Questions tagged [velocity]

Questions about the distance objects or gases cover in a fixed amount of time while traveling in space, being launched or descending. Also for questions about speed-comparisons.

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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 ...
Wolter's user avatar
  • 383
24 votes
3 answers
9k views

If you release a tool outside the ISS in space will it remain at the "same" place forever?

If an astronaut doing a repair outside the International Space Station (ISS) gently lets go of a tool into space, will it keep "flying" (orbiting) at the same spot relative to the ISS where ...
André Dias's user avatar
20 votes
2 answers
5k views

What eliminates the velocity when occupants return from ISS to earth, and how much?

The ISS has an orbital velocity of ~28000 km/h; the velocity $v$ relative to the landing site of the descent module is probably even higher than that most of the time. Once the occupants have landed, ...
Alexander Klauer's user avatar
19 votes
1 answer
3k views

Interstellar Travel Thought Experiment

I have been going over a bit of a thought experiment in my head lately. And wondering if someone more informed on the matter can share their thoughts Let's start with the premise that rocket/ ...
VapeLord86's user avatar
17 votes
4 answers
11k views

Are rockets faster than airplanes?

Rockets are fast. Faster than anything else somebody could fly with - at least intuitively to me. But - airplanes are fast too. A rocket typically flies vertically, an airplane mostly horizontally. ...
Volker Siegel's user avatar
15 votes
2 answers
9k views

If we can make an Alcubierre drive, how fast can it move a ship?

Assuming we ever manage to solve the energy generation problem (and whatever other problems may face it) and build a functioning Alcubierre drive, how "fast" would we be able to travel? That is, from ...
Kromey's user avatar
  • 331
14 votes
4 answers
4k views

Why did the space shuttle's altitude go down after reaching 108,000m?

I recently took a look at this little data sheet by NASA: Math and Science @ Work; Space Shuttle Ascent Time Altitude Velocity Acceleration Comment (s) (m) (m/s) (m/s^2) 20 1244 139 18.62 40 5377 ...
Cliff Miles's user avatar
13 votes
3 answers
536 views

A spacecraft is travelling at X units per hour. But relative to what exactly? Does it depend on the orbit? How?

If I am walking, the ground is stationary, and I move $X \frac{\text{units}}{\text{hour}}$ relative to the ground. If I am in low-Earth orbit, then I am still moving $X \frac{\text{units}}{\text{hour}}...
zoplonix's user avatar
  • 946
12 votes
2 answers
6k views

Why should the velocity through the nozzle throat be sonic?

I have read (even on this site), that exhaust gas velocity is (normally?) sonic (exactly Mach 1) through the choke point of a De Laval, or convergent-divergent, nozzle: At the "throat", where the ...
Bohemian's user avatar
  • 817
11 votes
2 answers
4k views

Why is Voyager/Pioneer so slow compared to Parker Solar Probe?

Deep space probes should be the fastest ones, due to incredible distances they are supposed to travel. AFAIK, Parker Solar (PS) will reach more than 600 000 km/h, incredible. On the other hand, ...
Zotyi's user avatar
  • 249
11 votes
3 answers
2k views

What is the fastest rover that has ever traveled on the surface of an extra-terrestrial body?

What is the fastest rover currently moving on the surface of another celestial body? At what speed with our technology currently does physics restrict our speed limits on the surfaces of solar system ...
Cornelis's user avatar
  • 7,503
10 votes
2 answers
1k views

What's the motion of two connected satellites orbiting the Earth after their separation?

Let's consider the following problem (it's a job interview question): two satellites are orbiting the Earth in a circular orbit; they are rigidly linked by a tether which is always pointing in the ...
g_don's user avatar
  • 433
10 votes
1 answer
951 views

How often do we get information from the Voyager spacecrafts?

Checking the JPL website for the Voyager spacecrafts (https://voyager.jpl.nasa.gov/mission/status/) I can see a distance input from the sun and earth. The description for the distance claims that "...
KingsInnerSoul's user avatar
9 votes
4 answers
3k views

What is the velocity of the ISS relative to the Earth's surface?

This was asked once before, but I believe there was no clear answer given and accepted. The ISS has an orbital period of 92.9 minutes, or 5574 seconds. If it were in a completely equatorial orbit, ...
Ludvig Nilsson's user avatar
9 votes
3 answers
4k views

Maximum velocity achieved by solar sail

What is the maximum (theoretical) velocity that can be achieved by solar-sail technology? Can we get close to the speed of light with that?
Tom11's user avatar
  • 603
8 votes
2 answers
2k views

Travel Speed in Space

I have read several questions and answers here concerning achieving speeds beyond the typical deep-space exploration missions. While speed increases near the Sun for example, that can't be applied to ...
APOSTOLOS KONSTANTINIDIS's user avatar
8 votes
1 answer
2k views

What is the velocity distribution of the exhaust for a typical rocket engine?

The exhaust velocity figure of a given engine is an average value. I'm curious to know how the distribution of velocities of the exhaust particles look. From a qualitative perspective, how does the ...
Ingolifs's user avatar
  • 6,448
7 votes
3 answers
3k views

What is the required burn to keep a satellite at a Lagrangian point?

