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Space Science Coverage / Re: Boyajians Star Updates And Discussion
« Last post by jebbo on Today at 09:41 AM »
Yes, lots of problems. I was just musing really to see if it could be made to fit more of the known data (i.e. Montet et al).

--- Tony
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SpaceX Mars / Re: Power options for a Mars settlement
« Last post by john smith 19 on Today at 09:34 AM »
The only problem with nuclear power is the disposal of waste and old reactors. These things are contaminated with radiation producing isotopes and chemically very poisonous elements.

Much less a problem with molten salt reactors, especially those which burn thorium.

Still a huge problem from fission products, transuranics and the rest
Depends on the design.

IIRC MSR's are quite efficient in terms of neutron production (no steel fuel pins to absorb neutrons for a start in most design) and quite tolerant of what's put in them. some designs have been proposed as "burner" reactors that take FP's and transuranics as fuel, fissioning them to release energy or irradiating them to shift them to different (potentially much faster) decay paths.

The result is a very small amount of high level waste
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SpaceX Mars / Re: Power options for a Mars settlement
« Last post by john smith 19 on Today at 09:25 AM »
Yes, my premise was that the colonists are paying for this. If not them, then who?

Yes, my premise was that the colonists are paying for this. If not them, then who?

Colonists could record their 'adventures' and sell them as subscriptions to Earthers.  There are a number of interesting virtual tourism (via robots) ideas already percolating.  Did that colonist just find a plant fossil? Is that bigfoot?  On Mars?  My god the programming possibilities are endless.  Oh then theres the hard work, exploring and finding resources to exploit.  If you sell everything and have money left over you dont need it on Mars - you need it in a interest bearing account on Earth that will enable you to buy needful things and have them shipped to Mars.  Companies that are less inclined to kill their employees can hire colonists to perform experiments, scout, harvest resources for return to Earth, do astronomy from Mars, whatever humans can think of and the colonists will be on Mars to do it, and not for free eh?

Perhaps better in this thread?

https://forum.nasaspaceflight.com/index.php?topic=41937.0
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Space Science Coverage / Re: Boyajians Star Updates And Discussion
« Last post by as58 on Today at 09:25 AM »
Problems with this include:
- lack of detected IR emissions, though I think we only ruled out IR from dust
- the shape of the asymmetric primary transit.  Not sure a planet + inclined rings really explains this
- the long term secular decline from Shaefer et al.

I'll just add a couple ;)

- Planetary ring system, which reflects at times at least ~3% of the total stellar flux, sounds... large. And reflective in backscattering direction.
- If the recent dip were the secondary eclipse, it being deeper in blue than in red doesn't follow naturally (as it does if the dip were caused by transiting dust). Maybe it could be done with just the right kind of ring particles to get the albedo and backscatter just so, but it feels contrived.
- It looks to me (not that I've checked that closely) that the relative timings of supposed primary and secondary eclipses and orbital phase modulated ring reflection don't match up that well.
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SpaceX Mars / Re: Power options for a Mars settlement
« Last post by john smith 19 on Today at 09:20 AM »
No, plain regolith and sulfates are both much richer in water than the air. Gypsum contains a lot of water and MSL and Opportunity keep finding lots of it.
In hindsight they sound much more accessible than drilling into a glacier, depending on the chemical and mechanical complexity and the energy bill for the extraction.

"No drilling" sounds like it beats "some drilling (to unknown depth)," all else being equal.

WRT to this thread I guess the question would be what would be the power budget for a drill that drills a well big enough to extract the amount of water (although I doubt it will be so convenient as to be pure ice  :( . In any case the ISRU will have to be designed to cope with the worst case ) needed to process the amount of propellant to refuel an ITS?
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I'm beginning to wonder if things fell apart with the selected contractor during contract negotiations and they've had to start over negotiations with the runner up.
Sadly possible.  :(

OTOH it could just be that the hold process following the Presidential election (I did not know that something at this level would come to a halt pending the winner's transition team looking over it  :( ) has lasted longer than expected as it's just not a priority on the Administration radar.
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Space Science Coverage / Re: Boyajians Star Updates And Discussion
« Last post by jebbo on Today at 09:02 AM »
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...

Agreed on the ~700 days. 

