# All Questions

10,659 questions
113 views

### Larger data rate, Oneweb or Starlink? [closed]

Which satellite constellation will provide the larger downlink data rate, in total and per satellite, Oneweb or Starlink? My consideration: starlink will operate in a lower orbit, with more ...
60 views

### How do I calculate re-entry velocity when decaying from a circular orbit?

I am trying to find the velocity of an object during re-entry so that I can calculate the peak heat flux but I'm a bit stuck. I know how to find the velocity of the original, circular orbit (300km) ...
1k views

### What are these giant NASA boxes?

In this answer I saw Figure 35 of the encyclopaedic ISS Interface Mechanisms and their Heritage and from the link I saw Figure 37, and I've included both below (click for larger size). What are these ...
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### How does Deep Space Network's DSS-14 transmit radar and receive it at (almost) the same time? (monostatic radar)

@Hobbes' concise yet thorough answer to the question What are monostatic radar observations, and how will Deep Space Network's DSS-13 be used to observe asteroid 1999 WK4's flyby of Earth? tells us ...
106 views

### What is the US president talking about re US/Japan dramatic expansion of military(?) cooperation?

According to the Bloomberg article Japan Astronauts to Soon Join U.S. in Trip to Mars, Trump Says: The U.S. and Japan will “dramatically expand” their cooperation in outer space, with missions to ...
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### What are monostatic radar observations, and how will Deep Space Network's DSS-13 be used to observe asteroid 1999 WK4's flyby of Earth?

NASA JPL page https://echo.jpl.nasa.gov/asteroids/1999KW4/1999KW4_planning.2019.html says of the radar observations during the close approach of asteroid 1994 KW4 (in part): Update on 2019 May 22: ...
2k views

### How does one “dump” or deplete propellant without changing spacecraft attitude or trajectory?

Occasionally one reads about a spacecraft "dumping fuel". It may mean expelling the propellant(s) as a liquid, or depleting them by burning them up. Although usually only fuel is mentioned, often ...
95 views

### Rocket Launch Simulation Source Code Locations

As you can take from the title, does anyone know where I could find the source code for a working launch simulation type application such as FlightClub for example?
44 views

### List of words and abbreviations like A-OK and MAG

Is there a list of casual, non-technical words, phrases, abbreviations and the like that have developed in any of the space agencies around the world?
2k views

### How feasible is the Delta-Glider?

In Dr. Martin Schweiger's freeware spaceflight simulator Orbiter 2016, a very popular(but fictional) spacecraft is the Delta-Glider. It is capable of take-off from a runway, has hover engines for ...
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### How do I calculate the change in the argument of periapsis after a plane change maneuver?

Let's say I have a spacecraft in an initial geocentric orbit with the following parameters: a = 7,960,000 m, e = 0.010, $\Omega$ = 180$^{\circ}$, i = 98$^{\circ}$, $\omega$ = 90$^{\circ}$, $\theta_0$ =...
154 views

### Apollo 15 State Vector recreation

I am trying to get the state vectors for Apollo 15 before, during, and after critical manoevers [sp]. IE TLI, LOI1, LOI2, lunar launch, preocking, postdocking, and TEI. I am a totally newbie at all ...
173 views

### Healing of bruises and internal bleeding in 0g

I heard an unsourced claim about wounds, bruises and internal bleeding healing much worse in 0g conditions than in normal gravity. Is it true? And if so - could you provide a quantitative comparison, ...
4k views

### How were these pictures of spacecraft wind tunnel testing taken?

The picture below from this answer shows four spacecraft wind tunnel tests from the 1950s. In addition to the test object, the bow shock and turbulence are clearly visible. How is this visualization ...
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### What are the benefits of cryosleep?

NASA is working on a so-called 'Cryosleep Chamber', but why do they need it so badly? There must be a lot of benefits attached to this technology..
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### What is that hissing and buzzing background noise on some of NASA Apollo audio recordings?