When a satellite reaches a Lagrangian point, it has a non-zero velocity $v_1$ because of the transfer orbit in which it had already been. What burn, say, $\Delta v$, one needs if the satellite is ...
user avatar
7 votes
1 answer
1k views

What is the terminal velocity of SpaceX Starship?

What is the terminal velocity of starship on earth and mars during descent? Has SpaceX revealed or hinted the values of projected surface area and drag coefficient of the vehicle?
Ashvin's user avatar
  • 2,644
7 votes
0 answers
110 views

Ingenuity Three Axis Velocity Derivation from Camera, Gyro and Altimeter

It seems that Ingenuity has a 4000 pixel camera, a gyro, inclinometer and an altimeter. Using these information, they are able to derive three axis velocity information. Thereby compensating for the ...
zephyr0110's user avatar
  • 2,911
6 votes
3 answers
14k views

How to calculate the speed of rotation of a given point on the Earth's WGS84 ellipsoid, about its axis?

Launches often happen near the equator in order to take advantage of Earth's rotation speed. This is why more launches are towards the East than towards the West. How can one calculate the speed of ...
Ed Rojas's user avatar
5 votes
3 answers
525 views

How fast could we go back to Uranus and Neptune?

Since SpaceX is making everything so much cheaper to launch into space. If we launch a pair of orbiters to Uranus and Neptune, how fast could they get there? They could be really light and small, so ...
BT_Cribo's user avatar
5 votes
1 answer
167 views

Are there planned sungrazing probes?

Reading about sungrazing comets, that can reach speed of +600km/s at perihelion, and about sungrazing comets being used as probes. Are there any planned mission involving a sungrazing probe, able to ...
user721108's user avatar
  • 4,290
5 votes
0 answers
2k views

Solar system galactic velocity vector relative to ecliptic plane

The Solar system moves through the Milky Way galaxy with velocity of 230 km/s. The ecliptic plane is located ~60 degrees with relation to the galaxy plane, according to this source. The page also ...
Sergiy Lenzion's user avatar
4 votes
4 answers
2k views

What is the fastest we could travel in space, or have ever traveled in space?

What is the fastest vehicle currently in space? With our current technology, at what point does physics start to restrict our speed in space?
Muze's user avatar
  • 1
4 votes
1 answer
666 views

orbital speed to maintain relative position to the Earth

I note that the orbital speeds of the planets slow down with increasing distance from the Sun. Say we have a space station orbiting the Sun at a distance of about 400 million kilometres (within the ...
user50566's user avatar
4 votes
1 answer
2k views

Minimum velocity needed to cross Karman line

When we travel in a car upwards on a slope (against gravity), we can keep driving the car at a constant speed without accelerating (without changing its speed). Theoretically, the only thing we need ...
Niranjan's user avatar
  • 3,758
4 votes
1 answer
362 views

At what point of travelling progressively faster around the Earth you are not going to fall back again?

My dad and I thought about a problem we had when discussing Earth's gravitational field. This wasn't the original question but I still would like to know the answer. So essentially my question is: Is ...
Casimir Rönnlöf's user avatar
4 votes
1 answer
350 views

What is the speed that we can reach using tsar bomba as a propellant?

The idea of using an atomic bomb as a propellant was introduced in project orion, but it did not work out because of the interdiction of using the atomic bombs. So I decided to calculate the speed ...
Taher's user avatar
  • 1,057
4 votes
1 answer
1k views

How do I calculate re-entry velocity when decaying from a circular orbit?

I am trying to find the velocity of an object during re-entry so that I can calculate the peak heat flux but I'm a bit stuck. I know how to find the velocity of the original, circular orbit (300km) ...
Tom's user avatar
  • 41
4 votes
0 answers
229 views

Fastest Manmade Object

I remember reading somewhere that during the cold war, a nuclear weapon was placed underground with a manhole cover on-top and then detonated. I'm pretty sure the manhole cover then went orbital ...
und3niable's user avatar
3 votes
1 answer
447 views

Calculate velocity vector of elliptical orbit given the position vector at that point, the instantaneous speed, the true anomaly, and the inclination?

Sorry if this is obvious, but I am an amateur at orbital mechanics and trigonometry was never my strong suit. I would like to calculate the velocity vector at a point in an orbit given: position ...
John Doe's user avatar
3 votes
1 answer
177 views

What is the fastest velocity to which something can be accellerated using a gravity assist [duplicate]

My understanding of gravity-assists (slingshot) is that they use some of a more-massive object's orbital energy to gain massive acceleration. What's the upper limit on how much velocity an object ...
bobsburner's user avatar
3 votes
0 answers
266 views

Exact speed/distance of JWST (& others in L1/L2 halo) from Earth; is it measured any differently than for more distant deep-space missions?

