For most people, space is a place they can only see from afar and not one they will ever visit themselves. Astronaut Ulrich Walter, on the other hand, was there – and describes what it feels like to fly into space and land back on earth.
There I am, lying on my back, legs bent, about 60 meters above the ground in the middeck of our 2,000-ton Columbia, one of the American space shuttles that is supposed to take us seven astronauts into space in a few seconds. This is the place and time I’ve been working toward for years. I close the visor and… hear nothing! I can only perceive the staccato air-to-ground radio traffic, reduced to the bare essentials. You are cut off from the outside world. You don’t hear anything anymore, and in the mid-deck, where my place is at the start, you can’t see anything either, except for the wall of drawers, or rather above one, which you have to stare at all the time and which you hope won’t happen to be one at the start dismissed from their drawers.
But then the start! The shuttle’s three liquid engines are fired six seconds before liftoff. As a result, the vertical shuttle swings slightly to the side because it is still held on the ground by bolts on the two white solid fuel boosters a few meters apart. Therefore, in these six seconds, the astronauts first swing forward about 1.5 meters and then back again, like in a swing ship – which you can feel very clearly. The shuttle vibrates and shakes so badly that it sends you through your bones, just like an earthquake.
And then you only hear over the radio: “SRB Ignition – Lift-Off!”
In 1993, author and astronaut Ulrich Walter flies into space for ten days. In his book “Hell Ride through Space and Time” he reports about the fear at the start, weightlessness, space sickness and the view of the earth. This text is an excerpt from the work.
The Solid Rocket Boosters are ignited and the shuttle takes off at the same time. Sitting inside, I don’t hear the overwhelming thunder that shakes the diaphragm of viewers outside (the IMAX theater is exaggerating a little here) and the bright, lashing crack of the solid-state boosters (which, on the other hand, I miss in IMAX).
The shuttle has taken off… and what do you feel? There is no trace of 3g, the notorious strong acceleration of three times the strength of gravity! The thrust of the drives, at least twice 1200 tons of thrust from the two solid-fuel rockets plus three times 185 tons of thrust from the three liquid drives, exceeds the 2000 tons of the entire system by a generous 50%; but the acceleration is no greater than that of an airplane takeoff.
Prof. Dr. Ulrich Walter has a doctorate in physics and is a scientific astronaut. Walter embarked with six other astronauts in late April 1993 aboard the Space Shuttle Columbia for the D-2 mission bound for Earth orbit. Since March 2003 he has held the chair for space technology at the Technical Elite University in Munich and teaches and researches in the field of robotics in space and system technology. His SPIEGEL bestseller The Devil’s Gone in the Black Hole, Hell’s Ride Through Space and Time, A Different View of the World and The Crazy World of Physics have been published byKomplett-Media Verlag. His documentary series Spacetime on YouTube was also viewed internationally by up to 3.3 million viewers per broadcast. His textbook Astronautics – The Physics of Spaceflight with 2.8 million downloads is the standard work for space travel at universities worldwide.
The solid fuel boosters are now the workhorses, pushing the shuttle through the cloud cover, and their elemental force defines the experience of the first two minutes of ascent. Their slightly uneven burning, caused by an inhomogeneous distribution of the fuel, gives the shuttle fast, strong acceleration shocks that shake it through and through and stimulate it to oscillate irregularly. Everything on board the shuttle is shaken mercilessly. It’s like riding at 100 km/h over cobblestones – and there is silent silence. Very few words are exchanged between Mission Control and the Commander.
Everyone involved knows that this is by far the most critical moment of the entire mission. If something unforeseen happens now, there is absolutely no salvation. Even the many improvements after the Challenger disaster in 1986 have not changed that. Solid fuel rockets are like New Year’s rockets – you can’t turn them off. Even blasting off the boosters wouldn’t help! Their thrust is so enormous that the high drag in the event of a sudden loss of thrust would hit the entire shuttle system and the entire shuttle would fall apart! So if, as was the case with Challenger, the jet of fire from a booster that had become porous burned its way into the external tank like a cutting torch – then as now, nothing could be done about it. In these two minutes, the crew is at the mercy of the shuttle. Hence this wordless silence.
