15

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 northern family is identical to the southern family but mirrored across the x-y plane. At each point, the family bifurcates from the planar Lyapunov family of ...


7

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 the error (the energy, the trajectory plane, your time of arrival, etc.) into one number. From my recollection, that number is on the order of 1 to 10 m/s. ...


7

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 stability boundary trajectories. These offer a significantly reduced delta V trajectory from the Earth to the Moon compared to a direct transfer. Two downsides ...


7

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 for the first time on the trip. It's - the sky is full of stars. Just like the nightside of Earth. But all the way here, we have only been able to see stars ...


6

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 resources already, but I can expand a bit and show some more of the family :) I have quite a few visualizations of the L2 southern butterfly family in the Earth-...


6

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 Orion in a trans-lunar trajectory, Orion vehicle has to carried out orbital maneuvers to reach a orbit near the Moon, so the limiting factor will Orion's ...


5

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 schedule and launch replacements or corrective hardware. LEO assembly allows for checkout and stress testing of hardware in a location where failure allows a safe ...


5

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 can search by "International Designator = 1998-067" and filter "On-Orbit" you will get every known object released (intentionally or not) by the ISS an the ISS ...


5

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


5

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 and Surveyor missions were on faster trajectories -- around 2.7 days from launch to lunar impact or landing. The early Soviet Luna series missions that I've ...


4

3 According to this list on Wikipedia the only launches to a Heliocentric orbit were DSCOVR, TESS and Elon Musk's Tesla Roadster. No other SpaceX rocket went beyond a geostationary transfer orbit (GTO). In launches to GTO the second stage is typically left in a decaying elliptical low-Earth orbit, until it re-enters the atmosphere. (see e.g. here, here or ...


4

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. Instead he proposes a different plan, the T.O.R.(TransWay Orbit Rendezvous). The first two passages can be found in the article @uhoh linked. At least Orion ...


3

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 satellites will have a total mass that's less than that. I could be an order of magnitude off. Most of these will be hypergolics so no oxygen, the remainder is ...


2

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.


2

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 push building blocks to the higher orbit. That way you have advantages of both. A big problem with LEO is the space junk. When you are done the higher orbit is ...


2

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 cargo is 1000 times the mass of the craft without cargo, it will need 1000 times as much fuel to make the same flight to Mars. The reason for this is the ...


1

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 technology. You'd also need large dishes on the ground instead of the small rod antenna now used in satphones. Military surveillance of space can be done ...


Only top voted, non community-wiki answers of a minimum length are eligible