magical never-ending supply of fuel, you have to worry about the g forces, since presumably you want to travel to this other star safely and comfortably.

Of course, it's possible that someone will eventually discover some new physics that allows us to get around some of these problems. But without that, it is pretty hard to imagine how interstellar travel could ever become feasible (other than Voyager-style probes that get there very slowly and don't carry humans).

On or off doesn't matter to the car at all during fueling.

The prohibition is to help prevent some human caused fire issues, namely generating static charge (sparks) by getting in and out of the car. You can proactively discharge the static harmlessly by touching the car's metal before you grab the fuel dispenser to remove it.

Carburetors and older/cheaper fuel injection systems use a mechanical switch to determine how much fuel goes into the engine. This switch is usually controlled by a float that is quite literally floating on some of the gas that is entering the engine. If too much gas is entering the engine, the float rises and pushes the switch closed. When the level of gasoline drops, the float sinks to allow more in.

The buoyancy of that switch is calibrated against the amount of gas that the fuel pump is delivering to the engine - which will be a fixed value. IE, if the fuel pump is delivering 1 psi of fuel to the engine, the float will be set to press on the switch with 1 psi of pressure when the fuel supply needs to be cut off.

Pumping fuel into your car can increase the amount of pressure in the system, which can increase the amount of pressure coming out of the fuel pump - particularly when the tank is near full.

So imagine that your tank filling up causes a pressure surge and that 1 psi of fuel normally coming out of the fuel pump briefly spikes to 5 psi. That's going to mean that the switch in your carburetor/fuel injector doesn't close and more fuel keeps going in even though the engine is full. That could potentially flood your engine.

A flooded engine can be anything from a minor inconvenience to something that burns out your starter motor.

You don't need air to push off of. Rockets, chemical thrusters, and ion engines work in space because they spit out some sort of propellant, spitting out mass in one direction pushes the ship in the opposite direction

nuclear bombs also work in space, you drop nukes behind you and they can push your craft in your desired vector

once you have reached your desired speed, you don't need to do anything to keep going. you WILL need to expend energy or mass to slow down when you reach your destination

I don’t have a reference for this, but I was told by my father that it dates back to the days when filling stations pumped gas for you and it was to help stop people from accidentally driving off before the pump jockey was finished. They didn’t have pop-off hoses then either, so driving off with the hose still in the filler hole could do damage all around.

You don’t^*

Where I am, gasoline and petrol are generally full service and they do not require or ask you to shut off your engine before filling your tank.

Contrast that with the full service LPG stations where they require you to turn off the engine to fill your tank even if your tank isn’t even connected to your vehicle.

^* Some restrictions apply. Please refer to local code for details.

Newton's third law of motion. For every action there is an equal and opposite reaction. If you push an object backwards, then that object will push you forward. When it comes to space travel we use the exhaust from the rocket. The act of pushing gas out the back of the ship pushes the ship forward. You can actually see this effect for yourself. Stand on a skateboard and throw a heavy object. You will accelerate in the opposite direction.

You push off your propellant. In order to make your ship move, you expell superheated gas out the back at extremely high velocity. Basically, you bring the stuff you push off of with you.

By analogy, if you're standing on a skateboard and throw a ball, you'll move in the direction opposite your throw. You may be resting on the ground, but you didn't push off of the ground. Rather, you pushed off the ball.

Also not mentioned is that the evap system could sense a leak and make a check engine if it runs with no vacuum.

You bring propellant with you and eject it in the opposite direction you want to go. Because momentum is conserved that causes you to move. You don’t need to push off anything.

You’ve identified why spaceships don’t use propellers or jet engines…there’s no air. Propellers and jet engines push air so they only work in an atmosphere.

So instead you have to push off something. The most common way is to create a controlled explosion and shoot the expanding gases out a nozzle. Smaller releases of gas can be used to make smaller changes, like to point slightly to the left or right, or to start or stop rotation.

Once moving there’s no air to create drag so once you’re going as fast as you want to go you turn your engine off and just coast along. You’ll still be affected by gravity, so you have to account for that. And there is a small amount of gas even in mostly empty space.

For interstellar travel there’s a different proposed solution to the problem. You see in order to use exploding gases to accelerate you fast enough to make traveling to another star achievable within the lifetime of the astronauts you’d have to use a lot of fuel, and fuel is heavy, and takes even more fuel to carry into space. Instead you can deploy a large sail and catch the wind coming off of the sun or fired from a laser on earth, similar to how a sailboat catches the wind. That can get you going to 10% light speed. You’d reach the nearest star in just about 40 years! We’re still a little ways off from being able to construct a sail thin and light enough while still being strong. But we’ll get there soon.

Spacecraft need to eject mass to move forward. Essentially they are pushing off parts of themselves, and leaving it behind.

That mass is often burnt exhaust gasses from rockets. For small adjustments they tend to use compressed gas directly since it's easier to control. No need to constantly start and stop a rocket motor.

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Much of the car is grounded back to the battery negative. Spark could happen anywhere then. Also not supposed to get in and out of the car to stay warm too. Higher chance generating static in winter

Yeah but what about the car being on increases the chance of a spark by the gas tank? I can understand sparks cause from static, or smoking while filling up, etc

Besides what's already posted, I'd think with a running car you would have a better chance of accidentally taking off with the hose.

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