# Tag Info

## Hot answers tagged the-moon

66

Oh, I can answer this one. In my structural geology class, we breezed over a few paragraphs on the tectonics of impact craters, but it was in the textbook, and, being space-related, I was intrigued. One note: while most of the papers you'll find are on our own geology, the moon isn't that different compositionally from Earth at all, so I'm assuming the ...

64

This discovery is news because the water found is in a sunlit area, the Clavius Crater. Previous water discoveries were all in 'cold traps', which are areas where sunlight cannot reach, so water resources on the moon for colonies or space exploration was thought to have been limited to permanently shaded areas - the rest was thought to have been boiled off ...

53

How to Protect and Preserve the Historic and Scientific Value of U.S. Government Lunar Artifacts summarizes the 1967 Outer Space Treaty thusly: These recommendations are consistent with international law, including the following: The 1967 U.N. Outer Space Treaty (OST), which provides, in part: That outer space shall be free for exploration and use by all ...

46

Assuming this isn't a troll question and you are serious about wanting to know what computers are used for in spaceflight (prior to 1988), NASA has a great resource for you: Computers in Spaceflight (PDF, 494 Mb) From the introduction: Computers are an integral part of all current spacecraft. Today they are used for guidance and navigation functions such as ...

34

There are three big advantages to Mars over the Moon for a longer term settlement. There is a thin atmosphere. The days are approximately 24 hours The gravity is about twice as high. Let's break these down one at a time. Atmosphere The thin atmosphere allows aerobraking, and can be useful in the production of oxygen. Electricity + Martian atmosphere ...

33

In the defense of NASA, SpaceX does not per se have an operational vehicle for the purposes they want to use SLS. (Yet, Starship is coming) However, missions to the moon using Falcon Heavy vehicles have been proposed by Bob Zubrin. Once SpaceX has an actual flying Starship/Super Heavy I think the situation will change. Ultimately the SLS program is ...

31

Not a soft landing. A soft landing requires the spacecraft having a thrust-to-weight ratio greater than one (otherwise it just falls faster and faster). Ion engines have a very low thrust to weight ratio, much smaller than one. On the moon, the surface acceleration is 1.625m/s², so the thruster must provide at least 1.625N of force for every kg of spacecraft....

30

The set of landing sites considered for all the Apollo missions was driven by a desire to sample a wide variety of lunar geology, but the order for them was chosen to make the first landings easiest and safest from a technical standpoint. The scientific rationale for site selection is described in detail in an appendix to the NASA historical document Where ...

29

So let's break down the answer into bite sized chunks... How do you transfer a spacecraft from one solar system body to another? There are two main things you need to do. Set up an orbit that intercepts the orbit of your target planet/moon. Time it so that your spacecraft intercepts the target orbit at the same time as the planet/moon you're trying to ...

27

First of all, the ground team could have, and in fact did, do most of the orbital navigation remotely. This report mentions the fact that the on board computer was secondary for Apollo 8, with primary being systems from the ground. The spacecraft did have to do a few things, including making some realtime adjustments during the landing based on the actual ...

27

Your spacecraft would need to be several orders of magnitude larger than the Saturn-Apollo. No human pilot has successfully performed a rendezvous without a computer. Note that rendezvous is bringing two spacecraft close together in orbit, position, and velocity. Docking is the actual physical contact between two spacecraft. The latter can and often is ...

27

It is news because the 6.1 $\mu$m wavelength measured is unique to $\rm{H_2O}$. All prior evidence included $\rm{OH}$ groups as well, thus did not show clear proof of presence of "$\rm{H_2O}$". So, now we know there is $\rm{H_2O}$ and not just any random $\rm{OH}$ group containing moleculas. Anyway, the amount measured still is ~100x less water per ...

26

In general terms any particles placed on an orbit by a single impluse will pass through the point that impulse was applied again one orbit later. So for dust kicked up from the moon surface it will arrive back at the surface somewhere (rotation and sub orbital trajectories mean most will not actually hit the landing site). This obviously does not apply for ...

25

Yes. One solution is a called a Wang bullet or Verne gun. The proposal actually aims to be capable of launching an intact payload (to Earth escape, and therefore also to the Moon). Obviously it would be easier if you just wanted to launch a steel slug. The proposal uses a nuclear explosion to convert water into high pressure plasma, which propels the bullet ...

24

The black thing on the right is a SNAP-27 RTG. and the box on the left is an ALSEP (Apollo Lunar Surface Experiment Package) that it powers. Here's a picture of the ALSEP for Apollo 12: And here is Alan Bean attaching it to the RTG with the antenna to make the barbell object in your original image: As to the second part of the question, it is clearly a ...

