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49 votes

What is an "octet" in the context of NASA's LunaNET Interoperability Standard? ("internet on the Moon")

An octet is an 8-bit byte. Historically, "byte" wasn't always 8 bits (and still isn't, with some architectures having different byte sizes today); "octet" is unambiguous and widely ...
Russell Borogove's user avatar
45 votes
Accepted

Why does Artemis I need a launch window?

There is an alarmingly thorough article about this on NASASpaceflights’s website (not affiliated to NASA itself). Lunar illumination at arrival plays a part; so does the maximum length of time for ...
Martin Kochanski's user avatar
39 votes
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What are the Advantages of having a Double-pane Space Helmet?

The outer pane is just a replaceable protection of the inner pane against scratches, dirt, and abrasion. The helmet on the suits for Artemis missions will also feature a quick-swap protective ...
Uwe's user avatar
  • 49.2k
36 votes
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What is an "octet" in the context of NASA's LunaNET Interoperability Standard? ("internet on the Moon")

Is "octet" just a fancy word for "byte" No, they mean very different things. A "byte" is the smallest unit of addressable memory of a specific CPU architecture. That ...
Jörg W Mittag's user avatar
24 votes

Why not crash the ICPS into the Moon?

The upper stage for Apollo 8 through Apollo 12 were sent into heliocentric orbit. On the last five flights, Apollo 13 through Apollo 17, the upper stages were instead intentionally crashed into the ...
David Hammen's user avatar
22 votes
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Why isn't the Delta IV Heavy ever used for crewed spaceflight?

What's the reason that they don't use the Delta Heavy for crewed flights to the Moon and beyond? The Delta IV Heavy isn't powerful enough to send Orion beyond low Earth orbit. Orion masses about 26.5 ...
Russell Borogove's user avatar
22 votes

Why does Artemis I need a launch window?

From an orbital mechanics standpoint, remember that: The Artemis launchpad is not located on the equator and does not launch into perfect 0-inclination equatorial orbits The planet Earth is inclined ...
Dragongeek's user avatar
  • 19.2k
21 votes
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What is the difference between the solid fuel Boosters of the Shuttle and Artemis?

(This answer assumes the the SLS SRBs are the same as the Five-Segment Boosters (FSBs) studied for a shuttle upgrade...I believe they are, but have not seen this explicitly stated). The thrust time ...
Organic Marble's user avatar
18 votes
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Cause for Artemis Spacecraft bumpy surface

TL;DR: Can you explain, what happened to the surface of the spacecraft? Foam insulation, applied during construction, similar to the orange TPS on the main core stage. Was it burned mildly like ...
blobbymcblobby's user avatar
17 votes

When cis-lunar Artemis astronauts and folks on Earth communicate via audio (e.g. EVAs) will they still step on each other's words like during Apollo?

Likely. Lightspeed lag will always be with us. Indeed it did sound different on the Moon--to the astronauts, they were being "stepped on", rather than the other way around. Ever been on a ...
Anton Hengst's user avatar
  • 10.8k
15 votes
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Are the Artemis 1 secondary payloads still viable?

TL;DR: (22/11/22 updated edit added at bottom) Are those batteries now flat? For some (definitely for one) it could be too late. For the lucky few, they had a recharge. Did NASA find a way to ...
blobbymcblobby's user avatar
14 votes
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What is the inclination limit for Artemis landings?

Ugh, you made me look at NASA requirements documents. NASA HLS-RQMT-001 HUMAN LANDING SYSTEM (HLS) REQUIREMENTS DOCUMENT states HLS-R-0071 Landing Site Vertical Orientation The HLS shall provide ...
Organic Marble's user avatar
14 votes
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How can Artemis 1 take so much longer for Earth-Lunar transit than the Apollo missions did?

The goal of the Apollo missions was to land humans on the Moon and return them to Earth. That requires a surprisingly large delta-V capability. (In terms of delta-V, is easier to land a vehicle on ...
David Hammen's user avatar
13 votes

Why does Starship need to transfer crew to/from Orion to land humans on the moon?

In the new NASA Artemis program, Starship needs to transfer crew to/from Orion. Why is this even needed? Because that is what NASA required for solicitation NNH19ZCQ001K_APPENDIX-H-HLS. A bidder ...
David Hammen's user avatar
12 votes

Why does Starship need to transfer crew to/from Orion to land humans on the moon?

