73

One thing to note is that these polls of the room are largely for-the-record - in other words, if a flight controller was sitting on a problem that would prevent the accomplishment of a major milestone, and didn't tell Flight about it until the poll, that flight controller would not be in MCC for their next shift. That said, and apologies because it's ...


22

Ceramic bearings are a relatively new concept. They were a hot research topic in the late 1970s and didn't become commercially available until the mid 1990s. The Far Ultraviolet Spectroscopic Explorer (FUSE), the first spacecraft on which these anomalous bearing failures were seen, was launched in 1999. It takes several years to multiple decades to design ...


20

Despite the many other (unsourced) answers stating the opposite, this is actually a very valid concern. Not from a physical weakness angle, but rather, even though a shuttle mission was a couple of weeks long at most, the Space Shuttle Program was concerned enough about the deterioration of hand/eye coordination and the length of time since the commander ...


17

Rockets can use different systems for attitude control (control thrusters, fins, gyroscopes, TVC, ...). Since you ask for the seconds after liftoff, the relevant system is TVC (Thrust Vector Control). TVC basically means that the engines themselves can gimbal to change the direction of the thrust. This can influence the attitude of the rocket by inducing ...


17

"Could be flown" is a clear yes, "could be flown to a landing" is another story. Most of the points you are listing can be accomplished using the backup system in the LM, the Abort Guidance System (AGS). I'll be using the LM Apollo Operations Handbook Volume I as the main source for all your specific points. An attitude / attitude rate reference is ...


13

For all modern rockets (and as far as I know, for all rockets ever, since at least the V2), the rocket isn't controlled from the ground, but by electronics (computers, for modern rockets) on the rocket itself. The rocket controls its path, stage separation, ullage motor firings, and anything else needed, with few exceptions. This is all pre-programmed. ...


11

The thruster configuration can be seen better in this image:(cropped from this document ). The attitude control thrusters are not in plane with the direction control thrusters. This Raytheon patent on MKVs states that "attitude control system includes multiple thrusters offset from the center of gravity that provide yaw, pitch and roll control." All four of ...


11

Human operators are generally not involved in separation, that's controlled by on-board computers according to the plan programmed into them. 2 way radio lets human controllers see what is going on and send commands if necessary.


10

You can travel in space without any navigation devices or computers at all, establishing suborbital flight and orbital flight is done by the rocket, it's accuracy there that matters and early manned rockets had no computers. De-orbiting is a matter of setting up the spacecraft to the right attitude for retro fire, which can be done by eye if need be, early ...


10

The No GO happens all the time. Many recent ULA and Spacex Launches get a NO GO - Most of the time its the Weather and the Range Telemetry guys. High Altitude winds , Range tracking failures , data drops etc. If you watch Spaceflightnow or any of the launch scheduling websites you see launch halts in the last 4 or 30 minute hold all the time, then the ...


9

This answer answers the title "Why does spinning help stabilisation" rather than specifically for launches. Context Before jumping into the answer it is worth looking at the background. With rigid bodies then adding a spin will help average out asymmetries. However neither rockets or satellites are rigid, they contain liquids and flexible appendages and ...


8

As others have pointed out, shuttle missions never lasted long enough to have serious concerns about the pilot or commander's physical abilities. Also note that the shuttle was a digital fly-by-wire system (no direct mechanical linkage), so the weight of the aircraft/spacecraft is irrelevant, and there's no reason to think the rudder pedals were ...


8

You really have three separate problems to solve, though it sounds like you're talking about only one of them. The total package is known as GNC, or Guidance, Navigation, and Control. A little more detail on the issues at play: Guidance: in which we try to figure out where we want to be This is entirely mission-dependent. Some missions just need to be ...


7

This is the (attitude) lost in space problem. This problem arises, for example, when a spacecraft is first released from the upper stage after launch or when a spacecraft awakens after having been shut down for a long time. Many modern star trackers have a "lost in space" mode to address this problem. Star trackers solve the lost in space problem the same ...


