Dawn taking chem makeup data at 385 km

Discussions ranging from space technology, near-earth and solar system missions, to efforts to understand the large-scale structure of the cosmos.

Re: CAPTURE!

Postby Darby on March 7th, 2015, 2:35 pm 

Marshall: here's a timely full-length article that takes a peek at the current state of affairs regarding gene splicing, eugenics and bioethics. It's a good read.

http://www.technologyreview.com/feature ... fect-baby/

BTW, perhaps a thread split is in order ?
Darby
 


Re: CAPTURE!

Postby Marshall on March 7th, 2015, 5:04 pm 

Intolerance of low gravity is a disease---curing this disease may or may not involve genetic intervention.
I expect that this disease will be addressed, partly because it seems related to osteoporosis, possibly also to kidney stones, better understanding of bone growth and bone loss can benefit a variety of people with a variety of problems.
And it could be there is a simple drug treatment who knows?

However I liked Doogle's post.

Your post showed a poll of American public with respondents split about 50-50 on the question is it OK to use genetic means to eliminate disease. I think this is a non-issue. As more medical problems are cured by genetic means, more people will accept the idea and be comfortable with it. and HALF the US population sampled is already pretty good. AFAICS

So if you want to start a thread about public opinion and bioethics etc etc, please start one. No need to bother about it in this thread which is primarily a CERES thread.

I take it for granted that one way or another human medical ingenuity will cure the proneness to ill health effects of low gravity.

At this point I want to move on to consider the NITROGEN problem.
Marshall
 


Dawn's next step: turnaround by 20 March at 77 kkm or less

Postby Marshall on March 7th, 2015, 6:47 pm 

Nitrogen is a key element for life. It is the 7th most abundant element (H, He, O, C, Ne, Fe, N,...)
http://en.wikipedia.org/wiki/Abundance_ ... l_elements
and Silicon is the next most abundant, after Nitrogen.

Silicon and Nitrogen are among the elements made and dispersed in supernova explosions, which among much else produce silicon nitride dust Si2N3.

The original gas and dust the solar system condensed from would have contained plenty of Nitrogen. One might guess that Ceres, since it is expected to be representative of early solar system material, would have abundant nitrogen bound up in its rocky core, unless the N was "cooked out" of the rocky material by melting.

Assuming the planetto still has a substantial part of its original N, one could expect traces of N to have percolated out into the icy mantle: soluble ammonia and ammonium salts.

I'd be especially interested in any proposed mission that would drill for samples of the icy mantle material and test for the presence of dissolved nitrogen compounds.

======current status======
Because of thrust outage caused by a fluke cosmic ray in September, Dawn approached Ceres with excess speed and will OVERSHOOT by more than 70 thousand kilometers! The plan is to cap distance at under 77 kkm And for maximum distance from Ceres to be achieved sometime in the period 15-20 March. The probe then will fall back towards Ceres and shape its orbit to a close-in circle passing over the north and south poles.

This recent video shows distance maxing out around 15 March---around 27 seconds into the 1 minute YouTube.



You can drag the time button to anything around 25 seconds, then start, and see what I'm talking about. In this trajectory animation the date is given. The sun is off to the RIGHT of the frame for most of the show. At the end they rotate to give some sense of the trajectory in 3d.
Marshall
 


Re: Prescient comment!

Postby Faradave on March 7th, 2015, 11:26 pm 

Marshall » March 7th, 2015, 5:04 pm wrote:Intolerance of low gravity is a disease...I expect that this disease will be addressed, partly because it seems related to osteoporosis, possibly also to kidney stones, better understanding of bone growth and bone loss can benefit a variety of people with a variety of problems.
And it could be there is a simple drug treatment who knows?


I didn't want to interrupt the celebration relating to CAPTURE! Can hardly wait for data and images.

Bisphosphonates look very promising. [1, 2] They are used to prevent osteoporosis (primarily postmenopausal) and can even be given as single annual dose, well in advance of space travel.

