# Tag Info

43

Velocity relative to what? There's no central universal point to measure velocity at, so your answer is likely going to change based on your frame of reference. New Horizons did indeed have the fasted launch velocity of any spacecraft that has left Earth (relative to Earth): After three years of construction, and several delays at the launch site, New ...

37

You're right: this has issues. You can insert a station into a circular orbit halfway between Earth and Mars, but because this has an orbital period also in between those of Earth and Mars, your station won't be in a usable position most of the time. So you'd have to fill the orbit with several station to always have one reasonably close. The fuel is also ...

28

Don't forget the lowly astronomer working at one of the observatories in the Atacama Desert, or one of the many indigenous peoples who preceded those astronomers. The combination of high altitude and latitude near the Tropic of Capricorn makes these people well-sited for being the Earth-bound people who are both closest to and furthest from the Sun at ...

21

No. Look at the numbers: 10000 kg. => Your rocket 73420000000000000000000 kg. => The moon 5972200000000000000000000 kg. => The earth 1989000000000000000000000000000 kg. => The sun To put this to scale, the rocket has a similar mass towards the moon as that of one human cell towards a human. You can ...

21

Yes, humans definitely have been to outer space. The easiest proof I can think of immediately is this video of commander Chris Hadfield demonstrating wringing of a wet towel on the ISS. Or this one — it contains more than 200 seconds long uncut shot of a̶b̶s̶e̶n̶t̶ micro-gravity. It also shows vast interiors of the ISS, which are technically challenging to ...

18

The problem here is that your standard of proof is ridiculous. By the same token, you'd have to doubt the existence of Moscow because you've never met anyone from that city. the only face to face eyewitness event that I can remember where humans actually observed an attempt to fly into outer space... Then your memory must not be very good. There have ...

18

Actually the main reason most launches begin vertically is to get away from the atmosphere, and atmospheric drag/heating as quickly as possible. This minimizes the amount of energy lost to friction, and the amount of mass needed to be used for heat shielding. There is at least one orbital rocket whose first stage is an aircraft: the Pegasus. It's carried ...

17

The manned Apollo Lunar Roving Vehicle from Apollo 17 holds the record of 17km/h achieved by Eugene Cernan. Apollo Lunar Roving Vehicle was also present on Apollo 15 and 16. For traditionally understood rovers - unmanned mobile landers, the fastest historically would be Lunokhod 1 and 2, capable of 2km/h. At current time only two rovers are still active ...

15

First, some perspective. The impact of a single fragment of the Shoemaker-Levy comet on Jupiter released an estimated energy equivalent of six million megatons of TNT (approximately 600 times the size of the world's nuclear arsenal), leaving an impact scar that was visible for several months afterward. That was obviously a bad day for Jupiter, but that ...

13

Roscosmos The Russians right now, will sell you a flight on a Soyuz, and you will fly, in the next few years if you have the money. Oddly the former Communists are most capitalistic about this endeavour. They are the only actual space tourist option that has actually flown real tourists to space. Once the Shuttle was retired, Soyuz missions became the only ...

13

When the amount of evidence, circumstantial or direct, for a given proposition vastly outweighs evidence against that proposition, most reasonable people are willing to accept the proposition as true. This does occasionally lead to having to change your mind about a proposition when new evidence comes along; this is how the scientific method works. In the ...

13

Like the lower left part of the image below. Define a set of pulsars through describing proportions between their frequencies. Define distances from each of them. This uniquely identifies a point in space, and the pulsars are very efficient "beacons" recognizable from very far. This would determine position of Sun. As for Earth, third planet, easy.

13

It's hard to guess what is in the mind of another contributor, but... Using a cycler model could involve a network of space ports, and the cycler would take the role of a "midway" space station (it taking care for the cargo for the portion of the journey between Earth and Mars) In Earth orbit, there would be a staging post or spaceport. Launch vehicles ...

12

It's not exactly how you put it, exhaust speed is not a maximum speed for a spaceship. While exhaust velocity does define thrust together with the rate of expelled mass and is given by: $$T=v\frac{\Delta m}{\Delta t}$$ where thrust $T$ is a reaction force that is a product of exhaust velocity $v$ and mass change $\Delta m$ in time $\Delta t$, you're ...

12

Mars cyclers have already been mentioned in the comments, with the Aldrin cycler being one example of them. The castle parts of them could be seen as ferries, and the visiting taxis as means of embarking and disembarking during visits of planets along their routes. And three or more bodies cyclers are also possible, for example the so-called resonant ...

