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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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
3 votes
1 answer
467 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
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
0 votes
5 answers
469 views

Is the launch of a rocket slow because the change in velocity (delta_v) should be as small as possible because of energetic reasons?

Does it make sense to keep the launch of a rocket slow because the change in velocity (a.k.a. delta_v) should be as small as possible because of energetic reasons?
FalconHeavy321's user avatar
0 votes
1 answer
76 views

Higher nozzle exit velocity generally means higher thrust right?

Higher nozzle exit velocity generally means higher thrust right? If that is the case, then a higher heat capacity could potentially lead to a higher exit velocity, thus higher thrust?
FalconHeavy321's user avatar
4 votes
1 answer
667 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
10 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
-4 votes
1 answer
111 views

Will the initial velocity of an object in space get multiplied if a constant acceleration is applied? [closed]

Imagine an object travelling in space in the speed of 60 Kmph which took acceleration x if accelerated with the same x, will the object travel faster than 60 Kmph or travel in the same speed cuz of ...
Glash's user avatar
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0 votes
1 answer
145 views

Could time illusion be used to send a spacecraft faster than the speed of light?

In this article (https://www.nasa.gov/feature/goddard/2022/hubble-spots-ultra-speedy-jet-blasting-from-star-crash) it says: The Hubble measurement showed the jet was moving at an apparent velocity ...
The Rocket fan'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
5 votes
3 answers
533 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
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
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
2 answers
307 views

How come satellites and space stations that travel through space at Earth's speed do not disintegrate?

What I mean, if Earth travels through space at 1,700 km/hour, when a spaceship or other object leaves its atmosphere, should it not stay behind? And if it is gravity that keeps it near Earth, should ...
Plinia Blue'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
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
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
0 votes
1 answer
79 views

Standing still to move forward [closed]

If our galaxy is tracking through space at ~1.3mm, couldn’t we arrive at point B if we came to a stop at point A. i.e. decelerate to -1 g
Driestcake'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
2 votes
1 answer
972 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
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
2 votes
1 answer
794 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
4 votes
0 answers
230 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
0 votes
1 answer
787 views

Terminal velocity on reentry?

I've seen many references to "terminal velocity" on reentry, e.g., prior to a Falcon 9 landing burn. And I'm confused by this. Because terminal velocity comes from drag which depends closely ...
user avatar
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
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
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
0 votes
1 answer
682 views

How much anti-matter is needed for an anti-matter propelled rocket to reach $P$ % ($P\lt{100}$) of the speed of light (c)?

I think this is a tough one. Imagine a rocket is produced which is propelled by a matter-anti-matter device. Its sole purpose is to reach high velocity. Which means the mass can be kept low, say $m$ ...
Deschele Schilder'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
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
1 vote
0 answers
436 views

What's the minimum speed for a spaceplane to reach outer space? [closed]

From a realistic point of view there must be a minimum speed in order to reach space in a suborbital spacecraft, let's say in a spaceplane. Like there's a first cosmic velocity (for orbit) and a 2nd ...
LoveForChrist's user avatar
1 vote
1 answer
467 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
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
0 votes
2 answers
202 views

Did a spacecraft ever use an atmosphere to accelerate away from a planet?

If a spacecraft enters flat enough into the Earth's (or another planet's) atmosphere it will "bounce off" the Earth at a higher speed. That method can be used if a spacecraft has not enough fuel to ...
user avatar
0 votes
0 answers
35 views

How can the download speed increase from space probes? [duplicate]

It always seems to be a genuine question that is How can we download data from far away probes in instant. When New Horizons reached Ultima Thule, it took us quite a few months to have a great picture ...
Pranay's user avatar
  • 482
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
2 votes
0 answers
817 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
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
0 votes
1 answer
125 views

How fast is space debris travelling? [duplicate]

How fast is orbital debris travelling? I believe the speeds would vary based on the debris size, so what would be the range of velocities in that case?
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
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
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
0 votes
1 answer
169 views

Is it theoretically possible to create absolute velocity?

I think I read somewhere that it's impossible to create absolute zero velocity because there is always a reference point? what defines the reference? I seen the comments here: https://www.quora.com/...
Steven Azari'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 ...
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
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
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
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
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
  • 6,458
0 votes
2 answers
154 views

What is a safe speed in space for spacecraft?

Does traveling fast as possible shortening the duration of the mission lessen chances of collision or mechanical failure, or does traveling slower in space in some way safer?
Muze's user avatar
  • 1