There are two types of cells involved in bone metabolism. Osteoblasts lay down new bone and osteoclasts consume existing bone. This way bone continuously responds to changing stresses and repair injuries (mostly microfractures). Bisphosphonates essentially ruin the taste of bone to osteoclasts, inhibiting absorbtion, which is exactly what you might want if they get over anxious. The lack of boney stresses in low g makes them go crazy as they decide that all that strength isn't needed. They'd be correct of course, if we weren't planning on a sudden return.

I thought it was touching that Leonard Nimoy narrated this Dawn promo. I'm sure he'd be proud.
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Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 12:05 am 

Thanks Faradave!
I wish I could give that post two Likes : ^)
True about Nimoy




====EDIT======
Useful links. I want to keep them handy:
http://www.dispatch.com/content/stories ... s-say.html
http://www.nasa.gov/mission_pages/stati ... s/239.html
http://en.wikipedia.org/wiki/Bisphosphonate
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 12:15 am 

It should be interesting to learn the pathway of information
bone stress some how gets translated into a signal that makes the osteoclasts less aggressive

They get the message that the animal DOES need the large bone mass and they absorb less.

You told the other side of the story: the bone is not getting stressed so they don't get the signal and they think
"all this strength isn't needed" so they speed up their process of absorbing.

I'll look up osteoclast and see what Wikipedia has to say.
=============
Among other things looked over the article on OPG (osteoprotegerin)
I gather it is associated with a certain known gene in humans and an analogous known gene in mice
It was given to mice who went up in space shuttle and it inhibited bone loss in microgravity.

I couldn't find any hint as to how bone stress translates into higher levels of OPG. Apparently it is produced under some circumstances by the osteoblasts. It inhibits the differentiation by which osteoclasts are produced.
Also looked at http://en.wikipedia.org/wiki/Osteoclast
and http://en.wikipedia.org/wiki/Osteoblast
The last was, for me the most informative. It had a short section on feedback which mentioned mechanical stress:
==quote==
Feedback from osteocytes
Feedback from physical activity maintains bone mass, and feedback from osteocytes limits the size of the bone-forming unit. A number of mechanisms regulate bone density including stress on the bone.[35] An important additional mechanism is secretion by osteocytes, buried in the matrix, of sclerostin, an interesting protein that interferes with a pathway that maintains osteoblast activity. Thus, when the osteon reaches a limiting size, it self-inactivates the bone synthesis pathway.[36]
==endquote==
http://en.wikipedia.org/wiki/Osteoblast ... osteocytes

Reference [35] (where I bolded) had an interesting abstract"
Curr Osteoporos Rep. 2003 Jun;1(1):5-10.
Osteocyte and bone structure.
Klein-Nulend J1, Nijweide PJ, Burger EH.

Abstract
The osteocyte is the most abundant cell type of bone. There are approximately 10 times as many osteocytes as osteoblasts in adult human bone, and the number of osteoclasts is only a fraction of the number of osteoblasts. Our current knowledge of the role of osteocytes in bone metabolism is far behind our insight into the properties and functions of the osteoblasts and osteoclasts. However, the striking structural design of bone predicts an important role for osteocytes in determining bone structure. Over the past several years, the role of osteocytes as the professional mechanosensory cells of bone, and the lacunocanalicular porosity as the structure that mediates mechanosensing have become clear. Strain-derived flow of interstitial fluid through this porosity seems to mechanically activate the osteocytes, as well as ensure transport of cell signaling molecules, nutrients, and waste products. This concept explains local bone gain and loss--as well as remodeling in response to fatigue damage--as processes supervised by mechanosensitive osteocytes. Alignment during remodeling seems to occur as a result of the osteocyte's sensing different canalicular flow patterns around the cutting cone and reversal zone during loading, therefore determining the bone's structure.
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 1:58 am 

We've used portions of this table before. Dawn may outperform these projections and reach turnaround earlier or at less distance. But so far this table has done fairly well as a predictor. It shows turnaround at 77 km on or around 19 March.

