Linked Questions

30 votes
10 answers
15k views

How many times do you have to circle the Earth to break orbit?

My science teacher asked us this, and nobody in my class knew. We guessed it would be three, but with no evidence. (Edit: The asker has not returned to clarify if they meant leaving the Earth-Moon ...
Patrick's user avatar
  • 309
15 votes
1 answer
18k views

What is a near rectilinear halo orbit?

A proposed option for the lunar orbit of a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway) is a near rectilinear halo orbit, or NRHO. This excellent answer discusses the ...
uhoh's user avatar
  • 149k
9 votes
3 answers
2k views

What asteroids have the least delta-v to reach?

I think the question needs very little clarification - specific asteroids and/or their asteroid orbit type would answer it. My own interest is in what would best suit targeting for asteroid mining on ...
Ken Fabian's user avatar
  • 1,042
16 votes
3 answers
2k views

Why would a mission to Sun-Earth L1 have an instantaneous launch window?

I was watching the webcast for Falcon 9 Flight 15 (launching DSCOVR) when they scrubbed their first launch attempt due to some issues during the terminal countdown. Before the scrub, the narrator ...
Nate Barbettini's user avatar
13 votes
1 answer
7k views

Why is a near rectilinear halo orbit proposed for LOP-G (formerly known as Deep Space Gateway?)

Why is a near rectilinear halo orbit a good place for a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway)? Are there specific logistical and orbital-mechanical advantages over ...
uhoh's user avatar
  • 149k
10 votes
2 answers
940 views

How many SpaceX 2nd stages are in heliocentric orbits?

I can think of one particularly famous SpaceX 2nd stage in heliocentric orbit that even has its own website: https://www.whereisroadster.com/ and I know one was used to send DSCOVR towards Sun-Earth ...
uhoh's user avatar
  • 149k
10 votes
2 answers
3k views

The design of the halo orbit of the James Webb Space Telescope

As I feel a little less uncomfortable with "halo" orbits, with this question, I would like to explore the practical aspects, in particular those related to the design of the James Webb Space ...
Ng Ph's user avatar
  • 2,734
5 votes
3 answers
2k views

How do spacecraft reach Lagrange points?

As I understand, to reach a Lagrange point the spacecraft would need to slow down. Also, can spacecraft passing nearby Lagrange points get captured within the point?
Bruce Vici's user avatar
9 votes
1 answer
408 views

How would you identify when an object in a Lissajous orbit needs station keeping?

Obviously, with the international space station you need to do some station keeping when you're falling into the atmosphere. However, I saw the following image showing the Halo orbit that the Deep ...
Magic Octopus Urn's user avatar
5 votes
1 answer
667 views

Why did we think that the object was gonna hit the Moon March 4th 2022? Who's been tracking and predicting it so closely?

The Guardian's 'Out-of-control' Chinese rocket falling to Earth... Oops, I mean Out-of-control SpaceX rocket on collision course with moon says that Bill Gray's Project Pluto/DSCOVR says that the 2015 ...
uhoh's user avatar
  • 149k
11 votes
1 answer
1k views

Low Energy Transfer within Earth-Moon system

Practical aspects of a total low energy transfer to the Moon have been seen in missions like GENESIS, which uses Weak stability Boundary legs of Earth and Sun to reach ESL-2. This four body model ...
Kuldeep Barad's user avatar
3 votes
1 answer
718 views

Rendezvouses in halo or lissajous orbits

If a spacecraft was in an EM-L2 halo/lissajous orbit, and another craft would was going to approach EM-L2 a few days later, could they rendezvous immediately or is there a limitation when the second ...
Bob516's user avatar
  • 6,949
1 vote
2 answers
269 views

How to prepare for an interview for a Pure Mathematics position at ISRO's Space Application Center?

I have completed a Master's in Pure Mathematics. I have read topics like Abstract Algebra, Linear Algebra, Functional Analysis, Topology, Cryptography, Course in C++, etc. Recently I found an ...
user avatar
4 votes
1 answer
436 views

Do ("non-halo") Lissajous orbits have stable/unstable manifolds?

The question Did DSCOVR travel “along the stable manifold of its future SE L1 Halo orbit” to get there? is specific to DSCOVR's trajectory from Earth to its primarily heliocentric orbit near Sun-Earth ...
uhoh's user avatar
  • 149k
1 vote
0 answers
98 views

How is it possible to connect trajectories at a Poincare section using the "bisection" method?

When constructing a heteroclinic connection (a connection between two different periodic orbits at two different libration points), the stable and unstable manifolds of two different libration points ...
John's user avatar
  • 1,377