The acceleration, the force with which one is pressed into the seat, has meanwhile slowly increased as the shuttle system has become lighter due to the spent fuel. Shortly before the final fire of the solid booster, exactly two minutes after lift-off, 1.8 g, i.e. 1.8 times the gravity of Earth, is reached. The burned-out boosters quickly lose their thrust to zero, and soon they are blown off.
When that’s over, the shuttle breathes a sigh of relief. One or the other can’t suppress a “Yeahhh” and everyone thinks the same way: The greatest danger is over! The problems that could still arise now can all be mastered somehow, they would no longer be so life-threatening.
After this liberating thrust hole, in which the boosters were blown off, only the liquid drives generate the thrust. Their burn is much more even than that of the booster. It has also left the dense, more turbulent parts of the atmosphere. There are hardly any vibrations to be felt. The entire harmonious power of the drives is now expressed exclusively in the steadily increasing pressure on the seat. After 4 minutes 20 seconds comes the “Negative Return Call” (which means that in an emergency a return to Kennedy Space Center and a landing there is no longer possible possible) from Mission Control Houston.
After a total of 7 minutes, when the huge, rust-red external tank is 90% empty and the shuttle system is less than 200 tons light, only then has the thrust from the three fluid engines increased to 3 g, so that you have to force yourself to breathe , because it is simply more pleasant not to breathe – despite shortness of breath – than to push your chest and heavy suit upwards by breathing.
The drives are now throttled and it goes on for another 1½ minutes at these 3 g. Then, just before the tank is completely empty, the commander lets you know: “In 10 seconds we have MECO” (Main Engines Cut-Off ), and within a few seconds he shuts down full thrust to zero. Just as suddenly, the pressure of 3 g is released into weightlessness – I’m in space!
Here in space you are immediately captivated by weightlessness, a feeling that never exists in this form on earth. First of all, this new experience does not have a beneficial effect on about 70% of all astronauts, who instead suffer from space sickness. You notice it yourself: Every quick turn of your body, every quick movement of your head makes you queasy. As a first countermeasure, many involuntarily pull their heads between their shoulders, which severely restricts head movements. This mitigates, but does not fundamentally prevent the course of the last meal to the top. Holding back only makes things more tedious. Grab the bag in your breast pocket and let things run free. Many also have headaches, back pain and persistent discomfort. Those who are no longer able to do anything have their colleague give them an injection of Phenagran (a sedative), their commander write them as “unable to work” for the time being and look for a quiet corner for the next few hours to cure their space sickness symptoms – preferably theirs bunk.
Now the good news: It’s all over after 36 hours at the latest, and then you can really enjoy weightlessness. If you now close your eyes in peace and let yourself drift slowly through the room, arms and legs slightly bent in a very relaxed posture, then there is nothing that could influence you and you can concentrate completely on your own feelings.
At first I felt like a dream repeating itself. When I was young, I often dreamed that I was walking down a sloping street in front of our house. I got lighter and lighter, and eventually I took off and floated. I wasn’t flying, I was floating, and nowhere else in everyday life have I ever had this feeling. And exactly this feeling that I had during the dream is almost identical to that in weightlessness. It is known among psychologists that the dream of running, taking off and floating is very common among people. So is this dream an unconscious experience of weightlessness? How can the body dream something very realistic that it has never really experienced? Or is this dream a pleasurable variation of the mind on the brief but dangerous zero-gravity experience of “falling” in everyday life?
