Unanswered Questions
1,049 questions with no upvoted or accepted answers
19
votes
0answers
1k views
Where is the TEA-TEB stored for the Merlin engines onboard Falcon 9?
The Merlin 1D engines can restart up to four times, they use the pyrophoric mixture of TEA-TEB (Triethylaluminum-Triethylborane) to ignite the engines. My question is where is this stored in the ...
17
votes
1answer
239 views
When have secondary payloads damaged the primary payload of a launcher?
Primary payload customers have traditionally been cautious when allowing secondary payloads on the same launcher. For example, a secondary payload is not trusted to have its own chemical propulsion ...
14
votes
0answers
259 views
Has SpaceX ever done a hot restart of a 2nd stage?
Another question highlighted this Space X commentary for the GRACE-FO launch:
Now in order to fly an efficient trajectory for both of the payloads, we’re actually now running the second stage ...
14
votes
1answer
820 views
What is the value of the cross-track angle between the two designated CRS-4 first stage recovery zones?
For the SpaceX Falcon 9 launch on its Dragon/CRS-4 cargo delivery mission to the International Space Station, according to Spaceflight 101, two downrange safety zones have been identified:
The SpX-...
13
votes
0answers
217 views
How did “the kid” (John Meisenheimer) calculate that there was a wave in the jet stream and Explorer 1 would be okay to launch?
This tough question links to the NASA YouTube video NASA 60th: How It All Began which shows a lot of really nice, historical file footage and stills.
After about ...
11
votes
0answers
137 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 ...
11
votes
0answers
142 views
How does increased environmental radiation affect medication potency, long and short term?
The issue of the effects of radiation on medication potency is not only important for long term stays in the ISS, but also very important for longer duration journeys and even for colonization.
One ...
10
votes
0answers
203 views
What were the hammerhead cranes used for?
During Apollo, the three Launch Umbilical Towers had a hammerhead crane at the top:
Until 1994, the Space Shuttle's Fixed Service Structures were topped by literally the same cranes. The linked ...
10
votes
0answers
492 views
Why does the YF-75D nozzle have such a strong spiral pattern?
Why does the YF-75D nozzle material have such a strong spiral pattern?
Is it a result/biproduct of a manufacturing process only, or does it have some specific function?
edit: The last, cropped ...
9
votes
0answers
79 views
Detailed information about the Soyuz descent module connection box?
Anyone have some detailed information about how all this connectors, located in the soyuz descent module?
Are they used only when they setup the Soyuz or they are ...
9
votes
0answers
135 views
Where are the Apollo forward heat shields currently located?
The Apollo Experience Report: Thermal Protection Subsystem explains that there are three sections to the Apollo heat shield:
The aft heat shield, at the "base" of the cone and adjacent to the SM. ...
9
votes
0answers
134 views
28V vs. 124V on the ISS
Apparently the US segment of the ISS runs on 124v DC, while the Russian segment is on 28v DC. Why the difference? I understand it is often safer to have several different voltages rather than one, but ...
9
votes
0answers
143 views
What's the role of the chainmail and scale armor on InSight's WTS?
It's like taken directly from a medieval armor...
The role of wind and thermal shield (WTS) deployed over the seismometer is in its name - protecting it from noise and thermal changes. This is fairly ...
9
votes
0answers
351 views
How are the Voyagers' thrusters configured in a novel way to minimize accelerations along Earth-spacecraft axis?
I've just read in Eshleman et al 1977 Radio Science Investigations with Voyager that the voyagers have:
...a novel attitude-control thruster configuration that minimizes accelerations along the ...
9
votes
0answers
422 views
What would have been the absolute maximum LEO payload of a two-stage Saturn V?
I read about the Skylab 1 mission in which SA-513 was used to lob the Skylab OWS into orbit. One source (http://forum.nasaspaceflight.com/index.php?topic=12519.20) gave some payload masses:
Total ...
