The furthest we have been is the Moon. If we want to travel
into deep space, beyond our own backyard, the Solar System, we’ll need a new
breed of spacecraft
It may be the
oldest cliché in town, but in the not too distant future science fiction will
turn into science fact. The fantastic spaceships of sci-fi comic books and
novels will no longer be a figment of our creative imagination; they may be the
real vision of our future.
Engineers and
designers are already designing craft capable of propelling us beyond Earth’s
orbit, the Moon and the planets. They’re designing interstellar spaceships
capable of travel across the vast emptiness of deep space to distant stars and
new planets in our unending quest to conquer and discover. Our Universe
contains over a billion galaxies; star cities each with a hundred billion
inhabitants. Around these stars must exist planets and perhaps life. The
temptation to explore these new realms is too great.
First things
first ― we’ll have to build either a giant orbiting launch platform, far
bigger than the International Space Station (ISS), or a permanently manned
lunar base to provide a springboard for the stars. Some planners feel we should
limit ourselves to robotic probes, but others are firmly committed to sending
humans. “There’s a debate right now about how to explore space” says astronaut
Bill Shepherd, destined to be the first live-aboard Commander of the ISS.
“Humans or machines ― I think they’re complementary”.
Space is the most hostile environment we will ever explore.
Even a single five-hour spacewalk requires months of training, and a vast
technical backup to keep it safe. The astronauts and cosmonauts who live aboard
the ISS will be there for only a few weeks or months; if we want to travel into
deep space it could take years. First we’ll have to find out just how long the
human body can survive in a weightless environment. In zero gravity, four pints
of body fluid rush from the legs to the head where it stays for the duration of
the mission. Astronauts often feel as if they have a permanent cold, and
disorientation can become a major problem. In space there’s no physical
sensation to let you know when you’re upside down and astronauts have to rely
on visual clues from their surroundings. A few hours after reaching orbit, one
in three of all astronauts will experience space sickness ― a feeling
rather like carsickness. And weightless conditions lead to calcium being
leached from the bones, and problems with the astronauts’ immune systems.
Trillions of
rocky fragments ― meteoroids ― roam our Solar System at speeds of
up to 150,000 miles an hour. A meteoroid no bigger than a grain of salt could
pierce a spaceship window. Protection from the extreme hazards of space is
going to need some clever technology. Space is also full of lethal radiation
― X-rays, gamma rays and the high-speed particles called cosmic rays.
Down here on
Earth we are protected by the atmosphere and by our planet’s magnetic field,
but in space long haul astronauts suffer gradual but irreversible radiation
sickness unless they are carefully shielded. Commander Shepherd is confident
the ISS will help us crack the problems “The ISS is going to answer a number of
questions about long range exploration in space. A lot of things are going to
be pioneered on the space station for future exploration”.
Saturn V is still the most powerful rocket ever built. But
even this vast 3000 tonne giant carried only enough fuel to send a tiny manned
capsule with just three men on a 250,000 mile journey ― a mere drop in
the cosmic ocean. It’s over a quarter of a century since the last man stood on
the Moon (Commander Gene Cernan on the Apollo 17 mission in 1972), and it seems
that it will be another quarter of a century before we return to build a
permanently manned base there. Bob Forward ― who earns his living from
designing spaceships of the future ― believes we’ll have to find a cheap
way of reaching the Moon before we think of living there. His slingshot concept
may seem radical at the start of the 21st century, but it is certainly
ingenious. “If you have something rotating quite fast around another thing on
the end of a string, it has a tendency to fly away. You have to decide when to
let go (from Earth-orbit) and ― like a trapeze artist catching his
partner ― you have to decide when to catch the payload (in lunar orbit)”.
A lunar base would become a viable stepping stone to deep space. In the 1990s,
the Clementine and Lunar Prospector spacecraft detected frozen water below the
lunar surface. This could be mined, melted and broken down to make liquid
oxygen and hydrogen rocket fuel needed to blast off into deep space.
But before we
leave the Solar System on our interstellar quest we will have to conquer it.
Mars will become our first target. Whether we’ll reach it directly from Earth,
from Earth’s orbit or from the Moon is anyone’s guess but Mars is far from
being a barren desert like the Moon.
Mars probably
has plentiful supplies of frozen water below the surface and even has 24-hour
days! Unfortunately the atmosphere is 95% carbon dioxide, with just a fraction
of the Earth’s atmospheric pressure and no protective ultraviolet layer.
Martian astronauts will have to live in sealed modules, and wear spacesuits to
venture outside. Mars would be a tiny colony, like the remote outposts of the
early Earth explorers. Mars itself will probably never be a stepping stone to
the stars, but it will help us learn if we can live in such a remote and harsh
place for years or even a lifetime.
Scientists are already experimenting with propulsion systems
that may travel much faster than today’s conventional chemical rockets.
Franklin Chang’s plasma rocket may be the answer. “In a plasma rocket you’re
continually accelerating,” he explains.
A trip to Mars
could be cut to 90 days, claims Chang. His rocket harnesses a nuclear process
to produce a hot gas plasma. The plasma is magnetically held in a rocket the
shape of a bottle and then expelled at very high velocity to provide
propulsion. The plasma has to be heated to millions of degrees. Chang believes
his system will be too good just to reach Mars. “I think it will quickly be
developed for interplanetary travel within our Solar System”. The plasma rocket
is now under development at NASA’s
Another new
method of propulsion is already flying through our Solar System. Pushed only by
an electronically driven ‘ion engine’, Deep Space One is already over 100
million miles from Earth. It works by ionising xenon gas and expelling it with
the aid of electric fields, so providing a gentle but constant thrust. The ion
engine provides a force about the same as a single sheet of paper exerts on
your hand ― far too weak to lift a spacecraft from the surface of a
planet ― but the continuous acceleration has already pushed Deep Space
One to a speed ten times higher than any of the manned rockets we use today.
To leave the Solar System and carry humans to the stars we
will have to find a way of travelling near to the speed of light. Even then a
journey could take hundreds or thousands of years. Travelling at 1/10 the speed
of light it would take over forty years to reach the nearest star, Alpha
Centauri.
One giant
source of free energy is our Sun. Bob Forward has designed the solar sail, a
craft that doesn’t have to carry its own fuel supply. It’s driven by the power
of the Sun’s rays, and it will be the fastest machine ever built. “The sunlight
bounces off the aluminium sails and in the process gives it a tiny push,”
explains Forward. Like the ion probe it will accelerate and accelerate. And
it’s not a total dream. NASA is already experimenting with deploying large
sails in Earth-orbit. Propelled by light, solar sails will travel thousands of
times faster than Apollo or the Shuttle.
Even with the perfect spaceship it isn’t going to be easy.
In his classic sci-fi novel 2001, Arthur C. Clarke used the concept of
suspended animation as a way for humans to cope with long space flights. He
imagined that we would be able to put the human body into hibernation ―
suspended animation ― to escape the boredom of long interstellar missions.
An even more
drastic measure might be to freeze the astronauts. We already use cryogenic
techniques to preserve dead bodies and store human embryos. Freezing living
adults may not be so far away, but perhaps we won’t have to do that. Perhaps we
should use our existing technology and send frozen embryos across to the far
corners of the cosmos.
It could certainly save on space. Then hundreds of years from now, billions and billions of miles away, the embryos will be thawed and their hearts will start beating. These space-farers of the future will not grow inside a mother’s body but will be incubated in a machine. They will be brought up by robot. It may seem strange and radical but one day it might just happen …