Questions asked again and again

Can you see the Great Wall of China from space?

This question is asked very often, and sometimes it is not phrased correctly, just like: "Can you see the Great Wall of China from the shuttle or from the space station?". Of course you can see it from there! (Although personally I was not able to see it, as our inclination was not enough, or to put it in other words: our mission did not take us over that Wall.) In the special programme "Looking down on the Earth with Marilyn Monroe" I thoroughly explained that everything larger than 30 metres can be recognised with the naked eye from a near Earth orbit. And of course also the Great Wall.

But the well-known rumour is as follows: "Is the Great Wall of China the only man-made work (incl. cities etc.) that you can see from the Moon?" As (unfortunately) I cannot answer this question from my own personal experience, I asked two of my Apollo colleagues - Charles M. Duke (Apollo 16, 5^th moonlanding, April 1972) and Eugene A. Cernan (Apollo 17, 6^th moonlanding, December 1972) - to enlighten us with the answer. Their answer was as follows:

Charles M. Duke (Apollo 16): "... I do not think that you can see anything created by mankind from the Moon. Nobody saw the Great Wall of China from the Moon. You cannot see any large cities or man-made objects from the Moon. It is already difficult enough to see the different continents from the Moon. ... It is a common misunderstanding that we were able to see the Great Wall of China from the Moon. I do not know how this came about."

Eugene A. Cernan (Apollo 17): "There are NO man-made objects that you could see from the distance of the Moon, neither with your naked eye nor with the monocular we had with us on the Apollo mission. ... Yes, you can see the Great Wall of China from 200-300 miles, from the Earth orbit of the shuttle, in space. I could also see the Dome Stadium in Houston on Gemini IX with my naked eye. But these things, including large cities, cannot be seen from the Moon neither during the day nor at night. ... You should realise that the Earth, which appears four times larger than the Moon , is covered in oceans and clouds. From the Moon, we see the Earth just as the Lord created it, we do NOT see any man-made objects."

I think this is an answer to this probing question once and for all.

Why does the shuttle turn right after the launch?

The shuttle turns around all its three axes shortly after the launch. I.e. the shuttle turns around its longitudinal axis (roll), rolls more and more "on its back" (pitch) and swings to the side (yaw); the turn around the longitudinal axis is the most visible one. These manoeuvres are mainly due to a slight swinging of the outlet nozzles of the boosters and the liquid engines, and rather not to the tail unit of the shuttle. "Roll" and "yaw" manoeuvres together take the shuttle into its previously determined inclination^[1]. And the change of the flight direction also makes it easier to fly back to the runway next to the launching pad in case of an emergency when the mission has to be aborted, e.g. because of a failure of the propulsion systems. Furthermore, the s-band aerials on the ground and of the shuttle are able to "see" each other better - radio communication improves. The "pitch" manoeuvre slowly turns the shuttle on its back, and together with the "yaw" the shuttle is brought to an Eastern path, as the shuttle is not only supposed to raise vertically into the air, but to transfer into an elliptical and later a circular orbit around the Earth. This position on the back makes it also possible that the crew is able to see the Earth's horizon - which is useful, but not really necessary. And last but not least - this is very important - the position on the back reduces the structural load of the whole system: The boosters push the system towards the top, whereas the shuttle pulls down the system because of the lift of the wings. The sum of these two differing forces determines the direction of flight, but they also strongly pull the braces which tack the shuttle onto the outer tanks. The increasing back position always generates a small negative flight wind attack angle pressing the shuttle onto the braces and thus lifting the strain on them. This acceleration force in the direction of the lower shuttle side is the reason why the astronauts feel as though they were sitting normally in their chair, although they and the shuttle are actually upside down.

How much does a shuttle mission cost?

Well, that depends^[2] (all details refer to 1992): At the end of 1996, the NASA estimated that the preparation of a shuttle for a new flight together with the operation of the flight as such was about $414 million. If you include the development cost for the shuttle dividing them among all the flights until the end of shuttle operations, approximately in 2007, the cost per flight is about $900 million. The slot for a mission, that is the right to be launched and integrated into the flight plan (or also be eliminated from it), is "already" available at the NASA for $45 million.

Why do the Americans not fly back to the Moon with their shuttle?

What happened with the Saturn V construction plans?

