73
Because shielding against radiation is heavy, and weight is the enemy of getting things into space.
CPUs are quite sensitive to radiation, and some types of radiation (cosmic rays) are not only quite good at penetrating most things, as they do, they cause a cascade of secondary radiation. To protect a device form any of this radiation getting through is not ...
68
While cosmic radiation is a problem, it's the same as with radiation on Earth: the risk is cumulative. The levels were low enough that missions of 1-2 weeks at this level did not pose a big health risk, so no shielding was necessary.
The big remaining problem was radiation from solar flares and CMEs. These produce so much radiation it wasn't possible to ...
65
In addition to what Russell Borogove says about cumulative risk you're operating under a false assumption--that there was shielding on the Apollo capsules.
Not only did the Apollo capsules not have shielding but shielding was considered undesirable. There are two main radiation threats in space: cosmic rays and solar flares.
Their "defense" against solar ...
64
Radiation exposure is a cumulative risk. The more radiation you receive, the more likely you are to develop cancers.
The Apollo missions took no more than two weeks to complete; the astronauts flying those missions accepted that dose of radiation with the health risks that come with it.
A manned Mars mission will take, at minimum, months of travel. For ...
59
There are a number of reasons why spacecraft electronics typically lag what is commercially available by several years.
Radiation tolerance
Electronics are very susceptible to radiation phenomenon that terrestrial electronics are largely protected from by the Earth's atmosphere and magnetic field. Common radiation-based failure mechanisms are Single-Event ...
59
RTG technology has been applied on Earth, many times, although not for transportation - they don't produce much power for their weight so any RTG powered vehicle would be very slow. Some pacemakers used to have plutonium batteries, and RTGs were used in remote sites to power sensors, lighthouses and the like in remote areas. It isn't used much anymore on ...
57
In order to properly assess this, you need to take a few things into account:
What are the typical exposure levels?
How would Solar Storms be protected against?
What kind of shielding do you need?
Much of my answer to this was taken with help from The Case for Mars, by Robert Zubrin.
First of all, let's start with the long term limits. As a starting point,...
54
They didn't, which is why the Apollo astronauts saw blinding flashes inside their eyes during the mission and then had a much higher probability of suffering from cataracts later in life.
The flashes were from Cerenkov radiation passing though their eyeballs, occurring as often as 2 per minute on the Apollo missions.
Of the 39 astronauts to suffer from ...
49
TL;DR: It was so busy getting stuff done, it didn't care.
Being old, slow, massive and inefficient (by any modern standards, not by those in 1965) is a huge benefit when it comes to radiation hardness.
Let's start with the memory: Changing a bit in current S(D)RAM cells is trivial - introduce a bit of charge in the wrong place and the bit is lost. This ...
48
Apollo solved the cosmic radiation problem in a counter-intuitive manner: by minimizing shielding.
Most cosmic rays are very-high-energy atomic nuclei; the rest are very-high-energy protons. When these particles strike something (eg. a sheet of aluminum), they generate a shower of secondary radiation. Any effective shield needs to be thick enough to both ...
38
The radiation dosage for a year on the moon is between 110 mSv and 380 mSv. On Earth, that dosage is 2.4 mSv, or higher, depending on where you are exactly. Bottom line, the few days in Lunar orbit would have aged the film due to radiation between 50-150 days/ day in orbit maximum, thus it would be the equivalent of film that was aged a few years at most. ...
34
A big part of it is reliability. NASA could probably put in an Intel Xeon chip made in 2012 that has a crazy high amount of processing power.
However, the chip that was used, the RAD750, has years of experiments and usage behind it, such as being used in a variety of spacecraft including:
Deep Impact comet chasing spacecraft, launched in January 2005 -...
30
One might think that spacecraft would be on the cutting edge of technology.
I wouldn't think this would be the case at all. If anything, NASA would want to use hardware (and software) that has been extensively tested throughout years of use, both in NASA and in industry as a whole. The last thing NASA wants is to find a bug in a spacecraft's system at an ...
28
RTGs are expensive to produce, can be politically inconvenient to use, and in the form of a plutonium-bearing device, represent a potential nuclear proliferation hazard (though all RTGs might be used to construct a "dirty bomb").
To compound the issue, their power output simply isn't very big... Perseverance's generator cost about 75 million USD ...
27
We know from the nuclear power industry that spent fuel storage pools are pretty safe places to be around, radiation-wise. They're actually safe to swim in, to a point, because they're serviced routinely by human divers. They just can't get too close to the spent fuel.
