ROOM
46
Astronautics
showers of secondary radiation, including neutrons.
They are also best absorbed by materials with a high
hydrogen content, the best being liquid hydrogen,
then water, plastics and perhaps liquid methane.
Neutrons are particularly hard to stop because, being
chargeless, they are not affected by electromagnetic
fields generated by other atoms and can penetrate
deep into tissues and cause a great deal of damage.
There are several ways to mitigate and block
these particles, also called ‘high-energy, high-
charge’ or ‘HZE’ (high atomic number and energy)
particles in some literature.
Designed to protect
A spaceship with a metal skin that uses plastic interior
walls and supports, with all possible supplies and
fuel tanks arranged to surround the crew quarters, is
the best option to start with. It adds no extra power
requirements; the mass is already necessary to the
structural integrity of the craft and the supplies are
necessary for crew survival needs. Water for the crew
can be distributed through a second hull to surround
the habitable areas of the ship.
These interventions will shield the crew from all
but the most powerful gamma rays and most but
not all of the galactic radiation. They will also help
mediate the effects of secondary radiation, where
a high speed atomic particle strikes a nucleus in
the ship materials causing a cascade of radiation
particles and photons, including neutrons.
The Orion spacecraft will use the mass that
is already on board to protect the crew of long-
distance missions to Mars. Supplies, equipment
and launch and re-entry seats, as well as water
and food will be used to protect the crew by
creating a temporary shelter in the aft bay of the
spacecraft, which is the inside portion closest to
the heat shield.
Active shielding
Engineers are working on several ways to protect
future space crews or colonists from very high
energy galactic radiation. One method that could
be very useful is generating a powerful magnetic
field, which could cause the charged particles
approaching the ship to curve around it - much as
the Earth’s magnetic field protects us here.
This would be done by producing two rotating
magnetic fields with opposite orientation. One
would be larger than the other with the second
field cancelling out the effects of the first except
outside the second smaller field. This would create
a magnetically neutral bubble around the ship, so
as not to interfere with equipment etc. with a larger
bubble of high magnetic strength farther out.
This shield system would run at low power
during normal radiation levels but could be made
much stronger during high radiation events by
redirecting all available ship power to this shield
system when a surge of radiation is detected.
Some engineers have looked at this type of
system and voiced concern about synchroton
radiation, which is produced when charged
particles travel on a curved path, but all of the
synchroton radiation would be photonic and in the
wavelength of radio waves and microwaves, and
possibly visible light causing a ‘Northern lights’
effect. Even if a severe event produced some
X-rays or gamma rays it would be a lot better
than letting the high-energy particles through. A
system such as this would also provide the added
bonus that some captain somewhere would be
able to order, “Shields Up!”.
Active radiation
shielding using 6+1
expansion coil
architecture.
Nigeria EduSAT-1.
Active radiation
shielding using high
temperature
superconducting
magnets.
NASA
