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The Spaceflight Thread
« Reply #180 on: November 07, 2018, 11:36:58 AM »
 

* EROSION.jpg (315.05 kB)

The Spaceflight Thread
« Reply #181 on: November 07, 2018, 11:48:35 AM »

The Spaceflight Thread
« Reply #182 on: November 07, 2018, 12:26:45 PM »
Here's a shot showing the one side booster having an issue during separation from the Soyuz abort flight.  It's the one on the left in the photo.



https://twitter.com/hashtag/%D0%A1%D0%BE%D1%8E%D0%B7%D0%9C%D0%A110?src=hash&ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1057941246390472709&ref_url=http%3A%2F%2Fnasawatch.com%2F



The Spaceflight Thread
« Reply #183 on: November 07, 2018, 12:38:12 PM »
https://www.youtube.com/watch?v=5HMwKwWnV4k&feature=youtu.be&t=1058

17:45

What did he mean by this? lol

That she will be coming back home with really bad bone density? ::)


The Spaceflight Thread
« Reply #184 on: November 07, 2018, 02:53:50 PM »
What did he mean by this? lol


Sounded like:

Quote
[...] I just, uh, congratulations, amazing, what an amazing achie--uh, thing that you've done [...]"


Seems legit.

The Spaceflight Thread
« Reply #185 on: November 15, 2018, 06:00:06 PM »
ust over an hour ago, Development Engine(DE)0525 completed a 650 second hotfire test with 113% Rated Power Level.  Originally the RS25 engine ran at 100%, over the years upgrades to the engine have allowed the engine to be run at levels higher than before.  Instead of recalibrating for the new 100% its easier to simply say the power level is at 113%.  They are testing some additive manufacturing(3-d printed) engine components



peace
Hog

The Spaceflight Thread
« Reply #186 on: November 15, 2018, 06:27:02 PM »
ust over an hour ago, Development Engine(DE)0525 completed a 650 second hotfire test with 113% Rated Power Level.  Originally the RS25 engine ran at 100%, over the years upgrades to the engine have allowed the engine to be run at levels higher than before.  Instead of recalibrating for the new 100% its easier to simply say the power level is at 113%.  They are testing some additive manufacturing(3-d printed) engine components



peace
Hog
I like that some Stoner/Rocker logic, coach and sales director motivation, and sales and marketing campaigns is being adopted by rocket scientists and engineers.... "but these goes to 11," "give 110% percent" etc.....

The Spaceflight Thread
« Reply #187 on: December 03, 2018, 08:55:50 AM »
And the next 3 have made it to orbit safely. 

Hey, what do you get when you put a Russian, an American and a Canadian in a tin can?

Congrats to David St Jacques and Anne McLain representing the Americas on orbit.



peace
Hog

The Spaceflight Thread
« Reply #188 on: December 03, 2018, 12:26:00 PM »
Soyuz MS-11 has successfully docked to ISS.

http://www.youtube.com/watch?time_continue=7&v=QUY9zjHn2NE

Currently the crews are equalizing the air pressures between the Soyuz Orbital and Descent stages.
Next event is hatch opening.

Attached pic shows the ISS with all the different cargo and crew vehicles docked to ISS after Soyuz MS-11 docked.

peace
Hog

The Spaceflight Thread
« Reply #189 on: December 03, 2018, 12:32:01 PM »
The Cosmonauts and Astronauts have doffed their Russian Sokul space suits as they're safely docked to ISS.

The Spaceflight Thread
« Reply #190 on: December 04, 2018, 12:29:14 PM »
And after a successful docking using the Soyuz automatic docking system, the Northrop-Grumman(formerly Orbital ATK) Cygnus and Space Exploration Tech Corp.'s Dragon cargo resupply vehicles BOTH do not dock to the ISS, they approach close-by and then are grappled via the CANADARM-2(SSRMS-Space Station Remote Manipulator System) and then berthed to the ISS under complete control of the SSRMS.  Here is the hatch opening of the ISS crew and Soyuz MS-11 spacecraft greeting each other.



