# Tag Info

58

They are burns, with the direction of the arrow roughly indicating the direction of thrust. Ascent Earth orbit insertion Trans-lunar injection Midcourse correction Lunar orbit insertion Burn to drop out of lunar orbit for landing (LM) Ascent from lunar surface (LM) Lunar orbit insertion (LM) Trans-Earth injection Midcourse correction Whew! Found a ...

51

The process was a great deal more sophisticated than pointing and thrusting, and the CSM was cooking along at over 1600 m/s, circling the moon every 2 hours. Mission control, however, had fairly precise tracking of the positions of both the CSM and the landing site, and they computed the correct time of launch to begin the rendezvous using powerful Earth-...

41

Short answer: Space stations have been refueled on orbit, as well as some small demonstration missions. Long answer: There is only a limited number of objects that this is even an option. There are 3 types of docking which have generally happened. Those involving manned spacecraft but not a space station, those involving a space station, and those with ...

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Assembling or fueling the Apollo spacecraft in Earth orbit from multiple smaller launches was considered; it's referred to as the Earth Orbit Rendezvous mission mode. The original EOR studies were based on the Direct Ascent mission plan, where the Apollo Command/Service Module would land on the moon with the help of an additional descent stage, then return,...

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It wasn't a non-issue at all, it was a complex technological problem to solve. When the Apollo program was conceived space flight was still in its infancy, humans had been in orbit, just. Orbital rendezvous was theoretically possible, but required technologies, techniques and procedures that nobody was sure could be developed in the time-frame: Precision ...

27

This is more of a physics question, but here goes: Both the piloted spacecraft and the rendezvous target are objects each in their own orbit, even though they may be separated by minimal distance and have minimal relative velocity one to the other. An object in an ideal orbit always travels in a plane of fixed absolute orientation around the center of ...

22

On one of the Russian web sites there is an interview with Rafail Murtazin, deputy head of ballistics department of the Energia corporation, who is described as the developer of the expedited rendezvous scheme. In brief, they have achieved this as follows (I apologize for possibly incorrect terms, please feel free to edit). Firstly, the ISS orbit is ...

19

Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change ...

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Russia has been using expedited rendezvous since 2012 with the uncrewed Progress and since 2013 with the crewed Soyuz. Expedited rendezvous is a huge bonus for a crewed vehicle. This is particularly the case with the Soyuz capsule, which is a bit cramped when it carries two people and very cramped when it carries three. The newest revision of the Soyuz fell ...

16

Gemini 4 was the first unsuccessful try of a rendezvous. They sought at that times it should be possible to rendezvous from a short distance by simply thrusting towards the docking object. They had to learn it the hard way that this strategy works only on very, very short distances and in a short time. The circumference of a low Earth circular orbit with a ...

16

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart: It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the ...

14

The long comment chain below this answer highlights the mis-conception that NASA astronauts as a whole did not understand the orbital mechanics of docking. As this comment points out, the mechanics was well understood at the time, and at least one astronaut had written a thesis on the topic a few years earlier: ... Aldrins thesis about orbital ...

13

They are very different things. A Lambert solver is one way to bring a spacecraft close enough to another spacecraft where that first spacecraft can use the Clohessy-Wiltshire (CW) equations to guide the way through the rendezvous process. The chaser (the active spacecraft in the rendezvous) can't use CW to make the transition from far away / far below to ...

12

The ISS is periodically refueled by its cargo supply ships. NASA's Robotic Refueling Mission has experimented with refueling satellites. DARPA's Orbital Express demonstrated hydrazine refueling (among other autonomous orbital maintenance operations) between two satellites in 2007.

11

They use orbital mechanics, never fight them. First of all let's be clear about directions in Space: The X-vector of the RIC (radial, in-track, cross-track) frame is called radial as it points along the radial position of the object w.r.t. central body. The Y-vector is called in-track and points, for circular orbits, along the orbital velocity direction. ...

11

In addition to the complexities of actually performing the docking there is the additional detail that the abort options are significantly reduced. If one always has the fuel for the return trip, one can abort at any time. By only having the means to return in orbit, one would have to first rendezvous in Lunar orbit, which means the abort options were ...

