SpaceX Tuesday...
Discussion
eharding said:
Some initial camera outages during that Starlink launch, but they showed the view from the first stage camera most of the way down including the landing - have they shown that live before? Interesting that the booster camera kept running whilst the ship camera froze just before touchdown - more vibration on the boat than the booster from the rocket efflux?
Probably just the antenna on the booster is a long way from the ionisation caused by the rocket burn?Beati Dogu said:
Talksteer said:
Got to be careful of these as for example the Gemini astronauts thought their ejector seat would kill them due to the pure oxygen in the cabin. This was actually false as the rocket wouldn't ignite until they were out of the capsule and fire wouldn't survive the windblast.
I'm not sure I'd want to try it all the same. All the ejection seat tests were done with a pure nitrogen environment. Using the ejection seats on Gemini would have required releasing the hatches with explosive bolts and firing them out of the way on little rockets first. Then there's the seat ejection mechanism itself, which also use solid rockets. All that in a pure oxygen environment would likely have been a disaster, even with a space suit on (as NASA found out later the hard way with Apollo 1). Gemini astronaut Thomas Stafford said he was glad they never had to use them. "We'd have been two Roman candles shooting off into the sand and palmetto trees".
That's even if the hatches did actually eject. On one test, witnessed by Gus Grissom and John Young, the hatches stayed put and the ejection seats slammed their test dummies right into them.
https://historycollection.jsc.nasa.gov/JSCHistoryP...
Gordon Cress was the test engineer for the Gemini ejection seats, he posted this responce to Tim Dodds video on the subject.
Gordon Cress said:
Tim, almost hate to add to the many many comments already here, but since I was deeply involved in the Gemini program..... First the Gemini vehicle was a spacecraft, not a capsule. NASA went to great lengths to make that distinction; it could change orbits, maneuver in space, dock with other vehicles, etc. The Mercury was a capsule; it could not change orbits, etc.
I was the project test engineer on Gemini for Weber Aircraft. We were tasked to design, test and qualify it for McDonnell Aircraft (MAC) and NASA. We, Weber Aircraft spent three years in providing an escape system that was the most sophisticated and complex system ever envisioned. It had to provide the astronaut occupants with safe egress and recovery from (1) a pad abort condition should the booster suffer a catastrophic failure. The system had to eject the occupants more than 500 feet away and bring them safely to earth via a personal parachute, (2) a high speed max Q condition during the boost phase, (3) a high speed Mach 4 ejection at 45,000 and (4) a high altitude ejection up to 70,000 feet. A whole lot more than those currently in service with the F-35, F-22, F-16, F-15, B-2, etc. Weber also provided the lightweight systems used in NASA lifting bodies M2-F2, HL-10 and X-24 in addition to those for the LLRV and LLTV ( have the filmed footage of Neil Armstrong, Joe Algranti and Stuart Present ejecting from it).
Astronaut safety was the primary concern throughout the program and every conceivable failure mode and environment was considered.
Secondly, you were correct in listing the reasons for ejection seats. Jim Chamberlain had always championed them and with good reason for the Gemini program. The weight of an escape rocket system would have been many times that of the seats and they'd have spent much fuel getting to a safe altitude where the vehicle parachutes could be relied on to affect safe recovery.
Modern ejection seats have provided a 90% safe recovery rate for the past 50 years. And a good deal of the 10% failures are pilots delaying the decision to eject. There were some spinal compression fractures in early Martin Baker seats before we realized the importance of keeping onset rates below 150 gs/sec. Once that was solved there have been very few back problems due to ejections. More than 12,000 pilots have had their lives saved by ejection seats and I think they'd take exception to your comments regarding the safety and capabilities of ejection seats.