If you need to get away from the ISS in a hurry, you dont want your lifeboat to have to be brappled by a CANADARM and then released to safety.  You want top be able to get to your lifeboat, close the hatches and jettison your lifeboat away from the ISS as quickly as possible. Of course this would be necessary in the most dire of circumstances. eg ISS gets hit by a not so "micro",  micrometeroid and is losing pressure at a very high rate. Let's hope that your Soyuz lifeboat isnt the structure that has been breached.

Due to the fact that crews that fly up to ISS on Soyuz space craft, almost always return to Earth aboard the same Soyuz spacecraft the "couches" that crew lay down upon prior to launch and prior to undocking from ISS, are vacuum molded custom "liner" for each crewmember, while it is possible to swap out these custom "liners" it is infrequently performed for safety reasons. The Soyuz hits the ground hard, it fires retrograde rocket motors just a few feet from the ground in order to reduce the G loading upon touchdown. The movie Gravity emphasizes the Soyuz retrograde rockets and uses them for propulsion to get to the Chinese space station Shenzous.

The amount of time that a Soyuz craft can remain in space is about 200 days, any longer and its propellants begin to decompose, so 200 days was chosen as a safe on orbit time for Soyuz.  This is why the current ISS crew who rode up on Soyuz MS-09 had to leave on December 21st whether there was new crew aboard ISS or not. The Soyuz MS-09 was reaching the end of their safety net in regards to the Soyuz vehicles on-orbit time constraints related to propellant stability.  That would have been horrible if the Soyuz MS-11 crew weren't able to reach ISS before the 21st be it due to technical issues, another abort or some other issue.  The 18 year
The Soyuz vehicle takes up to 3 humans to orbit, docks with the ISS, then sits there for up to 200 days on orbit, with its hatches open, acting as a lifeboat waiting just in case the 3 crewmembers need to evacuate to their Soyuz lifeboats.  One scenario is that the crew evacuates to the Soyuz and awaits further instructions with the ISS/Soyuz hatches in the open positions. The other emergency scenario includes crew retreating to their respective Soyuz vehicles, get inside and close the hatches.  There has been a few times where  a predicted piece of space debris or asteroid may come within a few kilometers. The crew enters their Soyuz crafts leaving the hatches open.  Occasionally a Debris Avoidance Maneuver(DAM) may be completed, but the amount or speed at which you can actually increase or decrease the altitude of the ISS's almost 1 million pounds is very limited.  The stations own thrusters can be used, and depending on what cargo/crew vehicles are docked to the ISS, their own propulsion can be used to not only change the ISS's altitude for DAMs, but also to boost the ISS's continually decreasing altitude.  While orbiting at around 408 kilometers(253 miles) the ISS is almost completely out of the Earths atmosphere, but there is still sufficient molecules of atmosphere to induce drag upon the ISS which decreases its velocity, the slower it travels the lower its altitude becomes.  It likes to orbit at about approx 28163km/17500mph  which gives you an Earth orbit every 90 minutes.  Compare the ISS orbit to the Hubble Space Telescopes altitude which is 540kms(336miles) which is about as high as the Space Shuttle Orbiter Vehicles to could reach, both for the Telescopes initial deployment on April 25 1990 during STS-31 and also during its various servicing Missions
Servicing Mission #1 STS-61 Endeavour in December 1993,
Servicing Mission #2 STS-82 Discovery in Feb 1997
Servicing Mission #3A STS-103 Discovery in December 1999
Servicing Mission #3B STS-109 Columbia in march 2002
Servicing Mission #4 STS-125 Atlantis in May 2009.  Servicing Mission #4 almost didn't occur as NASA administrator Shaun O'Keefe in the wake of the STS-107 Columbia entry failure didn't want to risk human lives to extend the service life of HST.  Well a new NASA administrator was installed in March 2005 and he, Michael Griffin OK'd one final serving mission if it hadn't, the Hubble Space Telescope would NOT be performing science missions at this moment.

