70
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Why wasn't an RTG used on the Juno spacecraft?
That is precisely it. Plutonium-238, which is used in the creation of radioisotope thermoelectric generators (RTGs) is very difficult to come by. There are plenty of news articles on this, from ...
- 5,626
38
votes
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Function of the separated, individual solar cells on Telstar 1 and 2? Why were they "special"?
The small separated cells had several functions.
Six individual units, the "solar aspect cells", were each oriented and attached as if they were on the sides of a cube to identify the spacecraft's ...
- 12.6k
37
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Why wasn't an RTG used on the Juno spacecraft?
Another interesting note is that this mission more than any other mission to the outer solar system can use solar power. Why? Juno is in a polar orbit, and will continually be in the sun. Solar panels ...
- 121k
28
votes
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Can the Mars lander's/rover's solar panels be cleaned?
Reasons not to provide mechanical means to clean solar panels on Mars:
and this is the primary reason: Wind on Mars occasionally blows the dust away. This means dust is not a major issue, but a minor ...
- 125k
24
votes
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Can ISS fold its solar panels?
The long boom holding the panels can be retracted (the term used instead of "folding").
It is not done lightly, for fear of not being able to reverse it. It has only been done a few times, once ...
- 178k
24
votes
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Mars versus the poles of Mercury WRT colonization
Your delta-v analysis doesn't account for the landing delta-v. On Mars, only a fraction of a km/s has to be done propulsively, on Mercury the entire landing will be propulsive.
You also don't account ...
- 10.7k
23
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What are the sources of light at L2? How will the James Webb telescope be powered?
The planned orbit for the JWST is quite a large halo orbit around Sun-Earth L2. It's very roughly elliptical, with dimensions of about +/- 350,000 km "vertically" (perpendicular to the Earth's orbital ...
- 149k
21
votes
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If we pick any point on the moon (except possibly the poles), is the sun visible for 13.66 days, and then not visible for 13.66 days?
Yes, the light cycle is about one month.
29.53 Earth days, to be precise. (the difference with your figure is because the moon is also orbiting the sun along with the Earth, and after a month the sun'...
20
votes
Why latest Landsat satellites have solar panel on only one side?
Solar panel technology seems to have caught up with power requirements on the satellite. Since price of components is really no object when building a system like this, super expensive panels with ...
- 17.8k
19
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What inspired the circular panels on the Phoenix Lander and InSight rover?
Good catch noting that Cygnus has the same solar panel design! Orbital ATK, developer of Cygnus, builds these panels under the "Ultraflex" and "Megaflex" brands, and did indeed ...
- 8,881
16
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Curiosity is still dirty! How will the ExoMARS Rover keep its solar panels dust-free and collecting sufficient power?
They will likely be relying on two things:
Since the rate at which dust will accumulate on the solar panels is pretty well known, they can estimate a lifespan of the rover. All space probes have ...
- 5,626
16
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How much light is there on the way from Earth to Proxima Centauri?
No, the power collected by solar panels is reduced by the square of the distance from the light source.
At the Earth's distance from the sun, the energy of sunlight is about 1300 watts per square ...
- 167k
14
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Why wasn't an RTG used on the Juno spacecraft?
I had the opportunity to tour JPL a few months ago and asked this exact question to our tour guide. The solar panels on it are enormous and typically, spacecraft going beyond the asteroid belt are ...
- 241
14
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Can a satellite work like a radiometer?
The Mariner 3 and 4 Mars flyby probes had angled vanes at the ends of their solar panel arms which provided passive stabilization of the spacecraft from solar radiation pressure:
- 167k
14
votes
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Could Stirling Engines work on sunlight alone?
Could Stirling Engines work on sunlight alone? With the heated side facing the sun and the rest in its own shade, could two contra-rotating Vacuum Stirling Engines and flywheels, in tandem, accumulate ...
- 149k
14
votes
Mining Helium-3 on the Moon and sending it to Earth?
On Earth, before a mineral or petroleum resource is mined/extracted, the deposit is delineated and evaluated.
Briefly, the process involves sending a some geologists and some drill rigs and their ...
- 13k
13
votes
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Making propellants on Mars: Why not just LH2/LOX instead of methane?
Liquid Hydrogen is difficult to deal with. The temperature must be 33 K or lower. Liquid Oxygen requires 90K, and Liquid Methane is similar. The temperature requirements are far less as such. The ...
- 121k
13
votes
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Could the International Space Station be fitted with solar sails?
Ignoring the ISS, the question is simply whether light pressure on the sail can counteract the drag on the sail from atmosphere. Light pressure near Earth is about $10 \mu Pa$ (with optimum geometry ...
- 19.3k
13
votes
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How long is a day on the Moon?
This may belong to Astronomy SE, but the $29.5$ Earth day figure, or more accurately the time in the third reference, is what you should be planning on when you or at least your instruments go to the ...
- 8,445
13
votes
Why don't rockets recharge in space using solar panels while orbiting similar to ISS for deeper space travel?
The ISS does not have any sort of electric propulsion system. It uses ordinary chemical rockets, either on visiting vehicles or its own rockets which are refueled by such vehicles. (https://en....
- 10.7k
12
votes
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Solar panels on Mars?
Well, we don't really know how much energy a Mars base would need, but we can make some rough estimates. Bases like McMurdo and Mawson have power capacities of several hundred to several thousand ...
- 5,626
12
votes
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Why can't solar panels work eternally for any space probe?
A glass cover isn't enough. The damage is caused by micrometeorite impacts. These are tiny particles that hit at high speeds (more than 1 km/s). You can't build solar panels to withstand that much ...
- 125k
12
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Largest solar panel (by area) deployed in space? Largest below/at/above GEO?
One solar array wing on the ISS, consisting of two blankets stretched out by a supporting mast, contains 32,800 cells that are approximately 8 cm by 8 cm, giving a total active area of approximately ...
- 17.2k
11
votes
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Are the ISS US Segment solar arrays double-sided?
Having worked extensively on the solar arrays over the last five years, I can say they do receive about a third of their power from albedo exposure to the back side.
This is further confirmed from a "...
- 17.2k
11
votes
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The Orbital Mass Accelerator Engine Theory
In theory, yes, if the accelerator and the spacecraft are of the same mass, they'll gain the same amount of velocity when they pass, and so they'll meet at a higher altitude on the opposite side. If ...
- 167k
11
votes
Accepted
Can a satellite work like a radiometer?
The drawing shows a Crookes Radiometer.
They seem to spin nicely in even a little bit of sunlight. The common explanation is light pressure on the black vanes.
Unfortunately, they don’t work that ...
- 12.6k
11
votes
Fast spinning solar cells to clear Martian dust possible?
From a mechanical, engineering view, having a brush on a robotic arm to clean the solar panel is more favorable, than rotating the panel. Having a current transfer between the rotating solar panel and ...
- 3,276
11
votes
How to move in space with just solar panels or without them?
Partial answer based on the constraints the question appears to have. Some solutions would not be considered practical by today's standards, but this doesn't appear to be asking for only practical ...
- 149k
11
votes
Nuclear or Solar power for satellites?
Virtually all satellites use solar power as power source.
The exception is the true nuclear reactors, exemplified by the Soviet RORSAT series, which needed more power for their radar surveillance.
...
11
votes
Largest solar panel (by area) deployed in space? Largest below/at/above GEO?
The largest in space is the International Space Station, as Tristan mentioned.
The largest outside of Earth's orbit is most likely either one of the two Jupiter (Distance) missions with solar panels, ...
- 121k
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