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Define "long"

You mentioned the Cape or Kwaj. Converting latitude to distance as a very rough approximation, Cape Canaveral to equator = 3100 km, and optimistically assuming standard 747 max cruise speed, that's something like 3.5 hours - is that not "long" enough for boiloff to become an issue? (Kwaj is somewhat closer to the equator, admittedly).
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AIUI, it's impossible with RP-1 under these circumstances. (But am still reading through Ignition!, so still a few more chapters to learn)
I hesitate to say impossible - RP-1 can get to a really, really fine mist, if you dump it out into a mach 1 airstream, and mixed with oxygen it could plausibly detonate.
I think you're going to have contrived circumstances to get a meaningful fraction to detonate though.
If you look at the CRS failure frame-by-frame, and work out the speeds of the various flame-fronts involved, they pretty much all look subsonic IIRC.
Tiny parts detonating - sure. Global mixing without ignition followed by a detonation of all of it - not a hope in hell.

There are a few failures that would cause a large detonation, e.g. a LOX downpipe or common bulkhead bursting that dumps a significant amount of LOX into the RP-1 tank, followed by some ignition source like another pressure release. This type of failure was investigated and then ruled out as a cause of the AMOS-6 anomaly.
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If people fly into space, at some point people will die in space.  Period.  How we feel about that depends on our perception of risk versus reward.  Now we are in the realm of fundamental human behavior.
 
I was a test engineer for many years.  Some of our tests were inherently risky.  That could not be prevented.  All we could do was try to quantify and mitigate the risk.  The usual criteria was to limit the known risk to one in a million.  It was impossible to get the known risk to zero, and it was impossible to quantify the unknown risks (since we didn't know what they were).  Then someone had to decide  --  is this test worth it?

We do the same thing unconsciously every day.  In 2016 37,461 people died in traffic accidents in the U.S.  Obviously, the risk that you will die the next time you are in a motor vehicle is not zero.  As a matter of fact in 2016 about 12 people died per 100,000 population.  Engineers have done everything they can to minimize the risk (within the design constraints) but about 10-15 people still die per 100,000 each year.  We as a people have decided that the reward associated with driving is worth the risk. (The numbers came from wikipedia.)

The only question is:  Is expanding into space worth the risk?
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SLS will continue and likely fly within the next 24 months.

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A recent assessment of the completion date for the first Space Launch System (SLS) Core Stage now puts it at the end of May, 2019, close to the middle of next year. The date indicates that production and assembly schedules are still sliding and is reducing confidence in meeting the June, 2020 date that was at the late end of NASA’s schedule forecast for the Exploration Mission-1 (EM-1) launch.

https://www.nasaspaceflight.com/2018/05/schedule-first-sls-core-stage-sliding/

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Nothing currently out there matches its capability

Due to its incompetent flight rate, most everything exceeds the capability of SLS to deliver payload tonnage over time.

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so why do you think NASA would suddenly cancel it now?

There are multiple, pressing reasons for a new-ish Administration and a new NASA Administrator to not wait terminate now:

Poor Flight Safety Projections -- The LOC projections for SLS/Orion are worse than for STS.  These systems will kill astronauts at a higher rate than the prior system, which two prior Administrations terminated because it killed astronauts at an unacceptably high rate.

Unable to Advance Exploration -- SLS can't put up enough payload in a year, or even over multiple years, to support NASA's Mars DRMs.  SLS can't even maintain the cadence of lunar missions from Apollo.

Schedules Slipping Into Political Irrelevance -- If the Administration does not win a second term, astronauts will not launch on SLS before the POTUS leaves office.  It looks increasingly likely that SLS will not launch at all before the POTUS leaves office.

Bad Industrial Policy -- Three US companies (BO, SX, ULA) currently field or are pursuing five different HLVs (BFR/BFS, FH, NA, NG, VH).  Properly managed, there could be great redundancy and a healthy domestic heavy lift market for the USG to rely on.  Improperly managed, there will be a glut of capability and contraction and shrinkage in US heavy lift capabilities.  The Administration should be consolidating USG heavy lift needs on these vehicles, not separating out and stovepiping USG needs.

Bad Workforce Policy -- SLS is wasting tens of thousands of highly skilled US aerospace workers' careers on a vehicle that duplicates and compares badly with private sector-led alternatives.  This is a very poor use of a limited and valuable national asset.

