Now that the East-West confrontation has essentially disappeared, the
first motivating factor has at least fallen away. We are now seeing the
consequences that no sound, long-term concepts for space travel have been
developed in the West. Even when attempts are made, the ensuing discussions
are generally very quickly stifled with the comment that there is no money
available or that it is not "politically feasible".
The biggest problem of all is doubtless the population growth. Every 35 years the human population doubles; however the Earth as our home is not becoming larger. In fact we are today already living from the substance. Within the last 50 years a major portion of all available raw materials has been consumed and even with an optimistic prognosis the fact remains that many important raw materials will become scarce in the next century. Even more people will thus have to share less and less space, raw material and energy.
The quality of life will thus unavoidably decline unless we succeed in reducing the population growth rate. Apparently this connection is not yet taken very seriously, at least a change in the trend is not yet in sight. At least in the third world it appears that a vicious circle of poverty, lack of education, large families and corrupt politicians impoverishes these countries even further.
It is thus certainly unrealistic to expect that the population growth rate will come to a stop in the foreseeable future. Rather it is more likely that due to poverty, illness and senseless wars a balance will develop for the available resources, as can already be seen to some extent today in Africa. The only way I see out of this gloomy prospect is for a massive effort be undertaken to make education and training of the population an international concern. Today there is already the inclination to no longer accept that human rights are an "internal affair" of a country. Hopefully we will also arrive at the point where withholding education in order to support corrupt regimes is no longer acceptable behavior. We can hope that communications technology and satellites can make their contribution.
The second major problem facing mankind is the direct result of the
first. A tremendous number of people wants to be fed, wants to enjoy a
certain standard of living and in order to survive cannot forego advances
in technology. This means that industrial production will not decline
in the future. But industrial processes burden our environment and
only the richer countries will be able and want to afford relatively "clean"
methods. The danger thus exists that we will be smothered by our own rubbish
and that we will have to live with constantly increasing risks of environmental
catastrophes.
Is this just "crazy" or a reasonable suggestion? A very decisive factor
is how far (i.e. expensive) outer space is from Earth in regards to transportation.
So far it is disproportionately expensive to transport payloads into outer
space. Currently 1 kg placed in orbit costs approximately 15,000 DM (US$
10,000). For all of the transport vehicles developed to-date, political
pressure has always required achieving results as quickly as possible.
The cost and efficiency of the vehicles played a secondary roll. Unfortunately
the same can also be said for the American space transport system, Shuttle,
because the originally reasonable concept was completely diluted by political
constraints, bureaucracy and special interests. In the meantime the Shuttle
flights are more expensive than conventional rockets.
In line with this approach, I would like to investigate the question about the transportation costs into outer space. In order to explain the method, I first wish to "answer" a question that could have been asked around the beginning of this century. (Whether it was asked and whether it was answered in this way is unknown to me and in this discussion irrelevant.)
After the Wright brothers had proven that aircraft could be kept in the air using suitable wings, some people may have asked whether someday persons or things could be transported regularly by aircraft across the Atlantic. Following the initial flight attempts this idea would have certainly been ridiculed. In fact however, it is possible in physics to formulate far-reaching conclusions based on minimal assumptions: even around the Wright brothers' era we knew that the air resistance of suitable wing profiles would amount to around 1/20th to 1/30th of the lift. An entire aircraft certainly has more resistance, let's say 1/10 of the lift. An aircraft that flies straight ahead must only generate as much lift as it weighs. It is not necessary to know much more than that to investigate the last question:
g = gravitational acceleration (9.81 m/s2)
m = mass of the aircraft
B is the energy content of the fuel, for example 42,000 kJ/kg for gasoline or kerosine.
When this value for energy content is inserted, s = 10,300 KM results, meaning that under these assumptions a regular service across the Atlantic (7000 KM) is without doubt possible.
Is this calculation realistic? Not exactly: for rocket motors the law in physics about conservation of motion must also be satisfied. The technological level determines how close we can approach the results prescribed by the law of conservation of energy. For our purposes, I will now be quite conservative and assume a conventional rocket motor to analyze the mass relationships. I use a hydrogen/oxygen propulsion system as a basis. Even in the long term this is certainly a good choice:
Mstart / Morbit = e ( Dv / Isp )
Dv = velocity needed to reach orbit
This formula already compensates 2 km/s for losses during launch from the Earth's surface. Furthermore, it can be assumed that the payload will only amount to approximately 50% of the mass arriving in orbit, so that in this simple calculation only 25 to 100 kg of LH2/LO2 (liquid hydrogen and oxygen) are required per kilogram of payload.