7

Yes. According to the NASA paper "Hubble Space Telescope Pointing Control System Design Improvement Study Results", in the first full paragraph on page 2, the author states The nominal control algorithm is a standard proportional-integral-derivative (PID) operating at 40 Hz using the rate gyro assembly measurements. If you want more information on ...


7

This is an attempt at the first part of your question: "are classical control algorithms better than machine learning approaches". Since I am personally more interested in launch vehicles, the answer is mostly about potential launch guidance applications with fuel-efficiency and safety in mind. I think it's okay because launch vehicles are the biggest areas ...


7

Yes, as long as you don't care where you end up Early spacecraft used electrical controls, but had no computers: Six Vostok each carried one person to orbit. The first flight carried the first man and the last flight carried the first woman into space. Six Mercury flights each carried one American astronaut into space, four of these into orbit. Although ...


7

The study was specifically of ITHACO reaction-wheel assemblies that proved to be highly prone to failure in the space environment. These assemblies used steel bearings. Interference with electronics is certainly possible, but would not be limited to reaction wheels. Demagnetization of permanent magnets would require such extreme conditions that it would be ...


6

I don't have any citation, but the first stage is doing all its own guidance and control; it would be insane to do it any other way. The "acquisition" called out at about 80km altitude is acquisition of signal, not of control. What exactly is being signalled and how the ASDS makes use of it is unclear. I've heard (again, without citation) that both the ...


6

Shuttle missions were normally no more than about two weeks long, unlike many-month ISS missions; Chris Hadfield spent 5 months on-station. The muscular atrophy effects of zero gravity take a while to fully develop, and the commander and pilot would certainly take the discipline of doing their zero-g exercises seriously. Their legs would be weak, but not so ...


6

As far as I know, no. In order to make a cylindrical rocket as light as possible, they are flown to minimize the side loads to the structure -- as close to a zero angle of attack as possible. If they wanted to use lift, it would increase the mass of the structure to be able to take substantial drag forces from the side. There would not be sufficient benefit ...


6

According to Thomas Kelly's "Moon Lander: How We Developed the Apollo Lunar Module", the primary driver for the positioning of the LM RCS quads was avoiding contamination of the windows with rocket exhaust: We argued engineering logic and practical issues, such as jet contamination effects on adjacent areas of the ascent stage. This latter ...


6

“Sailing a rhumb line” means holding a constant compass bearing. For short distances, this stays close to a great circle path.But at longer distances and/or higher inclinations, the rhumb-line path “tends north” of a great circle as shown in the Questions globular image. For a fast, short launch, a rhumb-line trajectory has the advantage of simplicity. As ...


5

I'm an aerospace engineer, and took courses in college on spacecraft navigation and control theory. However, I have not programmed a spacecraft attitude controller in my work, and I can't say I've heard of a "Quaternion Error Command" controller before. That said, these are the considerations I'd have off the top of my head when selecting a controller: is ...


5

You said it yourself, Lift is important for guidance and control. As a matter of fact a rocket is designed in such a way, that the center of pressure is aft of the center of gravity. The distance between CG and CP is also called the caliber stability margin measured in rocket caliber. You can use the fins of a rocket to control the direction and magnitude ...


5

Angling to get lift is going to increase the atmospheric cross-section of the rocket and so increase drag. For any reasonable angle of attack, the drag force is going to be much larger than the lift force, so I believe that for powered ascent it makes the most sense to minimize drag, which means zero AoA and zero lift. This also, as Mark Adler notes, ...


5

No. Charging of objects in low earth orbit is already a major design issue but it does nothing to prevent collisions. The relative velocities are too high for achievable charges to matter.


5

Depends on that do we call a "computer". Would a slide rule count? This extremely simple, hand held device can do multiplication, division, and also functions such as exponents, roots, logarithms and trigonometry. Some included specialized features for aviators. Or may I bring my Curta into spacecraft? It also has been highly favored by commercial and ...


5

Satellite control systems are usually created ad-hoc or based on existing in-house systems. For example, ESA reuses its own SCOS-2000 infrastructure. In Europe, there are many companies that develop SCS like SSTL, GMV, SCISYS, DEIMOS, TERMA, and many more. There are also some open source systems like Cosmos and yamcs. In all the cases, you will have to ...


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