76
votes
Accepted
The dreaded apocalyptic asteroid approaches Earth but lands safely on the Moon at zero relative velocity
In order to land on the Moon, you must, at some point, be moving towards the Moon (decreasing your distance from it, to be more precise, you may also be moving sideways) and close enough that the Moon'...
- 19.4k
64
votes
Accepted
Why did Voyager 1 lose speed after the sudden gain in speed from gravity assist?
It's the gravitational attraction of the Sun. Voyager was moving away from the Sun and was pulled back by its gravity. Since Voyager was not moving directly away from the Sun, it's trajectory also ...
- 19.4k
58
votes
The dreaded apocalyptic asteroid approaches Earth but lands safely on the Moon at zero relative velocity
@SteveLinton's answer is right, no matter how gently you try, by the time you get to the surface the Moon's gravity will have accelerated you to something like 2,400 m/s. There are ways to use the ...
- 149k
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 ...
- 18.2k
47
votes
Why didn't Voyager 1 and Voyager 2 crash on into Jupiter or Uranus when they approached near to these massive planets?
why weren't they completely attracted by their gravitational field?
How much a trajectory is changed, depends on 3 factors:
the mass of the planet,
the speed of the spacecraft,
the distance between ...
- 126k
36
votes
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Why is there currently so little talk about a Venus gravity assist for a crewed Mars mission?
The Venus flyby does indeed make the mission shorter, but it has some pretty serious negative consequences as well.
The mission spends much more time in deep space.
Approaching the sun will increase ...
- 121k
35
votes
Why did Voyager 1 lose speed after the sudden gain in speed from gravity assist?
Additionally, the probe has just passed a large planetary body with its own gravity well. The probe has to climb up out of that planet's gravity well which costs momentum.
There is a net gain in ...
- 681
32
votes
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Would an astronaut experience a force during a gravity assist maneuver?
If the only acceleration is due to the large mass's gravity, and the mass is not exceptionally large, or exceptionally close (i.e. close approach to a black hole or a neutron star), the astronaut will ...
- 167k
30
votes
Is there any limit to how many times you can increase velocity by repeated sling shot manoeuvres?
In theory, it might be possible, but in practice it is not. The problem is the sling shots (gravity assists) themselves take time.
Some years ago, we did a study of a possible flag ship mission to ...
- 2,611
29
votes
Accepted
Can we set up an orbiting transporter between Earth and the Moon?
This sort of spacecraft is known as a "cycler".
You hit on the problem with it: you have to match its trajectory/velocity exactly in order to dock with it, so if you can reach the cycler, you could ...
- 167k
28
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Is there any limit to how many times you can increase velocity by repeated sling shot manoeuvres?
Once you get going fast enough you will escape the system and won't be able to do any more slingshot maneuvers.
Edit: Yeah, you can still encounter bodies for slingshots. Once you are at escape ...
- 11.5k
25
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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?), ...
24
votes
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How much longer would New Horizons take to reach Pluto without the Jupiter slingshot?
It was said in here that the time to reach Pluto was shortened by 3 years. It's also said that after the Jupiter flyby the probe gained ~ 4 km/s accelerating to the speed of 23 km/s relative to the ...
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21
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Why didn't Voyager 1 and Voyager 2 crash on into Jupiter or Uranus when they approached near to these massive planets?
To add to the answers @Hobbes & @Steve Linton posted, the mission designers indeed knew Jupiter's gravity field quite well from the orbits of Jupiter's moons. But before the Voyagers arrived they ...
- 18.2k
21
votes
Accepted
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 ...
- 54.9k
18
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Would it be possible to go beyond Jupiter without making any slingshot?
It is absolutely possible, just not advised. New Horizons was launched at Solar System Escape Velocity, meaning it could have visited anywhere beyond Earth without stopping. It did visit Jupiter, ...
- 121k
15
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Why didn't Voyager 1 and Voyager 2 crash on into Jupiter or Uranus when they approached near to these massive planets?