John Young and Gus Grissom were not at the Randsburg Wash facility of China Lake when the hatch problem caused only one seat to be ejected. I was there and had Jim Lovell and Frank Borman with me. And the seat did not "blast through the hatch." The system works like this...when either occupant pulls his ejection control handle to fire an initiator, the hot high pressure gas is routed to both hatch actuators. The hatch actuator initiator fires to start the hatch opening sequence. As the hatch actuator piston moves up it releases the hatch latches and starts opening the hatch. When the piston reaches the top of the actuator and hatch is locked in the open position, hot gas is vented off to the rocket catapult (rocat). The catapult ignites and moves the seat up the rails. When the seat reaches the top of the rails, the catapult is stripped off and the seat rocket is ignited. In this instance, the o-ring on the piston failed and hot gas was vented off to
the rocat before the hatch was fully open. The seat moved up the rails and struck the hatch structure. This jammed the seat on the rails. Both the hatch structure and the seat headrest structure sustained some damage. The test dummy's helmet was cracked. When we were looking at the post-test damage, Jim looked over at Frank and inquired if maybe Frank might interested in trading seats; Frank thanked him for his kind offer, but decided that he was fully satisfied with his seat. MAC installed double o-rings on the piston and no further problems of this kind were encountered.
Since the seat is at the top of the rails when the rocket is ignited there is no flame inside the vehicle before that and no problem with oxygen environment.
While our astronauts are extremely intelligent, super test pilots and true American heroes, none of them that I'm aware have any experience whatsoever in escape system design. Several of them, including Tom S., did make derogatory comments about the Gemini seat system and that was unfortunate. They are human just like the rest of us, but their comments should not be taken as gospel.
Weber, MAC and NASA expended blood, sweat and tears for those three years (1962-1965) to provide our guys with the finest system available. It's very easy 50 years later to make derogatory comments regarding why certain decisions were made, but where were you when the decision had to be made?
Thanks for letting me vent!
If you'd like to follow my blog visit me at https://geminihistory.com/welcome-to-my-blog/
To add my further comment from stuff I do understand. To get something to combust you need a stable flame front which doesn't have air velocity exceeding the rate at which the flame propagates. In a gas turbine you do this by slowing the airflow from mach 0.4 (at high temp so around 600mph) to about 10-15m/s in the combustor by means of a diffuser, swirl injector and re-circulation jets. 20 cm later it's doing about 2000 mph once combusted.I was the project test engineer on Gemini for Weber Aircraft. We were tasked to design, test and qualify it for McDonnell Aircraft (MAC) and NASA. We, Weber Aircraft spent three years in providing an escape system that was the most sophisticated and complex system ever envisioned. It had to provide the astronaut occupants with safe egress and recovery from (1) a pad abort condition should the booster suffer a catastrophic failure. The system had to eject the occupants more than 500 feet away and bring them safely to earth via a personal parachute, (2) a high speed max Q condition during the boost phase, (3) a high speed Mach 4 ejection at 45,000 and (4) a high altitude ejection up to 70,000 feet. A whole lot more than those currently in service with the F-35, F-22, F-16, F-15, B-2, etc. Weber also provided the lightweight systems used in NASA lifting bodies M2-F2, HL-10 and X-24 in addition to those for the LLRV and LLTV ( have the filmed footage of Neil Armstrong, Joe Algranti and Stuart Present ejecting from it).
Astronaut safety was the primary concern throughout the program and every conceivable failure mode and environment was considered.
Secondly, you were correct in listing the reasons for ejection seats. Jim Chamberlain had always championed them and with good reason for the Gemini program. The weight of an escape rocket system would have been many times that of the seats and they'd have spent much fuel getting to a safe altitude where the vehicle parachutes could be relied on to affect safe recovery.
Modern ejection seats have provided a 90% safe recovery rate for the past 50 years. And a good deal of the 10% failures are pilots delaying the decision to eject. There were some spinal compression fractures in early Martin Baker seats before we realized the importance of keeping onset rates below 150 gs/sec. Once that was solved there have been very few back problems due to ejections. More than 12,000 pilots have had their lives saved by ejection seats and I think they'd take exception to your comments regarding the safety and capabilities of ejection seats.