Here's the key section that shows the turnaround. Ceres is at (0,0,0) so basically we want all three coordinates to be small, to stay at or oscillate around zero, and the total distance to be small.
Code: Select all
date      X          Y          Z        distance from Ceres
M14     68.4790    28.2510    -6.38793    74.35
M15     69.7223    27.7726    -4.80202    75.20
M16     70.7383    27.1819    -3.57051    75.86
M17     71.5002    26.8275    -2.34785    76.40
M18     72.0023    26.5440    -1.37327    76.75
M19     72.3581    26.2900    -0.12403    76.98
M20     72.4098    25.8411     1.05432    76.88
M21     72.2873    25.4277     2.33013    76.66
M22     72.0303    25.0319     3.22497    76.32


Z coordinate shows Dawn had been lagging behind Ceres in their race around the sun. It draws abreast with the planet on 19 March and even gets a bit ahead. Total distance also peaks on 19 March and declines thereafter. Y is the distance above Ceres' orbit plane---it is under control and has been gradually declining ever since 6 March.
The X coordinate is the distance outward from the sun, and it shows the troublesome overshoot. Dawn was forced by a fluke accident to approach from sunward too fast, causing it to overshoot by quite a lot. It is now using its thruster to slow that outward motion.

To provide context, here's the full table. It extends to 5 April.
Code: Select all
date      X          Y          Z        distance from Ceres
F17   -45.9972    6.4086    -27.2882    53.86           
F18   -38.555    9.71627    -28.2185    48.75
F19   -32.3324    12.4392    -29.202    45.30           
F20   -26.169    14.8491    -29.9728    42.46
F21   -19.6171    17.2648    -30.4689    40.14
F22   -13.2794    19.4975    -30.6993    38.71
F23   -6.73346    21.6416    -30.593    38.07
F24   -0.502056    23.4431    -30.212    38.24
F25     5.62894    25.0851    -29.7158    39.29
F26     11.407    26.4613    -29.1488    40.98
F27     17.2899    27.6663    -28.1919    43.11
F28     22.8583    28.5286    -27.0313    45.46
M1      27.9985    29.1842    -25.6846    47.90
M2      32.8862    29.7513    -24.1873    50.51
M3      37.6439    30.1647    -22.7166    53.31
M4      41.9734    30.4246    -21.3167    56.05
M5      45.8274    30.5605    -19.8726    58.55
M6      49.5028    30.6491    -18.2955    61.02
M7      52.8252    30.4896    -16.7451    63.24
M8      55.7681    30.3242    -15.1946    65.27
M9      58.5427    30.0761    -13.6441    67.21
M10     61.1564    29.769     -12.0671    69.07
M11     63.2886    29.4796    -10.5963    70.61
M12     65.1256    29.1961    -9.32939    71.97
M13     66.8636    28.8417    -7.90296    73.24
M14     68.4790    28.2510    -6.38793    74.35
M15     69.7223    27.7726    -4.80202    75.20
M16     70.7383    27.1819    -3.57051    75.86
M17     71.5002    26.8275    -2.34785    76.40
M18     72.0023    26.5440    -1.37327    76.75
M19     72.3581    26.2900    -0.12403    76.98
M20     72.4098    25.8411     1.05432    76.88
M21     72.2873    25.4277     2.33013    76.66
M22     72.0303    25.0319     3.22497    76.32
M23     71.7734    24.5653     4.24385    75.97
M24     71.1281    23.9983     5.08554    75.23
M25     70.1580    23.3604     6.02468    74.18
M26     68.9840    22.7402     6.74232    72.94
M27     67.6521    22.1023     7.46883    71.56
M28     66.0440    21.553       8.08901    69.94
M29     64.1702    20.9978     8.57630    68.06
M30     61.9597    20.5548     9.23193    65.92
M31     59.6842    20.2240     9.60404    63.74
A01      57.1311    20.0527     9.85212    61.34
A02      54.4022    19.8283    9.81668    58.72
A03      51.2408    19.6570    9.97616    55.78
A04      48.0025    19.6393    9.84326    52.79
A05      44.5782    19.8637    9.69264    49.75 