However, the inclined rings + trojans idea implies a ~12 year period, in which case what I was thinking was that the dip in the 2nd half of the figure could be when the proposed rings transitions from being reflective to being transmissive. However, I've done no modelling of this ...

--- Tony

Ok, I see. But if that dip is interpreted as rings transiting the star, the timescale looks too long (already ~2 years and doesn't look like it's even half way through when Kepler stopped taking data).

That wasn't quite what I meant ... and I've realised what I wrote confused two distinct parts of the amorphous idea floating around inside my addled brain :-)

To expand on what I was thinking:
- for a large fraction of the orbit, starlight reflects from the rings, declining slowly as the reflection angle changes, which you see in the first half of figure 3.
- when the reflection angle reaches a critical value, the reflected light drops off sharply and we're just seeing the light of the star.
- when the planet + rings *actually* transit, you get a drop-off due to both the planet and the rings
- and this accounts for the apparently large radius in the paper (~5RJ) of the supposed primary transit
- it also accounts for why we see such a large secondary transit

Problems with this include:
- lack of detected IR emissions, though I think we only ruled out IR from dust
- the shape of the asymmetric primary transit.  Not sure a planet + inclined rings really explains this
- the long term secular decline from Shaefer et al.

--- Tony
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As with every other LV, engines are critical.
Virgin Newton 3 is operational if not flight ready yet.

Masten doesn't have tested engine yet that we know of. NB tested 25klbs Broadsword is subscale of 60klbs flight version.

Blue have proven BE3 but BE4 has yet to be tested. Not sure which engine they are going with.

My pick is Boeing/Blue if it is BE3 else NG/Virgin.

Dave Masten did talk about doing smaller RLV for smallsat market if they miss out on XS1. If so 5-7 25klbs Broadswords would be all they need.
Good point. I'd forgotten Jess Sponable's comments about they wanted a near term solution and that excluded an engine development programme. I think Jon Goff mentioned the S.Korean RP1/LOX engine might have been a candidate for this because it was available now.

XCOR have done work on reciprocating pumps for upper stage use but I think they are still too small for this task. However let's not forget clustering as an option and XCOR's in reliable engine design for the Rocket Racing League.  The idea may have fallen through but they accumulated a lot of knowledge about what works and what doesn't in terms of reliable engine design.
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Yes - our broadband is a bit slow...
I suspected that was part of the reason they were reluctant to tie up the bandwidth. The site looks pretty isolated.  Literally in the middle of nowhere.  :(

That's right, but a company here called Gilmour Space Technologies is planning to build the hybrid ERIS launch vehicle with first launch in 2020.
Thanks for that. I've not heard of them before. Perspex and HTP sounds quite robust either pressure stabilized or with a steam driven turbopump.
Quote from: Steven Pietrobon
NZ Herald article on the launch delay. It has an interview with Beck who gives some more information on the triboelectrification criteria.

"If the cloud is below -10C there's a possibility of ice particles and if we travel through that cloud at greater than 3000 feet per second then we can generate a static charge and that's enough to cause damage to the electronics of the vehicle," he said.

http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11861622
People often forget that about half the Shuttle scrubs were due to weather. Since this is there very first launch ever it makes sense to wait a bit longer unless they're sure of a long enough period of clear skies.

I think what's often misses is how fast high altitude winds can be, so you need to what a large patch of sky to make sure by the time you're ready some cloud is not parked right in the path of the rocket.
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Space Science Coverage / Re: Boyajians Star Updates And Discussion
« Last post by as58 on Today at 08:51 AM »
Edit2: perhaps we *are* seeing phase modulation.  See  figure 3 of Ben Montet's paper (https://arxiv.org/abs/1608.01316).

I'm not seeing phase modulation in that figure, or at least nothing consistent with a ~700 day period orbit...

Agreed on the ~700 days. 

However, the inclined rings + trojans idea implies a ~12 year period, in which case what I was thinking was that the dip in the 2nd half of the figure could be when the proposed rings transitions from being reflective to being transmissive. However, I've done no modelling of this ...

--- Tony

Ok, I see. But if that dip is interpreted as rings transiting the star, the timescale looks too long (already ~2 years and doesn't look like it's even half way through when Kepler stopped taking data).
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