37
votes
How do we ensure an orbit of a satellite doesn’t interfere with existing ones?
And thus you detected the field of "space situational awareness"...
How do we assure an orbit doesn't interfere with other orbits?
-> We don't.
Dedicated organizations (civilian and/or ...
- 3,009
34
votes
How did theorists determine that the atmosphere attenuates enough to support unpowered orbits?
If 200 miles up counts as a low earth orbit height, then the appreciation is as old as Newton's Principia, that there was no atmosphere left there, and nothing like atmospheric drag to oppose motion.
...
- 1,102
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 ...
27
votes
Optimal depth for underground flyby?
The Optimal Depth is Precisely (Almost) No Depth
I solved this problem using a numerical differential equation solver to investigate a range of flyby approach angles. The results are fascinating!
I ...
- 2,131
23
votes
Accepted
If Earth had a second moon, where would it be positioned?
Certainly the Earth could have ended up with additional moons, and Newtonian physics can say some things about the kinds of orbits they might have, but there is a range of possibilities.
First of all, ...
- 8,789
21
votes
Accepted
Why does the point of burn on an orbit stay at a constant altitude?
When calculating propulsive manoeuvres, we usually consider them as impulses. That is, happening in a very short time. This is usually a good enough model for chemical rocket engines which deplete ...
20
votes
Can a meteor shower have a interval greater than 1 year?
This is really more of a question for Astronomy.SE, in general this doesn't happen, but circumstances can work out that it does, see the updated last few paragraphs.
Every meteor shower with an ...
- 5,110
20
votes
How did theorists determine that the atmosphere attenuates enough to support unpowered orbits?
The scale height is a useful way to describe how the atmospheric pressure decreases with altitude. From Wikipedia,
For planetary atmospheres, scale height is the increase in altitude for which the ...
- 2,396
18
votes
What caused the jitter in the DART video as it approached Dimorphos?
This is an extended comment to your self-answer, so I'm making it community.
From your answer,
As to why they weren't able to do a single, early course correction and just glide smoothly in for the ...
18
votes
Accepted
How do we define the aphelion of Earth?
The aphelion is usually considered to be the point of greatest actual separation, so this would include the (very minor!) gravitational effects of other solar system bodies. It's not the slight ...
17
votes
Distance from earth to another planet in solar system
Here's a short answer to get the ball rolling:
However, orbital parameters do not indicate where the body was at a specified date and time to calculate current position...
That's absolutely right, ...
- 149k
16
votes
Accepted
Why is the Orion capsule using 2 burns to transfer from the moon back to earth instead of one?
The drawing in this "flight plan" indeed looks like it would be trivial to
get into a direct Earth return trajectory without doing two burns and a low fly-by at the Moon.
The actual ...
- 14.6k
14
votes
Accepted
I'm building a CubeSat for a short 8-day mission in LEO followed by a fairly quick reentry, what range of orbits to consider?
You want a very low altitude, to maximize drag, to make the object deorbit quickly even if you never manage to establish control from the ground. The constraint is that you don't want to go too low, ...
- 7,413
14
votes
Accepted
What is the velocity of the ISS relative to the Earth's surface?
JPL Horizons has trajectory data for the International Space Station, SPKID = -125544
Revised: Nov 23, 2022
Trajectory is TLE-based. Predicts run for 4 weeks into future, but are of low accuracy for ...
- 2,396
13
votes
Accepted
Optimal depth for underground flyby?
Assuming a uniform planet with radius $1$ and gravitational parameter $1$, if $V_\infty$ is the speed at infinity and $r$ is the closest approach to the center, then the maximal speed is $V_m = \sqrt{...
- 1,935
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 ...
- 179
12
votes
Accepted
Major axis larger than total of apogee and perigee?
On the linked page, the apogee and perigee numbers don't include the radius of the Earth (they are measured from some theoretical Earth surface). They are altitudes. The semi-major axis does include ...
- 174k
12
votes
Could a space elevator launch a payload to a solar orbit?
Yes. If you could build the elevator, it could be used to launch satellites into prograde orbits with the same inclination as the Earth's equator. This includes solar orbits.
Changing orbital ...
- 15.3k
12
votes
Why is the Orion capsule using 2 burns to transfer from the moon back to earth instead of one?
Answer: The 2 burn transfer uses less fuel than the one-burn direct
transfer.
Orion was in a Distant Retrograde Orbit. “Distant” means beyond the Lagrange Points L1 and L2. “Retrograde” means ...
- 15.3k
11
votes
Help with fictional scenario: trapped in Lagrange Point orbit
For The Sun-Earth Lagrange points, trajectories to L3, L4 and L5 are time consuming, in the order of several months even for expensive "fast" trajectories. Regular low energy transfers take ...
11
votes
What's the motion of two connected satellites orbiting the Earth after their separation?
Many good things here, though a few of the assumptions made are not safe.
Before cutting the tether the velocity of two satellites is equal to the one of the system CoM
This can not be assumed. ...
10
votes
Accepted
Minimum delta V required to return a piece of metallic asteroid 16 Psyche to Earth?
Given the relatively low inclination of 16 Psyche (3.095°), and the fact that the line of apside is relatively close to the node line anyway, this can be approximated as a planar transfer.
Thus, this ...
10
votes
Would the Dzhanibekov effect be a problem for Von Braun Wheels?
No... a Von Braun wheel would not ever 'flip' from Dzhanibekov effect. The effect comes from spinning something about its intermediate (and inherently unstable) axis. A Von Braun station is spinning ...
- 2,952
10
votes
Help with fictional scenario: trapped in Lagrange Point orbit
It is so easy to die in space…
Being stuck in a Lagrange point is a bit dull: like being adrift in the Sargasso Sea. Isn’t it more exciting to be sucked into a raging hurricane?
A propellant-feed ...
- 15.3k
10
votes
Accepted
How close do gravitational 2-body hierarchy levels get?
The zone of influence of a larger body over a smaller body is known as the hill sphere. Within this sphere the gravitational attraction of the larger body will dominate its satellite and satellites ...
- 8,429
9
votes
Optimal depth for underground flyby?
Adding my own numerical time-step simulations here.
The effect seems to be quite subtle, only increasing the deflection angle by a fraction of a degree at shallow depth.
For a unit mass, with unit ...
9
votes
Help with fictional scenario: trapped in Lagrange Point orbit
While the question asks for a "Lagrange Point orbit" and current answers mention that Halo-type orbits (about Lagrange points) are slow, typically about half of the primary orbit (so of ...
- 149k
9
votes
Is it possible to create an analytical ephemeris from raw position and velocity of a Body?
It's possible, because that's partly how VSOP was made, but the amount of effort involved is immense. What you are describing is at the very least a doctoral thesis, if not several of them.
Why not ...
- 7,413
9
votes
What's the motion of two connected satellites orbiting the Earth after their separation?
Before the tether is cut, the angular velocity of the satellite is given by
$$
\frac{\mu m_1}{r_1^2} + \frac{\mu m_2}{r_2^2} = m_1 \Omega^2 r_1 + m_2 \Omega^2 r_2 = M R \Omega^2,
$$
where $r_1 = R - ...
- 942
8
votes
Accepted
What is the relationship between the radius of the Hill sphere and escape velocity?
This is where it goes wrong:
$$\Delta v = \sqrt{v_2^2 - v_1^2}$$
You're taking the difference of the squares of the velocities at a low lunar orbit, and the perilune of the transfer orbit.
But really, ...
Only top scored, non community-wiki answers of a minimum length are eligible