SpaceX Falcon 9 / Dragon 2 : SpX-DM2 - EOM/Return: August, 2020 : DISCUSSION

[Pete]

I'm puzzled as to why the reentry blackout was 6 minutes long.

This puzzles me because Apollo lunar return blackouts were just over 3 minutes, if I read it right and remember it correctly.

Given the higher velocity of Apollo, why would their blackout be roughly half of Dragon's?

Because the Dragon's reentry is at a *much* shallower angle,
thus allowing for lower peak g-force.

Apollo's nominal reentry hit 6.3-6.7g (Apollo 16 sniffed at 7.2g)

[yg1968]

To those wondering what can be done about the spectator fleet - The U.S. CG can stop, board and detain any U.S. flagged vessel anywhere in the World. Doesn't have to be inside the 12 mile limit.

However I suspect that unless CG (at Nasa's request) declare a keep out zone, there is little that can be done. A couple of tickets handed out is not going to put off anyone.

That's why we need keep out zones under the Artemis Accords too!

[joek]

Perhaps it is just an anomaly, but MarineTraffic.com shows that Go Navigator headed back out and is now sailing away from Pensacola, Florida. Probably not the case, although Stennis or Michoud could be a possibility if so.

Expect that given Doug & Bob are off, the primary interests are: (1) certain cargo, which may have departed with Bob & Doug; and (2) Dragon, which may be headed back to SpaceX Canaveral facilities?

[sdsds]

A NASA operated Gulfstream 3 is en route from Pensacola to Houston; expected arrival at 6:19 PM CDT. https://flightaware.com/live/flight/NASA5/history/20200802/2200Z/KNPA/KEFD

[CJ]

I'm puzzled as to why the reentry blackout was 6 minutes long.

This puzzles me because Apollo lunar return blackouts were just over 3 minutes, if I read it right and remember it correctly.

Given the higher velocity of Apollo, why would their blackout be roughly half of Dragon's?

Because the Dragon's reentry is at a *much* shallower angle,
thus allowing for lower peak g-force.

Apollo's nominal reentry hit 6.3-6.7g (Apollo 16 sniffed at 7.2g)

Thank you, Pete.

I wasn't aware of the higher Apollo Gs, that's almost in Soyuz ballistic reentry territory. Makes sense though, given both the speed and the entry corridor angle. 

I hope that the engineering reviews show that DM-2 was as successful as it now appears, because at the moment, to me it looks like a massive success. 

[Damon Hill]

Have not seen any info on landing accuracy?

We get some hints from GO Navigator taking 25 minutes to arrive. She was presumably stationed at the center of a predicted landing ellipse, and travels maybe 10kn (5 m/s)? So she was maybe 7.5 km away?

I find it interesting that they can parachute a fairing into the net on the recovery ship but they can't get closer than 7.5 km to the dragon parachuting down. Is that a safety factor, or a speed difference in the ships or a little of both/neither?

I don't know, but my guess is that it has to do with the type of parachutes. Falcon fairings use aerofoil-style parachutes which can be steered and thereby directed very accurately to a rendezvous with Ms Tree or Ms Chief. The chutes on Dragon are more standard round parachutes, which cannot manouever and so simply fall straight down, making their exact landing location somewhat less accurate.

Sent from my ONEPLUS A6013 using Tapatalk

This was researched and partially developed for the Gemini program, to enable dry landings.  On wheels.  Obviously didn't fly.

[mandrewa]

It's Jim Bridenstine's statement at the end that makes this press conference worth watching.
It isn't just what he quoted from Eric Berger, but it is all of Bridenstine's words.  I know
he has said similar things in the past but that doesn't make it any less important.

It's a complicated message he is trying to communicate and I don't know how many people get
it.  But he says it about as directly and clearly as it is possible to say.

[punder]

It's Jim Bridenstine's statement at the end that makes this press conference worth watching.
It isn't just what he quoted from Eric Berger, but it is all of Bridenstine's words.  I know
he has said similar things in the past but that doesn't make it any less important.

It's a complicated message he is trying to communicate and I don't know how many people get
it.  But he says it about as directly and clearly as it is possible to say.

And, as was said about Berger, he took an enormous amount of hate, during the confirmation process. I will continue my policy of prudent non-elaboration in not mentioning the reasons why. 

[yg1968]

The second press conference (with the astronauts, Elon and the Administrator) was much better. Much more positive. That's what I expected the first one to be.

[Jcc]

Any word on sonic booms along the entry path?

[TomH]

I'm puzzled as to why the reentry blackout was 6 minutes long.

This puzzles me because Apollo lunar return blackouts were just over 3 minutes, if I read it right and remember it correctly.

Given the higher velocity of Apollo, why would their blackout be roughly half of Dragon's?

Because the Dragon's reentry is at a *much* shallower angle,
thus allowing for lower peak g-force.

