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Unanswered Questions

737 questions with no upvoted or accepted answers
18
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 ...
14
votes
1answer
725 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-...
12
votes
0answers
204 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 ...
12
votes
1answer
789 views

What would a “Kármán plane” look like, a bird, or a plane?

If I understand correctly (which I might not), the Kármán line is roughly the altitude where a "Kármán plane's" upward lift force at the orbital velocity for that altitude would be equal in magnitude ...
12
votes
0answers
104 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 ...
11
votes
1answer
300 views

What orbital inclinations will be launched into from Scotland?

It has recently been announced that the A'Mhoine peninsula in Sutherland, Scotland will be host to the United Kingdom's first vertical launch site (assuming they can get anything done with just £30m ...
11
votes
2answers
372 views

How bright is a rocket launch?

How bright (in Watts, preferably, or lumens) is the plume from a rocket launch (e.g. a SpaceX launch)? Obviously in its direction of travel it isn't particularly bright, but what is its effective ...
10
votes
0answers
206 views

Does the Soyuz spacecraft chemically stabilize the hydrogen peroxide (H2O2) to remain ISS-dockable for 200+ days?

Hydrogen peroxide from the local shop (dilute, 2-3%) sometimes has a stabilizer to slow it's breakdown rate and increase it's "shelf-life", since we'd like to keep it around the house on our shelf for ...
10
votes
1answer
187 views

Why meteorological images have missing lines in the center?

I noticed strange blank line in the middle of completely valid images from VIIRS. . This looks like an error in the reception. Would have go unnoticed, unless the same blank line in the middle of ...
10
votes
0answers
137 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
343 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 ...
9
votes
0answers
178 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
145 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
172 views

What happened to the Atlas IV?

I was recently reading up on the Atlas rocket family, and I noticed that for some reason the numbering went from the Atlas 3 straight to the Atlas 5. Why did they skip number 4? I am familiar enough ...
9
votes
0answers
202 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 ...

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