10-16-18 David McClintock | Hayabusa2 notes
Notes by David McClintock:
Either there is an attached pdf file or here is
the link below to a remarkable document titled
Hayabusa2 Information Fact Sheet Ver. 2. 3 2018. 07. 05
http://global.jaxa.jp/projects/sat/hayabusa2/pdf/sat33_fs_23_en.pdf
It is a wondrously illustrated Intelligent Guide to the Hayabusa2 project.
It documents, compares, and contrasts both the first Hayabusa mission, spacecraft and instruments
with this second currently on-going Hayabusa2 mission.
That demonstrates a particularly Japanese brilliance: endlessly perfecting through incremental improvement.
The Japanese have demonstrated clever thinking and advanced technology to accomplish a great deal, economically.
The original Hayabusa mission cost came in at about $250 million US dollars.
They experienced some minor malfunctions but worked around them. The original Hayabusa was a great success.
It got to its target asteroid, took samples, and returned them to Earth. They learned a lot from the experience.
This second Hayabusa2 mission is costing $400 million US dollars
Hayabusa2 is much refined with added capabilities.
NASA is on a similar mission. It is a fine example of NASA's great technology,
but for their very first attempt to get samples from an asteroid,
NASA’sOsiris_REX mission has so far cost $983.5 million US dollars.
The Hayabusa2 document is something you could quickly scroll through, but
let me point out a few places you might want to pause at.
pages 4 - 6 covers the mission objectives. Good enough.
page 23 compares the original spacecraft with the improved second version, endlessly perfecting through incremental improvement.
page 32 is cute in describing improvements to the SMP Sampler.
Pages 33-35 the Impactor is designed to make a crater without contaminating what is to be found.
I showed a short video on the testing of the Impactor.
Page 38 landing data collecting rovers, they would scrabble around and float off if they used wheels for motion, so these make weak hops.
Hayabusa2 carries five (5) rovers (maybe they be called "hoppers") which it will drop onto the asteroid to collect data.
Page 39 Since we are into hopping, it is notable that the "Minerva II-2" rover will test four (4) different hopping mechanisms.
Page 41 features the German built "Mobile Asteroid Surface Scout" which I showed a video of.
It is impressive, but apparently can jump only (1) once! Germany 1 Japan 4
Page 48 Hayabusa2 tosses out "Target Markers"
These are darned cute little round 4 inch highly reflective bean bags
What a neat desk paper weight. I sure hope they'll sell commemoratives.
page 53 the Re-entry capsule must have been a really fun project to design, test and build. What an awesome moment for an engineer if at the end of the mission the re-entry seemed to fail...
page 68 they have come up with a most charming idea—which is to use the solar panels as sails.
Sunlight on the solar panels exerts pressure from the sun's incoming radiation.
Controlling the tilt of the panels with respect to the sun changes the pressure on the panels.
That differential pressure on the panels is used to change the spacecraft's attitude and orientation.
Most spacecraft deploy their panels and then orient the spacecraft to collect the most light.
Hayabusa2 needs to keep the spacecraft oriented to (a) best view the asteroid or to (b) best transmit to Earth. To maintain the desired orientations they move the solar panels a bit as needed.
Saves a lot of electric energy otherwise used by speeding up or slowing down spinning reaction wheels.
Saves a lot of fuel otherwise used by reaction thrusters (tiny attitude control rockets).
It is a very clever idea.
page 71 they greatly improved communications, avoiding drop outs when moving between Deep Space Network (DNS) stations.
page 73 by looking at a quasar (a star putting out highly regular pulses) from the spacecraft and from Earth and exchanging radio data between the spacecraft and Earth one can calculate with great precision where the spacecraft is and its motion. That information is used to update the forces from the four ion engines so as to steer the spacecraft as well as to vary the speed of the spacecraft (deltaV) to correctly intercept the target asteroid. With such advanced positioning they found they could use Ka band communications (four times faster data rate) over such long distances where Ka has been generally unsuitable.
page 74 has a way too short comment about "L5" that on its way outwards Hayabusa2 passed L5 and took pictures on April 18th, 2017.
To space-faring folks and to science fiction buffs "L5" is a term that bubbles up romance and mystery.