The relationship of payload (shuttle) to total weight of the system is designed so that the shuttle is able to achieve a maximum orbit height of 800km. So in the future the shuttle will be able to reach the International Space Station at a height of 400km, but it would never be able to reach the Moon at a distance of 380,000 km. Only the Saturn V rocket was designed to reach that goal. Contrary to the common opinion that the blueprints of the Saturn rocket would have been chucked out, they are stored on microfilm at the Marshall Space Flight Center in Huntsville/Alabama. But that does not mean that NASA would be able to build a new Saturn V and fly to the Moon or Mars again from one day to the next. The problem are not the plans, but manufacturing the component parts from the 1960s. There is hardly a component which is still manufactured today. Most of the production facilities would have to be set up again. And apart from that the former launching platforms were modified for the shuttle launches. It would mean enormous efforts for the NASA, and this is why they will certainly set up new launching platforms and a new, more modern rocket for this kind of flight.

How long is the unprotected human body able to survive in space without being harmed?

It may sound really surprising: at least 60 seconds, provided that you do not hold your breath, but rather on the contrary, you let the air escape from your lungs, and provided that the pressure drop is longer than 0.5 seconds, something which you can almost always assume. Because it is only enclosed air which expands in the vacuum, and not the solid, fleshly parts of the body. If you held your breath, the same thing would happen which also happens with careless scubadivers when they rise quickly from deep depths of water: the strong pressure burden bursts the lungs. You could also encounter problems with your middle ear, as it also contains air, but it is linked with your mouth by means of the Eustachian tube. Should this tube be blocked, because it is swollen as a result of a cold - that is why people often get an inflammation of the middle ear when they have a cold - then the air is not able to escape from the middle ear, and with quick pressure drops the eardrum bursts.

Of course these 60 seconds will not be very comfortable. After 6 seconds the body liquids are converted into vapour (theoretically the blood with 37°C boils with zero pressure). The vaporisation leads to a collapse of the lungs and the lack of pressure interrupts of the blood circulation. After 15 seconds your senses become disturbed because of the lack of oxygen supply, and after 20 seconds you become unconscious. You would then at least not notice the pain because of the nitrogen boils in your joints. But if after these 60 seconds at the latest the pressure rises again to normal levels, the body resumes its normal functions, and there are theoretically no long-term damages - but I would not vouch for it, as I haven't tried it out myself!

How do the emitted gases of the shuttle damage the ozone layer?

People time and again assume that the chemical residues of the solid fuel boosters could contribute to destroying the ozone layer. Three independent US-American teams determined the influence on the stratosphere (where the ozone functions as an active protection against UV light). The following comparisons show the shuttle's contribution is indeed very small. It should be mentioned beforehand that it is mainly the chlorine of the CFCs which damages the layer. These are the contributions to the chlorine content of the stratosphere:

            natural sources:          75,000 tons/year

            industrial sources       300,000 tons/year

            from the shuttle                 725 tons/year

This clearly shows that the shuttle's contribution only amounts to 0.24% of the industrial sources, and also only almost 1% of the natural, non anthropogenic sources, i.e. it is still below the natural fluctuation margin, even if the shuttle were launched every month. And by the way, the space debris, which burns up sooner or later in the Earth's atmosphere, only insignificantly contributes to the impairment of the atmosphere with its estimated at some tons/year.

How warm is it in space?

This question is more complicated than you would think. When you talk about the temperature on the Earth, you usually mean room temperature, i.e. the temperature of the air, leading within a very short amount of time to a temperature balance of all the bodies in a room. But that is not the case in space. You do not have any balancing air, so all the different components have their own temperature depending on whether the Sun shines on them or not, and on how near they are to the heater "Sun". A body far away from every star assumes the equilibrium temperature of space, the temperature of the so-called background radiation. It amounts to 2.7° Kelvin or -270° Celsius. A black part at the distance of Saturn is "heated up" by the Sun to already -160°C, and the shuttle side turned toward the Sun is already quite hot with +70°C. The temperature of the shuttle side turned away from the Sun can go down to -50°C. If the shuttle were able to fly to Venus, it would "stew" at temperatures of +120°C, and near Mercury it would "roast" at +270°C.

How did the Challenger astronauts die during the shuttle explosion in January 1986?

