Asteroid sample collecting spaceprobes.

Sandhi Yudha

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Tonight NASA's OSIRIS-REx will perform the first attempt for sample collecting at the 1999 RQ36 / 101955 Bennu asteroid. The plan is to return at least 60 gr of dust, sand and rocks to Earth. Hopefully one attempt is enough.




The OSIRIS-REx will not be the first spaceprobe collecting and returning astrrpod material to Earth, that will be the Hayabusa 2, if everything goes as planned. Hayabusa2 was launched on 3 December 2014 and rendezvoused with near-Earth asteroid 162173 Ryugu on 27 June 2018. It surveyed the asteroid for a year and a half and took samples. It left the asteroid in November 2019 and is expected to return to Earth on 6 December 2020.
 
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Sandhi Yudha

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The sample collection was successful, but NASA has still to find out how much material is collected.


 

kato

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The OSIRIS-REx will not be the first spaceprobe collecting and returning astrrpod material to Earth, that will be the Hayabusa 2, if everything goes as planned.
Actually the first one was Hayabusa 1, bringing 1500 grains from Itokawa to Earth in 2010.

Hayabusa 2 is the second spacecraft of virtually the same type, currently enroute back to Earth (planned to dump its reentry capsule on Australia in about 6 weeks). Unlike Osiris-REX, Hayabusa first bombed the asteroid - with a EFP shaped-charge projectile - in order to be able to sample sub-surface material. It also performed multiple samplings in different sites.
 

Sandhi Yudha

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Some bad news and good news.
The bad news ia that OSIRIS-REx is loosing small amounts of collected material (dust and sand).
The good news is that the spaceprobe succeeded to collect 400 gr of material, more than the 60 gr necessary to make this program successful.


 

kato

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Hayabusa 2 is the second spacecraft of virtually the same type, currently enroute back to Earth (planned to dump its reentry capsule on Australia in about 6 weeks).
To clarify: The planned arrival is exactly 6 weeks from today, on December 6th.

Hayabusa 2, after delivering the sample capsule, is planned to enter a 10-year extended mission involving a flyby at a larger L-Type asteroid in 2026 and a rendezvous and possible landing at a small, fast-rotating C-Type asteroid in 2031.
 

kato

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Attached below is a picture of one of the guns Hayabusa 2 carries.

These are single-shot guns firing a 77-grain projectile at 300 m/s, roughly comparable to .32 ACP in power on target. The projector assembly itself is about the size of a pistol (without grip). The projectile is 10mm riding on a sabot in a 17mm (.67-inch) diameter smoothbore barrel.

Operationally these are mounted above the sampler horn and fire into the ground from about 50 cm distance. Hayabusa 2 carries three of these, with two used at Ryugu and one remaining unfired for possible operation during the extended mission (it's been mentioned along with the single remaining target marker sphere).


haya.jpg

The mechanism of the gun is actually quite interesting - since they are used to kick up material for sampling they had to make sure operating the gun doesn't contaminate the sample.

The explosive used for combustion is a KClO4 / TiH2 mixture, essentially flash powder as used in pyrotechnics - the KClO4 acts as an oxidizer, the mixture is long-term stable over years. The combustion gasses are contained by a captive sabot - the sabot, driving the projectile forward, is caught at the muzzle, crushed against it (it's made of metal itself) and designed to seal off the muzzle to prevent gasses from exiting.

The projectile itself is made of pure Tantalum, which can be easily picked out of the sample. Since it is intended for operations in a vacuum it does not need to be quite aerodynamically shaped - see below, that's the bullet on the sabot. The cavity i think is for making the bullet intentionally bounce into an angle instead of continuing straight on when impacting.

haya2.jpg

In addition to the three guns Hayabusa 2 in weaponry also carried a 6.5-kg space mine with a shaped-charge EFP warhead that it threw at Ryugu to create a crater, digging up sub-surface material. For some measure of scale of that explosion, Hayabusa 2 moved to the opposite side of the asteroid before triggering it, with the explosion observed by a camera drone specifically deployed for that purpose.
 

Sandhi Yudha

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kato

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First chamber has been opened:

1608159550728.png

The actual color of the sample is rather coal black. The amount in the chamber should be on the order of several cm³. The larger grains there should be in the region of 3-5 mm diameter, about 200 times the size of the grains recovered by Hayabusa 1 from Itokawa.

The other two chambers should be opened today or tomorrow (Japan time). Since there were only two samplings on the ground one of the chambers should be mostly empty. Some finer dust was found in the sample catcher as well, i.e. outside the chamber.

In addition gas has been sampled both from the return capsule in Australia and from inside the sample chamber. As this gas does not match Earth's atmosphere by composition JAXA hails this as the first gas sample retrieved from deep space. The gas is produced by the solid sample outgassing as it is being heated (during reentry) and continues to go on due to the higher ambient temperature on Earth.
 

kato

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Its still unclear how much dust is collected from the asteroid.
The sample catcher has been weighed - that's that whole structure in the above image, which contains the three sample chambers. Material collected in these amounts to 5.4 gramms. This does not include the dust that has been found at the bottom of the chamber in which the sample catcher was housed during flight.

For scale of those 5.4g - the design requirement for Hayabusa 2 was 0.1g, the expected number about 1.0g, the "ideal conditions" retrieval for three samplings would have been about 10g.
 

kato

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Pebbles in Chamber C are considerably larger than in Chamber A above:

haya-chamber-c.jpg

This is the subsurface material excavated before the second landing by firing the SCI space mine at Ryugu (with the size and operating principle of an anti-tank mine).

The marked "artificial object?" in the top left so far hasn't been examined up close, but is presumed to be a piece of aluminium foil dislodged from the sampler horn when Hayabusa 2 fired its gun into the ground during the second landing right next to it.

Surface material from Chamber A similarly placed in an external container for comparison:
haya-chamber-a.jpg

Both images published by Jaxa today. Chamber B and C had been opened on the 21st, Chamber B was empty as expected.
 
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