# Questions tagged [aerodynamics]

the effect on a spacecraft of moving through atmosphere, how its density, pressure, temperature, flow velocity, and viscosity affect a craft, and how lift and drag can be used to modify that.

31 questions
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### What would a “Kármán plane” look like, a bird, or a plane?

If I understand correctly (which I might not), the Kármán line is roughly the altitude where a "Kármán plane's" upward lift force at the orbital velocity for that altitude would be equal in magnitude ...
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### How long does Max-Q last?

When watching rocket launches, the commentary or status reports often mention that the vehicle is "passing through Max-Q" - how long does the "passing" take? Is the event instantaneous or is there ...
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### Gliding into the atmosphere

The recent question about Cessna reentering from ISS got the answers that all imply a rapid drop. But from what I know, air drag is proportional: to square of airspeed to air density to attack ...
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### Reason for different “cone angles” of different space capsules?

Here is the Cargo Dragon: And here is the Orion: The "cone" that orion makes has a large opening angle - perhaps about 70 degrees. Meanwhile, the Dragon is almost cylindrical - the opening angle is ...
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### Would a balloon pop if dropped from space?

Could a "simple" inflated party balloon be dropped from space entering an atmosphere? The first case at orbital speed, the second case just outside the atmosphere and the third interplanetary? The ...
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### Just how much can tall skinny rockets bend? (roughly, safely)

Below is a GIF I prepared and used in an earlier question, and the answer seems quite reasonable. With a height to diameter ratio of about 70 m to 3.7 m (nearly 20:1) a weight-conscious design, ...
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### Is the definition of the Kármán line from Wikipedia right? [closed]

Edit: this question is about making clear that the Wikipedia's article about the Kármán line is an interpretation, not the definition ! Why not consider the Kármán line as a curved boundary that ...
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### How high could a weather balloon be used on Mars without rupturing? [duplicate]

What is the maximum height could a weather balloon achieve on Mars without rupturing? Assume that the balloon is adapted for Mars' atmosphere and gravity from standard high altitude balloons used on ...
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### Upper stage structural loads on ascent?

In another question, this came up: For example, if a Falcon 9 launches 20 tons of fuel to dock in LEO, how can the same upper stage be used to launch 40 tons of fuel to the same orbit? Doesn't it ...
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### How would a long pole be transported to space?

Can a long pole or a set of poles be strapped to the out side of a rocket (like a bottle rocket)or on the nose as an external payload without interfering with the aerodynamics of the rocket? How would ...
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### Why are the nose cones of current spacecraft less pointy?

You would think that with the quest for aerodynamic efficiency in current spacecraft that the nose-cones at the pointy end of the launch-vehicle would have a sharp taper, more so for craft that aren't ...
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### Why are the cells on grid fins square in shape?

What is the reason for the square shape of the cells on grid fins such as those on the Falcon 9 landed by SpaceX, on missiles, or other places?
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### Angle of attack, or displacement angle?

When I hear "angle of attack" or AoA, I think of an airplane. Usually, both the airfoil and the plane itself have a clearly defined 'top' and 'bottom'. In this case, the concept of angle of attack is ...
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### Can more thrust come from launching parallel to water?

Would having the exhaust of a rocket or air breathing engine in an early stage in close proximity to water on a horizontal launch provide more thrust? Could a rocket launch off water horizontally in ...
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### Can it be calculated that near the Kármán line the lifting force equals the centrifugal force?

According to Wikipedia about the Kármán line: In the final chapter of his autobiography Kármán adresses the issue of the edge of outer space: ...or 24 miles up. At this altitude and speed, ...
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### Can a reusable electric powered blimp stage for launch possible?

Originally this question asked about using blimps and electricity in replacement of boosters. As written then it was no good and got down votes. I had a few question marks and each question really ...
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### Can a reentry be done slowly?

The usual approach to reentry is fast and hot. There's a lot of energy to be lost, and doing it quickly has some advantages: You can dump energy into hypersonic air, and then leave that heat behind ...
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### Would a dimpled heat shield reduce heat transfer during reentry?

Would a large ceramic golfball absorb less heat on reentry than a standard sphere? From aerospaceweb.org: The difference in the flowfields around a smooth sphere and a rough, or dimpled, sphere ...
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### Optimal speed per altitude for orbit launch

On Kerbin, rockets have an optimal speed depending on altitude for maximum fuel efficiency, as You can save fuel by being close to your terminal velocity during ascent. Lower velocity wastes delta-...
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### How do the dynamic pressure evolves during reentry?

During launcher ascent, dynamic pressure evolution is describe in this answer for the Saturn V. I suppose this is comparable from one launcher to another. Given the protections designed for reentry, ...
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### Could rockets launched from the ground use wings in the stages?

Could a slower or smaller rocket take advantage of lift if all the stages had wings? Could the stages reduce splashdown impact forces by using a spinning seedpod-like design (as shown in the image ...
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### What's the atmospheric drag coefficient of a Falcon 9 at launch (sub-sonic, large fairing)

While I said just a few hours ago that "There's almost no such thing as a dumb question! this one just might sound like one. I'm making some slides about first principles thinking applied to ...
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### Did the Shuttle have a drag penalty for ascent with a negative angle of attack (AOA)?

@OrganicMarble's answer mentions Because the Orbiter wings developed lift at zero angle of attack, the high dynamic pressure portion of ascent had to be flown at a negative angle of attack, close ...
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### What are the pros and cons of Aerospike nosecones?

Some rockets, mainly (only?) ICBMs have Aerospike nosecones Why are they preferred in lieu of traditional nose cones? Illustrations: An aerospike nosecone on a trident ICBM Video including the ...
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### Why are the bottom of most stages flat?

When looking for rocket engine images, I noticed that the bottom of the stages are almost flat. That does not seem aerodynamic. I understand this is not a primary concern for upper stages (mainly ...
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### What aerothermal effects present significant challenges in supersonic retropropulsion?

One of NASA's plans for future mars entry, descent and landing missions includes an ambitious deceleration process involving retropropulsion in a supersonic airflow environment. I know that previous ...
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### What is the terminal velocity on Mars?

How would I calculate the terminal velocity of Mars? What is the terminal velocity of a balloon entering Mars' atmosphere? Would a balloon pop if dropped from space?
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### How great is the stress on a rocket at max-q [closed]

How much more stress does a rocket experience during max-q compared to other parts of the flight (such as when it is at rest on the pad)? Use data for any 'cylindrical' rocket if a specific example ...
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### Just how pointy does a rocket's nosecone need to be?

There are some beautiful images of the Qu8k rocket launch on this web page and I show a few below. There's a video (below) and the PDF Qu8k Final By Derek Deville, November 27, 2011 The stainless ...
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### Is it correct to apply the vis-viva equation to an airplane that flies in a straight line at the Kármán line?

The vis-viva equation models the motion of an orbiting body and it applies when the only force acting on the body is it's own weight. So is it correct to apply this equation to an airplane that ...
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### Where does the definition of the Kármán line on Wikipedia come from?

According to Wikipedia's article about the Kármán line: The Kármán line is the altitude where the speed necessary to aerodynamically support the airplane's full weight equals orbital velocity ( ...