How is the exact speed and distance from Earth of the JWST or any spacecraft in a Sun-Earth L1/L2 halo orbit determined? While deep space missions require ranging at hundreds of millions of kilometers ...
Tim's user avatar
  • 31
2 votes
1 answer
772 views

How do we get to Mars in a week (7 days)?

Looking at the times that are quoted to go to Mars (months) makes me wonder what speed do we need to get there in a week? Chemical rockets can get to ~4.5 Km/s, thermal nuclear rockets is about twice ...
Rodo's user avatar
  • 859
2 votes
2 answers
228 views

Modern ICBMs vs new Russia Weapons [closed]

If a modern ICBM can travel at speeds of 6-7 km/s (around 25000 km/h) and the speed of sound is 1192 km/h that's by my math Mach 21. So if a modern ICBM can travel at Mach 21, why are new hypersonic ...
Nelson Teixeira's user avatar
2 votes
2 answers
222 views

Is aerodynamic control in an exosphere possible, in case velocity is high enough?

Exospheres are different than the lower parts of atmospheres (if there are any): the molecules don't collide anymore and it doesn't behave like a gas. However, it still causes some tiny little drag on ...
Giovanni's user avatar
  • 438
2 votes
3 answers
1k views

Point Ahead Angle and Doppler Shift Frequency Changes Calculation with the tangential/radial velocity component for Inter-Satellite Link

While calculating the Point Ahead Angle we work with Tangential Velocity vector component and to calculate the Doppler shift i.e changes in frequencies, we work with Radial Velocity Vector component. ...
JOY's user avatar
  • 83
2 votes
1 answer
162 views

Knowing when to stop burning

Navigating in orbit usually relies on firing engines for some amount of time to achieve a specific velocity. This answer, for example, mentions "closed-loop guidance" for the ISS boosting. ...
loopbackbee's user avatar
2 votes
2 answers
211 views

How to calculate velocity components of a point on Mars surface w.r.t. Mars center?

I found altitude, speed and acceleration data of old mission Phoenix during EDL phase, but they are referred to Mars c.o.g. rather than to ground or to landing site: Position and velocity (...
jumpjack's user avatar
  • 3,033
2 votes
1 answer
944 views

How to calculate the velocity vector in the case of a hyperbolic orbit?

The problem I'm trying to get a formula to calculate the state vectors $\vec{r}$ and $\vec{v} = \dot{\vec{r}}$ on an orbit, given a true anomaly $\nu$. I'm following the process described here : https:...
Krafpy's user avatar
  • 273
2 votes
0 answers
86 views

Small Rocket Questions [closed]

I'm interested in space technologies and have basic understanding of rocket flights. When looking at large commercial rocket launches, i noticed that the lift of process from ground takes very long (...
sgt_johnny's user avatar
2 votes
0 answers
810 views

Getting the Velocity Vector in an Elliptical Orbit

I have a 2-D two body set up. I am using the vis-viva equation to get the velocity scalar of my elliptical orbit. I have the Semi-Major Axis, the radius, the eccentricity vector. I am sure I can ...
ryanq.feeney's user avatar
1 vote
1 answer
464 views

What would happen if you jumped out of a moving spacecraft?

I've watched a film where one of the characters claimed to have rapidly disembarked a moving spacecraft during a 5g burn (?!) and immediately wondered how he survived. For example, you're on a ...
Malekai's user avatar
  • 113
1 vote
2 answers
256 views

What can possibly accelerate space elevator to these types of extreme velocities?

Is it possible for a space elevator not to just reach speeds of a few hundred km/h, but much faster. Since in the future, people might want to go up to GEO to maybe work there and come back home on ...
The Rocket fan's user avatar
1 vote
1 answer
150 views

What is the equation to find how much fuel you need to reach a velocity? [closed]

Theoretically, I need to launch a rocket, and I need to find how much fuel I need to reach a velocity however I do not know the equation.
user46782's user avatar
1 vote
1 answer
189 views

How to calculate slowing effect of a planets gravity on a projectile that is launched upwards

The acceleration a ballistic projectile would experience at a certain height above a planet (neglecting any atmosphere) is given by $$a = -\frac{GM}{(R + h)^2}$$ where $G$ is the gravitational ...
justthisonequestion's user avatar
1 vote
2 answers
230 views

How to correct my real orbit and turn it into predicted ideal orbit?

I want to launch my ship to the purple ellipse orbit. But because of non-ideal world I have non-ideal ship orientation and non-ideal thrust impulse. So, my initial speed is a bit bigger and it's ...
Robotex's user avatar
  • 604
1 vote
0 answers
139 views

How to correctly change velocity in space?

The solver of the Lambert's problem gives me a hyperbolic velocity to move to some position on orbit. But the spacecraft is moving on orbit and changing the velocity takes some time. So, when I ...
Robotex's user avatar
  • 604
1 vote
0 answers
25 views

How do you balance speed and exposure time when trying to reduce heating? [duplicate]

I'm trying to understand how you choose your acceleration/deceleration and trajectory during launch and reentry to minimize aerodynamic heating.* Ignoring efficiency in terms of delta-v (best leave ...
TheEnvironmentalist's user avatar