X Y Z are coordinates relative to Ceres, which is (0,0,0), measured in kkm---thousands of km.
X is directed out from sun, in Ceres orbit plane
Y is directed perpendicularly up off the orbit plane, in Ceres' north pole direction
Z is directed forwards in Ceres orbit plane, the direction Ceres is moving, a negative shows the probe trailing behind.
I'll bring the current status page forward to have it handy so we can compare with actual progress.
Image
The table is not too far off if you think of the date in UT terms. It is still 7 March (10pm pacific time) but it is already 6am on 8 March by Universal Time. So the table, for 8 March, and the current status figure of 65.7 kkm more or less agree.
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 4:35 pm 

As Dawn reaches its maximum overshoot distance from Ceres its speed rel Ceres will go down to a small amount, basically sideways motion. According to our estimates for the trajectory that are tabulated here we can look for the speed to briefly dip below 15 m/s.
15 m/s on 20 March
14 m/s on 21 March
12.5 m/s on 22 March

After that, as it begins falling back towards Ceres, its speed will pick up gradually for a while.

Right now according to current status 8 March 18h UT, distance is 66.8 kkm and speed is 38 m/s
We expect the distance to max out at 77 kkm or less, and speed to get down to somewhere around 14 m/s
Marshall
 


Re: Piezoelectric biosensing

Postby Faradave on March 8th, 2015, 6:06 pm 

In addition to what you noted, collagen (a common protein found in bone) can indicate stress during weight bearing and moderate to high impact exercise (running), tricky to simulate in low G.

"Dry bone exhibits some piezoelectric properties. Studies of Fukada et al. showed that these are not due to the apatite crystals, which are centrosymmetric, thus non-piezoelectric, but due to collagen. Collagen exhibits the polar uniaxial orientation of molecular dipoles in its structure and can be considered as bioelectret, a sort of dielectric material exhibiting quasipermanent space charge and dipolar charge. Potentials are thought to occur when a number of collagen molecules are stressed in the same way displacing significant numbers of the charge carriers from the inside to the surface of the specimen. Piezoelectricity of single individual collagen fibrils was measured using piezoresponse force microscopy, and it was shown that collagen fibrils behave predominantly as shear piezoelectric materials.

The piezoelectric effect is generally thought to act as a biological force sensor. This effect was exploited by research conducted at the University of Pennsylvania in the late 1970s and early 1980s, which established that sustained application of electrical potential could stimulate both resorption and growth (depending on the polarity) of bone in-vivo. Further studies in the 1990s provided the mathematical equation to confirm long bone wave propagation as to that of hexagonal (Class 6) crystals." [1]

"It has been hypothesized that this is a result of bone's piezoelectric properties, which cause bone to generate small electrical potentials under stress."[2]
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Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby TheVat on March 8th, 2015, 8:41 pm 

Visitors might benefit from knowing there's a low-grav medicine thread, hiding inside an asteroid probe thread? It's fascinating...and I had no idea it was here the past few days.
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Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Darby on March 8th, 2015, 9:03 pm 

I'd suggested a thread split, but it didn't get any traction.

I have more to add on the second topic, but didn't want to keep dragging the ceres discussion off topic.
Last edited by Darby on March 8th, 2015, 9:05 pm, edited 1 time in total.
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Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 9:05 pm 

Hi BiV, glad to see you!
My basic thought here is that if two conditions are met Ceres is the most attractive new place in the Inner Sol.Sys. for humans and other life to take hold.
(Anything you think needs to be done on Moon or Mars can be done more economically by robotic proxies, which are better suited for work in dry vacuum and radiation encountered on surface of these places)
Those two conditions are:
A. adaptation of humans and other life they want to bring along, to low gravity, and the rest (artificially lit subsurface ice caves including lakes for aquatic life)
B.sufficient availability of nitrogen on Ceres

So it is essential for Ceres thread to have some discussion of medical questions relating to low gravity. Ceres gravity is 3%.