What do you feel in the state of weightlessness? The first thing you notice is that something important is missing. What is my relationship to the environment right now? Where is the ceiling with the lamps and where is the floor? I do not know it anymore. I no longer have a feeling for it either – and there really isn’t an up or down anymore! This missing relationship radically changes my perception. I no longer feel embedded in a world that just surrounded me, but all being is reduced to me. How can there be anything else that I no longer have any relation to? And even if there is something somewhere, isn’t it the same as if there weren’t? I have the elementary feeling of being alone. I am the world – nothing else!
This focus on the ego only makes you listen to yourself even more. What has changed about me? I notice that nothing weighs more. The clothing, which still keeps you warm, is weightless and floats around your body like a shell and is almost nowhere to be found. This is so quirky and unusual that you shake your shoulders a little to feel if the clothes are still there.
But it’s not just the burden of clothing that’s missing, the burden of one’s own body has also disappeared. No more body pressure on the soles of your feet like when standing or on your buttocks when sitting on the ground. The arms are nowhere as usual. It’s really strange: Only in this situation, where you can’t feel anything from your body any more, do you fully realize what stresses your body really has on earth, although it should be exactly the other way around! Only after this experience did I become aware of the barely perceptible drooping of my cheeks today. And that light butterfly feeling in my stomach area, I now know, is the pulling of the intestines under the influence of the gravity of the earth. In weightlessness there is simply absolutely none of that anymore. You are “completely carefree” in the truest sense of the word.
Totally carefree. How do I then actually notice whether I have a body if not from these external impressions? And your own answer is astounding: It seems as if he actually doesn’t exist anymore! Nothing, absolutely nothing, points to him anymore. Strange, a being without a body! But then what is it that I feel as my being? I had my body on earth, and only afterwards do I realize how I only defined my own being in the heaviness of the earth through the experience of my own body. I shake my shoulders slightly and tap my index fingers with both thumbs. Yes, he’s still there – I’m still there! But now, without him, am I still here? Of course I’m still here, I can feel it, otherwise I wouldn’t be able to ask myself this question! But that’s exactly it! The only thing left to me, what defines me, is thinking. So I think I am! That’s what’s so special about weightlessness: it’s reduced to you, to your spirit.
I look out expectantly and see… water! Nothing but deep blue water! My daily experience that the earth is practically all land is deeply shaken. Two thirds of the earth’s surface is water and not land! Here I really get it. It’s probably the Pacific Ocean and it will stay that way for the next half hour, which is the next 15,000 km. The little that you see is enough to amaze for the time being. Radiant white cloud formations artfully veil the blue of the sea. One might think that the earth in space arose from a Bavarian whim: The clouds together with the sea form a composition in the Bavarian national colors against the pitch-black background of space.
From a distance of 300 km the earth cannot yet be seen as a whole sphere, but the curvature of the earth runs straight along the upper field of view if the windows are arranged correctly. Now you can see for the first time what it means that the diameter of the earth is 12,750 km, but the atmosphere is only about 20 km thin. In this striking size comparison, our terrestrial protective shell appears like a wafer-thin layer of frost, so fragile that one might think that the slightest breath of wind would suffice to simply sweep it away and that every touch, every slightest tampering, would leave serious scratches. And in this frail, delicate layer everything that we call life takes place. Life, a balancing act between the mighty, impenetrable mass of earth and – a look to the side – the life-hostile nothingness of the universe! Man does not even inhabit the whole earth. Mankind is just an inconspicuous bacillus in an earth-encompassing soap bubble in the infinite sea of the universe.
“Höllenritt durch Raum und Zeit” by Ulrich Walter was published in 2017 byKomplett-Media Verlag.
