17 votes
Accepted

What is a near rectilinear halo orbit?

Halo orbit families exist near the L1, L2, and L3 librations points. This video focuses on the L1 and L2 halo families. There are northern and southern families at each of the libration points. The ...
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  • 674
8 votes
Accepted

How does a butterfly orbit move in 3D? Way to generate or visualize?

Sorry that I'm so late to this, but I worked with the butterfly family quite a lot when I was a student in Professor Howell's group so I feel compelled to answer! It looks like you found some good ...
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  • 531
8 votes
Accepted

How precise are spacecraft trajectory measurements?

The injection accuracy of the launch vehicle is typically measured in m/s, as the velocity change required to get the spacecraft exactly on the desired trajectory. This wraps up all the dimensions of ...
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  • 57.6k
7 votes

How could transfers between SEL1&2 and EML Lagrange points be utilized?

Can it be useful for spacecraft to move in a sequence between SEL's and EML's in order to lower their missions' delta-v requirements? Has it been done already? Yes and yes. You are asking about weak ...
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  • 64.2k
7 votes
Accepted

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

In fact, they are the preferred option among other staging orbits by analizing multiple factors: EARTH ACCESS: A study considering NASA SLS and Orion performances was carried out. Since SLS places ...
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  • 1,712
7 votes

Seeing stars from cislunar space?

Yes. They did see stars. Here is an excerpt from the Apollo 11 Transcript. 02 23 59 20 CDR: Houston, it's been a real change for us. Now we are able to see stars again and recognize constellations ...
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  • 5,798
6 votes
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What ever happened to 6Q0B44E - potentially the "artificial satellite (with) the farthest orbit around the Earth"?

Not definitive, but according to Identification of SST community support to reduce false positives in the identification of NEO imminent impactors (PDF): A similar case is currently being provided by ...
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6 votes
Accepted

How many Space Shuttle payloads ended up beyond Earth orbit?

Magellan (to Venus) Launched May 1989 on STS-30 Galileo (to Jupiter) Launched October 1989 on STS-34 Ulysses (to the Sun) Launched October 1990 on STS-41
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5 votes
Accepted

How fast are trips to the Moon for unmanned spacecraft typically?

Are most trips to the Moon actually around 3 or 4 days, and not the 5.0 days of a half-ellipse? The 5 spacecraft of the US Lunar Orbiter program took 3.8-3.9 days to reach lunar orbit. The Ranger ...
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5 votes
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How many spacecraft deployed from the ISS have escaped Earth orbit? Are there plans for any in the near future?

To Answer your question: How many spacecraft deployed from the ISS have escaped Earth orbit? None Are there plans for any in the near future? No A short proof: Public Sat-Catalog here You ...
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  • 2,549
5 votes
Accepted

What is Buzz Aldrin's T.O.R. plan? How does it work?

Buzz Aldrin is against the Artemis Program because it would be expensive as the SLS is not reusable (similar to the Apollo program and the Saturn V) and a single launch can cost up to 1.5 billion USD. ...
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  • 5,798
5 votes

What are the advantages and disadvantages of assembling a space station in LEO before sending it to its intended Lunar orbit?

Making this a community wiki answer so others may add to it as they see fit: Advantages LEO assembly allows less mission risk if assembly does not go completely as planned. It's much easier to ...
4 votes

How much fuel is being consumed by all spacecrafts in orbit?

BOE: 1000 active satellites, launched with 3 tons of fuel+oxidizer each for an expected lifetime of 15 years is 3000/15=200 tons of fuel+oxidizer needed per year. Note: 3 tons is too much, as many ...
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  • 121k
4 votes

Could Apollo's Sextant navigation use similar geometry as Marine Navigation?

Since I didn't have 50 rep points yet I've posted this as a partial answer. My research came up with the following from (for example) GIS Wiki's Sextant (similar wording in Celestial Navitagion ...
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  • 95
2 votes

Antenna wrap material suitable for lunar & cis-lunar environment

Plastic can be very useful for space, depending on the thermal and cosmic ray deflection properties required. You might use suitable PCB material such as Kapton FPC which is extremely flexible yet ...
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2 votes

Was Chandrayaan-1 recovered (tracked) only that one time in 2016, or is someone still keeping an eye on it from time to time?

It was not "spotted just once". Rather, it was tracked until its orbital motion became predictable: On 2 July 2016, NASA used ground-based radar systems to relocate Chandrayaan-1 in its ...
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  • 7,250
2 votes

What are the advantages and disadvantages of assembling a space station in LEO before sending it to its intended Lunar orbit?

LEO is a bit dangerous in my book. If anything goes wrong you may not have enough of a margin to fix things. Put the station in a little higher orbit and make your deliveries to LEO and use tug to ...
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2 votes
Accepted

How does fuel requirement change with mass when traveling from cislunar orbit to Mars?

To a first approximation, the amount of fuel required to send a spacecraft on a given trajectory (i.e. at a given velocity) is proportional to the mass of that spacecraft. So if the craft loaded with ...
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2 votes

How to find Horizons ephemerides or Spice kernels for the cis-lunar halo orbits of the Themis B & C) spacecraft?

It was hosted on the Berkely SSL server. Kernels located here: http://themis.ssl.berkeley.edu/data/themis/spice_kernels/ P.S: Thanks to David Stansby's HelioPy documentation.
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  • 455
2 votes
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How to estimate that receiving GNSS signals Earth while orbiting the Moon will still provide locations to about 200 meters of uncertainty?

Using Dilution of Precision (DOP)! I am ignoring the leakage and line-of-sight problems discussed in the comments and just focusing on the geometry. I created a simulation with 4 GNSS satellites ...
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1 vote

What ever happened to 6Q0B44E - potentially the "artificial satellite (with) the farthest orbit around the Earth"?

The wikipedia article 6Q0B44E says it. "6Q0B44E, sometimes abbreviated to B44E, is a small object, probably an item of space debris, that is currently orbiting Earth outside the orbit of the Moon ...
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1 vote

Are Sun-Earth Lagrange points SEL1 and SEL2 useful for communication and space surveillance?

For voice and video communications, a 1-second delay is annoying. 10 seconds is way too much to be useful. Current data networks don't tolerate 10-second delays either so you'd need new communications ...
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