67 votes
Accepted

Why not increase contact surface when reentering the atmosphere?

I've done a lot of work on this subject with researchers and engineers at JPL, NASA Langley, and NASA Ames. There are some interesting things that come out of high-fidelity CFM (Computational Fluid ...
Tom Spilker's user avatar
  • 18.3k
33 votes
Accepted

What causes a satellite's orbit to decay?

If satellites are truly far beyond the atmosphere, their orbits do not decay, except for very small perturbation effects like solar radiation pressure from the Sun or tidal forces from the Moon. But ...
SE - stop firing the good guys's user avatar
31 votes

Are rockets faster than airplanes?

Rockets are much faster than airplanes for most of their flight. Here's a graph of a Space Shuttle launch: The red line is speed. It's in ft/s, 1000 ft/s is 1097 km/h. So At about 45 seconds, the ...
Hobbes's user avatar
  • 128k
27 votes
Accepted

How could a hot lander enter Titan's atmosphere without setting its hydrocarbons ablaze?

In order for a combustion process to happen, you do not only need fuel, you also need an oxidizer. On Earth, that is usually the oxygen in the air. In Titan's atmosphere, there is no oxygen. This ...
SE - stop firing the good guys's user avatar
24 votes
Accepted

Earth re-entry from orbit by a sequence of upper-atmosphere dips to reduce kinetic energy?

Unpowered re-entry into an atmosphere is about trading orbital energy for heat. If the planet being orbited has radius $R$, then the additional specific energy of an elliptic orbit compared to being ...
Starfish Prime's user avatar
21 votes

Are rockets faster than airplanes?

A rocket isn't automatically fast - a small firework rocket may be no faster than a car. The important point is that rockets carry their own oxidiser and aren't limited by the need to interact with ...
Robin Bennett's user avatar
19 votes
Accepted

How can an *increase* in atmospheric temperature cause an *increase* in the atmospheric mass density?

The key concept is that for a satellite at a fixed altitude, when the atmospheric temperatures below its altitude increase, atmospheric expansion pushes more atmosphere up above the satellite! At the ...
Tom Spilker's user avatar
  • 18.3k
19 votes

What is the density of the earth's atmosphere at an altitude of four hundred kilometers?

What is the density of the earth's atmosphere at an altitude of four hundred kilometers? Variation with solar activity It can vary by a factor of 50 depending on solar activity (and the model that ...
uhoh's user avatar
  • 149k
16 votes
Accepted

How can a meteor gain energy in an encounter with the Earth even though these answers say it can't?

I am Patrick Shober (the lead author of the study). Thanks so much for checking it out! If you check out Figure 10 in the paper, I have plotted the specific angular momentum in the Sun-centered frame. ...
Patrick's user avatar
  • 431
15 votes
Accepted

Where can I find data for Atmospheric density vs. altitude?

In the Shuttle Mission Simulator we used the Jacchia Reference Atmosphere, it's good to 2500 km. IIRC it's not good low down so we used a standard atmosphere model for atmospheric flight regimes and ...
Organic Marble's user avatar
15 votes

What is the density of the earth's atmosphere at an altitude of four hundred kilometers?

The MSISE-90 model is available in digital form at http://www.braeunig.us/space/atmos.htm. A copy of the table is reproduced below. Note the dependence on solar activity, which imparts particlesto ...
Oscar Lanzi's user avatar
  • 8,505
14 votes
Accepted

Requesting an in depth explanation of heat created during atmospheric reentry,

The term "friction" is a misnomer. The source of heat is adiabatic compression - gas on trajectory of the reentering object is compressed against its leading surface, and as result heats up. On ...
SF.'s user avatar
  • 55k
13 votes

What causes a satellite's orbit to decay?

The Wikipedia article on orbital decay lists a number of reasons, in addition to atmospheric drag: Tidal effects An orbit can also decay by negative tidal acceleration when the orbiting body is large ...
Ivan Borsuk's user avatar
12 votes

Could thermal energy be collected by dragging a thermoconductive device against the outer atmosphere

No: The heat produced by atmospheric reentry isn't a happy side effect of returning to the earth, it's a byproduct of the fact that your satellite/orbiter has enough kinetic energy to be circling the ...
1337joe's user avatar
  • 7,206
12 votes

ISS achieving lift by using it's solar panels

I can see your reasoning, however it's not going to work. Aerodynamically the byproduct of lift is drag, meaning when you create lift you also create drag as well. An efficient wing creates less drag ...
GdD's user avatar
  • 20.3k
12 votes
Accepted

Can dust be in orbit around a spacecraft which orbits the Earth or Moon?