We use these pools for short-term storage because water is a really good radiation shield....
27
The spectral data came from the surface of the material only a few atoms thick which is exposed to hard vacuum. The solar wind has ions of many materials. It is mostly hydrogen, which as an ion is just a proton. Or hydrogen atoms. Either one can react. The solar wind is not very energetic but it contains small amounts of other elements like oxygen and ...
25
tl;dr: The UV index is primarily concerned with the level of UV-A that can cause sunburn and, potentially, skin cancer. The actual UV-A flux at Mars is not dramatically different from that at Earth (less because of distance, more because of no attenuation). *But the big difference is the unattenuated UV-C and UV-B!
The total solar constant at the Earth is ...
24
At first glance, the RTG does not pose a risk.
It is powered by Pu-238, which is primarily an alpha emitter throughout its decay chain. Alpha particles can be stopped by a sheet of paper. An astronaut is perfectly safe in his suit, even if the RTG were disassembled and the Pu lying around unprotected.
The RTG is built to survive a launch failure, i.e. it ...
23
Yes, it absolutely would! The radiation on Europa is about 5.4 Sv (540 rem) of radiation per day. Looking at this guide, and assuming you want to meet OSHA standards of 5 rem per year, you would need to only allow 1 part in 40,000 of the base radiation to make it through. The website linked indicates you want a mass of about 375 pounds/square foot to only ...
22
Radiation can affect film - but bear in mind the radiation around Chernobyl was, truly, extremely high. The radiation in our region of space is not as extreme.
Also bear in mind that the earlier Lunar Orbiter probes used film cameras, the pictures were developed and scanned automatically (by machinery on board) and the results transmitted to Earth. The ...
21
The South Atlantic Anomaly is a region of high particle flux above the Atlantic Ocean off the coast of Brazil, caused by a slightly lower magnetic field above this point on the Earth. The problem it causes satellites is that above the anomaly, the magnetic field being weaker allows particles to get closer to the Earth. These particles can damage detectors ...
21
In space (within the Solar system), you will get mostly two types of "radiation" that have health consequences:
Photons of various energy, from long wave radio to gamma rays.
High-energy charged particles, mostly electrons and protons ejected from the Sun upper atmosphere (this is known as the solar wind).
Main source for these is, of course, the Sun. ...
20
There's a pretty good Wikipedia page about it, which lists a couple of options:
Water makes for fairly good radiation shielding (also discussed with land based radiation here), but is relatively heavy and is consumed during flight.
Liquid hydrogen is also good, and is used as fuel, so it will already be on board. However, this too is consumed during flight....
19
NASA studied the effects of radiation on film. Bright spots are just one of the possible results. Other effects include an increase in the amount of noise, and a decrease in contrast and color response. These effects are not easily detectable to the untrained eye and without access to the original material.
In this study, NASA also experimented with ...
19
Not exactly "over the top" (still through the outer portion of the belts), but yes, it appears so, according to this source.
There are simplified trajectory plots shown in the link.
Also this source
quotes a letter from Van Allen himself:
...the outbound and inbound trajectories of the Apollo spacecraft cut through the outer portions of the inner belt ...
18
No. Most International Space Station (ISS) spacewalks last in the order of several hours, often up to 8 hours during more difficult and time-consuming repairs and installations, and some nearly 9 hours*. And the station, in its roughly 93 minutes orbit is never in Earth's shadow for that long.
There are both advantages as well as disadvantages to ...
18
Light interacts with fresh metal surfaces in only the first few atomic layers. What makes metals "metals" is the very high electron density, and we can think of that electron "plasma" as having such a high plasma frequency that the light barely penetrates a tiny fraction of a wavelength before being re-radiated backwards by all those ...
17
The two specific modules are protected by two mechanisms:
TeSS Polyethylene radiation protection tiles and bricks
Water storage bags attached to the walls making a "water wall"
High densities of hydrogen are good at radiation protection, and water is a good hydrogen source that needs to be stored on the ISS. Another good source of dense hydrogen is ...
17
A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles (320 by 32,190 km)) passing the radiation belts will receive about 2,500 rem (25 Sv) per year (for comparison, a full-body dose of 5 Sv is deadly). Almost all radiation will be received while passing the inner belt.[31]
25/365 = .07
5(Sv) / .07 = 71.2
So you have to spend ...
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