82
votes
Accepted
Why were the Space Shuttle's main engines placed on the orbiter?
The quick answer--so they could get the engines back--has already been provided, but I'd like to offer some more historical context to that design decision.
Note that the shuttle as originally ...
- 11.2k
69
votes
Accepted
How (the heck) did Lunokhod 2 drive, navigate and survive a ~40 kilometer drive over four months on the Moon using 1970's technology?
A few interesting videos about the lunokhod rovers:
Tank on the Moon
The Lunokhod Rovers - It Happened in Space #7
Secret Soviet Lunar Rovers and Extra Terrestrial Cars - Lunokhod,
Mars Rovers
The ...
- 13.3k
67
votes
Why can't they just drop a solar winch down from a shuttle and have planes fly up and clip things on?
Because space isn't about going high; it's about going fast! For example, in a 400 km orbit (like ISS) you need a speed of about 27,500 km/h or 7.66 km per second.
So if you would extend a ...
- 12.6k
60
votes
Accepted
Is the mass of paint relevant in rocket design?
When the shuttle External Tank stopped being painted white, the weight savings was ~600 lbs (~270 kg).
This is not a tremendous amount from a vehicle standpoint, but the tank was carried almost to ...
- 189k
56
votes
Accepted
Why do the Russians use these fence-like interstage fairings?
It's all to do with ullage in the fuel tanks. Newton's laws of motion mean that when a rocket is no longer firing and no force is being applied, the rocket receives no acceleration. It continues at ...
- 6,213
55
votes
Accepted
Falcon 9 design: Why is the cargo fairing so much wider than the lower parts?
The diameter of the stages is the largest size that can be transported by road without extensive "outsize load" issues (permits, having to move traffic lights and signs out of the way etc.). This ...
- 130k
55
votes
Why aren't rockets built with truss structures inside their fuel & oxidizer tanks to increase structural strength?
There's almost nothing to be gained by a truss. The load being applied is along the axis of the tank. A simple hoop of material is very strong in this orientation. (Try it with a piece of paper, ...
- 11.7k
48
votes
Why were the Space Shuttle's main engines placed on the orbiter?
So that the reusable engines could be reused.
If they were mounted on the expendable external tank, they would have been thrown away each mission.
- 189k
44
votes
Accepted
When did the concept of "stages" enter rocketry?
The first multistage rocket is much older then one might think. Its from the 14th century CE.
Huolongchushui or fire dragon issuing from the water (Chinese: 火龙出水; pinyin: huolóngchushui; literally: ...
- 6,967
41
votes
Accepted
What if something goes wrong during the seven minutes of terror?
No. By the time that NASA receives the signals from the spacecraft indicating that EDL has started (i.e. some indication of entry interface), whatever has happened has already happened. That's the ...
- 15.4k
40
votes
Accepted
Why Doesn't the cooling system on a rocket engine burn the fuel?
It's inside a pipe with no air, oxygen, or another oxidizer.
The fuel in the cooling channel is contained, it's not exposed to air or oxygen. As such, it can't ignite. There's no way for it to burn.
...
- 9,517
38
votes
Accepted
Why did SpaceX retire Falcon 1?
The Falcon 1 was less profitable to maintain, and it didn't have the customer base to support using it. A Falcon 1 launch cost around $10 million, of which about 10% was profit. They also considered a ...
- 122k
37
votes
Accepted
Why was there a minimum height for astronauts?
Everything that must interface with the human body must be designed to fit a certain range of body sizes. For example, in the early days of shuttle when airline-like operations were envisaged, the ...
- 189k
36
votes
Is it common and good engineering for a pair of cables to be easily plugged into each other's connectors in modern spacecraft
Off the top of my head I can think of several failures caused by miscabling.
On Apollo 6 the signal to shutdown a malfunctioning second stage engine was cabled to a different engine, resulting in two ...
- 189k
34
votes
Accepted
Do spacecraft ever release unneeded gases into space?
You bet. Not only gases, but astronaut pee as well! Which could result in spectacular light shows.
