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Unanswered Questions

841 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
769 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
238 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 ...
13
votes
0answers
122 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 ...
10
votes
1answer
461 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
175 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
189 views

Why were large solid-fuel rockets so rare in the past?

When the Germans projected the A4 missile, they discarded solid-fuel propulsion and went on to circumvent the enormous technical difficulties of building a liquid-fuel engine from scratch. Germany had,...
9
votes
0answers
189 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
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0answers
283 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
150 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
219 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 ...
9
votes
0answers
899 views

How does JAXA's “Int-Ball” manage airflow to optimally navigate inside the ISS?

above: From the BBC's Japan's zero-gravity space drone sends first pictures from ISS. This is JAXA's GEM internal ball camera, or "Int-Ball". Kawaii! It looks like it uses a three axis attitude ...
9
votes
0answers
90 views

Is loss of flexibility a concern with crew on the ISS?

Videos of people on the ISS make it clear how little they need to bend or stretch, and how their joints stay in their neutral position most of the time as they float around - elbows, knees and hips ...
9
votes
1answer
229 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 Earth-...
8
votes
0answers
244 views

Could dusters be installed on solar panels on a mars lander?

I see on the interwebs that the lander Insight is about to land on Mars and the NASA PR describes the solar panels as producing 600-700W now and 200-300W when covered in dust. Is there any reason why ...

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