Several days ago I invited Darby to start a thread (it could be over in Medicine) about low gravity if he wants. He has not yet followed up on the suggestion. In the meanwhile feel free to bring info HERE about gravity effects and possible adaptation. It is extremely relevant to Ceres! I am concerned with a permanent expanding human population. Women should be able to have healthy babies in 3% gravity. People should be able to enjoy jumping and flying around in subsurface spaces, grow flowers and fruit trees, raise chickens.

So I value any contribution about low gravity adaptation that you can bring to the Ceres thread :^)
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 8th, 2015, 9:45 pm 

Let's not forget about the NITROGEN question either! Here's an excerpt from a few posts back:
Marshall » Sat Mar 07, 2015 3:47 pm wrote:Nitrogen is a key element for life. It is the 7th most abundant element (H, He, O, C, Ne, Fe, N,...)
http://en.wikipedia.org/wiki/Abundance_ ... l_elements
and Silicon is the next most abundant, after Nitrogen.

Silicon and Nitrogen are among the elements made and dispersed in supernova explosions, which among much else produce silicon nitride dust Si2N3.

The original gas and dust the solar system condensed from would have contained plenty of Nitrogen. One might guess that Ceres, since it is expected to be representative of early solar system material, would have abundant nitrogen bound up in its rocky core, unless the N was "cooked out" of the rocky material by melting.

Assuming the planetto still has a substantial part of its original N, one could expect traces of N to have percolated out into the icy mantle: soluble ammonia and ammonium salts.

I'd be especially interested in any proposed followup Ceres mission that would drill for samples of the icy mantle material and test for the presence of dissolved nitrogen compounds...


Anybody have any info bearing on likely abundance of N?
Nitrogen seems to be abundant at some OUTER Sol. Sys. bodies e.g. in the form of ammonia, and Ceres is sometimes said to be more similar to moons of Jupiter and Saturn than to the other stuff in the asteroid belt. But there are significant differences (closer in so more sunlight, less able to hold gas atmosphere, etc...)

Ample N absolutely essential to have a self-sustaining expanding colony of life based on local in situ materials.

If Ceres doesn't have N then the next best thing might be polar ice caps on Mars, again with ice roof as shielding from radiation, taking advantage of Mars CO2 atmosphere with its 2.7% nitrogen. I looked into that some years back and wound up dubious because the Mars polar ice does not seem thick solid and structurally sound. Subject to seasonal change etc. Ceres with estimated 100 km thick icy layer is appealing by comparison. More security and room for growth. So I'm hoping that nitrogen does turn out to be available on
Ceres.

The low gravity is really appealing because less danger hassle and cost getting on and off.
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 9th, 2015, 1:08 am 

As a check on how reliable a predictor that table is, as of morning (6am) UT of 9 March the table says distance 67.21 kkm for 9 March, so let's compare with current status.
Current status says 67.84 kkm as of 6h UT on 9 March. Not too bad. The table seems to like the early morning of the day in question, I've been noticing.

Maybe I should make the comparison consistently at an even earlier time, like 2h aka 2am UT on the date in question.
that would be 6pm, or allowing for daylight savings, 7pm pacific time of the previous day
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Darby on March 9th, 2015, 8:23 pm 

Brief addendum regarding:

Probably best for the time being to assume it's something in the regolith family until it can be scrutinized more closely.


I just stumbled across a paper (linked below) in the Cornell AP Database that provides a detailed analysis of the surface composition of Eros, Itokawa, Lutetia, and Vesta, and Regolith seems to be very commonplace. Based on that, I'm leaning towards the same applying to Ceres as well.

Asteroid Surface Geophysics
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Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 9th, 2015, 8:29 pm 

Good thinking. It needs some kind of (probably thin) crust to cover the icy material. Ice, unprotected, would sublime away leaving a residue that might also be classified as regolith. So one way or another it has this rubbly crust. And BTW the crust is really dark. only 10% reflective.