Because that's what NASA asked for. The mission architecture for Artemis consists of: Lunar Gateway, a permanent space station in a Near-Rectilinear Halo Orbit, used as pretty much what the name says:...
Jörg W Mittag's user avatar
10 votes

Why is the Orion spacecraft so big?

The Orion capsule can carry 6 because that is what the NASA requirements it was designed to satisfy asked for. Unbelievably these requirements date from 2004. Orion then was supposed to be a multi-...
Organic Marble's user avatar
10 votes
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How difficult is it to convert a hypergolic based Moon human lander to a cryogenic one?

There will likely be significant differences in the required tankage, if nothing else. The paper Lunar Lander Conceptual Design shows a comparison between landers with similar payload requirements ...
Organic Marble's user avatar
9 votes
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What is the connection (if any) between the new Artemis mission and the two Artemis spacecraft (Themis-B, -C)?

There is no connection between the current unmanned ARTEMIS mission and the recently proposed lunar lander. (Source: I'm the Science Operations Center manager for the current THEMIS and ARTEMIS ...
Jim Lewis's user avatar
  • 931
9 votes
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Is there a certain plan on how Houston will talk with the Artemis 3 crew?

In the original draw, Artemis 3 would have docked to the "Lunar Gateway" (or a smaller replacement) from where the Lander would be deployed. Lunar Gateway would be on a highly elliptical seven-day ...
CallMeTom's user avatar
  • 3,298
9 votes

How can Artemis 1 take so much longer for Earth-Lunar transit than the Apollo missions did?

Apollo burned a lot of fuel in exchange for a quicker mission. Back in the 60's the spacecraft had a very short lifespan, mostly limited by the capacity of the batteries. Nowadays battery capacity is ...
Innovine's user avatar
  • 4,625
9 votes

Space Suit for Artemis, why two contracts instead of only one?

One of NASA's fundamental principles is Dissimilar Redundancy, meaning, having (at least) two providers that share no critical path. They do the same thing with all of their commercial partnerships: ...
Jörg W Mittag's user avatar
8 votes
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Does the Artemis III mission have a backup plan if the astronauts are unable to ascend from the Moon?

It's worth noting that at this time, there isn't enough details on Artemis to know for certain. The program is only a bit of a concept at this time, with the hope to have it more fully fleshed out ...
PearsonArtPhoto's user avatar
  • 121k
8 votes
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Which RS-25s are on the Artemis 1 rocket?

Building on the information found in my answer to this question (which answers part of the question above "Is there a listing of which SSMEs are planned for each Artemis flight" and gives ...
Organic Marble's user avatar
8 votes
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What are we going to do on the moon?

I understand that (after the early stage), we will assemble gateway and have starship flights to the moon. That is not certain. SpaceX won a contract to develop a Human Landing System based on ...
Jörg W Mittag's user avatar
8 votes

Why does Artemis I need a launch window?

If you look at the flight path animation (too large for SE), you'll see it makes two gravity assists from the Moon. So the moon needs to be in a specific point in its orbit so that they line up. ...
Greg Miller's user avatar
8 votes
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Are Artemis missions launched into a free return trajectory like the Apollo program?

The Apollo program spacecrafts were put on a free return trajectory after during the TLI maneuver. Not after Apollo 11. The only Apollo missions that were launched into a free return trajectory (I'm ...
David Hammen's user avatar
8 votes

Why will Artemis II not orbit the Moon?

Artemis II will have Orion conduct proximity operations testing in preparation for docking with HLS on Artemis III. The ICPS (Interim Cryogenic Upper Stage - SLS block I's final stage) will be used ...
Infinite_Maelstrom's user avatar
7 votes

How difficult is it to convert a hypergolic based Moon human lander to a cryogenic one?

A lander with storable propellants needs to keep them at close to room temperature, for a minimum of several days. A hydrolox system will take up much more volume due to the low density of LH2, and ...
Christopher James Huff's user avatar
7 votes

Why is the Orion spacecraft so big?

Leaving aside the very valid political elements of the Orion design choices. As noted in the question, many costs/weights in manned space flight are fixed per craft regardless of crew size. A computer,...
GremlinWranger's user avatar
7 votes
Accepted

Why doesn't NASA just again build the Altair LM or a modified Apollo LM for the Artemis project?

Apart from the $12B development cost, Altair required Ares V to launch it and its Earth Departure Stage, without which it would never have gotten close to the moon. SLS doesn't have the capability to ...
Christopher James Huff's user avatar

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