As example: https://archive.org/details/Apollo10/10-030702_4-OF-6.wav Buzzing, sometimes pulsating and rather loud background sound, very annoying. Reminds me of old time dial-up modem or something ...
89 views

### What is the function of this Merlin engine's tube, and why is it getting red hot?

In the video of the recent SpaceX Starlink launch, one view of the Falcon-9 2nd stage engine shows a cane-shaped tube that glows red hot at the "handle" end and seems to get hotter over time. ...
107 views

### Can rocket engine like NERVA be used to get into low earth orbit or higher?

I have heard of nuclear propulsion, however I wonder that is it possible for it to launch into space, and if so, how much fuel would it need?
107 views

### Did moving a Shuttle Remote Manipulator System (RMS) from one Orbiter to another have any impact on operations?

This question Did each Shuttle have its own dedicated Canadarm? and its answer discuss the five different robot arms used in the shuttle program and how they were moved from Orbiter to Orbiter. ...
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### Cost of Lunar base in today's dollars: reference government report about a lunar base written in 2009? [closed]

What would the current cost be? Costs of an International Lunar Base from September 24, 2009 Below is a link: https://www.csis.org/analysis/costs-international-lunar-base
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### How radioactive might the Moon's surface water be? Could it be unsafe to drink?

NASA Chief Scientist Jim Greene asks: Can we go (to the Moon) and drink the water? The source of the water in this case would be ice deposits to be found in permanently shaded areas on the Moon. ...
1k views

### Is the Starlink array really visible from Earth?

I was browsing YouTube when I came across this video, recorded from a sky gazer who apparently spotted the Starlink satellites. In my lifetime, I haven't seen many satellites in the night skies (maybe ...
86 views

### What caused these strange lights around the Falcon 9 grid fins (Starlink launch)?

Early in the video of the launch of the first sixty SpaceX Starlink satellites we can see that after stage separation the first stage grid fins open. Around that time there are some phenomena I don't ...
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### Using the distance components to calculate minimal dV randezvouz trajectory

The are objects on 100 circular orbits, 1 object on each orbit. One orbit is said to be initial (I) and others are final (F) . ...
154 views

### Have mechanical wrist watches been successfully used in space?

Has a mechanical wrist watch been successfully used in spaceflight? Have there been any problems using them that are related to the many unusual aspects of the spaceflight environment, perhaps ...
82 views

### What just didn't happen with NASA's Moon-to-Mars directorate?

The Spacenews.com article Sirangelo leaves NASA after exploration reorganization scrapped says: WASHINGTON — A former space industry executive who joined NASA to guide its revamped lunar ...
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### Shortest ever F9 2nd stage burn for the largest ever F9 payload? (Starlink Mission's SES-2 burn time of 3 seconds)

According to the SpaceX broadcast the first SpaceX Starlink launch (24-May-2019) is notable for reasons including being the heaviest ever Falcon 9 payload to date. At roughly ...
303 views

### Did each Shuttle have its own dedicated Canadarm?

Five Canadarm robotic arms were built. Five space shuttle orbiters were flown to space. Did each orbiter have its own dedicated Canadarm? Or were they rather moved around from orbiter to orbiter, ...
59 views

### Getting from LEO to a station in geostationary orbit and docking with it using a Hohmann transfer?

How long would it take for a spacecraft with a mass of 30,000 kg, to go from LEO to reach and match the speed of a space station in geostationary orbit so it could dock with the station, using a ...
101 views

### What were the Top 10 Shuttle Risks in John Young's “famous letter”?

Whilst reading A Technical History of the External Tank I ran across this comment: Although the problem has not recurred, John Young, in his famous top ten Shuttle risk letter ...
255 views

### Why didn't Project Mercury advance to an orbital flight on their second mission?

Manned programs are noted for progressing through a series of flights. Early missions focus on basic hardware and simple tasks; as the technology becomes proven, the scope and duration of later ...
131 views

### Human-rating the Saturn V using modern standards

Would a complete Apollo-Saturn stack (like e.g. AS-506) be human-rated according to the latest human-rating process (NPR 8705.2C) of NASA? If not, what are the biggest show-stoppers? This question ...
84 views

### Is there a term for the activity of weightless astronauts hanging out on walls or ceilings?

Weightless astronauts often sit, stand, walk, or sleep on (or near) surfaces that (with gravity) we would normally call walls or ceilings. I reference such a phenomenon in my comment here: I would ...
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### Apollo CSM RCS maximum number of simultaneously active engines?

