Questions tagged [space-travel]
218 questions
141
votes
2 answers
How many photons are received per bit transmitted from Voyager 1?
As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons are (1) transmitted and (2) received per bit?
Craig Gidney
- 7,172
115
votes
6 answers
Could we send a man safely to the Moon in a rocket without knowledge of general relativity?
I'm wondering if it's possible to send a man to the Moon using equations consistent with Newtonian gravity and without the elaborate tools of Einstein gravity. Are the predictions made by Newtonian gravity sufficiently precise to plan a successful…
Dargscisyhp
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84
votes
4 answers
Where does the extra kinetic energy come from in a gravitational slingshot?
I read in this answer in this site that the KE a free-falling ball acquires is not originated by the attracting body but that energy was actually stored in the ball when it had been lifted to the height it dropped from.
In this way, it was said,…
Cory Baumer
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62
votes
4 answers
If I'm floating in space and I turn on a flashlight, will I accelerate?
Photons have no mass but they can push things, as evidenced by laser propulsion.
Can photons push the source which is emitting them? If yes, will a more intense flashlight accelerate me more? Does the wavelength of the light matter? Is this…
Hello World
- 725
55
votes
2 answers
How long would it take me to travel to a distant star?
Suppose I wanted to travel to one of the recently discovered potentially Earth-like planets such as Kepler 186f that is 490 light years away. Assuming I had a powerful rocket and enough fuel, how long would it take me?
John Rennie
- 367,598
41
votes
6 answers
Could someone jump from the international space station and live?
Felix Baumgartner just completed his breathtaking free-fall skydiving jump from $120,000\,\text{feet} = 39\,\text{km}$ above the Earth, breaking the speed of sound during the process.
I was wondering if the next step could be jumping from the…
Reactgular
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39
votes
10 answers
Why don't modern spacecraft use nuclear power?
The Voyager 1 & 2 spacecraft launched in 1977 with Plutonium as their source of electricity. 34 years later they claim these two spacecraft have enough power to last them until at least 2020. That means they'll have had enough power to last them at…
John Conde
32
votes
3 answers
Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be?
note: This is a question about relativistic effects. I've included some detail about the spacecraft and its orbit for background, but the question is about relativistic effects and their observability.
When the Parker Solar Probe passes within 8.5…
uhoh
- 6,089
30
votes
4 answers
Why don’t astronauts “push” spacecraft?
Perhaps it goes without saying, but according to Newton’s laws “every action has an equal and opposite reaction”. How do astronauts, especially those inside small spacecraft like the Crew Dragon, not “push” the spacecraft when they bounce and push…
26
votes
4 answers
How to travel between two stationary worlds in the least amount of time? (time dilation)
Let's imagine there are two, isolated, stationary worlds in space (called A and B), very far apart from each other. I live on World A, and some aliens live on World B.
I want to learn about the aliens on World B by talking to them in person. My…
Joshua Wise
- 363
23
votes
7 answers
Project Hail Mary - Why does a return trip to another star require 10x the fuel compared to a one-way trip?
In Project Hail Mary by Andy Weir, the protagonist states that sending a ship to another star and bringing it back would take ten times as much fuel as a one-way trip. The relevant quote is:
"Sending a ship to another star probably took an absurd…
Siddharth Singh
- 339
21
votes
4 answers
Is it possible to sail "close hauled" with a solar sailship?
I have not been able to find a clear or decisive answer about this. On Earth, a ship sails close hauled when the ship is, to some degree or another, facing into the wind. This is made possible with sails that are rigged along the length of the ship…
readyready15728
- 545
17
votes
4 answers
Why are spacecraft made to "spin" after launch?
At some point after launch, usually just before or after separation from the last booster stage, spacecraft are often made to "spin" (about the axis of their trajectory)? See e.g this You Tube video. What is the reason for this spin?
orome
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16
votes
4 answers
How would we see a near-lightspeed object emitting light?
Consider an object travelling near the speed of light relative to us (let it be a spaceship or a star), which is emitting light (consider it monochromatic resulting from a two level electronic transition).
Regarding the different relative time in…
cinico
- 1,334
16
votes
3 answers
"To come back to Earth...it can be five times the force of gravity" - video editor's mistake?
I've watched The Truth About Gravity With Professor Jim Al-Khalili | Gravity And Me | Spark where astronaut Chris Hadfield says at 3:55:
To come back to Earth is violent
Then after several seconds of music and video of descent
it can be five…
Martian2020
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