The cabin of the shuttle where the astronauts were was not destroyed during the explosion. The visible part of the explosion was the deflagration of the remaining fuel of the external tanks. The later forensic report clearly states that the impact of the explosion did not cause fatal injuries to all the astronauts. At least some of them were still conscious after the explosion, this was also deduced from the manually activated emergency oxygen installations, which were meant to be for emergencies on the launching platform. The explosion however catapulted the leaking cabin to a height of approx. 30 km, where there is so little oxygen that you remain conscious only for a few seconds - the astronauts did not have a protective suit with emergency oxygen as they have today. And they did not recover consciousness until the impact on the sea. This very hard impact with a speed of about 350km/h certainly killed all the astronauts. Their bodies remained in the depths of the sea for several weeks, until they were recovered. After the medical examination they were buried.

How probable is a new shuttle disaster?

After about 120 shuttle flights at the moment, according to an investigation of the Science Applications International Corp. of San Diego, NASA estimates a probability rate for a new disastrous accident of 1-to-145 (one disastrous event in 145 flights). The flight statistics of manned US missions from February 1997 shows a probability of 1-to-56 (if you also consider the fatal accident of the Apollo-1 ground tests). So from a purely statistical point of view, the expected risk is three times lower than in the past 30 years. And the risks of a Russian flight are quite similar.

If you ask yourself what is the critical point of a mission, the lion's share, 60% of the mission risk (1-to-248) is attributed to the launching and ascent stage. And here the most critical points are the three liquid engines (1-to-410)^[3], the two solid fuel rockets (1-to-1152), the shuttle with its complicated electronic and hydraulic system (1-to-4700), and last but not least the external tank (1-to-11,223). If you refer all the fatal failures to one complete mission, the shuttle with its hydraulic system and the tiles (landing!) are the most fragile points with 1-to-397, closely followed by the liquid engines with 1-to-410, the new solid fuel rockets with 1-to-1152, and, negligible with 1-to-10,000 and less, all the other shuttle systems. A fatal risk of a collision with a piece of space debris (1-to-15,000) is negligibly small compared with these figures.

Just two comments regarding these figures. Not only do they all contain an insecurity of plus-minus 50% (mission risk 1-to-145 more specifically means 1-to-76 up to 1-to-230), but just like any statistical figure they cannot make any statements regarding one individual mission. A fatal failure could occur during the next mission or only after the 145^th, or even after the 230^th mission.

But you only get the right feeling for these figures if you compare them with fatal risks in everyday means of transportation. The probability of a German national to suffer a fatal traffic accident during his or her 75 years of life exactly amounts to 1-to-100^[4], and the probability of businessman who is a frequent flier to die during a flight accident is 1-to-590.

How much does German astronautics cost?

First of all, it is quite interesting to have a look at what Germans think it might cost. According to a survey of the Institute of Economic and Organisational Industry of the University of Munich from 1996, most Germans (68%) estimated that the yearly tax expenditures per person would be 25 to 2500 euros. This opinion, that astronautics is expensive, goes hand in hand with another, widespread opinion, which was verified by the survey, that astronautics may be useful, especially for environmental and climate research, and it may have the potential for new high tech developments - in other words, astronautics may be important for our future, but it is definitely too expensive. We are in accordance with the assessment regarding the importance of astronautics, the costs however are far more modest: In 1996 every German citizen paid 9.70 euros for astronautics. 6.60 euros were paid to European astronautics, the ESA, and only 3.10 euros for national astronautics. Every German citizen (and, to be fair, I only include the West Germans as the preparations started already in 1987) only paid € 0.77 per year for the execution of the German D-2 mission, the mission I participated in as an astronaut. The German citizens themselves say that they are willing to spend that relatively small amount for astronautics (apart from a few exceptions who do not want to pay anything at all). In the light of the many new and important results I think it is inappropriate that certain politicians claim that manned as well as unmanned space travel is far too expensive, and that Germany cannot afford it.

How much do astronauts earn?

This much is certain: astronauts have to be idealists. You cannot make a lot of money as an astronaut. A civilian joining NASA as a new astronaut, gets a gross salary of about $ 45,000 per year in the beginning (as at the end of 1996). During his career as an astronaut he continually gets promoted, and may earn up to $ 85,000. But to be fair, it should be added that usually American salaries are lower compared with German ones. With reference to the German salary level, that would amount to about € 50,000 to € 100,000. The NASA astronauts with a military background as pilots (and that is most of them), who still have their rank and title, earn about the same amount. The ESA astronauts are better-off. Their base salary as newcomers amounts to € 70,000 and may be increased up to € 85,000 (taxes already deducted!) - older astronauts with more experience and management tasks can even get more.