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I'd expect any active hydraulic hold-down latches to disengage sometime before ignition in the launch sequence. Actual lifting of the hold-down clamps would best be accomplished in sequence with the 'hold-up' retraction and QD retraction using a single actuator and linkages. Similar to the Soyuz launch mount: the clamps that hold the booster down are released by the stanchions that hold the vehicle up lifting upwards, which are able to lift when the weight of the booster is removed from them via counterbalance masses, which happens when the engines are ignited and producing greater than 1:1 TWR. Or think 'toggle lock' if you're familiar with firearms breech locking systems.

I don't think you want that.  You would prefer to be able to ignite, verify that all engines actually start and operate nominally, and only then release the rocket.  Otherwise, if there is some problem that causes multiple engines to not start, but enough start to reach e.g. 1.05:1 TWR, the rocket would lift off, but it would not be capable of reaching orbit (too much gravity losses).

Saturn V e.g. was forcibly held down until all five engines were running nominally, and I believe Falcon 9/Heavy is also held down the same way.  (IIRC, the Space Shuttle had frangible bolts or nuts holding it down, that were only released after all three main engines were running nominally; but once the SRBs were lit, there was no return.)
Personally I'm skeptical of this concern, especially when it comes from someone like Dan Dumbacher

There's no one in charge of NASA's mega-moon program. And the countdown clock is ticking.

For those of us less acquainted with Dan Dumbacher, what makes his words untrustworthy?

(I do note that the same concern is raised, and has been raised previously, by others, including ASAP (the Aerospace Safety Advisory Panel).)

Dumbacher served as deputy associate administrator of NASA's Human Exploration and Operations Mission Directorate from 2007 to 2014. I guess the thinking is that he likes a top-down approach with a lot of NASA oversight. The same can probably be said of ASAP. Although Dumbacher said that SLS was probably the last of its kind which was surprising given the role that he played in the past.
Other US Launchers / Re: US Launch Schedule
« Last post by Salo on Today at 03:43 pm »
Planned Flights
Flight        Date                    GRC Experiment
NG-18      October 2022      SoFIE MIST
SpX-26    November 2022    
SpX-27    January 2023    
NG-19     February 2023    CM-HT SoFIE RTDFS
Might it also be a "let's just do it and see what happens" kind of thing for the old idea of not having any heat shield tiles? An opportunity for relatively low cost to see just exactly how the hull of a full starship vehicle with whatever propellants are left on the inside performs during entry, even if it inevitably breaks without any perspirational cooling. If it fails super quickly, then they know "yeah thats never gonna work without tiles".

Maybe this combined with thermal paint?
I wouldn't assume a payload has to be large/heavy just because it's going on Starship.

All it takes is for Starship launch costs become <$40M for a F9 sized payload to GTO. At that point it becomes cheaper than launching on F9. Add the $8-10M profit margin and SpaceX profit margins per launch would be maintained regardless of what vehicle the payload is launching on. Current basic price (cost +profit) on F9 is ~$50M. Eventual price could get to <$30M before end of decade for Starship launch to GTO.

An active NG as a competitor and GTO payloads could get to truly big sizes since a 10t sat would cost less to launch then than a 3t sat would now.
Starlink 4529, from the recent 4-26 launched, failed soon after launch and should reenter in the next few hours after a week in orbit..
Two more Starlinks, 1322 and 2306, are expected to reenter on Sunday.
Personally I'm skeptical of this concern, especially when it comes from someone like Dan Dumbacher

There's no one in charge of NASA's mega-moon program. And the countdown clock is ticking.

Quote from:
And only now is NASA rushing to create a single management structure to handle it all.

“I keep seeing the pieces of the puzzle but we’re struggling with how the pieces of the puzzle are actually going to fit together and work together,” said Dan Dumbacher, executive director of the American Institute of Aeronautics and Astronautics and the former head of NASA’s Human Exploration and Operations Mission. “There’s a lot of things that have to be figured out.”