It refers to a Lagrange point. There are 5 such places in the case of two massive bodies, like our planet Earth and our Moon. Lagrange points are positions in an orbital configuration of two large bodies, wherein a small object, affected only by the gravitational forces from the two larger objects, will maintain its position relative to them.
As the two larger bodies move about (as does our planet and its moon) the Lagrange points move too but stay in the same relative position with respect to the two big bodies.
They are an ideal parking place.
Artificial satellites have been placed at L1 and L2 with respect to the Sun and Earth, and Earth and the Moon, for various purposes, and the Lagrangian points have been proposed for a variety of future uses in space exploration. You could put a "small object" (actually a gigantic huge spinning wheel or cylinder) in a Lagrange point and it would just stay there, always the same distance from Earth and Moon.
Books and novels have been written about building such gigantic wheels or cylinders as a habitat for millions of human beings. The spinning is of course to create the one Gee gravity we are used to. It would be one hell of an engineering and construction project, but a worthy alternative habitat for humanity.
Science fiction has wondered if "alien visitors" would park something to observe us.
Scientists have wondered if miscellaneous junk would collect there, trapped by the equi-gravity.
So Hayabusa2 took pictures. Apparently they did not see anything.
(for conspirators, "or so they say..." :)
See: https://en.wikipedia.org/wiki/Lagrangian_point where there is a rotating GIF image that illustrates the five Lagrange points of a two body system like Earth and Moon.
page 94 they will set off an Impactor to make a crater and a lot of stuff will come flying out. As it is not safe to be in the way of the debris during the impact, they will move Havabusa2 safely out of the way around the asteroid. From there, they would not be able to see what's happening with the Impactor, ah so! But they've brought along a DCAM3, a little robotic digital camera, their third version apparently, to take pictures. Again, think what a neat project for some engineer:
"Hey, Soji! Got a little project for you. Build a little camera so we can track the impact. It can't be bigger than such and such, needs to weight less than so many grams and not need more than this many milliwatts. Oh and it has to have autonomous orientation control, be remotely managed with the usual communications suite. Can you get me your ideas by next Tuesday?"
page 109 This is THE iconic image everyone uses to answer the question "how big is it?"
The picture the Americans use always compares something to the Empire State building.
The French show the Eiffel Tower.
The Japanese use the Tokyo Tower and Tokyo Skytree.
Since we are in Mexico, I used Mount Orizaba…
page 116 starts a crash course on the different types and families of asteroids.
You'll be able to amaze folks with your knowledge of asteroids and how they come along in C, S, D, X types, and V types which seem to contain volcanic rocks so we wonder where those came from. And then there are meteor types...
The Murchison Meteor Event (a mere entry on page 121) is interesting to look up in Wikipedia because it was a meteorite that landed in Australia fairly recently (by when we had superb lab equipment) and exhaustive studies of the pieces triggered an entire re-thinking about what asteroids might teach us.
The Murchison was full of organic molecules...
page 128 encapsulates everything I touched upon in a very short time: spinning solar system, planet formation, asteroids, and in a blue box---> the chirality (left and right handedness)
of amino acids...
Finally, pages 135 & 136 show the orbit of asteroid BENNU the one that NASA is going after with their Osiris_REX mission
Link for Bennu mission
https://www.space.com/39958-asteroid-bennu.html
Bennu is only 200 meters in diameter, it is considered the asteroid most likely to crash into the Earth, not very probably at all but still just maybe the most probable one anyway. As Force equals mass times velocity squared, Bennu could become an extinction event. So NASA’s going out there to see how we would play that ball, maybe a No 7 iron, or a putter...
For the latest news on Hayabusa2
http://www.isas.jaxa.jp/en/missions/spacecraft/current/hayabusa2.html
My introductory video was to show the formation of the solar system as a centrifuge, separating stuff.
That resulted in different categories of planets, gas giants out there, metal core planets closer in. That process separated asteroids into different types as well.
The source video was at https://www.youtube.com/watch?v=yXq1i3HlumA
but the original length was nearly five minutes long.
What I showed was captured from Youtube with ClipGrab (free) and edited down with Movie Maker (free) to just a few minutes to greatly punch up and shorten the presentation.