This happens for several reasons:
Spacecraft and the tanks inside them are built to be as light as ...
- 189k
33
votes
Accepted
Why does the ISS cupola have Interior Protective Sliding Windows
That's a "bump shield" used for filming the IMAX movie A Beautiful Planet.
According to IMAX, their desire to film from aboard the Cupola forced
them to design an "exclusive bump shield made of a ...
- 189k
33
votes
Accepted
How is thrust transmitted from strap on boosters to the central core?
It’s a sense of scale issue. As much as the struts might look like flimsy bits of drainpipe, those rockets are around 15 meters wide, and the struts are more like the heavy steel beams used to hold up ...
- 2,267
33
votes
What changes to Voyager could have been made?
Knowing what we know now about Titan's thick and resistant-to-surface-photography atmosphere, choosing a Pluto flyby for Voyager 1 over a Titan flyby would perhaps have given more exciting results. ...
33
votes
Accepted
Why is the Delta IV Heavy taller than the Delta IV Medium?
The fairing is bigger (Taller) for larger payloads.
- 80.5k
32
votes
Why aren't rockets built with truss structures inside their fuel & oxidizer tanks to increase structural strength?
Because they don't need to be.
Clearly the current design of rockets can be successful. So adding truss structures to the current design would add weight for no reason and take away from the payload ...
- 189k
32
votes
Accepted
Why was the Space Shuttle Orbiter's in-orbit time limited?
I found the answer in the EGIL Console Handbook (not online). This was the flight control position responsible for the Orbiter's electrical system.
The Station to Shuttle Power Transfer System (SSPTS)...
- 189k
30
votes
Accepted
What is the "emergency crush core"?
The landing legs have a honey-comb filler that can compress to absorb significant energy of a hot landing.
(Source: @SpaceX)
- 316
29
votes
Accepted
Why weren't Saturn V and the Soviet N-1 Moon rockets made larger in order to simplify Lunar missions?
In order to use the direct ascent method of landing on the moon, which is where the entire vehicle descends and leaves the moon, you would need a rocket an order of magnitude bigger than the Saturn V, ...
- 20.4k
29
votes
Accepted
What is the most aerodynamic Satellite?
The only satellite I know of that was shaped to have low drag was GOCE, which orbited at 250 km.
Since it was vital to ensure that the measurements taken are of true gravity and not influenced by any ...
- 130k
29
votes
Has SpaceX chosen to drop the Transpiration cooling of Starship? If so, why?
Despite SpaceX's high-tech reputation, SpaceX aren't where they are today because they made massive technological leaps or pushed the envelope of science--after all, just doing science doesn't earn ...
- 21.7k
28
votes
Accepted
Why are RTGs different colors?
Answer: Thermal radiating coating technology has improved, so they are no longer forced to be sub-optimally black in visible light. They can now be white and reflect incident sunlight to improve ...
- 151k
26
votes
Is it common and good engineering for a pair of cables to be easily plugged into each other's connectors in modern spacecraft
Not in flight but this 1996 NASA lesson learned document lists multiple instances of mis connected cables during ground assembly and test including on Galileo.
It in turn references JPL documents ...
- 25k
25
votes
What are the "disks" seen on the walls of some NASA space shuttles?
2 ) The blue patches are Velcro. Velcro was ubiquitous throughout the crew compartment.
1&3 ) Those disks weren't seen in the real Orbiter Waste Management Compartment (WMC). Instead the inside of ...
- 189k
24
votes
Accepted
How feasible is the Delta-Glider?
The specific impulse figure of 40kN•s/kg (i.e. exhaust velocity of 40km/s) and the 31.5km/s of delta-v achieved thereby is not achievable with current propulsion technology -- it’s about 10 times the ...
- 172k
24
votes
Accepted
Why did the Apollo 13 tank #2 have a heater and a vacuum?
tl;dr
The heaters are there to control the pressure in the tank
The tank is of double-walled construction with a vacuum between, like a Thermos bottle, because the oxygen is at cryogenic temperature
...
- 189k
Only top scored, non community-wiki answers of a minimum length are eligible