John Young and Gus Grissom were not at the Randsburg Wash facility of China Lake when the hatch problem caused only one seat to be ejected. I was there and had Jim Lovell and Frank Borman with me. And the seat did not "blast through the hatch." The system works like this...when either occupant pulls his ejection control handle to fire an initiator, the hot high pressure gas is routed to both hatch actuators. The hatch actuator initiator fires to start the hatch opening sequence. As the hatch actuator piston moves up it releases the hatch latches and starts opening the hatch. When the piston reaches the top of the actuator and hatch is locked in the open position, hot gas is vented off to the rocket catapult (rocat). The catapult ignites and moves the seat up the rails. When the seat reaches the top of the rails, the catapult is stripped off and the seat rocket is ignited. In this instance, the o-ring on the piston failed and hot gas was vented off to
the rocat before the hatch was fully open. The seat moved up the rails and struck the hatch structure. This jammed the seat on the rails. Both the hatch structure and the seat headrest structure sustained some damage. The test dummy's helmet was cracked. When we were looking at the post-test damage, Jim looked over at Frank and inquired if maybe Frank might interested in trading seats; Frank thanked him for his kind offer, but decided that he was fully satisfied with his seat. MAC installed double o-rings on the piston and no further problems of this kind were encountered.
Since the seat is at the top of the rails when the rocket is ignited there is no flame inside the vehicle before that and no problem with oxygen environment.
While our astronauts are extremely intelligent, super test pilots and true American heroes, none of them that I'm aware have any experience whatsoever in escape system design. Several of them, including Tom S., did make derogatory comments about the Gemini seat system and that was unfortunate. They are human just like the rest of us, but their comments should not be taken as gospel.
Weber, MAC and NASA expended blood, sweat and tears for those three years (1962-1965) to provide our guys with the finest system available. It's very easy 50 years later to make derogatory comments regarding why certain decisions were made, but where were you when the decision had to be made?
Thanks for letting me vent!
If you'd like to follow my blog visit me at https://geminihistory.com/welcome-to-my-blog/
Short summary is the various pyro charges are not comparable to the Apollo 1 fire, while everything would be soaked in oxygen you don't have a mass of combustable material next to the source of ignition like you do with the electrical fire. If anything all the oxygen soaking would do is make sure that the pyrocharge burns in totality.
Second issue is that you are only spending ~0.1 of a second in the cabin, just the ejector phase of the system is going to accelerate the astronaut to a velocity that would blow out the flames, once the rocket fires you are going way to fast for any flame to remain lit. Once you are outside in the air the oxygen concentration is normal so nothing should be burning.
The reason I imagine that they used nitrogen on the test article is to preserve the cabin for multiple shots including ones which fail. Not particulary a concern for the optional system.
Eric Mc said:
Yeah what would an actual Shuttle pilot know.
See my post above regarding Astronaut promulgating second hand stories on systems vs actual engineers who were specialists on their individual bit of kit.Go to NTRS and find that Columbia survivability study, short answer is they don't know nobody has really tested or modelled what are the limits on suited re-entry.
Regarding the plume stuff like go-pros, thin foils, electrical cables and ordinary paints survive being much more deeply into high altitude rocket plumes than an ejecting astronaut would.
There is plenty of evidence on high speed ejections (up to Mach 3).
The outcome isn't always great.
As far as I know, only one person has ever successfully ejected over Mach 3 - and the other occupant of the aircraft died. The only emergencies that have occurred above that speed have all resulted in 100% fatalities.
Manufacturers spent a huge amount of effort in designing and developing escape pods and capsules for high speed aircraft in an effort to overcome the shortcomings of using seats at Mach 2 or above. They were never that reliable either.
The only way to get people away from a wayward rocket is using some sort of rocket extraction system pulling the capsule or spacecraft clear. That is why ALL current spacecraft designs use this system.
As I said, these people do know what they are doing.
The outcome isn't always great.