After a few days, however, you then know “your” earth and you begin to see connections, overarching properties that you would never have expected before. For example, people have learned to recognize continents by their colors. Whenever you look down and see land, you know what continent you are over, because each continent has its distinctive color! South America, for example, is dark green. The color of the rainforest dominates this continent. Africa with its extensive Sahara desert and the adjacent steppes and savannas presents itself in an ocher brown tone. Australia: the entire continent a deep crimson! Indonesia with its many islands, whose rainforest is always in the haze, also a dark green sea of color. Europe? In the south it is still a friendly light brown, otherwise only grey-green – should the equally desolate clouds, for once, allow a view of the ground. Even the clouds, a desolate grey. And here one begins for the first time to derive the simple but correct astronautical rule of thumb: Where man cannot live, in the ice and sand deserts, the world is beautiful and where man lives, can live, the world is not or not so pretty anymore!
It is also very gratifying to see the futility of what seem to be important human problems. The news on television, full of state and military as well as diplomatic disputes. From space, the earth has a very different face. Humans don’t matter to them. She could do just as well, maybe better, without him. In their stoic calm, people are as important to them as bacteria are to humans. State borders? Nothing of the sort characterizes the earth. Boundaries only exist in our heads, infiltrated since the first days of school! What matters are countries and continents. Two exceptions, perhaps: the dead straight border between Israel and Egypt – it runs visibly along the eastern edge of the Sinai, and the equally straight border between Angola and Namibia, 200 km north of the Etosha Pan in southwest Africa. Here as there, however, it is not the border itself that becomes recognizable, but the stark contrast between the extensive land use between the neighboring states.
For the astronaut who just wants to look at the earth, the onset of the three quarters of an hour of night may seem wasted time at first. A little later, when his eyes have adjusted to the darkness, the earth at night is a very special spectacle.
First there are the evening heat thunderstorms, which drag on into the earthly morning. The play of lights from the lightning, muffled by the clouds, reminds me in two ways of the flashes of detonating bombs seen from an airplane during night raids in old World War II films. Despite their destructive effect, they emanate a magically captivating spell. Out of context, it flashes in quick succession, sometimes here, sometimes there. Sometimes, however, lightning flashes that flashes up to a hundred kilometers through the clouds, leaving a meandering trail. Unlike the terrifying thunderstorms on Earth, a thunderstorm seen from space looks rather spooky, lacking a very earthly ingredient up here – thunder!
If extraterrestrials ever come to the conclusion, based on evidence, that the earth is inhabited by intelligent beings – although it is debatable whether there really is intelligence on earth – then this realization will surely come to them when it is night on earth. Because at night, when clouds are not obscuring the view, people determine the image of the earth.
These glaring, sharply defined lights of the cities, linked to their suburbs by the cobwebs of the streetlights, are a striking sign of the existence of higher beings. Man has subdued the night. Nowhere can this be seen more clearly than from space. Civilization presents itself as a branched lymphatic system that runs through the land and borders the sea, because it is precisely on the coasts that people prefer to live.
Milky Way. This word regains its very own meaning in space. In order to be able to enjoy the splendor of the starry sky in all its beauty, however, the lights on the flight deck have to be turned down completely. The fascinating thing is not only the enormous number of stars that are revealed, but their merciless clarity. Like the finest needle pricks in a velvet carpet that is backlit, they seem so immovably nailed to the firmament. No sparkle breathes apparent life into them. Their mute existence simply expresses the infinite stillness of the universe.
As beautiful as the view of Earth may be, as an astronaut, and especially as a scientific astronaut, you actually sacrificed the vast majority of the mission time to work. But it’s always the same with memories: Only the beautiful and haunting experiences stick, the monotonous work is quickly forgotten, and time flies by in the truest sense of the word.
After ten busy but wonderful mission days, I head to my seat and prepare for gravity re-entry by reading through the checklist as I did at launch, particularly the emergency cue card. That gives me the peace of mind that I have everything under control.
Finally, a precautionary measure: so that the circulation does not collapse the first time they stand up after landing, the astronauts are required to increase the amount of fluid in their bodies. This requires swallowing several salt tablets and drinking lots of water. The salt binds the water in the body and does not allow it to be immediately excreted by the kidneys. In any case, this procedure is much more pleasant than having to drink several liters of salt water. We are now ready to re-enter Earth’s atmosphere.