A starting point for checking orbital stability is the Sphere of Influence for short term stability (or rather, to select a suitable frame a reference in the patched conic approximation), and the Hill ...
SE - stop firing the good guys's user avatar
12 votes

Earth re-entry from orbit by a sequence of upper-atmosphere dips to reduce kinetic energy?

When Does an Orbit Stop Being an Orbit Low Earth Orbit is (rough) 7.8 km/s. This is the lowest amount of energy you can have in an orbit of the Earth. If you try to create a lower energy orbit, you ...
codeMonkey's user avatar
  • 1,633
11 votes
Accepted

Why does in-flight mission abort often ends in ballistic high-g reentry?

When you're in orbit you have velocity roughly parallel to the atmosphere, a flat-ish shape angled properly can "fly" across it in a lifting entry where you can dissipate energy in the thinner upper ...
GdD's user avatar
  • 20.3k
11 votes
Accepted

How hard does atmospheric drag push on the ISS? Is it more than one pound?

Here is a rough estimate. The ISS's height drops at the rate around 10 meters per day. The energy of a body of mass $m$ in a circular orbit of radius $r$ is $E=-\frac{\mu m}{2r}$, so $$ Fv=\frac{dE}{...
Litho's user avatar
  • 2,040
10 votes

How can an *increase* in atmospheric temperature cause an *increase* in the atmospheric mass density?

The scale height is proportional to temperature. As the scale height increases, the density above about one scale height increases. (The density below that decreases.) This is what you'd expect if the ...
Mark Adler's user avatar
  • 58.2k
10 votes

Why not increase contact surface when reentering the atmosphere?

There is a fixed amount of energy which has to be dissipated. You can, to some extent, choose how fast this is done -- more air resistance (either by getting into thicker air or having a bigger ...
Steve Linton's user avatar
  • 19.6k
10 votes

Are rockets faster than airplanes?

Rockets don't actually mostly go up, they try quite hard to go up as little as possible. While flying, gravity is always accelerating you downwards at 9.8 m/s^2. This means that any fuel spent ...
the_Demongod's user avatar
10 votes
Accepted

Why does a satellite with a higher mass fall slower?

That's a great software-based experiment! What is this about? It's about drag and Newton's 2nd law of motion! $$F = \frac{dp}{dt} = ma$$ but in the context of orbital mechanics. We can re-arrange ...
uhoh's user avatar
  • 149k
10 votes

Exactly how "Ferrari-like" was GOCE? Was its drag coefficient as low as the car's?

The ion propulsion was run continuously to compensate for drag immediately. The drag force varied strongly during each orbit (i.e. changing from night to day), typically between 4 and 12 mN on its 1 m²...
asdfex's user avatar
  • 15k
9 votes
Accepted

What is typical lifetime of GTO rocket stages before reentry?

The typical lifetime of an upper stage rocket body (in GTO) varies from few weeks to few decades. This large variation is due to the sensitivity of the orbital evolution to the initial launch ...
Harish's user avatar
  • 390
9 votes
Accepted

Could SpaceX's Starship's landing and restart process work on Titan?

Getting There: In general there is "the quick way" and "the efficient way" to get to the outer planets. The trade-off is between the capability of the launch vehicle and the time-...
BrendanLuke15's user avatar
9 votes

Why does a satellite with a higher mass fall slower?

From Force=Mass*Acceleration for a given starting drag force (from the constant drag area, altitude and velocity) increasing the mass will reduce the acceleration (deceleration in this case) slowing ...
GremlinWranger's user avatar
8 votes
Accepted

Is aerodynamic lift ever useful in rocket flight?

Angling to get lift is going to increase the atmospheric cross-section of the rocket and so increase drag. For any reasonable angle of attack, the drag force is going to be much larger than the lift ...
Russell Borogove's user avatar
8 votes
Accepted

Shear forces between Shuttle, tank, and boosters - what pushes what?

The three SSMEs provide 568 tons of thrust, the Orbiter has a weight in the region of 100 tons incl payload. The Orbiter always exerts a positive force on the tank from liftoff to MECO, no matter what ...
Hobbes's user avatar
  • 128k
8 votes

Where can I find data for Atmospheric density vs. altitude?

We recently had a similar requirement and created a RESTful web API that wraps the original code of the NRLMSISE00 and the JB2008 models. The API is open and available here for anyone who needs it. ...
Team Amentum's user avatar

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