71
votes
Where does space begin on planets without atmospheres?
Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights.
Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 ...
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49
votes
Accepted
How did the X-15 control attitude above the Kármán line?
The X-15 had a reaction control system for all three axes using thrusters with hydrogen-peroxide monopropellant. There was an automatic as well as a manual mode. The manual mode used a single three-...
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46
votes
Which object has been to space the most times?
The Space Shuttle Discovery has been to orbit a total number of 39 times, more than any other shuttle vehicle (source: Wikipedia). Contrasting that to other candidate objects:
Space Shuttles Atlantis,...
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40
votes
How did the X-15 control attitude above the Kármán line?
The X-15 has a reaction control system. In this image, it's item 2, 13 and 28, labeled 'ballistic control system'.
It was operated via a joystick.
Detail of two of the thrusters:
- 128k
35
votes
Where does space begin on planets without atmospheres?
Ultimately, "the edge of space" is an agreed upon convention. In other words it is essentially arbitrary, something which only humans even care about (well maybe space aliens too <grin>). Yes, ...
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23
votes
Accepted
Which was the first liquid non hypergolic engine to be reignited in space?
It would seem to be the RL-10A used on Atlas-Centaur. According to a NASA document "Successful Restart of a Cryogenic Upper-Stage Vehicle After Coasting in Earth Orbit."
Atlas-Centaur AC-9, ...
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13
votes
Accepted
Why is FAI considering lowering the Karman Line to 80km?
tl;dr: The FAI is doing that because they were convinced by Johnathan McDowell's proposal, one that he first forwarded 25 years ago. The FAI's statement must refer to his recent paper on the topic. ✅
...
- 149k
12
votes
Accepted
What is the practical use of the Karman line?
The Karman line is used for two things:
to legally separate the airspace above a country (over which the country has jurisdiction) from space (over which the country has no jurisdiction).
to ...
- 128k
11
votes
Accepted
Minimum velocity needed to cross Karman line
When you ask about the minimum velocity needed to cross the Karman line there are 2 things you could mean. The first thing is that you could mean the minimum velocity needed on the ground going ...
- 6,149
10
votes
Accepted
Did the Soviet Union put an unmanned satellite in "very low orbit"above the Kármán line which used aerodynamic attitude control?
I found a few references to the Zenit 4 M/MK/MKM series of reconnaissance satellites, which may have been equipped with stabilizers to help them maintain attitude in tenuous atmosphere, but the ...
- 170k
9
votes
Accepted
Is there some fundamental limitation that would prevent steam-powered rockets from reaching space?
There's no fundamental physical limitation, but there's certainly a practical one. The rocket equation is $\Delta V = V_{Exhaust} \ln(M_{Total}/M_{Dry})$.
The exhaust velocity of a typical chemical ...
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9
votes
Accepted
How much delta V did the V2 have?
I am finding significantly different specifications for the V2 from different sources (Astronautix, Wikipedia) -- probably because they weren't all built the same -- but assuming a gross liftoff mass ...
- 170k
8
votes
Where does the definition of the Kármán line on Wikipedia come from?
Immediately before the definition section, Wikipedia references Kármán's abstract concept from his autobiography:
In the final chapter of his autobiography Kármán addresses the issue of the edge of ...
- 170k
8
votes
Where does space begin on planets without atmospheres?
Where does space begin on planets without atmospheres?
Where the ratio κ=1 for the ion cyclotron and ion collision frequencies - for Earth that is 118 ± 0.3 km.
The lunar surface is surrounded not by ...
- 3,274
8
votes
What did Karman's original "Karman line" calculations look like?
This is an interesting question and something I had never considered before.. and I think that's kind of the point. The Karman Line has been taken as a fairly universal boundary of space (in the US at ...
- 471
8
votes
Temperature and Pressure Gradient across Kármán line
Just so you are aware - the Kármán line is not a physical thing. It is an imaginary boundary, that gives a rough, easy to remember height for the border between Earth and space of 100km (although ...
- 13.7k
8
votes
Accepted
Why isn't the Kármán line itself considered to be in outer space?
I do not think there is a useful distinction to make here.
Any border you designate will be somewhat arbitrary. Any time you set one, someone else will argue. And setting the border to be exclusive or ...
- 6,957
7
votes
What would a "Kármán plane" look like, a bird, or a plane?
Based on your initial stipulations, and the wording provided by Wikipedia, the altitude Karman was calculating was the altitude where, at orbital velocity, the lifting effect of aerodynamic forces on ...
- 584
7
votes
Accepted
At what point does an object lose 50% of escape velocity?
As a spacecraft drifts outwards, slowing down, it stays at escape velocity. The current escape velocity, that is. Escape velocity depends on distance and an object further out needs less velocity to ...
6
votes
Is the definition of the Kármán line from Wikipedia right?
Why not? Because the people who started using the Karman line didn't see the need for a more refined definition (e.g. because nobody was going to attempt aerodynamic flight in this region).
The ...
- 128k
6
votes
Is the equation showed below the right one for an airplane flying at the Kármán line altitude?
I think I solved it... I'm not sure but I think I'm on the right path.
You were very close to the right solution, and you were very correct the linked equation is useless in describing actual ...
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5
votes
Accepted
what is the relevance of ion cyclotron and ion collision frequency ratio
Answer: Cyclotron and ion collision frequencies define the boundary between the Ionosphere and the Magnetosphere.
There is a continuum of decreasing gas density from Earth’s surface to space. So any ...
- 24.8k
5
votes
Accepted
When is/will be the symposium to revisit the Karman line and consider the "McDowell line"?
Symposium will not be held. Source: I asked Jonathan.
- 4,484
5
votes
Accepted
With a 10% increase in Earth's mass, would the Karman line move up or down, and by how much?
It would move Down!
By the definition of the Karman line on wikipedia, the lift force and the "centrifugal force" must be equal to the gravitational force and, therefore, each other. This gives the ...
- 2,502
5
votes
Could you skim along the Karman line using a parafoil?
Using a naive lift calculation at 100km runs into several issues. As you go above about 50km your mean free path for the atoms in the atmosphere is becoming long enough that you no longer have a '...
- 23.4k
4
votes
Karman line analog on other celestial bodies
I will elaborate a bit on Mark's answer starting from the basic formula
$R\rho = 2m/(A*Cl)$. Above the troposphere, the density falls exponentially as $rho = rho_0 \exp(-h/H_0)$ where $H_0$ is the ...
4
votes
At what conference did the "von Kármán line" arise, and was discussed for the first time?
It appears this was suggested in 1959 at the First Colloquium on the Law of Outer Space:
Jastrow, Robert. "Definition of Air Space." Proceedings of the First Colloquium on the Law of Outer Space,. ...
- 484
4
votes
Accepted
Would the >100 km "knee" in Earth's atmosphere still be where MFP exceeded scale height if it were pure Ne or Ar?
There are a lot of phenomena at play here.
First of all, you already mentioned there's a factor of changing atmospheric composition. This one is easiest to understand. Consider a very simplistic model ...
- 1,030
4
votes
Accepted
How can I calculate the weight a aero-spacecraft occupant experiences during sub-orbital but non-ballistic trajectories?
My interpretation of your question is this:
At 0 horizontal velocity, an aircraft needs to provide 100% of its weight in upward force to maintain its altitude.
At orbital velocity, with the surface ...
- 170k
3
votes
Accepted
Is a Kármán Rocket Possible?
Why are the rockets not razor sharp
Because then the payload fairing would spend a lot of mass for space that wasn't useful to enclose a payload.
skinnier
The skinnier the rocket, the worse its ...
- 170k
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