All Questions
7,084
questions
11
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3
answers
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How to calculate the planets and moons beyond Newtons's gravitational force?
The question Calculating the planets and moons based on Newtons's gravitational force was pretty much answered with two items:
Use a reasonable ODE solver; at least RK4 (the classic Runge-Kutta ...
- 149k
15
votes
2
answers
7k
views
How to calculate data rate of Voyager 1?
I've read the following passage in the answer to the Quora question How can Voyager send a signal strong enough for us to receive, in spite of its enormous distance from us? And how can it have the ...
- 153
19
votes
2
answers
2k
views
Is this what station keeping maneuvers look like, or just glitches in data? (SOHO via Horizons)
I've been enjoying the JPL Horizons web interface and after I discovered the incredibly extensive database associated with SOHO (Solar and Heliospheric Observatory, also see sohowww.nascom.nasa.gov) ...
- 149k
37
votes
4
answers
16k
views
Effect of atmospheric drag on rocket launches and benefits of high altitude launch sites
What is the approximate influence of atmospheric drag on the cost of rocket launches? Is it beneficial to have launch sites located at higher altitudes?
Cape Canaveral is at sea level, but I've ...
- 1,675
94
votes
6
answers
19k
views
How much bigger could Earth be, before rockets wouldn't work?
hint: Apparently the Tsiolkovsky rocket equation does not actually say that you can launch a conventional rocket into orbit around an arbitrarily large and massive body.
I'm looking for a number ...
- 149k
14
votes
3
answers
8k
views
How to best think of the State Transition Matrix, and how to use it to find periodic Halo orbits?
I'll state my mathematical question about the state propagation and state transition matrices first, then show you a simple problem for which I would like to use these concepts to generate a densely ...
- 149k
61
votes
7
answers
6k
views
How do we know the Apollo Moon landings are real?
Since about 1976, conspiracy theories denying the Moon landing and claiming it was all faked have cropped up. As a website devoted to answering questions about space exploration, we receive questions ...
12
votes
3
answers
3k
views
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 ...
- 149k
35
votes
7
answers
15k
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How could a 90 m/s delta-v be enough to commit the space shuttle to landing?
Wikipedia claims (although with no citation) that in order to make the space shuttle land, an initial powered delta-v of 322 km/h was applied in orbit, retrograde to the shuttle's orbit. 322 km/h is ...
- 7,322
13
votes
1
answer
7k
views
Why is a near rectilinear halo orbit proposed for LOP-G (formerly known as Deep Space Gateway?)
Why is a near rectilinear halo orbit a good place for a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway)? Are there specific logistical and orbital-mechanical advantages over ...
- 149k
5
votes
2
answers
2k
views
How do SDP4's "Deep space" corrections to SGP4 account for the Sun's and Moon's gravity?
The Simplified Perturbations model SGP4 is used to calculate Earth satellite state vectors (position and velocity) using standard ephemeris data encoded as TLEs (Two Line Elements). According to ...
- 149k
18
votes
1
answer
7k
views
What happens to JWST after it runs out of propellant?
JWST will be orbiting L2 which is unstable equilibrium thus will require propellant for station keeping. JWST will carry propellant for 5-10 years.
What will happen once it runs out of propellant? ...
- 283
15
votes
1
answer
18k
views
What is a near rectilinear halo orbit?
A proposed option for the lunar orbit of a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway) is a near rectilinear halo orbit, or NRHO.
This excellent answer discusses the ...
- 149k
14
votes
1
answer
1k
views
What sort of orbital elements are used to describe halo orbits?
For standard orbits we can use Keplerian elements, TLE, or other similar. These don't make much sense for Halo orbits, which are not around a central body, but around a Lagrangian point, and follow an ...
- 54.9k
17
votes
4
answers
4k
views
Are some Halo Orbits actually Stable? (stable orbits about unstable Lagrange points)
update: some more sources; the broken site spacecraftforall.com/a-new-orbit used to have an interactive simulation, here's an old screen shot:
Hat tip to @NgPh for finding this Space College page ...
- 149k
23
votes
4
answers
8k
views
Starman/Roadster in a=1.795 AU orbit, now what's the method to this madness?
The question SpaceX's 4,425 satellite constellation - what's the method to the madness? received an excellent answer explaining the rationality behind the madness plan.
Elon Musk's tweet (spotted ...
- 149k
4
votes
2
answers
434
views
Quantitatively, why will optical communication be better than X-band for deep-space communications?
In a question about communicating with Voyager, an answer asserts:
[70 meter dish antennas deployed in space] just isn't done, and it probably won't be, since optical communication is definitely ...
- 1,023
49
votes
11
answers
41k
views
Could it be possible to launch a rocket from a balloon?
