Readers’ Questions

Black Holes, Soyuz vs Shuttle and Galaxies Colliding

Today we have three readers’ questions that our resident space expert, Robert Brand (Echoes of Apollo), will try to answer with the help and comments from our readers.

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Black Hole and lensing effect

Black Holes

Reader and student  “Mistry Best” asks “I don’t understand the theory of massive black holes. Can you help”

Echoes of Apollo: Rather than us trying to reinvent the wheel, I suggest that you try a source like Wikipedia or your science teacher, preferably both.

Here is the link to the Wikipedia article: http://en.wikipedia.org/wiki/Black_hole

You also asked about singularities. These can come in many forms so it is best to know a bit about black holes first and then we can look for a good answer for you another time.

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Soyuz vs Shuttle

Usman Munawar: Hi, I just have a question about the difference between the Space Shuttle and the Soyuz and why does it take three days for a Shuttle to get to the International Space Station (ISS) and for Soyuz it only takes 3 hrs.

Soyuz TMA-7

Echoes of Apollo: There are a few reasons for the Soyuz speed and the Shuttle’s slow pace.

Soyuz has to get there reasonably fast as it does not have the supplies to wait around. The same returning to earth. The Shuttle needs to do inspections of the heat shield tiles once in orbit and can also do science before reaching the space station. They can also do some science after leaving the ISS. The Shuttle has a bigger payload than Soyuz and must take advantage of the longer path to minimise the fuel drain. There are many reasons, but the tile inspection takes a day and that is fairly recent as the foam falling off the main tank is an issue and we have only come to realise this in recent years. Where the shuttle can wait for the right weather when landing, Soyuz needs to be down in a few hours (preferably). So, Soyuz is fast, but has to be fast, but it is a new vehicle every time and the Shuttle is almost 30 years old, so the Shuttle is bogged down with safety procedures. It also must enter the earth’s atmosphere at 0.5 degrees and has a long approach path where Soyuz can be up to 5 degrees and is fast once committed to descent. Soyuz can tolerate much more heat and speed than the Shuttle’s Tiles and leading edges can handle.

Usman Munawar: Yes, thanks a lot, that explains a lot. One more thing what would be the earliest date the Ares 1 would have a flight to the space station? Moreover, what would be the benefit in terms of time with Ares 1? I hope that would not require a lot of inspection time as the space shuttle and the pay load capacity for it would be the same as the shuttle.

Echoes of Apollo: We are looking at around 2015 before NASA has a working human space flight capability with the Ares system. Whether this will be an Ares 1 or Ares V version is not yet clear. The reason that the Shuttle does an inspection is to know at the first opportunity whether they will need repairs or rescue. The Ares will not have this problem as there are no leading edges or tiles to damage. Unlike the Shuttle, the Ares capsule and payload will be at the top of the vehicle and ice and any other material cannot damage them. There should be no or little inspection time. There were only brief system check for the Apollo systems before proceeding with their missions with both Apollo Skylab and Apollo moon missions. Ares 1 would be mainly a taxi vehicle to space while Ares V will be a heavy lift vehicle. If NASA use other companies for “taxi” trips to the ISS, they will not need Ares 1 capability.

John Sullivan: I really liked this article. The question was raised by me as well earlier about why it takes so long to get a Shuttle down to Earth as there is technically a “landing opportunity” (weather permitted) over KSC at least once, and most days twice a day. When the Shuttle ascends the tank separates and the Main Engines cut off at less than 68 miles altitude. Entry Interface (EI) – the first encounter with the atmosphere on the way back happens at a higher altitude – 74 miles. In other words, ascent with the Shuttle is all about speed in VERY rarefied (thin) air, but not about altitude. From the upper reaches of the atmosphere the OMS engines are fired to “tweak” the altitude mainly by adjusting speed – not course. The course of the Shuttle relative to the orbiting Space Station is mostly determined by launching towards the right direction in the tiny “launch window,” where Earth, the pad, and the passage of the ISS are all in the right place at the right time. Returning also includes timing of lining up the spinning Earth and the target runway with the ringed orbit around Earth above by the separated return vehicle. The “course” of ascent is mostly set by the “roll maneuver” and there isn’t much deviation, but returning to Earth there is an “aerobraking” technique not unlike turning on a ski slope that allows course changes to refine the “cross-range” delta between where the PIM (momentum) is taking the Shuttle and where the runway is. It’s a unique capability that the capsules have only in limited experimental form. The Shuttle basically “deorbits” from the high altitude of the ISS – 200-250 miles. (The Hubble was 100 miles higher, and so was Atlantis last year). When I asked a NASA insider why it takes so long, his best answer was “it takes 1000 people to get the Shuttle ready for launch, but only the astronauts aboard can prepare the world’s most complicated vehicle ever built for landing.” Another 5-star article, and thank you very much. I always learn a lot.

Echoes of Apollo: John’s last statement must be tempered with the fact that before the astronauts can bring back the Shuttle, they must upload landing information from the earth for their approach. It would be very hard to bring back the Shuttle without this data upload with all the flight parameters precalculated for position, conditions and other variables. Remember, although the Shuttle passes “over” the Kennedy Space Center up to two times a day, there are thousands of miles difference in the orbital position on different passes. Basically we are saying that it passes close enough to land, but that approach path will be very different each time. The fine details are left to the ground crew and uploaded before landing is attempted.

Here is a story we did on the STS-128 landing – note the initial high angle of attack during initial re-entry. It is not sustained as the shuttle needs to fly and to stay cool:

http://echoesofapollo.com/2009/09/11/sts128-headed-for-edwards-landing/

Navigation Software Uploaded for Edwards

The weather at the Kennedy Space Centre is poor and outside of the limits for the shuttle landing. The Edwards Air Force Base has been activated for Discovery’s landing and is prepared and waiting. The last shuttle mission to land at Edwards was STS126

The Crew has suited up in their orange pressure suits and they have been drinking fluids in preparation for returning to normal gravity.

