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43 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

With the helium tightly sealed inside? No. Once the density of the atmosphere is as thin as the density of the helium gas, the buoyant net upward force is gone and the balloon stops going further up. ...
rfl's user avatar
  • 6,465
29 votes
Accepted

Is it possible to statically generate lift with the difference in pressure like wings?

The cartoon is missing a key feature: the flow beyond the wing is downward. This is necessary to create lift. The lift force is balanced by a force on the air, Newton's third law in action. This force ...
John Doty's user avatar
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27 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

I think some people are misunderstanding your question: you're asking if a helium balloon can be used as propellant, the same way if you release a balloon it will fly through the room. The answer is ...
AccidentalTaylorExpansion's user avatar
25 votes
Accepted

Earth magnetic field space elevator. No cable

Setting aside the technical details, the biggest problem with this idea would be Earnshaw's theorem, stating that it is impossible to stably levitate a magnetic dipole in another magnetic dipole's (...
Andréas Sundström's user avatar
22 votes

Is it possible to statically generate lift with the difference in pressure like wings?

If you have a difference in pressure, then fluid will flow to equalise that pressure unless restricted by a barrier. If you have a barrier then that's a balloon, if you don't have a barrier than you ...
Pioneer_11's user avatar
15 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

I'll start from the premise that a helium-filled party balloon has risen through the atmosphere to the point of buoyant equilibrium without otherwise changing significantly, and we then let the gas ...
Scott McPeak's user avatar
12 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

No This is essentially analogous to asking if an inflatable boat can fly. A helium balloon will ascend until it reaches the atmospheric "surface", and then it will stop and float. In much ...
Ruadhan2300's user avatar
11 votes

Do helicopters and planes fly by different reasons?

The basic principles are exactly the same. A rotor blade is sometimes referred to as a rotary wing. An airfoil is an airfoil, no matter where you put it. All subsonic aircraft wings, whether fixed or ...
Guy Inchbald's user avatar
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11 votes

How much vacuum is needed to lift?

At 101.325 kPa (abs) and 15°C the density of air is 1.225 kg m$^{-3}$, so a balloon made of massless but very rigid material will lift 1.225 kg for each cubic meter of volume.
mike stone's user avatar
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10 votes

Is it possible to statically generate lift with the difference in pressure like wings?

The purpose of wings is to generate this lift in a dynamic situation. If there is a low pressure area and a high pressure area in a system and they are connected, then air will flow from the high ...
Cort Ammon's user avatar
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9 votes

Antigravity force in powered precession gyroscope

This scheme gets invented every 20 years or so and then gets promptly disproved both by experiment and by dynamical analysis. For example, I thought that I had invented this very scheme with my ...
niels nielsen's user avatar
8 votes

The physics of airplane flight

Lift counters Weight. Thrust counters Drag. They are at right angles to each other. I could explain how airplanes fly, but John S. Denker has the best explanation I know of. High-school teachers know ...
Mike Dunlavey's user avatar
7 votes
Accepted

Is the downforce of rain on airplanes negligible?

The impact of new drops even in heavy rain has only a small effect. From force x time = change in momentum $$F\times 1 = 0.021 \times 10^{-3}\times 1000\times 9$$ where the 1000 is for the density of ...
John Hunter's user avatar
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6 votes

What really allows airplanes to fly?

Nib's answer is correct. The highly upvoted answer from Sklivvz starts promising but then throws in some incorrect statements: Explanations showing a wing profile without an angle of attack are ...
Koyovis's user avatar
  • 317
6 votes

Dimensional Analysis: How to choose the repeating variables?

