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50 votes

Do you need to burn fuel between gravity assists?

Yes, Trajectory Correction Maneuvers (TCMs) are always performed during cruise phases, whether before or after gravity assist flybys. This NASA tutorial serves as a good general reference. One source ...
Tom Spilker's user avatar
  • 18.3k
48 votes

What are "Ohms burns" in the context of Scott Kelly, KSP, and the Space Shuttle?

That's a mistranscription of OMS Burn, or Orbital Maneuvering System burn. The OMS system is how the shuttle changed its orbital characteristics. You can read about it here. One, two or more might ...
BobT's user avatar
  • 1,221
48 votes
Accepted

Why is it so hard to build crewed rockets/spacecraft able to reach escape velocity?

Delta-V to LEO is about 10 km/s. From there to C3 (Earth escape) is another 3.2 km/s. It's just another 30% delta-V. The problem is the Tyranny of the Rocket Equation. More delta-V means more fuel. ...
Schwern's user avatar
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42 votes
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How does a spacecraft know that it is in orbit?

The Juno spacecraft has no means to directly measure and compute that it is in orbit. It did not send any such confirmation message. All it sent was an FSK tone indicating that it had completed the ...
Mark Adler's user avatar
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38 votes
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Why is it most efficient to change orbit inclination while crossing the equator?

Why is it the most energy efficient to change orbit inclination while crossing the equator? Specifically, it's most efficient to do a plane change at one of the two "nodes" where the origin ...
Russell Borogove's user avatar
36 votes

James Webb orbit insertion

How can JWST brake without turning around? Answer: JWST does not. From More Than You Wanted to Know About Webb’s Mid-Course Corrections!: One interesting aspect of the Webb launch and the Mid-Course ...
blobbymcblobby's user avatar
34 votes

Why is it so hard to build crewed rockets/spacecraft able to reach escape velocity?

It's not hard, it's just expensive. We know exactly how to do it. Compare this to building computer processors with 1nm transistors, or making reliable self-driving cars. Those are both things that we ...
spacetyper's user avatar
34 votes

When burns are made during inefficient parts of the orbit, where does the lost energy go?

After writing my comments, I started writing a new answer. That got long, so here's a shorter one. The "energy of an orbit" may be poorly defined and depending on the definition, is not ...
Anton Hengst's user avatar
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33 votes
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Do all artificial satellites have engines?

Most satellites do have a thruster system of some sort on board. Indeed, the lifespan of a satellite is often determined by how much fuel it can carry, because once it runs dry, it'll start to slip ...
Darth Pseudonym's user avatar
29 votes

Why is it most efficient to change orbit inclination while crossing the equator?

A great aid to intuition is to remember one principle about orbit changes: if the engine is off, the orbiter always returns to same point one orbit later. So for any orbit change, if you want to do ...
jpa's user avatar
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25 votes
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This ISS trash deployment looks more like 2 feet than 2 inches per second, was it too fast or are these articles incorrect?

What's the root cause of the disparity between what the article says and what's shown in the video? There is no disparity. The article says you need a minimum velocity of two inches per second [bold ...
Jörg W Mittag's user avatar
25 votes

Are there any studies about "ping pong" cyclers between gas giants?

In a sense, this "ping pong" is what cycler orbits attempt to do, you are just overestimating the power of flybys. To make the distance between Jupiter and Saturn in just 4 years (one way?), ...
SE - stop firing the good guys's user avatar
23 votes
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Lowest delta-v maneuver to reverse the direction of a satellite in LEO?

Reversing direction is a special case of inclination- / plane-change. Here's one way to find a better upper bound on the necessary delta-V for a 180 degree plane change: Assume a 2-body system (i.e. ...
pericynthion's user avatar
  • 10.1k
23 votes
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Was SpaceX's launch of Formosat-5 more vertical than normal for any particular reason?

FORMOSAT-5 was deployed directly to a 720 km circular orbit, with only a single burn. In order to do a circular orbit so high, one has to have a more vertical ascent then would be typical. Basically, ...
PearsonArtPhoto's user avatar
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23 votes
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Using Mars' inner moon Phobos as a brake

This wouldn't really work. Phobos is tiny, and its gravity is proportionally weak (in some areas, the escape velocity is around a slow jog), so first off, any sort of gravity assist you do is going to ...
Darth Pseudonym's user avatar
22 votes
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What is the delta-v required to get a mass in Earth orbit into the sun using a SINGLE transfer?