12

Wolfram Alpha can do things like this easily, handling the units for you. Just entering "time to travel 1 AU at an acceleration of 25 g" gives the answer. The result is 9.7 hours. You can click on "Show formula" to see the formula used. It is one step beyond T=Distance/Velocity. That gets you up to 0.03 c (click "More units"), so relativistic effects ...

12

The Alcubierre bubble could get to Alpha Centauri in less than 4 years according to outside observers, not just observers riding inside the bubble--the exact time depends on the exact 'shape' of the warped spacetime in the bubble, but the theory allows you to fine-tune the bubble to give as short a time as desired. The fact that observers outside the bubble ...

12

It would stand still, because of the equal and opposite force rule (aka conservation of momentum). On earth's surface it's possible to have a self-propelled butt-kicking machine by having a slow "wind-up" phase alternating with an abrupt "kick". During the wind-up, static friction with a ground surface holds the vehicle in place, but the kick phase can ...

10

Not in terms of physical damage, no. Rockets and spaceships and all the energy they contain is just so very, very, very, very small compared to everything. There is one possibility for large scale damage though, even if it is very unlikely. There is a very small chance that some kind of virus or bacteria carried on a vehicle to some destination might just ...

9

That depends on how much time you want to spend. Space is frictionless, you could move a planet by applying a force of 1 N. It would just take a very long time for the planet to move 1 m in response to that force. Because space is frictionless, you can use basic physics to calculate the information you need. $F=ma$, and from $a$ you can derive the object'...

9

This is the result of two physical facts: that gravity, pointing toward the center of the Earth, is the only way to define "down", and that most of the Solar System is quite close to a single geometric plane, the ecliptic, which sort of is like the rectangle you describe. It's also partly because most of our communications are essentially two-dimensional, so ...

8

We do not know yet. The main issue is a lack of empirical data. There are only four specially trained volunteers with more than one year exposure to microgravity. We'd need hundreds of volunteers under different gravities to measure the difference (it is however plausible to assume that the effects are gradually dependent on the level of gravity). ...

8

If you want speed, look for mass. Things closest to the Sun will tend to be moving the fastest. For example the Messenger spacecraft reached almost 63 km/s when in an elliptical orbit who's perihelion matched Mercury's position. In the 2nd plot you can see the red line (speed wrt Mercury) drops to a very low value in 2011, that's when it entered into ...

8

The highest speed was recorded by an Apollo Lunar Roving Vehicle: The rovers were designed with a top speed of about 8 mph (13 km/h), although Eugene Cernan recorded a maximum speed of 11.2 mph (18.0 km/h), giving him the (unofficial) lunar land-speed record. Unmanned rovers have much lower top speeds. Their speed is limited by the amount of terrain ...

8

Before launch, NASA (or whatever space agency a particular astronaut is affiliated with) keep their passports and visa, and bring it back to them when they land. Since the astronauts land in Kazakhstan, they need their official documents so they can leave the country and go back home. This is Canadian astronaut Chris Hadfield's reply to the question ...

8

Which is the reference point? is not answerable because we are free to choose any point and velocity as a reference to calculate the position and velocity of an object. There isn't any universal reference point. What defines the reference? You do! Some points are much more useful for certain types of calculations, but it's purely a personal choice. ...

7

The advantage of progressive orbit-raising is that it can be done with very short burns near perigee, maximizing the Oberth effect. You can look at it as either the Oberth effect saving fuel relative to doing one long burn, or as saving engine weight relative to doing one short burn. The disadvantage is that it takes weeks instead of days to get to the ...

6

Right I'm going to assume the constant power your ship is capable of producing is actually a constant force your ship is under. (i.e. your ship is using some purely electrical form of acceleration - no loss of mass due to propellant). The basic law of physics behind this is that as you approach the speed of light you mass increases. Therefore to maintain a ...

6

The only absolute limit imposed by physics is the speed of light, but with our current technology -- reaction engines based on Newton's laws of motion -- we're limited by practical engineering issues and Tsiolkovsky's rocket equation to speeds on the order of 1/10000 of the speed of light.

5

A space station has the advantage that it can tightly control what comes in. It is the perfect quarantine. Unlike the cargo hold of a ship, every gram of weight is meticulously accounted for. Unfortunately, there's no way to fully clean a human (without killing them) and once you've sealed them inside the space station, the advantages end. Living on a ...

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