![]() So- orbit maintenance (or stationkeeping) is required, but there's more recovery time than in a flatter Earth-Moon halo like Artemis flew. In an NRHO, the lower stability index means that a missed maneuver or a perturbation affects your orbit less, and there's more time to recover before the spacecraft escapes the orbit. In a flatter, less stable halo, if you miss a stationkeeping maneuver or have an unexpected perturbation, you might escape from the halo in just a few weeks or less. They also provide really great lunar south pole coverage, since they whip quickly around the north pole and spend almost all of their time in the southern hemisphere. ![]() Why are they special? As discussed in Ryan Whitley's paper you linked to, they're favorable for transferring into and out of, which is nice when your spacecraft is meant to be a staging ground for exploration, with other ships coming and going. That bifurcation marks the lower limit of the NRHO portion of the halo families. You can see it for the red L2 line for the blue L1 line that point is below the lunar surface and isn't included in the plot. ![]() There's another bifurcation on the far left of those plots, where the stability index is equal to 1. See how the stability indices are bounded (with a value of 3 or less) until you hit a perilune radius (rp) of 16,000 or 18,000 km, and then the stability indices begin to grow quickly? We've defined "NRHO" to lie to the left of that bifurcation- those halos with bounded stability properties. You can see a plot of the stability indices of the L1 and L2 halo families, a zoom of the NRHO portions of the two families, and the butterflies as a bonus, in Figure 2 of this paper:Ĭheck out the top plot in Figure 2b. That is, they're marginally stable, or nearly so, in a linear analysis. We've defined the NRHOs as those members of the halo families whose stability indices are bounded. The Near Rectilinear Halo Orbits are the tall, nearly-polar ones that get really close to the Moon. The family thus evolves out of plane, as you see in the video, and it keeps growing and approaches the smaller primary (the Moon if we're working in the Earth-Moon system). You can step up in the z direction and find another member of the halo family. That is, the first halo in the family is planar, and it is also a member of the kidney-bean-shaped Lyapunov family. The northern family is identical to the southern family but mirrored across the x-y plane.Īt each point, the family bifurcates from the planar Lyapunov family of orbits. There are northern and southern families at each of the libration points. This video focuses on the L1 and L2 halo families. Halo orbit families exist near the L1, L2, and 元 librations points. Berry, 2017, Targeting Cislunar Near Rectilinear Halo Orbits for Human Space Exploration Barton, 2017, Orbit Maintenance and Navigation of Human Spacecraft at Cislunar Near Rectilinear Halo Orbits Martinez, 2015, Options for Staging Orbits in Cis-Lunar Space These might be good places to start.įor convenience I've managed to find some links to some of the papers listed at the end of the video. There are some visual clues in the video, especially here and here but the captions are minimal. This excellent answer discusses the various tradeoffs between different lunar orbit options and explains why the NRHO appears to be such a good candidate.īut what is a near rectilinear halo orbit to begin with? Is it different than a "normal" halo orbit or just a subclass? Is there such a thing as a "true" rectilinear halo orbit as well? What makes it so special? In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a. “ orbital”, in Trésor de la langue française informatisé, 2012.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.Orbital ( feminine orbitale, masculine plural orbitaux, feminine plural orbitales) “orbital” in Diccionari de la llengua catalana, segona edició, Institut d’Estudis Catalans. ![]() Orbital ( masculine and feminine plural orbitals)
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |