# Tag Info

82

As explained in the answer that Organic Marble dug up, aerospatial "nominal" is really a shorthand for something like within the allowed tolerances around the nominal (i.e. specified) value. We can speculate about how that shorthand evolved. Example: Assume the thrust of an engine according to its design and specification -- its nominal thrust -- is 45 kN, ...

80

Yes. NUTI => NASCOM User Traffic Interface NASCOM => NASA Communications NASA => National Aeronautics and Space Administration Found by parsing this list of over 14,000 NASA acronyms It also contains a vast number of second order acronyms, but the example above is the only third order acronym I could find through initial analysis.

69

I'll go with Emily Lakdawalla who in her blog post about stationkeeping in Mars orbit wrote (emphasis mine), What is a geostationary orbit like at Mars? I have to pause here for a brief discussion of semantics. The authors of this paper discuss "areostationary" for Mars orbits as opposed to "geostationary" for Earth, and Wikipedia uses the same convention,...

52

For a powered descent to the surface of a massive body like the Moon, it turns out to be most fuel efficient to do all your deceleration at the very end of the trajectory, right before impact. (This is because if you decelerate sooner than that, you will be in flight longer; the longer you're up, the more fuel you need to spend counteracting gravity ...

48

So far as I can tell, it was first a saying used by military personnel as the phrase "Rapid Unintentional Disassembly", for a phrase when a gun broke apart if you misused it. This was used by a book for Navy Personel in 1970, so I suspect it was in use for a while before then. This seems to have evolved from that phrase somewhat over the years. The earliest ...

48

Good question. I work on the Curiosity team, and I hear "geology" all the time, but never "areology." Too bad, really, since it's a great word, and I love the R/G/B Mars series.

46

Jupiter being a gas giant is not about its appearance, as another answer stated. It's only about the mass distribution of a planet. Jupiter's mass is 320 Earth masses, while we know from the Juno mission that the rock/ice in the core account for 5–25 of these Earth masses. So the rest of about 300 Earth masses is gas. Thus Jupiter is a gas giant. It is ...

45

It's even simpler than a German-American disagreement. It's use of ambiguous units. The term "specific X" means the amount of X you can get from a unit mass of something. For instance, in batteries, specific energy means the total amount of energy you can get from one unit mass of battery. As described in the Wikipedia article, *specific impulse" is the ...

44

It has many names, depends on who you ask. In English, one name for our moon is simply the Moon. Notice the article the and the capitalization making it a proper noun. This is similar in convention as the Galaxy for our own galaxy that is otherwise also known as the Milky Way. But the word galaxy actually already implies something related to milk in Greek ...

44

I gave an example of one a while back in this answer: Alternate version by Magic Octopus Urn Alternate version by Eric Duminil

28

The basic difference between docking and berthing methods is as described by @OrganicMarble and the linked article, that berthing involves the robot arm and docking does not. The reasons why one is used rather than the other was discussed by the NASA PRO in a recent webcast. Obviously, if the vehicle is not capable of docking it must be berthed; however it ...

28

Geostationary orbits are synchronous orbits, which are also circular and equatorial. You could describe orbits around other planets in the same way, as circular, equatorial & synchronous orbits. For Mars, the terms areostationary and areosynchronous are (sometimes) used. This follows the convention of how apsides are named, so it is likely that the ...

27

But I still don't completely understand what is or isn't ullage in rocket science context. Ullage technically is the space in a tank of liquid which is gas-filled instead of liquid-filled. For a propellant tank, it's important that the ullage volume be kept away from the inlet that leads to the engines, because you want the liquid going into the engines. ...

24

We are "in space", in fact everything that exists and has a physical presence is. But what we usually mean by it is to describe "outer space" conditions of near (or hard) vacuum, where atmospheric pressure is already low enough to affect matter differently than under true atmospheric conditions, for example at atmospheric pressure below triple point of water....

23

The Soyuz line all the way back to the R-7 has straps or cables connecting the boosters to the core. The straps, plus a "socket" on the core catching the front tip of the booster, are apparently how they're held on. One of the straps, near the base of the booster, is shown highlighted in blue here: This RussianSpaceWeb page has a rendering of the boosters ...

23

These boosters are called “strap-on” because there is little structure besides the separation mechanism holding them on, and the rocket is still a viable launch vehicle without them. In a few designs, like the Atlas V, the number of boosters can be customized per-mission. Also, in some cases the booster design is shared between launchers like the Shuttle and ...

23

A search on arXiv for "areology" produces no results. A search on ADS produces two results (one of which has the subtitle "The Geological Environment of Mars"). So the term is hardly ever used in titles of scientific publications. From google scholar, there seems to be a few publications about LIBS that use the term. In conclusion, it ...

21

Here's a reference from 1967 in "The MAC Flyer", Volume 14, Issue 5. This appears to be a periodical of the US Military Airlift Command. I have not been able to locate full text (but would certainly appreciate updates).

20

The “Sailboat Island” gets its name from a Poincaré Surface-of-Section (SOS) plot of potentially stable S-type family of orbits in the Pluto-Charon system. From NASA Ames' blog post titled Playing Marbles at Pluto. Looking at the Dynamic Dust Environment. Generators, Sweepers, and Sweet-Spots by Kimberly Ennico: Othon Winter (UNESP Brazil) spoke about “On ...

20

The terms docking and berthing have a nautical origin. Smaller ships come into port under their own authority and dock. Large ships instead are berthed. They come to a stop outside of the port, relinquish control to the port authority, and are towed into port by tug boats. Docking with the International Space Station is essentially a controlled collision ...

19

Both are correct, it just depends on who/what is doing the action (sucking/blowing). Consider the following scenario. You have two large tanks, sitting in your garage (presumably on planet earth). One has a vacuum in it at 0.01 ATM, the other has some pressurized air, lets say at 10 ATM. The two tanks are connected by a sealed pipe with a valve in the ...

17

I can't say that the terminology is consistent across all users, but where I work (at JPL) we use aerobraking to refer to many light dips to lower an orbit, aerocapture to refer to a single deep dip to bring a hyperbolic approach to an elliptical orbit, aeroentry or simply entry to refer to an entry into an atmosphere with no exit, and aeroassist as a ...

17

While not exactly space exploration there is at least one fourth order acronym for NASA earth observation systems (mostly earth sensing satellites). EPR - EED2 Program Roadmap EED - EOSDIS Evolution and Development EOSDIS - Earth Observation System(EOS) Data and Information System EOS - Earth Observing System NASA - EOSDIS Acronym List

16

I am not aware of anyone using a Kármán line on another planet, but it's not hard to calculate. I get about 88 km for Mars. The equation is $r\,\rho(r)={2m\over A\,C_L}$, where $r$ is the radius of the Kármán line from the center of the body, $\rho$ is the density as a function of the radius, $m$ is the mass of the aircraft, $A$ is the planform area, and \$...

16

To add to @aramis' excellent explanation on clarity and ability to discern the go/no-go launch status check polling, these seem to have been introduced to NASA's (and U.S. in general) launch terminology during the first manned spaceflights of Project Mercury. I wasn't able to find a good example for Project Mercury launches, but I did find this video of ...

16

Edit: Thinking about this some more, the answer is a result of physics: gases exert pressure (due to molecules bumping into each other). This is what causes a gas to expand to occupy all available volume. The only force at work is a repellent one, so the answer must be "blown out". In everyday language, there are some exceptions. We say a vacuum cleaner ...

16

The space shuttle throttled down its main engines from the normal setting of approximately 104% to around 67% as it was passing through the region of max dynamic pressure ("max q"), to make sure that the certified dynamic pressure limit was not exceeded. Once the threat had passed, the engines throttled back up. If you plotted throttle level vs time on a ...

15

This latest (second powered) test flight of the SpaceShipTwo was really interesting to watch (YouTube video, the "feathering" aerobraking starts at 2:14 into it), but this currently unique to The Spaceship Company designs (owned by its sister company Virgin Galactic that's itself within the Richard Branson's Virgin Group) approach to aerobraking was actually ...

15

Project Mercury used imperial units of measure. For example, the Mercury spacecraft main instrument panel indicated altitude in FT (feet):        The Mercury spacecraft main instrument panel from Project Mercury Indoctrination, May 1959 (Source: NASA. Click for full size) They used statute miles as a measure of distance in ...

15

It's more a question of semantics, rather than a physical reality. An ocean would probably be thought to have a clearly defined surface. On the other hand, terminal velocity is only about 5m/s, which is a moderate running speed (Usain Bolt does 10 m/s). This gives you an idea about how thick the gas really is. In fact, one of the Pioneer Venus probes kept ...

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