As far as I know, only one person has ever successfully ejected over Mach 3 - and the other occupant of the aircraft died. The only emergencies that have occurred above that speed have all resulted in 100% fatalities.
Manufacturers spent a huge amount of effort in designing and developing escape pods and capsules for high speed aircraft in an effort to overcome the shortcomings of using seats at Mach 2 or above. They were never that reliable either.
The only way to get people away from a wayward rocket is using some sort of rocket extraction system pulling the capsule or spacecraft clear. That is why ALL current spacecraft designs use this system.
As I said, these people do know what they are doing.
Eric Mc said:
There is plenty of evidence on high speed ejections (up to Mach 3).
The outcome isn't always great.
As far as I know, only one person has ever successfully ejected over Mach 3 - and the other occupant of the aircraft died.
If you're talking about the SR71 incident, in the words of the survivor, "I hadn't initiated an ejection." The aircraft broke up around them.The outcome isn't always great.
As far as I know, only one person has ever successfully ejected over Mach 3 - and the other occupant of the aircraft died.
"My seat belt and shoulder harness were still draped around me, attached and latched. The lap belt had been shredded on each side of my hips, where the straps had fed through knurled adjustment rollers. The shoulder harness had shredded in a similar manner across my back. The ejection seat had never left the airplane; I had been ripped out of it by the extreme forces, seat belt and shoulder harness still fastened"
I don't think this makes your point incorrect however....
Was discussed on the NSF stream earlier. It has varied a lot for the first 4 tests. I believe they said SN8 was 75 days! SN11 was the fastest with around 20 days. They said if all pre-flight tests went to plan, weather good, no other issues (like FAA rep not being there) it could be possible for SN15 to fly in a week.
Edit: Cross posted with Smiljan.
Edit: Cross posted with Smiljan.
F20CN16 said:
Was discussed on the NSF stream earlier. It has varied a lot for the first 4 tests. I believe they said SN8 was 75 days! SN11 was the fastest with around 20 days. They said if all pre-flight tests went to plan, weather good, no other issues (like FAA rep not being there) it could be possible for SN15 to fly in a week.
Edit: Cross posted with Smiljan.
Useful illustration of the timelines for SN8 - SN11 plus SN15 to date:Edit: Cross posted with Smiljan.
https://chrisbillington.net/starship_timelines.htm...
I may be wrong, but I believe they installed a thrust simulator jig into the launch stand last week and now SN15 is sat above it. So I’m not sure if the raptors have been installed yet? They craned the jig in over the launch stand, so I’m not sure if they will carry out tests and then have to move the rocket to remove the test jig?
The Raptors won't be on it yet. The thrust puck design is new apparently, so they want to test it out first.
I believe they can remove the hydraulic actuators from the stand once they're happy and then fit the engines without moving SN11 again.
Meanwhile the Russians have successfully launched Soyuz MS-18 to the ISS this morning. They should arrive at 11.07 GMT.
I believe they can remove the hydraulic actuators from the stand once they're happy and then fit the engines without moving SN11 again.
Meanwhile the Russians have successfully launched Soyuz MS-18 to the ISS this morning. They should arrive at 11.07 GMT.
Beati Dogu said:
The Raptors won't be on it yet. The thrust puck design is new apparently, so they want to test it out first.
I believe they can remove the hydraulic actuators from the stand once they're happy and then fit the engines without moving SN11 again.
Meanwhile the Russians have successfully launched Soyuz MS-18 to the ISS this morning. They should arrive at 11.07 GMT.
As the crane is up there, possibly staying there ( they're having another one delivered in parts), may be easier to move it to the other stand and install them rather than remove the thrust test equipment, as they will probably need to test BN2 once that is assembled.I believe they can remove the hydraulic actuators from the stand once they're happy and then fit the engines without moving SN11 again.
Meanwhile the Russians have successfully launched Soyuz MS-18 to the ISS this morning. They should arrive at 11.07 GMT.
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