Unanswered Questions
920 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 ...
16
votes
0answers
281 views
Why is the exhaust plume of Falcon 9 upper stage shaped the way it is?
The (single) Merlin 1D vacuum engine's exhaust plume has a symmetric shape, comprising of six distinct "inner" plumes. Why does it have this shape?
Is it due to the shape/configuration of fuel ...
14
votes
0answers
139 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
1answer
784 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-...
11
votes
0answers
195 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 ...
10
votes
0answers
89 views
How safe are launch escape systems?
Are there any published numbers for any crew vehicle for the probability of LOC (loss of crew) given the launch escape system has been activated? I am interested in both design goal numbers and ...
10
votes
1answer
541 views
Have spacecraft ever dipped below the Karman line and then safely continued spaceflight?
The item in Science Alert's A Harvard Astrophysicist Says Outer Space Is Actually Closer Than We Think (see also Science; Outer space may have just gotten a bit closer) talks about the recent Acta ...
10
votes
0answers
327 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 ...
10
votes
0answers
435 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 ...
10
votes
0answers
238 views
How do domes in lunar impact melts develop, and might they be hollow?
On the floors of young craters of the Moon, smoothly rounded domes are visible in some spots. Lalande crater has 4 of them, each around 200 m across.
Here are less regular ones on the floor of ...
9
votes
0answers
241 views
How did NASA's Deep Space Network encode and broadcast music to Opportunity?
@Ingolifs's answer to the question What was the last message to Opportunity today (13 Feb '19)? quotes ArsTechnica's Opportunity did not answer NASA’s final call, and it’s now lost to us:
Late ...
9
votes
0answers
201 views
How is Dragon-v2 prepared for being docked for months at ISS?
The Dragon spacecraft is being certified for manned spaceflight. If it's to replace Soyuz, though, it will have to serve as an escape pod for the crew. The current delivery missions are proving its ...
9
votes
0answers
302 views
Does the “17” really mean anything with respect to GNSS orbits being rational factions of a sidereal day?
This answer suggests that the orbital periods of the four large GNSSS contstellations are linked to the sidereal rotation period of the earth by rational numbers with 17 or 34 as the denominator in ...
9
votes
0answers
159 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 ...
9
votes
0answers
246 views
What were some of the first two stage rockets flown?
The first US two stage rocket was bumper, a combination of a german V2 liquid fuel rocket with an US second stage.
The Soviet Union had the R-1 and R-2 based on the V-2.
In this list, the R-7 is the ...