These numbers are definitely too pessimistic because numerous possible improvements are not considered. Certainly an aircraft in routine service into outer space would employ an air-breathing engine during the first segment of the flight. Since it is thus not necessary to carry along oxygen for consumption during a significant portion of the flight, the Isp of the motor would increase during this segment to 20,000 m/s.
Likewise left out of consideration is the probability that electrically powered modules will be used to achieve a high orbit so that only a low orbit will have to be reached with the LH2/LO2 space transportation system. The costs for the transfer into the higher orbit will be predominantly capital expenses since such a module will only contribute a small mass. It is therefore quite conservative to use the lower value of the mass relationship just calculated for the remaining considerations.
Based on 25 kg of LH2/LO2 per kilogram of payload, the resulting energy requirement amounts to an energy expense of 125 kWh per kilogram of payload, or 5 DM/kg (at 0.04 DM/kWh).
If we assume that a mature space travel industry can provide transportation with the same efficiency as the present-day air travel industry, meaning at four times the energy cost, it will cost around 20 DM to carry 1 kg of mass into orbit. The transport from space back to Earth requires only a quarter of the energy, meaning that we can expect around 5 DM per kilogram.
As mentioned at the beginning, the costs today for transportation
into outer space lie nearly 1000 times higher! The reasons for this discrepancy
are not primarily technical, but are a consequence of the different goals
set for the space flight industry. Up until now no serious efforts have
been undertaken to create a truly efficient reusable spacecraft.
In fact the computed transportation costs lie only insignificantly higher than today's air freight rates, by at most factor 2. This means that commodities whose price substantially exceeds 100 DM/kg are made only slightly more expensive due to the transportation. In other words, the physics of space transportation predicts that transportation can be cheap enough that an industrialization of outer space will not be appreciably hindered by the transportation costs.
It is expected that fossil fuels will become scarce in the coming century. Furthermore we will certainly be able to supply only a portion of the world's energy needs from solar power. Hence, it appears to me to be unavoidable that the nuclear industry will continue to gain in importance, whether we like it or not. Thus portions of the nuclear industry would likely be one of the first candidates for relocation into outer space.
The current directives and procedures for granting approval certainly cost much more than transporting materials into and back from outer space. At these rates, the disposal could even be considerably cheaper that the terrestrial alternatives, even when additional security measures to prevent accidents are considered.
But many other industries have products whose manufacturing processes
also damage the environment or endanger life and which are costly enough
to justify production in outer space.
The picture of the 21st century, as I have outlined it, has the same "mistake" as all futuristic projects: very large investments are necessary until the efforts start to bear fruit. The present-day industries are certainly not in any position to make such long-term investments. In such situations in the past, the governments have had to underwrite the projects until they could carry themselves. In the case of industrialization of outer space, the problem is more difficult because it will involve more than a single country, it is a global undertaking.
Until now the East-West rivalry has prevented us from embarking on this tremendous effort. The end of the Cold War has perhaps opened the chance to pursue jointly those projects that will create a more livable world for mankind in perhaps 50 or 100 years. There is hope today for the first time that the crazy armament production which has consumed unbelievably large funds and resources can be reduced to a significantly lower level.
This would also release an enormous industrial potential which could be used for the tasks just described. To be sure, all of the politicians are still under shock due to the changes in the international situation and the immediate problems resulting therefrom. But perhaps there may be a chance within this proclaimed new world order to undertake such long-term tasks in serious manner.
The development of outer space is currently at nearly the point where flying was after the trans-Atlantic crossing by Charles Lindbergh. We know that it is possible and important aspects have already been demonstrated. At least one area, that of communications satellites, is commercially useable. There is also another parallel to flying: transportation of the mail was one of the first commercial applications of the young flight technology.
The currently extremely high transportation costs oppose a truly broad usage of outer space. The clear consequence is that the development of a space transportation system which can be used as easily as the present-day aircraft should receive the highest priority. Furthermore, intensive research of the Moon is very important because we still have no clear picture of what raw materials are available for future human activities there.
In conclusion I would also like to mention a side effect of the proposed usage of outer space. In the past several years, it has become increasingly difficult for young people to find tasks that represent a genuine challenge. A society, which can satisfy its younger generation materially but intellectually provides scarcely more than game halls, should not be surprised when general aimlessness and frustration spread, resulting in various social problems. I believe that we owe it to our youth to undertake tasks that advance mankind and with which young people can identify.
I hope that I was able to show in this article that despite all the
complaining space travel has become even more important today. We are indebted
to the communications satellites that many people are better informed today
and that power-hungry politicians find it increasingly difficult to deceive
and keep the populace uninformed. If development continues along these
lines, perhaps a new world order will truly arise in which major projects
are undertaken for their true value and not only for prestige. Then there
is hope that our world will be still habitable with quality for the upcoming
generations.
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on 22May95