Laika the dog was the first animal in space, aboard Sputnik 2. According to this answer, her mission was intended for 10 days, but Laika survived only 2 days due to the spacecraft overheating. Wikipedia claims that she was to be euthanized by poison in her last food ration, had her mission lasted the full duration.

Sputnik 2 also passed through the Van Allen radiation belts, even though they were not discovered until later.

Assuming that the thermal and environmental control systems of Sputnik 2 worked properly so she could have survived for 10 days, what would be the effect of the exposure in Sputnik 2 to 10 days of radiation in the Van Allen belts? Would physiological or neurological changes be noticeable? Would Laika have survived this radiation?


2 Answers 2


Humans have passed through the Van Allen belts and lived, but you know that.

The outer belts are the highest radiation ones, and those are out beyond the ~1600km maximum of the Sputnik 2 orbit.

From a Applied Physics Lab document I get an average radiation dose of the Van Allen belts (unspecified inner or outer) of 50Gy/year. Taking a full 10 days of Sputnik 2 at that value (ignoring the large orbital range) gets about 1.37Gy total dose. OK, but what does that mean?

Well, that is less than the daily radiation dose my wife went through for her cancer treatments. And the accumulation, in a human, didn't really kick in for over a week. Yes, full body vs localized, but still I believe that, unless dogs are much more sensitive to radiation, Laika would live just fine.

To check that, Radiation Research has an article stating that the LD50 for adult beagles is 258 rads (2.58Gy) at 15R/min (50Gy/year is 0.01rad/min). So, the 1.37Gy is half of the LD50 but it is spread over a much longer time (10 days, not 10 minutes).

  • $\begingroup$ That LD50 value was for (uncharged) gamma radiation but not for charged protons and electrons. $\endgroup$
    – Uwe
    Commented Jun 16, 2020 at 22:16
  • $\begingroup$ @Uwe There shouldn't be much of a difference - electrons and photons have a weighting factor of 1, protons of 2 with respect to the damage they do to living tissue. $\endgroup$
    – asdfex
    Commented Jun 18, 2020 at 17:15

The flux values of the charged particles radiation vary heavily depending on position within the Van Allen belts and are influenced by solar storms.

At the magnetic equator, electrons of energies exceeding 5000 keV (resp. 5 MeV) have omnidirectional fluxes ranging from 1.2×10^6 (resp. 3.7×10^4) up to 9.4×10^9 (resp. 2×10^7) particles per square centimeter per second.

The proton belts contain protons with kinetic energies ranging from about 100 keV, which can penetrate 0.6 µm of lead, to over 400 MeV, which can penetrate 143 mm of lead.

Source: https://en.wikipedia.org/wiki/Van_Allen_radiation_belt#Inner_belt

These particle counts and kinetic energies should be transformed into the absorbed energy per mass to get a value with the unit Sievert or Gray.

Sputnik 2 had an elliptic orbit:

Semi-major axis 7,306 kilometres (4,540 mi) Eccentricity 0.0990965 Perigee altitude 211 kilometres (131 mi) Apogee altitude 1,659 kilometres (1,031 mi) Inclination 65.33°

Source: https://en.wikipedia.org/wiki/Sputnik_2

So it is very difficult to estimate the lethality of the radiation dose received by Laika within 10 days.


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