Opportunity Cost -- On top of the workforce, SLS, Orion, and their grounds systems consume a few billions of taxpayer dollars a year.  Even allowing these programs to proceed through first launch will waste around another $10 billion that could be spent on actual human space exploration systems, not another, duplicative ETO segment that may only launch a couple times, if ever.

Bad Management -- From tilted welding tool foundations to leaning launch towers, the program has been beset by bad execution and oversight at the subcontractor, contractor, and government levels -- often for elements that don't even involve the actual flight systems.  This bodes very poorly going forward.

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I agree, soon as BFR becomes operational, everything currently flying or in-work become obsolete over night

It's not about BFR.  Musk could get run over and SpaceX could vanish tomorrow, and it would still be a very poor and wasteful decision to continue with SLS.

A new Administration and a new NASA Administrator provide an opportunity to consciously and seriously reconsider the path forward.  It is unfortunate that they are not taking advantage of this opportunity.

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but its unreasonable to think NASA should cancel its POR

NASA does not have a POR for human space exploration.  It has an ETO segment some years from operation, a nascent small robotic lunar lander program, and amorphous plans for a second space station that was very poorly rebranded for the new Administration.
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SpaceX BFR - Earth to Deep Space / Re: Elon The Boring Company
« Last post by kenny008 on Today at 02:23 PM »
The quoted figures for travel time (12m) distance (25km) and headway (30s) point to a top speed of ~110-125km/h or around 75mph. At such speeds and headways, thinking time is 10s and breaking time is 20s is over about 300m at 1.5m/s² (a smidge harsher than the hardest-breaking trains on Londons 100s headway Victoria Line)

All the smarts can be on the vehicles. The tunnel can be rigged with passive markers for position, each car knows where it is and transmits its location to the signalling system, which lets all other vehicles know. They're autonomous cars, not trains.

We've seen such on-board systems repeatedly spoofed in real-world situations now.  A public transit type application has to be fool proof.  It has to work when a vehicle loses power and can't report its position, or when it stops or wrecks and fills the tunnel with smoke so that following vehicles can't see it, Etc.

 - Ed Kyle

Most current public transit systems are nowhere NEAR foolproof.  Most of the above ground rail infrastructure still has not been back-fitted with Positive Train Control technology; we currently depend almost entirely on the operator to prevent collisions, maintain safe speed, etc.  This is very much a non-problem with a newly-design, relatively simple system.  I have not heard of ANY railway or public transit systems (which are the closest analog) being "spoofed."  Autonomous vehicles on the road in unusual lighting, with pedestrians and unknown obstacles in the way?  Sure.  But a vehicle in an enclosed, restricted access track?  I'm pretty sure engineers can pretty easily put a nearly fool-proof system in place to prevent 2 vehicles on a glorified track from hitting each other.

There are other potential problems with this system, but 2 vehicles hitting each other is pretty low on my list of concerns.
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What about LOX boiloff on the flight? Chris's article says that the carrier aircraft will eventually be able to provide LOX servicing, but in the meantime I would assume that such long pre-launch flights would be problematic from that point of view.

Define "long"
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I wonder if Launcher One & Cosmic Girl could launch from Guiana Space Center get a zero degree inclination for GTO Launch?

Why?  It can fly from the Cape or Kwaj to the equator to perform the mission.

What about LOX boiloff on the flight? Chris's article says that the carrier aircraft will eventually be able to provide LOX servicing, but in the meantime I would assume that such long pre-launch flights would be problematic from that point of view.
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Chinese Launchers / Re: Shijian 19?
« Last post by ZachS09 on Today at 01:49 PM »
Shijian 18 was on the second CZ-5 mission and the Chinese have said that the third CZ-5 will carry Shijian 20.

Have the Chinese said anything about Shijian 19?

I believe they stopped mentioning Shijian 19 after the news came out that Shijian 20 would be launched on the third Long March 5.

So, my assumption on that satellite is that it's being put into storage until a future launch.
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That An-124 should get to the Cape in about 3 hours.  Assuming it has a satellite on board.
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I wonder if Launcher One & Cosmic Girl could launch from Guiana Space Center get a zero degree inclination for GTO Launch?

Why?  It can fly from the Cape or Kwaj to the equator to perform the mission.
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