|RUSSIA WILL DEVELOP SPACE ELEVATORS
MOSCOW. (Yury Zaitsev for RIA Novosti) – Nikolai Sevastyanov, president
of the Energia Rocket and Space Corporation, said Russia will build the
first permanent lunar base in 2015.
NASA managers claim that U.S. astronauts will land on the Moon in 2018 and
manned lunar bases will subsequently be established. Chinese scientists
are also spotlighting their intention to exploit the Moon’s natural
resources. However, delivering payloads from the Earth to the Moon and
back is a major problem hindering the Moon’s colonization. The same can
be said about future manned missions to Mars.
Chemical-propellant launch vehicles with hydrogen-oxygen engines will not
prove effective in this case. For instance, the Proton rocket, with a
650-metric-ton lift-off weight, orbits 22-metric-ton spacecraft and can
also launch 6.5-metric-ton interplanetary probes (that is 1% of the
lift-off weight). Preliminary estimates show that a Martian mission would
involve a 600-metric-ton spacecraft, which cannot lift off from the Earth.
Consequently, its components must be assembled in outer space. But it
would take 100 Proton rockets with a total lift-off weight of 65,000
metric tons to orbit all spacecraft elements.
Nor can Russia’s heavier Angara space system provide the solution. The
U.S. Apollo Moon program, which relied heavily on Saturn V launch vehicles
in the 1960s, proved a dead-end option because one Saturn V rocket costs
$2 billion to operate. Moreover, the United States will spend an estimated
$10 billion on a new heavy-duty launch vehicle featuring Space Shuttle
components and due to cost the same $2 billion per launch.
As for the unique Soviet-made super heavy Energia launch vehicle, the last
word in rocket technology, it can orbit 105-metric-ton payloads, or 4.3%
of its lift-off weight. Energia rockets with a total lift-off weight of
50,000 metric tons would therefore be needed to launch all elements of the
Martian spacecraft. Finally, modern chemical-propellant rocket engines are
about to reach the limit of their performance capabilities.
Experts are now contemplating electric rocket engines with an enhanced
specific thrust (the ratio between a rocket engine’s thrust and
working-medium flow per second) of between 1,200 and 1,400 seconds for
interplanetary flights, which is 5-10 times more than liquid rocket
engines. But a spacecraft with electric rocket engines would take much
longer to reach its destination because it could not attain an optimal
Scientists from the Space Research Institute of the Russian Academy of
Sciences have developed a unique space elevator for lunar and Martian
missions. Although a bit slower, the new system will cut back on
interplanetary delivery expenses.
A space elevator consists of satellites, spacecraft and payloads linked by
long, thin, flexible elements. The simplest system links two spacecraft by
means of a cable with a length of several dozen or even several hundred
kilometers. This tandem, which resembles a space sling, revolves around
its center of gravity, which in turn has a predetermined orbit. Either of
the two spacecraft can therefore launch a payload along any required
trajectory without any rocket engines.
The foundations of the space-elevator theory were laid by Russian
scientists. Konstantin Tsiolkovsky, the father of astronautics, suggested
using a space-tether system to create artificial gravity aboard orbital
stations. Fridrikh Tsander, an early Russian space visionary, advocated
placing a space elevator with a 60,000-km tether on the Moon. He believed
that gravitational and centrifugal forces would stretch the tether and
allow it to be used as a cableway to transport payloads.
In 1965, the Central Machine-Building Design Bureau, headed by leading
rocket scientist Sergei Korolev, a member of the Soviet Academy of
Sciences, started preparing for the first space-tether experiment. The
Bureau, which later changed its name to Energia Rocket and Space
Corporation, planned to link a Soyuz spacecraft to the last stage of the
launch vehicle using a steel cable. Unfortunately, this project was
mothballed after Korolev’s death and resumed by Energia only 20 years
Several space-elevator experiments were conducted as part of U.S.,
Italian-U.S. and U.S.-Japanese projects. Not all of them were successful;
nonetheless, experts managed to accomplish some of their objectives.
In the last few years, the Space Research Institute has studied the
possibility of building a space-elevator cluster that would deliver
payloads from the Earth to the Moon and back.
Theoretical studies and experiments showed that the cluster should
comprise two cableway systems, one in a low circular and the other in a
low elliptical Earth orbit, and one cableway in a circular equatorial
lunar orbit. The dimensions of all three cableways should create different
gravitational potentials at each end. By adjusting tether length, it will
be possible to change each orbital system’s angular speed of rotation.
The space-elevator cluster will exchange payloads between orbital
cableways. In essence, two-way freight traffic would turn such cableways
into a transportation artery.
Most importantly, the system’s components would exchange mass and
energy. For example, a system in a low circular orbit would act as a sling
and place a payload into a higher elliptical orbit, where it would be
captured by another cableway. The lower “sling” would then lose part
of its energy and move to a lower orbit.
The same would happen when a payload is transferred from a high elliptical
orbit to a near-Earth cableway.
The space elevator will thus deliver equipment to the Moon and bring back
lunar rock and soil. Its launch frequency, the main criterion of its
cost-effective performance, depends on the time needed to restore the
“launching” cableway’s initial altitude.
The required cable length and rotational speed around the center of
gravity will ensure identical trajectories when transferring a payload
between lower and upper cableways at predetermined intervals. Reliable
grips are needed to prevent dangling during rapid relative movements of
payloads and the sling itself.
With this in mind, scientists have suggested an optimal cable-inclination
angle in relation to the sling’s vertical movement at the link-up point.
The payload and the sling grip will therefore remain near each other for
considerably longer periods of time.
The Space Research Institute has already conducted several experiments in
water and confirmed the main parameters of the projected Earth-Moon-Earth
transport system. Calculations show that the new system will weigh 28
times less than the payload it will deliver to the Moon during its entire
Meanwhile, the fuel burned by conventional rocket engines would weigh 16
times more than their payload.
The need to exploit the Moon and Mars will serve as the main incentive for
developing space elevators as mankind looks for new places to settle.
Yury Zaitsev is expert at the Space Research Institute, Russian Academy of