Reading the RCS subsystem manual, it seems like each RCS quad of the Apollo SM consisted of four hypergolic engines. Am I correct in saying that all four engines of each of the four quads could be ...
141 views

### Separating fact from fiction, how to get from this radar image to this GIF?

The NBC News article Mile-wide asteroid and its tiny moon to zoom past Earth this weekend; Dubbed 1999 KW4, the "binary" space rock will skim past our planet harmlessly at a distance of 3 million ...
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### How were the Vega balloons deployed?

The Vega mission included balloon deployment into Venus' atmosphere. Deploying weather balloons on Earth is easy, but i imagine it is quite complicated in other planets' atmosphere from a spaceship. ...
68 views

### Iapetus - Destabilized rings to mountains?

I was reading an article about a ring that was destabilized out of orbit on one of Saturns moons. I got there by looking for mountains because of this question (unrelated mostly). Here's a picture of ...
4k views

### Why aren't space telescopes put in GEO?

I don't know of any space telescope that has been placed in geosynchronous orbit among the communication satellites. I wonder why not? In GEO, a space telescope could use a single stationary radio ...
132 views

### How many motors on the new Mars 2020 rover? (and other questions)

With so many different motors on the new Mars 2020 rover, I'd like to ask if each motor programmed to operate independently or can the different motors operate in sync with each other? Also, as a ...
2k views

### What is the function of the corrugations on a section of the Space Shuttle's external tank?

There is a section of the Space Shuttle's external tank that appears to have large corrugations. I spotted them and saw how deep they are in a photo in this answer, a cropped section of which is shown ...
1k views

### What happened to boiled-off gases from the storage tanks at Launch Complex 39?

Both Apollo and the Shuttle launched from KSC complex 39, and used liquid oxygen and liquid hydrogen as propellants. These cryogenic liquids were held in storage tanks near the perimeter of each ...
165 views

### Could we build a sunlight regulator to orbit the sun and help with global warming? [duplicate]

like less sunlight around the poles would be good. if we put it in orbit close to the sun we may not need it to be that large. we can keep it in good position with RF cavity thrusters and mini ...
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### What is the formula for Legendre Polynomials from EGM96 calculated in F447.f program?

The F447.f program is designed to calculate the geoid undulation for EGM96. I'm trying to understand how it accomplish this calculation. I stuck in ...
126 views

### Project Mercury capsule switch orientation

I noticed that the majority of the toggle switches in the Mercury capsules move in a left-to-right manner. This seems unusual to me, since Gemini, Apollo and the Shuttle all predominantly use up-down ...
81 views

### Impact of Constellations on Space Debris and Launch Windows

With the decline of massive GEO satellites and a big increase in smallsat and cubesat, especially those in constellations, I wonder what their impact is on space debris. Those smaller satellites do ...
132 views

### Why is multi-spool pump very rare on rockets?

The only one I know of is the LP LOX pump on RD-0120. A multi-spool design is already a default for jet engines, which are basically turbine-driven air pumps. A multi-spool pump can save at least the ...
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### Why did the cones of the Mercury and Gemini capsules have a neck?

As highlighted by the green double-arrow lines in the pictures below, the Mercury and Gemini capsules had a (roughly) cylindrical "neck" at the end of the capsule cone. If they had instead followed ...
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### Where will BioSentinel be relative to Earth while running experiments?

The Space.com article In 2020, NASA Will Send Living Things to Deep Space for First Time Since Apollo describes (among other things) the BioSentinel spacecraft, and links to a NASA BioSentinel fact ...
182 views

### How was the Space Shuttle boat tail transported back to the west coast?

(moved from Aviation) The question Did the Space Shuttle boat tail used in the transport configuration save fuel? about the Shuttle boat tail prompted me to wonder how it was transported back to the ...
84 views

### What Constitutes A Combustion Chamber?

I have been reading about combustion chambers and noticed they seem to just be an empty space with the fuel and oxidizer coming in one end and the nozzle at the other end. If the shape below were ...

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