Apollo's nominal reentry hit 6.3-6.7g (Apollo 16 sniffed at 7.2g)

Thank you, Pete.

I wasn't aware of the higher Apollo Gs, that's almost in Soyuz ballistic reentry territory. Makes sense though, given both the speed and the entry corridor angle. 

I hope that the engineering reviews show that DM-2 was as successful as it now appears, because at the moment, to me it looks like a massive success.

Apollo had to have a steeper entry angle due to its 25,000 velocity. D2's reentry velocity is around 17,200 mph. If Apollo had hit the atmosphere at D2'shallower angle, its higher velocity would cause it to bounce off the atmosphere and careen off into space. So not only is the entry transit corridor shorter, the transit velocity is faster. Both factors decrease the blackout time of Apollo.

I believe that D2 also has more control than Apollo over its angle of attack and thus its ability to generate lift, creating a gentler and longer entry profile, thus reducing the G forces.

[mlindner]

Any word on sonic booms along the entry path?

During the coverage they had a satellite phone call with someone on the recovery boat and she said they heard a sonic boom near landing site.

[Cherokee43v6]

Perhaps it is just an anomaly, but MarineTraffic.com shows that Go Navigator headed back out and is now sailing away from Pensacola, Florida. Probably not the case, although Stennis or Michoud could be a possibility if so.

Expect that given Doug & Bob are off, the primary interests are: (1) certain cargo, which may have departed with Bob & Doug; and (2) Dragon, which may be headed back to SpaceX Canaveral facilities?

Heading for the SpaceX facilities at Canaveral makes the most sense.  After-all, SpaceX will need their proprietary equipment to properly service the vehicle to off-load propellants and make the vehicle safe, as opposed to the temporary safeing that is done aboard ship.  Most likely they are not allowed to add risk by transferring it to ground transport and hauling it over the roads amidst civilian traffic.  Thus, leave it on the boat away from other potential traffic and bring it to the proper facility.

[yg1968]

https://twitter.com/MilesDoran/status/1290082383002087424

[Jeff Lerner]

https://twitter.com/MilesDoran/status/1290082383002087424

Had Dragon landed in the Atlantic, would there have been the same number of pleasure craft ?...wondering if this is a Gulf vs. Atlantic issue....don’t recall any of this happening during Mercury, Gemini and Apollo....all those spacecraft landed in ocean waters...

Also, somewhat disappointed in the CG response..they explained what happened but didn’t offer any solutions for next time.

[LouScheffer]

Have not seen any info on landing accuracy?

We get some hints from GO Navigator taking 25 minutes to arrive. She was presumably stationed at the center of a predicted landing ellipse, and travels maybe 10kn (5 m/s)? So she was maybe 7.5 km away?

If I recall correctly, during the first Apollo flights they put the carrier in the center of the ellipse.  Then they started worrying they might get *too* accurate and hit the ship, and moved it out of the ellipse.   So the 7.5 km may not be the error, but a safe standoff distance.

[DaveS]

https://twitter.com/MilesDoran/status/1290082383002087424

Had Dragon landed in the Atlantic, would there have been the same number of pleasure craft ?...wondering if this is a Gulf vs. Atlantic issue....don’t recall any of this happening during Mercury, Gemini and Apollo....all those spacecraft landed in ocean waters...

I think you're forgetting that those missions were recovered by the US Navy. You got to be special kind of stupid to go anywhere near a US Navy vessel. If it had been the USN of the USCG, those boaters would have stayed well away as the USN has far more expansive rights to get rid of them than the USCG. If I recall things correctly, a USN vessel essentially "owns" the waters around it and has the right to self-defense against any and all vessels that get within a certain distance of it.

[sdsds]

Fantastic, just fantastic!

I agree with the earlier comment that the accuracy of the splashdown was "fine."

I also note in webdan's graphic the location of the aircraft is just legible, and it's a good bet the spacecraft is in the water at the center of that circle. (Attached again here for convenience.)

[Brovane]

https://twitter.com/MilesDoran/status/1290082383002087424

Had Dragon landed in the Atlantic, would there have been the same number of pleasure craft ?...wondering if this is a Gulf vs. Atlantic issue....don’t recall any of this happening during Mercury, Gemini and Apollo....all those spacecraft landed in ocean waters...

Also, somewhat disappointed in the CG response..they explained what happened but didn’t offer any solutions for next time.

Previous ocean landing sites were far away from land and the continental US.  The Demo-2 landing site was close to the continental US that small recreational boats could easily make the trip. 

[Oersted]

BTW, in the minutes before and during comms black-out Elon's body language displayed a LOT of nervousness. Constant fidgeting and running hands through his hair. Coupled with his very unstilted and unscripted remarks at the 2nd presser it's just good to see him being so straight-forward and passionate about his job, which is obviously more like a calling to him.