Mission Control have just radioed that the shuttle is “GO” for the de-orbit burn.

The de-orbit burn will take Discovery out of its current orbit and place it on a trajectory for entry over the Pacific Ocean. Discovery will then do a series of braking maneuvers before heading for a landing at Edwards Air Force Base in California. Discovery will make a 210-degree right-overhead turn for approach to Runway 22 , touching down at 8:53pm US EDT – 5:53 pm US EDT
This description of the Re-entry from the NASA website:

Re-entry and Landing

The commander begins the de-orbit burn by firing the orbiter’s engines to slow its speed and take it out of orbit. Using the RCS engines, the orbiter is turned around so that it is moving backwards at a slower speed. To maneuver the orbiter while it is in this position, the commander uses the RCS engines to control roll, pitch and yaw motions. The OMS engines (space engines) are then fired, taking the orbiter out of orbit and thrusting it into the earth’s upper atmosphere. The RCS engines are used one last time to turn the orbiter around so that it is moving nose forward and pitched up slightly. In the upper reaches of the atmosphere the vehicle’s motions of yaw, pitch and roll are controlled by the RCS engines. As the atmosphere thickens, the airplane control surfaces become usable. The orbiter re-enters the atmosphere at a high angle of attack (about 30 degrees). This high angle of attack is used to direct most of the aerodynamic heating to the underside of the vehicle where the heat resistant tiles give the greatest amount of protection.

At an altitude of approximately 30 miles, the orbiter makes a series of maneuvers and S-turns to slow its speed. At 9.5 miles in altitude and at a speed of Mach 1, the orbiter can be steered using its rudder. The on-board computers fly the orbiter until it goes subsonic (slower than the speed of sound: Mach 1). This happens about 4 minutes before landing. At this time the commander takes manual control of the orbiter and flies a wide arc approach. At 7.5 miles from the runway, the orbiter is flying about 424 miles per hour at an altitude of 13,365 feet. About 2 miles from the runway, the orbiter is flying at nearly 360 miles per hour on a glide slope of 22 degrees.

Once lined up with the runway on approach, the orbiter continues its steep glide slope of 18 – 20 degrees. The commander levels the descent angle at a final glide slope of 1.5 degrees by performing a “flare maneuver”. The nose of the orbiter increases its pitch (noses up) which slows its speed. The orbiter touches down at a speed of about 215 miles per hour. It is slowed and eventually brought to a stop by the speed brake, wheel brakes and a drag chute.

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Galaxies Colliding

Hayley Brown asks: Hi there, we have a galaxy coming towards us in about 2 billion years time. First, is human kind going to be around and if we are where would our solar system end up being ?? Because the other galaxy is larger than ours and it has bigger black holes are we going to be sucked in or just spun off into different part of space?

Echoes of Apollo: Okay, I have not looked that far out, but we know what happens to other systems. It can be catastrophic and we could be thrown into the heart of the system where were would not survive. Even nearby or distant supernova or exploding stars could deal us a cosmic ray death blow that would cause our extinction. If we survive this, the milky way galaxy would basically pass through and be spread out into a different shape or most likely it could be caught up into a new merged galaxy due to gravitational forces (most likely). It all depends on size, rate of intersection, range, angle and so many other things. The black holes at the heart of galaxies would not be likely to get us, but plenty of other things are including collisions and dust clouds too dense for our solar wind to withstand. A close enough encounter with another large star could also change our earth’s orbit and that would be catastrophic.

As for whether we would be around in 2 millions years, just look at how we have changed and evolved in the last few million of years. It is very likely that we would be unrecognisable from our current appearance if we survived that long without blowing ourselves up. Given technology advances, we may have even abandoned earth or even this galaxy as a home.

This stuff is nice to speculate about, but we cannot even predict things that are 10 years away so to try and imagine what we are like in 2 billion years is a bit of a stretch. I look forward to others’ comments.

Hayley Brown: thank you very much that’s the only thing about the universe that had me really puzzled:-)

Echoes of Apollo: Wow, I’d better ask you the questions in future! – No, seriously, we will never know enough and we keep correcting what we think we know – such as water on the moon. The biggest things to puzzle me and others a the moment is dark matter and dark energy. It is a big one and probably will have a lot to do with what happens in the answer to your question above. I just avoided it. The more we know, the more we wll realise what we don’t know.

Dan Anderson: We don’t know anything till we see it with our eyes…

Pamela Dobey Holt Peters: I’ll second that last sentence.

Echoes of Apollo: I found this animation of the Miilky Way colliding with the nearby Andromeda Galaxy.

http://www.rug.nl/cit/hpcv/VR_visualisation/Astronomy/CollidingGalaxies/coll_galaxies

After hundreds of million years, the two spiral galaxies merge into an elliptical galaxy with two large ‘tails’ as gravity drew them together after they initially passed through each other. The link to the animation is at the bottom of the web page.

Echoes of Apollo: Here are some more interesting links:

http://www.spacetelescope.org/goodies/posters/screen/merging_galaxies.jpg

http://sciencenotes.wordpress.com/2008/07/09/galazy-zoo-succeeds-advances-science/

http://www.msnbc.msn.com/id/24282959/ this last one mentions the upcoming impact between the Milky Way and the Andromeda Galaxy

Mark Koehn: From what I’ve read there is so much space between individual stars that there should actually be no real stellar collisions and our star will probably be a red giant at that point in time anyway.

Echoes of Apollo: True on all counts, but there will be some collisions, especially near or at the cores.

Mark Koehn: I agree with you there.

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