23

Because there are no super heavy-lift launch vehicles flying right now. In fact, simply by existing, SLS will be the most up-to-date and the most efficient super heavy-lift launch vehicle since the Saturn V (Shuttle is debatable). Super heavy-lift launch vehicle, Proposed designs When looking at current SpaceX rockets, the Falcon Heavy are human certified. ...

23

“Do I have a very naive concept of space travel?“ - honestly, yes you do. Here is an excerpt from Don Eyles’s wonderful book Sunburst and Luminary: An Apollo Memoir: Guidance would be processed every two seconds, repeatedly correcting and refining the trajectory based on new data from navigation. Into the guidance equation, with each turn of the crank, went ...

22

The lowest orbit achieved would probably be PFS-2, a small satellite deployed from Apollo 16's service module. It was intended to go into a 55x76-mile orbit (88.5x122 km), but due to variations in the Moon's gravity field, it made passes of six miles (9.6 km) or less before crashing into the Moon's surface. There are very few stable low orbits around the ...

21

Yes, viable Streptococcus mitis was found on the Surveyor 3 camera returned by Apollo 12. This is described in the report Analysis of Surveyor 3 materials and photographs returned by Apollo 12 (25 Mb, 308 pages). Eleven different sites among the various parts which were returned were swabbed; each was cultured in 3 kinds of bacterial or fungal growth media ...

20

Does pork-chop plots exist for Earth-Moon System? No, because the concept doesn't make much sense. The Earth-Mars configuration and Mars' eccentricity makes the cost to send a vehicle from Earth to Mars vary by a huge amount. Pork chop plots are a useful way to visualize these huge variations. The cost of sending a vehicle to the Moon on the other hand ...

20

The short answer is: Tsiolkovsky rocket equation. You need some velocity to achieve some position (an orbit or a body) in space. Farther a position - more velocity. More velocity - more propellant mass, and this relation is not linear and not in favor of velocity. $$\Delta v=v_e \ln(m_0/m_f)$$ where: $\Delta v$ - theoretical maximum increment of velocity, \$...

18

Possession is 9/10 of the law. If you somehow get there and steal the flag, it's not like any Space Marines are going to jump out from behind a crater rim. Law needs to be enforceable. Maintaining ownership of the flag is a different issue. You can kiss your chance of being free on US soil goodbye, especially if you're a citizen. Laws would be found, made up,...

17

It perhaps become clearer when stating what rockets do. They change velocity. In space terms, that's delta-v. A rocket stage can only change your velocity some limited amount. Different targets in space require different amounts of velocity change (Low orbit: 8km/s, low Moon orbit: 12km/s) If your rocket stage can not give all the velocity change you need, a ...

17

"Lowest possible lunar orbit..." As pointed out in comments and in answers to the linked questions Are low, polar lunar orbits in general relatively stable? Moon orbit station-keeping delta-V budget What's the floor for stable retrograde lunar orbits? Besides Luna, what celestial bodies exhibit lumpy gravity? very close orbits around any body ...

13

Unfortunately steam rockets would not be practical because they're not very efficient. I don't know how much you know about rocket propulsion so I'll begin with a discussion of one of the most important metrics: exhaust velocity, the speed of the gas coming out of the engine's nozzle. The higher that speed, generally the more efficient the engine. There ...

13

It’s a long journey, but it’s all “downhill” — once the spacecraft leaves the moon’s gravitational sphere of influence, Earth’s gravity brings it home. The process of leaving the moon is called “trans-Earth injection” or TEI; the rocket engine on the CSM fires for about two and a half minutes, adding about 1000 m/s to the spacecraft's speed in lunar orbit, ...

13

Looks like it was indeed Goddard. Key search term was 'flash powder' not gunpowder. The Smithsonian has a box built and used by American rocket pioneer Robert H. Goddard in experiments in 1916 to determine the amount of magnesium flash powder to be carried in a unmanned rocket to strike the surface of the Moon to signal its arrival. Source: https://...

12

A bit below and to the left:                           Note that the size of the red dots is not representative of the size of the Earth or Moon. Where was Voyager 1 when the photo was taken? According to the catalog page for PIA23645 (also linked above). The photograph was taken 1990-02-14 04:48 GMT. This is an abomination; GMT hasn't existed since the ...

12

Things that don't count, but could be confused for engines: Four "breadboard articles" BA-1 to BA-4 were built as prototypes of the plumbing. Three of these were used to feed engines during testing on HA-1 to HA-3. PRA-1 to PRA-6 were more advanced plumbing prototypes used on PA-1. HA-1 to HA-4 were "test rigs" in which ascent engines could be mounted for ...

12

It's actually a rebound effect that occurs with an impact forming a large crater. https://www.lpi.usra.edu/education/explore/shaping_the_planets/impact-cratering/ explains: Central peaks – Peaks formed in the central area of the floor of a large crater. For larger craters (typically a few tens of kilometers in diameter) the excavated crater becomes so ...

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