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Yes ! During an experimental docking manœuvre, a Progress spacecraft crashed into Mir and rendered the Spektr module uninhabitable. On June 25, 1997, the Progress M-34 spacecraft crashed into Spektr while doing an experimental docking maneuver with the Kvant-1 module. The collision damaged one of Spektr's solar arrays and punctured the hull, causing a ...

10

Shuttle, for rendezvous sensors, used the Ku-band in radar mode and an optical sight (the Crewman Optical Alignment Sight or COAS). Closer in there was a laser radar mounted on the docking system called the Trajectory Control System (TCS) that used reflectors mounted on the target vehicle to get range and range rate. (The highlighted box is a different ...

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First, the Gemini IV maneuver was station-keeping, not rendezvous. Since the target was the just-separated upper stage, the two spacecraft were already rendezvoused, and point-and-burn would have worked if they'd done it properly. According to the Gemini IV mission report, the main causes of station-keeping failure were a mix of procedural mistakes and ...

9

I'm going to hazard and say it's not very likely, more to human reaction time than anything. If one has to assume that the computers are not available for the quick launch sequence, one also has to accept that they are not available to control timing. Here's a blurb about the thruster capacity in the various nodes, from Spaceflight 101. SKD, the Soyuz ...

9

For the first part of your question, and assuming an equatorial orbit, it depends on the orbital altitude, but maths are simple enough to start with: $$T = 2\pi\sqrt{\frac{a^3}{\mu}}$$ Where $a$ is semi-major axis (in our case Moon's equatorial radius of 1,738.14 km, plus mean orbital altitude above it), and $\mu$ is standard gravitational parameter of the ...

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NOTE: My answer applies specifically to Space Shuttle (STS) operations. In general, it is quite safe to say that it is never desireable that the chaser plume the target to any significant degree during rendezvous/proximity operations. A cursory overview of the Space Shuttle Orbiter's Reaction Control System (RCS) is shown below (page taken from a 2002 ...

9

I'm in search of a similar answer, so I thought I'd start one here and let others offer input. Here's what I've found so far. Reading list I'll start to compile some general links here. Books Biesbroek, 2016. Lunar and Interplanetary Trajectories. Springer International Publishing, Switzerland. George and Kos, 1998. Interplanetary Mission Design Handbook:...

8

A very detailed timeline is provided by NASA. Some of the key elements: Agena was in a 299 km circular orbit. Gemini launched 1 orbit later. Gemini's trajectory was such that it was in a 160x272 km orbit. This was well below Agena, and was thus moving in nodal point, although the effect was small. Several maneuvers were done on orbit. The first was to more ...

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The simplest answer is that McDivitt thrusted the Gemini Spacecraft towards the Titan second stage in the same direction that both two objects were travelling. The two were separated far enough that it would take several minutes for Gemini to reach the Titan second stage with amount of thrust generated. If they were in a zero-g field with nothing else ...

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You can change orbits by slowly spiraling out, but then it isn't a Hohmann transfer anymore. In the extreme case of very low thrust, this will mean your orbit is almost circular at all times. You'll also burn more delta-v than with the Hohmann transfer, because on average you add orbital energy while your speed is lower. Wikipedia has this to say: It can ...

7

Sorry, but it's impossible to explain this without referring to orbits. When you are in orbit, your altitude and your linear velocity (speed in the direction of the orbit) are inextricably linked: your linear velocity is proportional with the square root of the altitude (radius). As a result, any change in speed inevitably changes your orbit. The ...

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The explanation in the frame of the body T that McDivitt was trying to approach is this. When he turned the thrust on, the spacecraft acquired velocity $\mathbf v$ towards the body. The Coriolis force $-2m\mathbf{\Omega}\times \mathbf v$ acted on the spacecraft, where $\mathbf \Omega$ is the angular velocity of the rotation of the body T in the orbit around ...

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I didn't see this referenced anywhere so I'm including it for completeness. Feel free to merge it in with another answer. STS-41G (launched October 5 1984) included a secondary payload called the Orbital Refueling System (ORS). Here's a description from the Press Kit ORBITAL REFUELING SYSTEM (ORS) The Orbital Refueling System experiment is a ...

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No. (Unless it has been done as part of a secret mission.) NASA's Space Technology Mission Directorate had plans for just that called Cryogenic Propellant Storage & Transfer (CPST), which would have launched a mission to demonstrate both the transfer of cryogenic propellent, and its storage in space for a long period of time. Unfortunately it was ...

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