""In October 2006 Griffin gave the final go-ahead, and the 11-day mission by Atlantis was scheduled for October 2008. Hubble's main data-handling unit failed in September 2008, halting all reporting of scientific data until its back-up was brought online on October 25, 2008. Since a failure of the backup unit would leave the HST helpless, the service mission was postponed to incorporate a replacement for the primary unit.""

While the Space Shuttle Program was up and running, the ISS was kept at a lower altitude than it's current 408 kilometers/254miles.  I remember the altitude being around 330-340kms(205-211 miles) when the US Space Shuttle was in operation.  This lower altitude was used in order to help the Space Shuttle get the heaviest payloads up to the ISS orbit.  For every degree above Florida Kennedy Space Centers 28.5 the Shuttle lost roughly 500 pounds of cargo capacity. Since the ISS orbits on a 51.6 inclination thats 23.1 higher for hHazakistan launches than KSC USA launches.  23.1 x 500 pounds=11,500 pounds.  So launching to the ISS 51.6 orbit automatically causes the payload capacity to take a hit of 11,500 pounds.
NASA's answer was to either to increase thrust, or to lighten the load(For each pound of weight reduction, the cargo-carrying capability of the shuttle spacecraft was increased almost one pound.), or both. 
In order to increase thrust the 5 segment solid rocket booster(SRB) which provided 3.6 million pounds of thrust was developed to make up that penalty, the usual SRBs were 4 segment units providing just over 3 million pounds of thrust each.  It should be noted that the new SLS super-rocket will use 2 of the new 5 segment SRBs, which have yet to fly. They have only been fired in full scale development firings.  Both the newer 5 segment and the 4 segment Solid Rocket Boosters fire for approx. 122-127 seconds.
In order to lighten the load, NASA decided to once again lighten up that massive aluminum External Tank(ET) which holds all the Liquid Oxygen(LOX and Liquid Hydrogen(LH2) that the 3 RS25 Space Shuttle Main Engines would require to fire at 104.5% for over 8-1/3 minutes or approx 500 seconds.

There have been 3 iterations of the External Tank(ET):

1) Standard Weight Tank (SWT)35,000 kg (77,000 lb) inert.  This tank was used for the test flights, STS-1 though STS-4 and for 2 operational missions, STS-5 and STS-7.  The first 2 tank for STS-1 and STS-2 were painted white in order to protect the Spray On Foam Insulation(SOFI) from UV damage as they weren't exactly sure how long these test launches would be sitting out on the pad exposed to the elements. As it turns out, the SOFI darkens in colour the more it is exposed to UV light.  Newly sprayed tanks will have a very light brown colour, while tanks exposed for some time will be darker in colour.  Often times you'll see dark brown acreage interspersed with very light brown sections.  This is where some foam has had to be removed in order to access some portion of the tank for repairs. Then once repairs/testing was completed, new SOFI would be applied and seeing that these portions or re-applied foam have not yet been exposed to UV light whereas the rest of the foam has already been exposed, large variations of light to dark brown colours are visible.
For STS-3 and 4 the ETs were NOT painted white, as such, 600 pounds were saved simply by the weight of the paint being absent. Another several hundred pounds were saved by removing the proven unnecessary anti-geyser lines that ran the length of the tank.

2) Light Weight Tank(LWT) each weighed approximately 30,000 kg (66,000 lb) inert. The first LWT was flown on STS-6 and the last LWT was used on the STS-107 Columbia flight which failed during the entry phase of the mission.
""The weight reduction from the SWT was accomplished by eliminating portions of stringers (structural stiffeners running the length of the hydrogen tank), using fewer stiffener rings and by modifying major frames in the hydrogen tank. Also, significant portions of the tank were milled differently so as to reduce thickness, and the weight of the ET's aft solid rocket booster attachments was reduced by using a stronger, yet lighter and less expensive titanium alloy.""

