Discussion in a previous post centered on getting to space and into an orbit near Earth. This post is about how spacecraft return from orbit. Some returns are under control and some are not.
Launch to orbit requires giving a spacecraft a large amount of kinetic energy of motion (KE) and a large amount of gravitational energy (PE) due to its altitude. The large amount of work done to gain those energies comes from the potential energy released by an engine(s) as fuel burns. Once in orbit with engine(s) off, the total of those two energies (KE+PE) stays constant except for the small decrease due to the small atmospheric drag at high altitudes. If the orbit is a circle the two energy quantities are unchanging.
If the orbit is an eccentric ellipse, the quantities do change but not their total. The next graphic shows an eccentric orbit of an Earth satellite. When it passes closest to Earth (perigee), the KE is at its maximum value and the PE is at its minimum. Font size was changed to illustrate their inequality. When at its farthest point in orbit (apogee), it is going slowest with minimum KE and is at its highest altitude with maximum PE.
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I’ve been enjoying the book Endurance by Astronaut Scott Kelly. He tells of his life before becoming an astronaut and of his year in space aboard the International Space Station from March 2015 to March 2016. He and his identical twin brother Astronaut Mike Kelly were studied extensively to see the effects of long duration space flight on the human body. This study is an important one for the planned trip to Mars. The Twin Study is ongoing. Here are some of the latest articles about it.
The book provides countless behind the scenes looks at the lives of space explorers. I highly recommend the book to the space enthusiast. Part of Kelly’s duties now include travel to stores and special events to promote the book. My son attended a book-signing event near him and bought a copy for me. Kelly was invited to Talks at Google on 24 Nov 2017 where he spoke for about an hour about his experiences. You can watch his talk at this link.
I am a strong believer that we humans are capable of amazing and wonderful things. When we set our minds to a goal and work together, we can accomplish the most difficult of tasks. As Scott Kelly ended his talk, he spoke of how he feels about the potential of mankind. This is exactly how I see it.
Just before 6:20 am, I looked to the western sky. Flying from the SW was the very bright International Space Station. Next to it, moving parallel, was another dim point of light. I realized it was the SpaceX Dragon which had been released a few hours earlier for its return to Earth with 4100 lbs of cargo.
I grabbed my iPad and set up in an east facing window with hopes of capturing the two in a NightCap app photograph. Dragon was too dim to show. But, ISS, the Moon, Jupiter, and Mars all shined bright in the 2 minute exposure. The ISS moved southeast toward the lower left.
Spaceflight Now and SpaceX confirmed splashdown of Dragon in the Pacific.
How will the Moon look on any date in 2018? What will it look like on your birthday? Find out at NASA Dial-a-Moon. Enter any month, day, and universal time (UT) hour to see a high definition image. The composite images of Dial-a-Moon are made from those of the Lunar Reconnaissance Orbiter (LRO) in low altitude orbit around the Moon since 2009. Here is the link for southern hemisphere readers.
You may leave the universal time (UT) at the default 1 value. If you are a curious type, Universal time conversion can be done at this link. Enter UTC in the lower right box if it isn’t already set. You can switch from 12 hr to 24 hr at the bottom of the entry boxes. You may also enter any other local time in the upper left box. Go back to Dial-a-Moon to enter the UT.
The collection of accurate images of the Moon for each hour have been made into a movie lasting about 5 minutes. Try watching full screen. Versions of the movie are available for readers in the northern and the southern hemispheres.
I explain the peculiar wobble and tipping motions at this blog post.
The Iridium 21 satellite passed over my part of Iowa this morning before sunrise. I set the iPad Air 2 on a firm base pointed at an angle toward the NNW sky. At 6:02 am, I started the 102 sec exposure using the NightCap Camera app, same as for the ISS pass three days earlier. The satellite was going north as it entered the frame at the top. After about 30 sec, a highly reflective mirror-like antenna cast a beam of sunlight down toward me. It brightened to several times more than the planets Venus or Jupiter ever get. Then it dimmed and continued north.
Taken with NightCap Camera | ISS mode | 102 sec | click to embiggen
Another satellite passed at the same time going toward the upper left from north-to-south. It is very faintly visible to the left of the flare. According to the Heavens Above database for my area, it was either a Russian satellite, or an Ariane rocket body.
An email notified me of a pass over my region by the International Space Station. The large bright object is always fun to see as it crosses the sky. First visibility was at 6:15 pm in the southwest low in the tree branches at the lower right of the image. It rose higher in the southern sky toward the upper left and passed the Moon in the southeastern sky. There is disappeared as it went into the darkness of the Earth’s shadow.
I used an application on my iPad called NightCap Camera to record a time exposure of nearly 5 minutes. It has a setting designed to capture ISS passes. With the iPad pointed almost due south, it recorded more than the ISS. A passenger plane with its blinking lights moved right-to-left across the field of view starting under the edge of the roofline. A few moments later another plane moved, this time left-to-right, parallel to the first. I kept recording the image. When I examined the image later, I noticed another object had entered the frame from the top before I closed the shutter. It was probably a polar orbiting satellite. I hadn’t noticed it as it was quite dim in the sky.
Sometimes you get surprised with more than expected. I like when serendipity happens.
Click to embiggen
I recently read a post by fellow blogger The Belmont Rooster about the scientific naming of plants. In his post, he described with examples how the names are determined according to some rules and criteria. The system brings the many plants of the world into a naming hierarchy with allowances for special cases and situations. If you like plants, check out his blog.
Knowing that I am an amateur astronomer, he asked if the stars also have a naming system. I said they do. It seemed a topic worthy of some discussion. Come along with me. To set the stage, we will start with some music. Thank you, Willie.
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