Let's try and understand how gravity works in space. This is kind of key idea to understanding lots of issues in space travel and astronomy.
So imagine a space probe, or rock, which is heading in ...
- 19.4k
15
votes
Accepted
Will Dragonfly flyby Jupiter en route to Saturn?
Here is a paper which among other things includes the results of a trajectory search. They say
Gravity assists of Earth, Venus, and Mars were included with a patched conics assumption. Jupiter was ...
- 19.4k
14
votes
How much longer would New Horizons take to reach Pluto without the Jupiter slingshot?
Depending on the time of launch, there were 4 different major plans for the NH mission profile. The first 3 involved Jupiter flybys, and would have an arrival date of 2015, 2016, or 2017. The last was ...
- 121k
14
votes
Can we speed up spacecraft to suitable interstellar travel speed using oscillating gravity assists on planets on opposite sides of the solar system?
Accumulating 0.1c (30000 km/s) with gravity turns alone within the bounds of Solar system isn't possible. Reason is: system escape velocity (sometimes referred to as third cosmic velocity) is about ...
- 387
14
votes
Accepted
Could Starman get ejected from the Solar System?
Definitely - it could be ejected. But Earth would only play a minor role.
Starman now counts as a Near Earth Object, being any object crossing Earth's orbit. Any such object is occasionally in Earth'...
- 21.3k
14
votes
Accepted
How much does a swing-by change the orbit of the planet?
The mass of the Voyager is $\approx$ 825 kg.
The mass of the Jupiter is $\approx 1.9 \cdot 10^{27}$ kg.
According this question, the Voyager accelerated from $\approx 10.2 \frac{km}{s}$ to $\approx ...
- 3,276
14
votes
Rockoon on steroids
Before I start my answer:
This is not a rockoon anymore, since there is no balloon part. It's just a quirky air launched rocket.
My answer:
No.
What you are doing is:
Phase 1: Climb with a plane
...
- 12.6k
14
votes
Have space probe gone to unplanned destinations?
Back in 1983 the International Sun-Earth Explorer 3 spacecraft (ISEE-3) was diverted, via a very small ∆V and Earth-moon gravity well manipulations, from its Sun-Earth L1 halo orbit to a rendezvous ...
- 18.2k
14
votes
Is there any limit to how many times you can increase velocity by repeated sling shot manoeuvres?
There are practical limitations besides just time. I don't know the whole math involved, but a very high speed, very close pass to a massive object like a planet will not result in much deflection, if ...
- 121k
13
votes
What are the disadvantages of gravity flyby assist?
Arthur Dent caught the basic problem with gravity assists - you can't decide where and when you can use them - you must plan your mission around opportunities for gravity assists, and that means a ...
- 54.9k
13
votes
Accepted
How do we come up with the gravity assist (or slingshot) formula?
You get that formula simply using the Pythagorean theorem, also known as vector addition. The link already provides $v_{2x}=v_1\cos\theta+2u$ and $v_{2y}=v_1\sin\theta$. Then you simply compute the ...
- 58.5k
13
votes
Would an astronaut experience a force during a gravity assist maneuver?
The astronaut will be accelerated by the gravitational pull of the body they are passing, but they won't "feel" it in a qualitative sense like they do during an engine burn. This is because ...
- 3,687
13
votes
Accepted
Gravity assist (flyby/slingshot) from an asteroid?
Asteroids are too small to give a meaningful boost from a flyby.
During an encounter, the relative entry and exit speed is equal
$$ v_{in} = v_{out}$$
The only thing a mass does it bend the direction ...
12
votes
What are the gravitational assist effects on the inclination of a probe's trajectory, from passing by Jupiter at different latitudes?
Yes, Jupiter can make a trajectory perpendicular to the ecliptic, which is exactly what it did for Ulysses, which observed the poles of the Sun:
The function is just vector addition. It depends on ...
- 58.5k
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