Astronomy and space exploration

cheapchips said:
I assume they're not winging it too much!
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You'd think. But private corporations are often much more cavalier about this sort of thing than government agencies. And government agencies aren't great at it. You'd think the corporations would be concerned about the reputations of their products, but I'm not sure that works out in practice.

cheapchips said:
The steel on the Hopper is much thicker than the drinking can thinness of orbital rockets (or the prototype Starships they're building)
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Because of how incredibly expensive it is to lift weight into orbit with rockets, it's highly unlikely that there are very wide engineering tolerances at play, regardless of the design. Building the rocket for more durability means adding weight, and adding weight means sacrificing payload. Rockets in general require much more fuel than payload. It looks like the StarHopper is intended to refuel in flight, but that too will be expensive.
 
KimB said:
Because of how incredibly expensive it is to lift weight into orbit with rockets, it's highly unlikely that there are very wide engineering tolerances at play, regardless of the design. Building the rocket for more durability means adding weight, and adding weight means sacrificing payload. Rockets in general require much more fuel than payload. It looks like the StarHopper is intended to refuel in flight, but that too will be expensive
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You're confusing up the Hopper with the actual Starship. The Hopper's not an orbital rocket. It won't fly higher than 500m. Possible source of confusion was the nosecone that fell over. That was pretty much made of tin foil but was only cosmetic. They decided not to make a second one. The tank section is made from quite hefty steel.

The two Starship prototypes being built at the moment will be more as you describe. Their tanks are much thinner and are barely able to support their own weight. They won't be ready until later this year/early next so the Hopper lets them test a bunch of things in the interim.
 
cheapchips said:
You're confusing up the Hopper with the actual Starship. The Hopper's not an orbital rocket. It won't fly higher than 500m. Possible source of confusion was the nosecone that fell over. That was pretty much made of tin foil but was only cosmetic. They decided not to make a second one. The tank section is made from quite hefty steel.

The two Starship prototypes being built at the moment will be more as you describe. Their tanks are much thinner and are barely able to support their own weight. They won't be ready until later this year/early next so the Hopper lets them test a bunch of things in the interim.
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Ahh, okay. If it's just a tech test vehicle, then I'm not at all concerned.
 
LightSail 2 becomes first spacecraft to change orbit using sunlight
By Korey Haynes | Published: Wednesday, July 31, 2019

LightSail 2 took this picture of itself, with Earth in the background, while deploying its sail on July 23.
The Planetary Society

The Planetary Society, a non-profit organization focused on space exploration, has successfully transferred their LightSail 2 spacecraft from one orbit to another using only the power of sunlight, a first. The recent success not only proves the effectiveness of solar sailing technology, but also opens up a new, more cost-effective way to propel small spacecraft.
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http://astronomy.com/news/2019/07/l...rst-spacecraft-to-change-orbit-using-sunlight
 
NASA's TESS Exoplanet Hunter Goes Above and Beyond in Mission's 1st Year
By Sarah Wells 20 hours ago Science & Astronomy

The satellite has already found 24 confirmed exoplanets, a few of which may be habitable
HqeYsM3dhKyoCX7dnL5RUS-320-80.jpg

Artist's illustration of NASA's Transiting Exoplanet Survey Satellite (TESS).
(Image: © NASA's Goddard Space Flight Center)

CAMBRIDGE, Mass. — NASA's newest planet hunter is one year older and 24 identified exoplanets wiser.

The team behind the Transiting Exoplanet Survey Satellite (TESS) held the mission's first annual science conference here this week, a year after the spacecraft began gathering data from Earth orbit.
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https://www.space.com/nasa-tess-exoplanet-hunter-first-year.html
 
Tardigrades: 'Water bears' stuck on the moon after crash
August 7, 2019
The moon might now be home to thousands of planet Earth's most indestructible animals.
Tardigrades - often called water bears - are creatures under a millimetre long that can survive being heated to 150C and frozen to almost absolute zero.
They were travelling on an Israeli spacecraft that crash-landed on the moon in April.
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When spacecraft leave Earth they are bound by the Outer Space Treaty not to contaminate their environment.
"You might say it was broken in 1969 when Neil Armstrong and Buzz Aldrin were there, which is true, but since then we've become much more aware of how we should preserve these planetary bodies.
"I don't think anybody would have got permission to distribute dehydrated tardigrades over the surface of the moon. So it's not a good thing."

If the tardegrades are on the moon, it's very unlikely they'll be able to spring back to life without being reintroduced to water.
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https://www.bbc.com/news/newsbeat-49265125
 
I have mixed feelings in planetary preservation. It seems pretty important to the experts so who am I to argue. In the other hand, surely DNA sequencing for any carbon based life would identify it as being something you didn't bring with you.

As for wiping out another planet's organisms, I say go for it. If a planet's life has been unable to make rockets after 4bn years they're too lazy for our respect. Plus we're really, really good at mass extinctions. :???:
 
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I have mixed feelings, as well. I assume that before sending humans to another planet we will already know if something's there. If we can't detect it by all reasonable means, maybe that means that life there doesn't play such an important role in the planet's biosphere. We don't even know if the mere fact of going there may destroy native organisms which we may have detected or not.

