69 votes
Accepted

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 ...
Phiteros's user avatar
  • 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 ...
Bob Jacobsen's user avatar
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37 votes

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 ...
PearsonArtPhoto's user avatar
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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 ...
Hobbes's user avatar
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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 ...
Organic Marble's user avatar
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 ...
Christopher James Huff's user avatar
23 votes
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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 ...
uhoh's user avatar
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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'...
CuteKItty_pleaseStopBArking's user avatar
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 ...
Dragongeek's user avatar
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19 votes
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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 ...
marked-down's user avatar
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16 votes
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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 ...
Phiteros's user avatar
  • 5,626
16 votes

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 ...
Russell Borogove's user avatar
15 votes

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:
Russell Borogove's user avatar
14 votes

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 ...
C. Spencer's user avatar
14 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 ...
Oscar Lanzi's user avatar
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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 ...
uhoh's user avatar
  • 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 ...
Fred's user avatar
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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 ...
PearsonArtPhoto's user avatar
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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 ...
Steve Linton's user avatar
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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....
Christopher James Huff's user avatar
13 votes
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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 ...
Tristan's user avatar
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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 ...
Phiteros's user avatar
  • 5,626
12 votes
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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 ...
Bob Jacobsen's user avatar
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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 ...
Hobbes's user avatar
  • 128k
12 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, ...
PearsonArtPhoto's user avatar
  • 121k
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 "...
Tristan's user avatar
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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 ...
Russell Borogove's user avatar
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 ...
peterh's user avatar
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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 ...
uhoh's user avatar
  • 149k
11 votes
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What was the first Soviet spacecraft that could recharge its battery it each orbit? Where were the photovoltaic cells made?

Looks like the first Soviet satellite with solar power capability was Sputnik 3, launched on the 15th May 1958, losing out to Vanguard 1 which was the first satellite with solar power launched only ...
Starfish Prime's user avatar

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