Application of the Buckingham Pi Theorem for your problem goes as follows. 1.) List and count the $n$ variables in the problem. Here we have a lift force $F$, speed of the aircraft $V$, sound speed ...
TRF's user avatar
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6 votes
Accepted

Generating lift by Naruto running

If you wanted to get an estimate of how fast you'd need to be moving in order to lift yourself with air deflection from running, you need to establish a couple of important parameters: Body weight $p$...
aghostinthefigures's user avatar
6 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

Helium is used in balloons because it is lighter than air, which is the reason why such a balloon rises. That’s why it only works up to a certain altitude. Once you’re high up enough, air becomes so ...
interstellxxr's user avatar
6 votes
Accepted

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

After reaching this height, can the helium balloon be used as a propellant, the same way if you release a balloon, it will fly through the room? Sure. There's pressure built up in the balloon ...
HiddenWindshield's user avatar
5 votes
Accepted

Boundary Layer Physics and Bernoulli Principle

Bernoulli is a statement of conservation of energy in a fluid flow. As such, it is only valid for inviscid flows. It is still useful for real fluids because in the interior of the flow viscous effects ...
Ben51's user avatar
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5 votes

The physics of airplane flight

For any airplane to fly level at a constant altitude, the amount of lift generated by its wings must be equal to its weight. If lift exceeds weight, the plane climbs. If weight exceeds lift, the plane ...
niels nielsen's user avatar
5 votes

Can anyone explain this thrust - weight - lift paradox for airplanes?

The thrust is used to keep the plane at a constant speed $v$ in horizontal direction. It compensates the friction, which would slow the plane down. However, the lift is due to Bernoulli's equation $p +...
Semoi's user avatar
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5 votes

Trains - can aerofoils reduce friction?

The friction that trains must overcome is almost purely air resistance, not rolling resistance. Rolling a steel wheel on an equally hard surface (i.e. the rails) is extremely efficient. Adding wings ...
polwel's user avatar
  • 1,335
5 votes

Can astronauts fly like birds in the space station?

Winged flight is possible in microgravity, as shown by these pigeons on a parabolic flight. Clearly some adjustment to flying technique is required based on the need to generate thrust and not lift. ...
FTT's user avatar
  • 1,625
5 votes

Can a balloon start from Earth and fly to the Moon, using Helium for lift to the top of the atmosphere and then as propellant?

A fundamental challenge you will run into is that bouyancy and rocket propulsion want to opposing things. For bouyant lift, you want low densities. This means relatively low pressures. However, for ...
Cort Ammon's user avatar
  • 49.7k
5 votes

Is it possible to statically generate lift with the difference in pressure like wings?

It's worth noting that the diagram you've shown is a common misconception; it's almost identical to the one on this NASA webpage explaining what's known as the "transit time" myth. In fact, ...
anaximander's user avatar
4 votes

Why don't rockets tip over when they launch?

There are a couple of things at work here. First - the rotational inertia of the rocket is quite large. That means that if it were to "fall over", it would do so very slowly Second - it only "falls ...
Floris's user avatar
  • 119k
4 votes

A drone, or any lifting vehicle, enclosed in a container. Will it lift along with the container?

The reason why it will not work is because the air that the drone is pushing down will push the bottom of the container down too. Imagine yourself in a box half your height. Will you be able to get ...
Alex Doe's user avatar
  • 1,025
4 votes

Suppose we do this experiment in a vacuum, will the small pieces of paper behind the bottle be blown?

Using the kinetic theory. The reason there is motion behind the bottle is that the particles of gas bounce off other particles of gas to move those behind the bottle. If there is only one particle of ...
Ponder Stibbons's user avatar
4 votes

Why is the drag of the plane flying less than the lift?

The two formulas are almost the same, so why is drag less than lift? Drag is less than lift because aerospace engineers are generally competent at their jobs and so they design the shape of aircraft ...
Dale's user avatar
  • 102k
4 votes

What is the bare minimum of air density you need to fly a helicopter?

The lift generated by a helicopter is linearly proportional to the air density (as it is for planes). To fly we need the lift to be greater than the weight of the aircraft, so as the density reduces ...
Nick's user avatar
  • 1,418

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