At any rate, if there's life on another planet we can explore, I'm pretty sure we will find out so that the milestone of finding alien life may be achieved, no matter what
 
vjPiedPiper said:
I still hold out hope that VISIMR tech will eventually become useful. It's high impulse but low thrust, so it still works for unmanned long journey space travel.
If they can manage to get the thrust up a bit more it becomes a lot more useful.
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It's very unlikely to. The problem is not how it performs against normal rockets, it's how it performs against Hall effect thrusters.

The reason VASIMIR was interesting when it was being designed was that the existing American ion drive tech was mostly gridded ion thrusters. Those were originally chosen because they were much easier to initially implement than the alternatives, but turned out to have a few hard to fix flaws that compromise their long-term reliability. Compared against them, VASIMIR seems like a very good solution, even though it's extremely complicated and complex and a lot of work needs to be done to make it practical.

However, while the Americans were working with gridded thrusters, the Soviets poured all their ion drive research into Hall effect thrusters, and were much more successful than the Americans. Soviet/Russian HET are not experimental tech that needs a lot of new research; since the 70's, they have flown >240 thrusters in space with a 0% failure rate. In addition to reliable, HETs are structurally very simple, which also makes them light and cheap.

NASA still spends some money on VASIMIR, but at this point it very much seems like HETs are the superior technology, and western satellite operators, which were very reluctant to use gridded-ion propulsion and not very interested in VASIMIR either seem to be willing to make the jump to HET.
 
Today I was thinking about the transit method to detect planets. We already have TESS out there (just mentioning a recent example, not that this telescope is the first time we use this method), which is nice, but I wonder what are the chances that our tools are in the proper vantage point to study planetary systems... or that other planetary systems are aligned for us to be able to detect them this way.

Also, I was thinking about direct imaging and how this method can improve over time. We already have pictures of protoplanetary discs, such as this one (HL Tauri):
220px-HL_Tau_protoplanetary_disk.jpg

Which is of very high quality, IMO, so I wonder why is it so difficult to picture an exoplanet.

Do you have any news on ongoing projects that aim to drastically improve the detection and even imaging of planets?
 
It really depends on what you're trying to achieve. If you just want a picture, well then we already have those, but they are just dots. If you want a resolved image, or some even just some real science from the unresolved dot, then that's a different thing altogether.

Of the most productive detection methods to date the transit method gives arguably the most information about the detected planets. Size and mass, giving at least some constraints on the composition, plus the potential to do atmospheric studies in the best cases. In terms of science bang for tax-payer buck this is currently the best value for money.

Direct imaging is really, really difficult unless you choose your targets carefully. The primary reason it is so difficult is the contrast ratio between the host star and the reflected light from the planet. It works best in the cases that are almost diametrically opposed to the transit method, ie. large planets orbiting faint host stars (=> larger contrast ratios) at large orbital radii (=> larger angular separation on the sky). If you want an optical image of an Earth-like planet, and to maybe perform spectroscopy on the atmosphere to search for biomarkers, then these are not the planets you are looking for. These are the images we already have.

After that life gets tough. You're talking very large mirror, probably space-based, maybe space-based interferometry. There are mission concepts, and have been for a long time now. Nothing particularly cheap though. I don't know what NASA might do, other than wait until after JWST is launched to commit that sort of money to another astronomy mission. The ESA roadmap at that mission scale is mapped out until the mid 2030s. As it stands everybody else is irrelevant. Some radical new concept might come along that does the whole thing on the cheap, or someone like Jeff Bezos decides to throw a few billion at the problem.
 
hoom said:
Yep JWST but also 30m Telescope & European Extremely Large Telescope are supposed to be capable, I think Giant Magellan is a marginal possibility
1024px-Comparison_optical_telescope_primary_mirrors.svg.png
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I didn't know the OLT, and now I'm in love, so it hurts to read that "cancelled".

Oh, regarding GMT, it won't be ready next year.
 
Well, maybe. As I said it really depends what you mean by direct imaging of exoplanets. It's already been done from the ground, eg.

https://en.wikipedia.org/wiki/HR_8799

but note that the closest-in planet has an orbit at 14AU. That's between Saturn and Neptune in our own Solar System. Note also that they are gas giant planets a little larger than Jupiter.

These new telescopes will be far better than Keck and allow imaging if planets in closer-in orbits. If you want images of a 1 Earth-radius planet in a 1AU orbit, well... we'll see. Earth is 9% of the radius of Jupiter, the projected surface area is less than 1% of Jupiter so the contrast ratio is >100 times smaller.

Adaptive optics and nulling interferometry might get you there. TBH I'm a little out of the loop on the details of the instrumentation planned for these new larger telescopes. It has changed a lot over the years. You need to be a little careful about the way the capabilities are portrayed in the media, as a lot of the detail gets lost.
 
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