There are several (commercial) organisations looking into alternative means to launch space-bound rockets. One commonly proposed method is to use a large airplane as the launch platform. This method ...
- 593
37
votes
3
answers
57k
views
How to programmatically calculate orbital elements using position/velocity vectors?
I would like to build some orbital mechanical software from scratch. I feel that this would be a great way to learn the steps required to calculate different Kepler orbital elements of an object, plot ...
- 5,974
30
votes
7
answers
4k
views
What technological hurdles prevent the development of a space gun?
Ever since Jules Verne wrote "From the Earth to the Moon" space guns have long been proposed as a method of launching objects into space. And for non-human, non-fragile payloads they make sense as the ...
- 3,037
29
votes
4
answers
12k
views
How is the altitude of a satellite defined, given that the Earth is not spherical?
The altitude of a satellite is the distance between the Earth's surface and the satellite, but the Earth itself is not spherical. At the equator the Earth's radius is 21 km more than at the poles, and ...
- 513
27
votes
1
answer
5k
views
SpaceX's 4,425 satellite constellation - what's the method to the madness?
The BBC article SpaceX aims to launch internet from space discusses the SpaceX proposal for a dense array of over 4,000 LEO satellites for global internet coverage, and links to SpaceX non-...
- 149k
26
votes
2
answers
2k
views
How did the tangential thrusters for the 2014 LDSD test spin-up then spin-down so nicely?
I just watched the NASA JPL video of the 2014 test of the Low-Density Supersonic Decelerator (LDSD).
Tangential thrusters are used to spin up the craft for stability before the main rocket ignites. ...
- 149k
21
votes
2
answers
3k
views
Going from LEO to lunar using only low-thrust ion propulsion - can it be done?
@SF.'s question What are the parameters of the new Iodine electrical rocket engine developed by RSC Energia? links to the short RT article 'Ten times cheaper': Russian space company testing iodine ...
- 149k
60
votes
4
answers
60k
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Why not build Saturn V's again?
Why is the US developing a new rocket and spacecraft as opposed to building the Saturn V and Apollo stacks again?
The SLS / Orion development programs certainly can't cost less than the unit cost of ...
- 6,712
26
votes
5
answers
3k
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How well can Voyager 1 separate Earth signals from Solar noise these days?
This is a follow-up question to Can Voyager 1 receive signals from Earth? and this and this answer. UPDATED: see additional information and discussion below.
As it continues to move farther from the ...
- 149k
10
votes
2
answers
4k
views
General guidelines for modeling a low thrust ion spiral?
I've been told that for low thrust ion spirals, delta V would be the difference between speeds of departure and destination orbits. For example the delta V between a 7.7 km/s LEO and a 3.1 km/s GEO ...
- 15.6k
10
votes
2
answers
5k
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How does one dogleg from Florida to a sun-synchronous orbit?
From NASA Spaceflight's article SpaceX Falcon 9 launches first NRO mission with NROL-76:
The NROL-76 launch was not to be targeting a sun-synchronous orbit, typically used by the NRO’s optical ...
- 149k
211
votes
6
answers
24k
views
Can I borrow a lunar rover?
According to Wikipedia there are 3 LRVs sitting on the moon, in very well defined locations. Would China, or whomever gets to the moon with a person next, be able to get in and drive around in an LRV ...
- 27.1k
27
votes
10
answers
5k
views
Puzzler - which spacecraft(s) incorporated real wood structural elements?
Not a trick question, but a real puzzler - which spacecraft or spacecrafts incorporated real wood structural elements?
- 149k
26
votes
4
answers
5k
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Does the NK-33 engine require subcooled kerosene so cold that it turns to wax?
It was mentioned in this answer and in several other places on the internet that the kerosene fuel used by NK-33 engines needed to be subcooled enough so that it reached the same density as the LOX, ...
- 149k
20
votes
3
answers
24k
views
How can I plot a satellite's orbit in 3D from a TLE using Python and Skyfield?
I have obtained a Two Line Element (TLE) of a satellite in Earth orbit from Celestrak at https://celestrak.org/NORAD/elements/ and I would like to use it to calculate an orbit.
How can I calculate the ...
- 149k
18
votes
1
answer
2k
views
How strong and "hot" is the wind on the payload after the fairing is deployed at ~110km?
In the question What makes 21st century fairings so valuable that they'd potentially be recovered and re-used? I said:
21st century fairings are much more than passive rooftop boxes to "keep the ...
- 149k
12
votes
2
answers
3k
views
How (the heck) are military satellites with (apparently) classified TLEs still showing up on sat map websites?