Keeping track of progress, let's try comparing to our table for 10 March AS OF NOW, namely the zero hours UT of 10 March.
Current status says 34.9m/s and distance 69.3 kkm. for 0h on 10 March. Table says what?
Bingo :^) 69.07 kkm. Quite close. So maybe this table will be a good guide to what to expect, in a rough approximate way. I got it from an acquaintance some weeks back and it has done reasonably well so far.
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 10th, 2015, 7:45 pm 

Current status for the eleventh, as of 0 hours UT. distance 71.08 kkm and speed 31.7 m/s
Let's compare with the table.
viewtopic.php?f=72&t=28348&p=277664#p277510

Table, for 11 March, says distance 70.61 kkm. It isn't great but still it gives some numerical idea of the wide outward swing and the turnaround we expect to happen in just a little over a week. (If not sooner!)

As a rough estimate, speed seems to be going down about 3 m/s per day and according to table we expect it to go down to around 14 m/s (from the current 32) by turnaround, so that would take about 9 days from the 11th, so about the 20th. OK that makes sense.
Meanwhile we expect the distance to go from present 71 kkm to a peak distance of 77. That is not much lee-way. We'll see if it stays within that estimate or overshoots some. Here's the relevant part of the table:
Code: Select all
M10     61.1564    29.769     -12.0671    69.07
M11     63.2886    29.4796    -10.5963    70.61
M12     65.1256    29.1961    -9.32939    71.97
M13     66.8636    28.8417    -7.90296    73.24
M14     68.4790    28.2510    -6.38793    74.35
M15     69.7223    27.7726    -4.80202    75.20
M16     70.7383    27.1819    -3.57051    75.86
M17     71.5002    26.8275    -2.34785    76.40
M18     72.0023    26.5440    -1.37327    76.75
M19     72.3581    26.2900    -0.12403    76.98
M20     72.4098    25.8411     1.05432    76.88
M21     72.2873    25.4277     2.33013    76.66
M22     72.0303    25.0319     3.22497    76.32
Marshall
 


Re: Dawn's next step: turnaround by 20 March at 77 kkm or le

Postby Marshall on March 10th, 2015, 8:26 pm 

Have you tried fitting these two current status views together? Orion's two shoulder stars are in both frames. It is a kind of 3d imagination exercise. Move Dawn back away from the sun until you can look a few degrees down and to the right and be looking directly at Ceres, or a few degrees to the left and up and be looking at the sun.
Image
Image
http://neo.jpl.nasa.gov/orbits/fullview1.jpg
http://neo.jpl.nasa.gov/orbits/fullview2.jpg
In the second you can see Ceres as usual smack in the center but dark because it is partly sunward of Dawn, Dawn is on the unilluminated side of the planet.
But you can tell what direction the sun is, from Ceres, by the thin illuminated rim on the upper left sector of the Ceres disk.

Now is an especially good time to learn to put the two current status views together mentally because Orion is in the picture. there is an overlap of the background stars. That will change eventually. the star background especially of the Ceres view is always changing as Dawn swings around and sees Ceres from different angles.

In the Sun view the two Orion shoulder stars are the two bright ones currently down where it says the speed relative to Sun:by the "17.23 km/s"
Marshall
 


Re: Dawn may overshoot 77 kkm. Ceres now in Orion belt

Postby Marshall on March 12th, 2015, 1:09 pm 

In the current status (12 March) view of Ceres from Dawn's perspective, Ceres covers one of the stars in Orion's belt. the Sun, not shown, is about 20 degrees up and to the left of Orion's belt, outside the view frame. Dawn arrived with excess speed which has carried it past Ceres. This one-minute video shows the plan to cope with this. It has distance maxing out between 15 and 20 March after which the spacecraft swoops back in and winds into a circular orbit.