Actually the answer is a bit more complex than "Earth orbits at 30 m/s, so you have to stop that velocity and drop in. Thus the delta-V is 30 km/s." The question states that you start from Earth orbit,...
Tom Spilker's user avatar
  • 18.3k
22 votes

Do all artificial satellites have engines?

Short answer: no. most small satellites (like the cubesat you saw) don't have engines. Rocket engines are complex, and therefore expensive, and these small satellites are usually used in an effort to ...
Hobbes's user avatar
  • 128k
21 votes

How does a spacecraft know that it is in orbit?

Using attitude determination devices, (including doppler shift of radio signal from Earth), it can determine* its location and velocity relative to Jupiter, and from that data, and knowing Jupiter ...
SF.'s user avatar
  • 55k
21 votes
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What is the smallest body in which a sling shot maneuver can be performed?

How small do you want to get? $F=G{Mm \over r^2}$ applies regardless of size. If you remove enough disturbances from other bodies you can get two neutrons to orbit a common barycenter on gravity alone ...
SF.'s user avatar
  • 55k
21 votes
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What are the benefits of supersynchronous transfer orbits?

This is a partially copied answer from this closely-related question: The other answerer focuses on the straight-up dV savings which occur when you're launching from a very inclined launched site. I'm ...
Anton Hengst's user avatar
  • 10.7k
21 votes
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Why does the point of burn on an orbit stay at a constant altitude?

When calculating propulsive manoeuvres, we usually consider them as impulses. That is, happening in a very short time. This is usually a good enough model for chemical rocket engines which deplete ...
SE - stop firing the good guys's user avatar
20 votes
Accepted

What happens to JWST after it runs out of propellant?

This Northrop Grumman video (starting at 09:31) illustrates JWST's orbit in a non-rotating (normal) frame. It's really in an orbit around the Sun about 1% farther ...
uhoh's user avatar
  • 149k
20 votes
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Delta-v to move from GEO to GEO

Theoretically, you can go anywhere in GEO for an arbitrarily small ∆v - you raise your apogee a little bit, which slows you down, wait until you've phased to your destination latitude, then re-...
Russell Borogove's user avatar
19 votes
Accepted

What are "Ohms burns" in the context of Scott Kelly, KSP, and the Space Shuttle?

Since the questioner also asks "why are two needed" and the other answer didn't address that: Early shuttle missions flew a "standard insertion" ascent. This required two burns of ...
Organic Marble's user avatar
19 votes

What kind of mission objective would make a parabolic escape trajectory desirable?

Why zero excess velocity? Well, with almost zero excess velocity you can stay near Earth, but not too near. For example, the Spitzer space telescope did this to communicate with Earth while avoiding ...
Camille Goudeseune's user avatar
19 votes
Accepted

What is the equation that relates delta v of a rocket to time taken to complete an orbit?

There is actually no relationship between the two. In a simple 2-body problem, each orbit starts and ends in the same place with the same velocity vector. The "delta" in "delta-v" ...
Woody's user avatar
  • 22.1k
19 votes

At which direction do you apply thrust to perform an inclination change maneuver?

To change an orbit's inclination, you need to apply thrust in the normal/anti-normal direction. The normal/anti-normal direction are some of the 6 main directions you can change your velocity. There ...
The Rocket fan's user avatar
18 votes

How do orbital boosts affect the structural integrity of the ISS?

Yes. It is considered (sorry I don't know exactly how much, but probably a LOT - they track the torque on individual bolts during construction for example). They had an accident a while ago where a ...
Innovine's user avatar
  • 4,625
18 votes

When burns are made during inefficient parts of the orbit, where does the lost energy go?

The sum of all mechanical energy will be the same after your ideal burns. The difference will be that the portion given to your exhaust will be greater for higher burns. For a burn farther away from ...
BowlOfRed's user avatar
  • 6,882
18 votes
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During orbital rendezvous, at what distance and approach velocity does the transition from orbital mechanics to “boating around” occur?

Orbital mechanics always apply. For shuttle the two different operational phases were referred to as Rendezvous Ops and Prox Ops The breakpoint between the two was defined in the Space Shuttle Flight ...
Organic Marble's user avatar

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