As I first noted in this comment I couldn't get TLEs for the recently launched OFEQ-11 spy satellites from space-track.com. When I looked at Search Resuls: OFEQ 11 Satellite details 2016-056A NORAD ...
- 149k
1
vote
2
answers
917
views
What is the highest non-optical frequency used or tested for use in deep space communication?
For dish antennas used to transmit a signal over large distances, the on-axis gain scales as $D^2/ \lambda^2$ or $D^2 f^2 / c^2$ where $\lambda$ and $f$ are the wavelength or frequency and $c$ is the ...
- 149k
48
votes
1
answer
39k
views
How often does ISS require re-boosting to higher orbit?
I know that ISS, being in low Earth orbit, requires regular boosts. But I can't seem to find information on how often does this happen. Is it done during each resupply mission, only during some of ...
- 695
30
votes
1
answer
59k
views
What is the current cost-per-pound to send something into LEO?
As a student of economics and finance I would love to learn more about the cost structures of sending a payload into orbit.
More specifically -
What is the cost-per-pound to send something into LEO ...
- 5,974
28
votes
3
answers
7k
views
How hard do you have to throw something off the ISS to make it deorbit?
During Expedition 41 Reid Wiseman and Alexander Gerst replaced a failed pump on the outside of the ISS. I am guessing they took the broken pump back inside the ISS and returned it to earth in one of ...
- 383
15
votes
2
answers
7k
views
What is the ISS drag?
ISS constantly loses altitude to air drag and other forces (tidal, electromagnetic). While finding that rate in the sources isn't that hard, with orbital mechanics of altitude loss actually increasing ...
- 54.9k
13
votes
5
answers
1k
views
Why doesn't thermal radio emission from a DSN "hot dish" completely swamp the benefits of a cold LNA?
The 70 meter DSN dishes are often used to receive the weakest signals, and so their receiver LNAs have cryogenic front-ends in an assembly that also contains a LHe refrigerator and vacuum system. If I ...
- 149k
12
votes
2
answers
1k
views
Why is FAI considering lowering the Karman Line to 80km?
I ran across this FAI statement
The Karman line is the 100km altitude used by FAI and many other organisations to mark the “boundary” of space . In the last few years there have been many scientific ...
- 7,780
11
votes
1
answer
5k
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How have space suits dissipated the heat removed from astronauts?
I never thought about this until reading the comments below this answer. To radiate something like 150W (a very conservative lower limit of human + suit systems heat production - see @Uwe 's comment ...
- 149k
9
votes
2
answers
1k
views
How do spacecraft measure their own charge?
The discussion in the NOAA legacy page Space Weather Prediction Center Topic Paper: Satellites and Space Weather (found here) lists:
Types of Spacecraft Anomalies
Spacecraft anomalies are ...
- 149k
8
votes
3
answers
1k
views
Why does Earth's atmospheric density have a big "knee" around 100 km? Is there a good analytical approximation?
I've used a quick very rough approximation of the drop of atmospheric density with altitude in this answer and in this answer by using a single exponential and scale height parameter, but that's not ...
- 149k
7
votes
1
answer
968
views
How can I verify my reconstructed gravity field of Ceres from spherical harmonics?
Based on @DavidHammen's very helpful answer I've made progress reconstructing the gravity field of Ceres from the Dawn radiometric data. The question there contains further information, but suffice it ...
- 149k
6
votes
2
answers
2k
views
Did the NASA PhoneSat actually try to use the GPS from the phone itself?
I was reading this article about NASA's PhoneSat Flight Demonstrations and came across this sentence.
"To achieve this, NASA's PhoneSat design makes extensive use of commercial-off-the-shelf ...
- 149k
5
votes
1
answer
1k
views
Rotating in orbit?
Reading this question (Is the cupola, on the inside of the ISS, cold or warm to the touch?) prompted me to wonder about an object in orbit's orientation as it orbits its host object. For example, ...
- 2,788
4
votes
3
answers
970
views
Has the Curiosity rover ever communicated directly with Earth via its high-gain antenna? Signal strength & data rate?
In the question How does Curiosity know how to point and move it's high gain antenna in real time? I show an image of the hexagonal, articulated high gain antenna on the curiosity rover, as well as ...
- 149k
65
votes
3
answers
168k
views
How fast will 1g get you there?
If you have the energy for a constant 1G thrust, how long would it take to get to the planets in our solar system? How long for the 5 nearest solar systems?
Assuming turn over and decelerate at ...
- 27.1k
54
votes
2
answers
49k
views
What is the purpose of the jets of water often under rocket engines during launch?
I have watched several STS launches, and noticed that there were always huge jets of water that would begin right before the rocket engines lit. They were right under the rocket, mounted to the pad.
...
- 18k