75 minutes or half an orbit before landing, the commander first turns the shuttle so that it flies tail first. For us this is completely irrelevant, yes, you don’t even notice it, because in weightlessness there is no up and down. Exactly one hour before landing, the orbit drives are fired against the direction of flight for three minutes, whereby the orbit speed is reduced by only 300 km/h: Instead of 28,000 km/h, we are now only flying at 27,700 km/h. However, this seemingly insignificant change is enough to propel the shuttle deeper into Earth’s atmosphere in a slightly elliptical orbit.
In the meantime, the commander has brought the shuttle back into the regular flight attitude and turned it at 35 degrees against the direction of flight. The shuttle gradually loses altitude, and in this phase of the approach the on-board computer controls the shuttle in such a way that the speed will remain constant at 27,700 km/h for the next half hour. The air resistance at these altitudes is therefore only used to reduce the flight altitude at constant speed. You don’t notice much of this approach phase. The aerodynamic drag forces remain so low that the corresponding gravitational forces also remain below 0.2 g, and since you are firmly strapped into the seat with the belts, these weak forces are not yet noticeable. Only an object thrown slightly towards the ceiling, for example a ballpoint pen, shows how deeply one has already immersed oneself in the atmosphere. If it no longer hits the ceiling, but instead slowly reverses its trajectory beforehand, then you know it’s going downhill.
25 minutes until touchdown. Air friction forces have increased greatly, causing the tiles on the underside of the shuttle to glow at 1500°C. The air is heated up so much that radio traffic is also cut off for the time being. You hardly notice the rise in temperature in the suit. You might be sweating with excitement because now the shuttle is shaking significantly. The air density at this 120 km altitude has increased to such an extent that the shuttle behaves aerodynamically and the gravitational forces have increased so much that the anti-g suit has to be inflated. The anti-g suit protects against the pressure of air cushions on the legs and intestines from the blood sinking into the lower body and thus from a blood supply deficiency, i.e. a blackout of the brain. This is when the commander takes control of the shuttle. From this point on, he also reduces the shuttle’s speed through various rolling and turning maneuvers.
12 minutes before touchdown, the heat on the tiles has reduced enough for radio traffic to resume. The shuttle is now 55 km above the Edwards Air Force Base runway and traveling at a speed of 12,000 km/h. I inflated my anti-g suit vigorously again because the g load had increased to 1.3g. This is unusually exhausting after the weightlessness in space. One hears the Commander’s announcements being pushed out more and more; he too fights against physical weakness. I’m glad I’m sitting and not having to stand and hold my weight.
5 more minutes. Now the actual approach to the runway begins. The shuttle shoots at a distance of 25 km, at 2.5 times the speed of sound and in an oblique downwind approach towards the runway. It then performs a precisely defined turning maneuver that puts it exactly in the direction of the runway. The commander now only needs to adjust the shuttle’s angle of attack so that it flies towards the touchdown point at a gliding angle of 22 degrees, almost like a stone for a pilot. The speed has further reduced to 700 km/h. 30 seconds before touchdown, the commander pulls the shuttle’s nose up, reducing the glideslope to 1.5 degrees and slowing the speed to the landing speed. The landing gear is only extended 15 seconds before landing because the previous high speed could have ripped off the landing gear. The shuttle finally touches down at almost exactly 400 km/h: touchdown.
However, one hardly noticed the touchdown, the Commander landed the shuttle so gently. Only by counting down the pilot’s altitude was one able to know exactly how far it was until touchdown. The commander now holds the nose of the shuttle into the airstream for a long time after touchdown, so that the shuttle continues to lose speed. When the front landing gear finally touches the ground, the drogue parachute deploys; its effective deceleration of the shuttle can be clearly felt in the shuttle. Exactly one minute after touchdown, the shuttle came to a standstill. I lean back and relax and know: the earth has us again!