You can see how the ion thruster is used to slow the probe's speed and shape its orbit.
The image of Ceres is exaggerated over-large and its rotation is far from realistic---but that's just details, the main thing is to show the trajectory.
Current status (12 March) shows the probe's distance from Ceres to be over 73 thousand kilometers.
Comparing that with the projections in our table I have concluded that Dawn will not make the turnaround as soon as originally expected. It will overshoot the 77 kkm turnaround goal.
If that happens, it's not the end of the world. But it will delay our getting really close-up pictures of Ceres.
Marshall
 


Re: Dawn may overshoot 77 kkm. Ceres now in Orion belt

Postby Darby on March 12th, 2015, 1:25 pm 

If it's still moving at around 30 m/s, it still needs to dump about 16 m/s to get down to the required 14 m/s, and at -3 m/s/dy max thrust that's a little over 5 days ... call it 6-7 days if you factor in the decreasing pull from ceres with increased distance (I'm feeling too lazy ATM to work it out precisely).

It still looks close enough not to lose sleep over. Personally, I'm amazed they've done as well as they have, given the fuel quandry and malfunctions to date.
Darby
 


Re: Dawn may overshoot 77 kkm. Ceres now in Orion belt

Postby Marshall on March 12th, 2015, 6:45 pm 

I'm amazed too. they've done a great job. Orbiting two separate bodies. Using an essentially untried solar electric propulsion system that takes plotting an entirely different kind of trajectory. Splendid pictures of Vesta.

The time is now roughly 0 hours UT on 13 March, so let's compare our table of predictions with current status. Current status says distance 74.0 kkm.The table says to expect 73.24 kkm on the 13th so we are over by around 3/4 of a thousand km.

Current status also says speed is 26.4 m/s, basically 12 m/s left to get rid of. Well that's not so bad!

Might make the turnaround nearly on schedule. I'll bring the trajectory timeline diagram forward.
Om.jpg
Marshall
 


Re: CAPTURE!

Postby Darby on March 13th, 2015, 4:16 am 

Darby » March 7th, 2015, 2:35 pm wrote:Marshall: here's a timely full-length article that takes a peek at the current state of affairs regarding gene splicing, eugenics and bioethics. It's a good read.

http://www.technologyreview.com/feature ... fect-baby/


And now for an example of an article (from the same author) covering some of those advocating that we haul back on the proverbial reins until we have a better idea of what we're doing ...

http://www.technologyreview.com/news/53 ... oratorium/

p.s. I still think a threadsplit would be helpful here.
Darby
 


Re: Dawn may overshoot 77 kkm. Ceres now in Orion belt

Postby Darby on March 13th, 2015, 6:20 pm 

Marshall: NASA posted 4 easy space related math problems to celebrate PI Day, which I copied into the Pi Day Thread. As the OP of the Pi thread, I took the liberty of solving the first one, and since the second one concerns ceres I thought I'd draw your attention to it. :-)
Darby
 


Re: Overshoot crested, Dawn falling back towards Ceres

Postby Marshall on March 20th, 2015, 11:27 am 

Thanks for posting the math problems. I checked them out. Ceres problem seemed easy and topical.

Current status is only approximately reliable. It may differ by a percent or so from what Rayman says in blog but that small discrepancy doesn't matter. Turnaround seems definite now.
Yesterday the reported distance was 78.43 kkm and today it is 78.37 kkm
Its all closer in from here on!
Marshall
 


Re: Overshoot crested, Dawn falling back towards Ceres

Postby Marshall on March 20th, 2015, 11:40 am 

An unspoken challenge, in the approach to circular orbit around Ceres, is to get the orbit plane skewed to the right of the sun by about 5 degrees, so that dawn will stay out of Ceres' shadow for the whole mission.
This angle will increase as the sun direction progresses counter-clockwise and it becomes increasingly crucial as the probe spirals in closer and Ceres fills more and more of the sky.
Marshall
 


Re: Piezoelectric biosensing

Postby Darby on March 29th, 2015, 7:25 pm 

Faradave » March 8th, 2015, 6:06 pm wrote:In addition to what you noted, collagen (a common protein found in bone) can indicate stress during weight bearing and moderate to high impact exercise (running), tricky to simulate in low G.


Pending some future consolidation of all the zero gravity physiology & eugenics related posts (both here and in the gale crater thread) into a dedicated thread, I'll post this here ...