Dumbacher, who warned Congress this spring that NASA’s “piecemeal, uncoordinated approach is doomed to failure,” is among a number of agency insiders, veterans and oversight authorities who are sounding the alarm ahead of the maiden launch of the Space Launch System, the biggest rocket ever built, and the Orion capsule that are set to blast off in late August.

As pointed out in the article, the NASA Authorizations bill is forcing NASA to change its structure. For now, NASA has a manager for each Artemis mission but not an Artemis/Moon to Mars program manager. It seems that Congress wants NASA to have a single person in charge of the Artemis/Moon to Mars program. 

Here is what the NASA Authorization bill says:

Quote from: page 367
(1) MOON TO MARS OFFICE.—Not later than 120 days after the date of the enactment of this Act, the Administrator shall establish within the Exploration Systems Development Mission Directorate a Moon to Mars Program Office (referred to in this section as the ‘‘Office’’) to lead and manage the Moon to Mars program established under paragraph (2), including Artemis missions and activities.

NASA said that it would comply with this provision:

Quote from: the Politico article
President Joe Biden signed the NASA Authorization Act last Tuesday and the space agency says it now intends to overhaul the management structure.

“Yes, it’s in the bill and NASA will comply,” Jackie McGuinness, NASA’s chief spokesperson, told POLITICO.

But even NASA’s biggest boosters aren’t sure it’s enough. Rep. Don Beyer (D-Va.), who chairs the House Space and Aeronautics Subcommittee and co-wrote the NASA bill, says the Artemis program “is an inspiring, ambitious, and monumental initiative.”

“I want NASA to succeed,” he told POLITICO.

But that means instituting a more disciplined approach to “manage moon-to-Mars and its elements in an integrated way,” he said.

Beyer also said he is eager to receive a progress report on the new mandate — but that won’t come until six months from now, long after the planned first Artemis flight.

Incidentally, this is an example of a substantive provision in an Authorization bill that is not directly related to authorizing funding but that has an impact on NASA. So Authorizations bills do matter.

I don't know which approach is better. Jim Free seems to prefer having a manager for each Artemis missions where as Congress prefers a manager for all Artemis missions, i.e., a Moon to Mars program manager. Perhaps a combination of these two approach is possible.
Starlink 4529 reentered over northeastern China at 1702 UTC Aug 17.
The SLS isn't actually getting the humans it is carrying all the way to the surface of the Moon, like the Saturn V was able to do. So it is a misnomer to imply that.

Saturn V was not any more capable of getting people to the surface of the Moon, or to a low lunar orbit, than SLS is (will be)...

Sorry, but you are wrong and Ron is right. A single Saturn V launch carried ALL the elements to put 2 humans on the surface of the Moon and return them (and the CMP) safely back to Earth: CSM and the lander.

A single SLS launch will NEVER carry ALL the elements to put humans on the surface of the Moon and return them safely back to Earth. Not even Block 1B or even Block 2 will be capable of doing so. Every proposed lander is either too large or too heavy to be co-manifested with Orion on a Block 1B or Block 2 launch.

And yes, I am quite aware of the fact that the launch vehicle does not actually land the crew on the surface of the Moon. The stuff it carries does that. But that does not change the fact that a single Saturn V launch fully enabled a crewed landing on the lunar surface, whereas a single SLS launch will never enable a crewed landing on the lunar surface.

This is true, Saturn V had better TLI payload capability but this also ignores the increased capability and weight of said landers for Artemis as well as the Crew Module Orion.  It's not an apple to apples comparison. 
Right. All that SLS needs to be used for is sending crew to TLI. Which means it doesn’t need more than the 25t TLI it has now (doable with an upgraded Vulcan Heavy or Falcon Heavy or using LEO rendezvous with an earth departure stage launched on unmodified launch vehicles… or actually, take a page from Constellation and use an HLS as a major stage, used here for Earth departure of Orion). And technically 15-20t would be enough for 4 astronauts if Orion wasn’t designed oversized and overweight (slightly disproportionate for the increased crew size, partly due to Ares I heritage, but not THAT bad compared to Apollo… although Soyuz—originally designed for lunar and tested as part of Zond—shows a far more efficient approach is possible).
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