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21
A villa in LA?

That lot will never be worth that much.  The only fun that owner is ever going to have with that lot is mowing it.
A small villa.  If it's just speculation, and it's no big deal to them, who cares?  Maybe they'll get stuck with it, maybe they'll get a story to tell.
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ISS Section / Re: Trash from the ISS may have hit a house in Florida
« Last post by deltaV on Today at 12:40 am »
NASA has confirmed that the item was part of some trash that was released from ISS and was supposed to burn up in reentry and didn't: https://blogs.nasa.gov/spacestation/2024/04/15/nasa-completes-analysis-of-recovered-space-object/.

Hat tip https://twitter.com/SpcPlcyOnline/status/1779981435996188720

An article (doesn't add much though): https://spacepolicyonline.com/news/nasa-agrees-iss-debris-hit-home-in-florida/
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If you have questions about what was said, you can listen to the press conference:



Some notes from that conference:

NASA reaching out to industry, JPL, all NASA centers, want proposal to get samples earlier than ~2040 program of record is tracking given funding limits, want within decadal survey MSR cost estimates (roughly $5-7B). Prefer heritage tech. Needs to be the samples collected by Perseverence, but may not bring back all of the samples if that helps reduce costs. Releasing request for funded-study proposals ~tomorrow, responses due May 17, then they'll award some 90 day funded studies, finish by ~fall. No mention of planetary protection. FY '24 planning to spend $310M on MSR, FY '25 requesting $200M for MSR.

My comments:

I'm guessing that details of planetary protection rules will be key to whether the cost cutting miracle that NASA is hoping for happens. I hope NASA is taking a hard look at which planetary protection rules are really necessary and which are nice to have. Even if NASA can't compromise it would help if people knew more about the planetary protection rules, e.g. where is and isn't a special region.
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https://twitter.com/BoeingSpace/status/1779985780791800080

Quote
@BoeingSpace
#Starliner is now loaded onto the transporter that will roll it out of our factory tomorrow, April 16. It will head to
@ulalaunch's Vertical Integration Facility to be integrated with the #AtlasV rocket for the Crew Flight Test launch on May 6.
25
This is why I argue the "optimal" booster engine cluster has the chambers densely packed together in a honeycomb, with nozzles extending downward to form sawtooth hexagons.

The actual curvature of the nozzle is rotationally symmetric (no weird structures or loads), it's just extended to fill the "corners" with more nozzle. This maximizes your achievable Isp vs thrust density curve (with a given chamber), since you don't waste any area on the bottom of the rocket.
Question:  Is it necessary to have sawteeth in the interior of the pattern?

I'd guess gas would flow into in the voids and do the job of the missing sawteeth.

Gas undoubtedly flows, but without the nice optimized bell contour to push against it doesn't contribute to thrust in a significant way.

I expect the net gas flow through those voids is actually outwards (downwards), because of gas being entrained by the exhaust plumes.

What pushes the booster upwards is Newtons 3rd law:
"To every action, there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts."

When you accelerate exhaust downwards, there must be a force on the back end of the booster that actually pushes it.
This force exists, and it is gas pressure excerted on the bottom of the rocket.
Mostly on the nozzles, but not only on the nozzles.

At sea level the nozzles are over-expanded. The pressure in the exhaust stream is lower than in the surrounding air, so the exhaust pulls in air from its surroundings. If you have densely packed nozzles, this pulls a partial vacuum between these nozzles, but this partial vacuum reduces the pressure in between nozzles, which increases the expansion, so you end up with an equalibrium where no more air is "pulled in"  (this looks different for the outermost engines that are exposed to the atmosphere, which is why you end up with giant shock diamonds as if you had one giant nozzle the size of the rocket)

As Superheavy climbs, this equalibrium between the entrapped gas between nozzles and the nozzle exhaust remains the same. It's below
sea level atmosphere, but as the booster rises, the "outside" atmosphere pressure gets even lower. Even as the booster leaves the atmosphere, as long as all engines are running there is entrapped gas between the nozzles, replenished by recirculating exhaust and kept at more or less the same pressure it had just after launch. This pressure excerts a force per area on the booster. AKA it generates thrust.

This thrust is exactly the same as you would have if you would increase the nozzle sizes and have them meet in a hexagonal pattern - except in the latter case you could no longer gimbal the inner engines since they would be densely packed.

Of course this "trick" only works if the entrapped gasses can't escape elsewhere. So your outer ring of engines should be "dense" - I think with SpaceX switch to "unshielded" Raptor 3 it no longer will be.
26
Try Skylab back in the 70's. The ATM had, among other solar instruments, a white light solar coronagraph for imaging

Isn't comparable to a perfectly sized occultation disc 380000 km away which provides much sharper views deeper into the corona.
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Why does a cubesat 400 km up have an obvious beneft over a sounding rocket going 100 km up for a 4-minute event?

1. Because it could have a visual light camera on board which is missing on the sounding rocket payloads.
2. Because pointing a camera from a cubesat towards a known target is much easier than from a sounding rocket.
3. Because data transfer of high quality images from a cubesat to the ISS is easier than from a sounding rocket payload reaching 400 km altitude.
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Sounding rockets can do that better and more often if there was need. 

So we have a good quality photo of the corona taken in space already? Or was it taken with one of the 3 rockets launched during this eclipse?

Try Skylab back in the 70's. The ATM had, among other solar instruments, a white light solar coronagraph for imaging - you guessed it - the solar corona. It came complete with a trained solar physicist to operate it.

There's also the unmanned fleet of solar observatories stretching back to the early 60's. Total eclipses are a natural coronagraph that allow a few short minutes of observation for those lucky enough to be in the path of totality with no clouds. From my viewing location in Cleveland the morning's clear sky had been polluted by jet contrails which instead of fading away got larger and merged leaving the entire sky covered with a high thin haze which blocked most of the corona (should be able to sue the bastard airlines for that). Fortunately, that's not a problem in space where the satellites can use a coronagraph to make an eclipse any time that they want.

But if you really want a photo from space of the solar corona during last week's eclipse, the attached photo is from the SOHO satellite at the moment of totality. It's been up there observing for 29 years. No silly cubesats needed.
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Any word on what caused the uncontrolled roll SS had in this flight?
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