The crew for the "One Year Endurance Mission" arrived safely at the ISS, as part of a dedicated science mission to learn more about the effects of long term zero gravity on human physiology and performance.

Image

Article: http://www.space.com/28931-one-year-spa ... aphic.html
Darby
 


66 kkm, 2.5 kkm/day, adaptation to 3% gravity issue

Postby Marshall on March 29th, 2015, 8:36 pm 

Hi Darby, thanks for contributing this! As discussed already, human adaptation to permanent residence in low gravity---including reproduction, birth, growth--- is absolutely essential to our settling in the subsurface ice mantle of Ceres.

Absolutely essential to the importance of Ceres in human history!

That is why I started discussion of adaptation to low gravity in this thread.

And why I would like all the discussion we can get, here in the Ceres thread, of whatever adaptation might be relevant to eventually making a permanent home there.

I've suggested several times you also start a low-gravity thread in MEDICINE subforum. I would be happy to follow it and copy relevant excerpts here. Neither thread would "take away" from the other. Might synergize :^)
Marshall
 


Re: 66 kkm, 2.5 kkm/day, adaptation to 3% gravity issue

Postby Marshall on March 29th, 2015, 9:42 pm 

Really interesting list of questions!
==quote==

YEAR IN SPACE STUDY KEY QUESTIONS:

How will astronauts perform mentally and physically after a year in space?

What changes are there to brain structure and sensory/motor abilities?

How do bodily fluids shift?

How are visual acuity and eye health affected?


How do the blood vessels change?

What is the risk of osteoporosis (brittleness of bones) and bone fracture?

How do microorganisms within the body change?

TWINS STUDY KEY QUESTIONS:

Does space travel accelerate atherosclerosis?

How do an individual’s genes affect fluid shifts and vision degradation?

How does space travel affect the genes, chromosomes, DNA and RNA?

How does space travel affect the immune system?
==endquote==

I can imagine that some individuals are genetically more prone to fluid pressure build-up in head (eyes, brain) if deprived of gravity. Excess pressure in eyeball (e.g. glaucoma) can degrade vision.
Marshall
 


Re: 66 kkm, 2.5 kkm/day, adaptation to 3% gravity issue

Postby Marshall on March 29th, 2015, 10:29 pm 

To review the basic idea underlying the thread. Looking for planets with Earth-size gravity, breathable atmosphere, and plenty of water is a needle-in-haystack pursuit.

On the other hand lower mass iceball planets are common. We have something like a dozen (counting giant planet moons) in the Solar System. They form naturally.
So the key to a "diaspora" is learning to live and prosper in subsurface ice, with sealed in bubbles of atmosphere.

Ceres is the nearest such iceball---potentially the model of a desirable place for humans to colonize.

1000 km diameter, 3% gravity, 30% water, plus a lot of minerals. If you can learn to live in subsurface Ceres you can probably find similarly habitable small planets pretty much anywhere you go. So this is it. With the Dawn mission we are quite possibly taking a first look at humanity's exo future.

Problems to address: power supply, lighting the subsurface habitat, nitrogen compounds, health and reproduction in low gravity, other plants and animals, the general problem settlers face: how to have a self-sustaining growing population able to expand its living space.
Marshall
 


Re: 66 kkm, 2.5 kkm/day, adaptation to 3% gravity issue

Postby TheVat on March 30th, 2015, 12:12 am 

Chris Hadfield, the Canadian astronaut, perhaps best known for his video singing Space Oddity on the ISS, has talked (quite amusingly) about the perils of fluid shifting upward in the body in micro-G....I recall an interview where he mentions not liking his singing voice in space because the sinuses depend on gravity for normal drainage....so his were profoundly congested all the time. As someone who can get pretty congested in the sinuses (god bless horseradish), I wonder if my genes are not optimal for space. I also come from several generations of people prone to motion sickness, another way to land on NASA's reject list I'm sure.

Year in Space study should add some useful data....wondering if they always have to use graphics with gentleman parts...some astronauts do have lady parts. (Mars, I mean Ceres, needs women!)
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