Community Digest

Top new questions this week:

How did the U.S.S.R manage to rotate the N-1 from horizontal to vertical?

The title says it all - but I heard that NASA considered horizontal integration for the Saturn V couldn't be considered, as lifting the rocket to a vertical position would require an immense ...

history soviet-union n-1  
asked by Woodman 30 votes
answered by Organic Marble 29 votes

Advantages of launching very large rocket while submerged, buoyant, in a body of water

I vaguely remember reading about some supposed advantages of launching very large rockets (Saturn size and larger) from underwater in an ocean or similar large body of water. I was recently reminded ...

launch rockets launch-site  
asked by Basil Bourque 18 votes
answered by GremlinWranger 28 votes

Apollo altitude vs rate-of-descent schedule

In the final phase of the Apollo landings, the commander would go into "P66 attitude hold" mode, where the computer maintained a steady rate of descent while allowing the commander to change the ...

apollo-program lunar-landing lunar-module  
asked by Russell Borogove 13 votes
answered by Organic Marble 15 votes

Why do SpaceX expect the Falcon 9 rocket to explode during the in flight abort test?

This article - - states that after 88 seconds, the first stage engines will shut down, and an automated abort command will be sent to the ...

spacex crewed-spaceflight falcon-9  
asked by Spaig87 10 votes
answered by uhoh 24 votes

What likely is the chemical composition of the thin piece of material on the surface of Mars on the image below?

When looking for the damage on the wheels of Curiosity on the raw images i came upon the image below. (in fact, it is part of an image ) Part of an image captured by Curiosity on sol 1729 (June ...

mars identify-this-object curiosity geology  
asked by Cornelisinspace 10 votes
answered by Oscar Lanzi 3 votes

Why does launching east result in an orbital inclination equal to the latitude of the launch site?

As mentioned briefly in this answer and this Everyday Astronaut video: And just as a reference, if you launched straight east out of Kennedy Space Center, you'd be on a 28.6° inclination which ...

orbital-mechanics launch launch-site inclination  
asked by ifconfig 9 votes
answered by Ludo 20 votes

Are the lines on the wheels of the Mars 2020 rover wavy? If so, why?

CNET's NASA narrows down Mars 2020 rover names: Hello, Fido? includes the image below. I'm not sure if the rover is moving and a rolling shutter was in use, or if the lines on the wheels are really ...

mars nasa rovers mars-2020  
asked by uhoh 8 votes

Greatest hits from previous weeks:

If Starman is heading to Mars, why is he still spinning so we see the earth?

If Starman is heading to Mars, why is he still spinning so we see the earth? Shouldn't he always be pointing away from the earth?

launch spacex falcon-heavy  
asked by hwp08 20 votes
answered by OnoSendai 21 votes

How does GPS receiver synchronize time with GPS satellites?

GPS satellites transmit time values regularly, but if we put in consideration the time delay between the satellite and the receiver, the time value received wouldn't be accurate insofar as I know GPS ...

artificial-satellite time gps  
asked by digiogi 33 votes
answered by BowlOfRed 23 votes

Why not build Saturn V's again?

Why is the US developing a new rocket and spacecraft as opposed to building the Saturn V and Apollo stacks again? The SLS / Orion development programs certainly can't cost less than the unit cost of ...

apollo-program cost saturn-v sls orion-spacecraft  
asked by dotancohen 53 votes
answered by Russell Borogove 73 votes

Could it be possible to launch a rocket from a balloon?

There are several (commercial) organisations looking into alternative means to launch space-bound rockets. One commonly proposed method is to use a large airplane as the launch platform. This method ...

launch spacecraft-development balloons  
asked by Nallath 42 votes
answered by AlanSE 18 votes

What are the choices today for orbital mechanics simulation software?

I used to be familiar with the various choices out there for orbital mechanics simulation software. Alas, those days are gone. What are the choices today, preferably sorted by platform? This ...

orbital-mechanics software astrodynamics  
asked by Erik 103 votes
answered by Erik 27 votes

Do the planets really orbit the Sun?

We often say that the planets orbit the Sun, which is usually a reasonable approximation. But in reality both Sun and the planets orbit the center-of-mass/center-of-gravity of the whole solar system, ...

gravity solar-system  
asked by CodesInChaos 114 votes
answered by Vedant Chandra 141 votes

How do I find out how far Falcon Heavy's Starman is from earth right now?

I cannot find out how far from earth Starman of the Falcon Heavy is right now, or at any time for that matter. How would I find the distance?

spacex falcon-heavy tesla-roadster  
asked by Holger L 15 votes
answered by PearsonArtPhoto 12 votes

Can you answer these questions?

How do two-line element sets handle rev numbers > 99,999?

In a two-line element set (TLE), five characters in line 2 -- columns 64-68 -- are for the rev number. ( But some satellites have been around the ...

orbital-mechanics artificial-satellite two-line-elements  
asked by user3358338 3 votes
answered by uhoh 0 votes

Is there a tool for modeling what power requirements different satellite modules have?

Reading about FADsat made me think of this because it does exactly that. Maybe a better question is does anyone know of a tool like FADsat?

geostationary power modeling  
asked by Olivaw 3 votes

Mass of a circumlunar power transmission line?

The most easily available power source on the Moon is solar power. This has the obvious drawback that the night is two weeks long, during which you would probably still need power for a base to ...

the-moon power lunar-base  
asked by Hohmannfan 2 votes
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