3) Super Light Weight Tank (SLWT)
58,500 lb (26,500 kg) inert.
Length: 153.8 ft (46.9 m)
Diameter: 27.6 ft (8.4 m)
Gross Liftoff Weight: 1,680,000 lb (760,000 kg)

LOX Tank
Length: 54.6 ft (16.6 m)
Diameter: 27.6 ft (8.4 m)
Volume (at 22 psig): 19,541.66 cu ft (146,181.8 US gal; 553,358 l)
LOX mass (at 22 psig): 1,387,457 lb (629,340 kg)
Operation Pressure: 34.736.7 psi (239253 kPa) (gauge) (absolute)

Intertank (portion of the ET where the Liquid Oxygen Tank and the Liquid Hydrogen Tank came together.

Length: 22.6 ft (6.9 m)
Diameter: 27.6 ft (8.4 m)

LH2 Tank
Length: 97.0 ft (29.6 m)
Diameter: 27.6 ft (8.4 m)
Volume (at 29.3 psig): 52,881.61 cu ft (395,581.9 US gal; 1,497,440 l)
LH2 mass (at 29.3 psig): 234,265 lb (106,261 kg)
Operation Pressure: 3234 psi (220230 kPa) (absolute)
Operation Temperature: −423 F (−252.8 C)

The SLWT was first flown in 1998 on STS-91 and was used for all subsequent missions except for STS-99 Endeavour and STS-107 Columbia
""The SLWT had basically the same design as the LWT except that it used an aluminium-lithium alloy (Al 2195) for a large part of the tank structure. This alloy provided a significant reduction in tank weight (~3,175 kg/7,000 lb) over the LWT. Manufacture also included friction stir welding technology. Although all ETs produced after the introduction of the SLWT were of this configuration, one LWT remained in inventory to be used if requested until the end of the shuttle era. The SLWT provided 50% of the performance increase required for the shuttle to reach the International Space Station. The reduction in weight allowed the Orbiter to carry more payload to the highly inclined orbit of the ISS.""

The Core Stage of the new Space Launch System which uses 4 of the same engines as the Space Shuttle, in fact 14 of the 16 remaining RS25-D engines have in fact already flown to space on Space Shuttles. The other 2, Main Engine (ME) 2062 and ME-2063 were built in 2010 and 2014 respectively. Both ME-2062 and ME-2063 are due to fly on EM-2, the first crewed SLS mission which will fly 4 astronauts in a multi-trans-lunar injection (MTLI), or multiple departure burns, and includes a free return trajectory from the Moon. Basically, the spacecraft will orbit Earth twice while periodically firing its engines to build up enough velocity to push it toward the Moon before looping back to Earth.


1) fire burning in microgravity
2) Space Shuttle External Tank cutaway
3) Solid Rocket Booster segments for EM-1 there are 5 segments for each booster for SLS
4) External Tank from STS-1 Columbia just after being jettisoned and allowed to fall back to the Indian Ocean.  The black marks at about the shoulder level below the curvature of the nose are from the Booster Separation Motors which fire and actually push the SRBs away from the External Tank and Orbiter Vehicle. There are 3 Booster Separation Motors at the top of each Booster, their exhaust impinges against the ET and blackens it.  The very end of the ET is blackened as there is major heating and convection currents which burn the end of the ET.


5) A short clip which shows the forward Booster Separation Motors burning and pushing the SRBs away from the External Tank.  This happens at about 146,000 feet about 123 seconds after they first ignited.  They are only jettisoned after the thrust chamber pressure in each SRB is less than 50psi.  The front Reaction Control System is fired in order to keep most of all the soot and dirt from these Booster Separation Motors off of the front facing windows of the Orbiter.  See how toasty black the rear end of the ET gets. 
Here is the Booster Sep Motors video



The Spaceflight Thread
« Reply #191 on: January 06, 2019, 07:55:19 PM »

The Spaceflight Thread
« Reply #192 on: January 06, 2019, 08:17:38 PM »
Kewl video, tnx.

The Spaceflight Thread
« Reply #193 on: April 21, 2019, 04:19:38 AM »

The Spaceflight Thread
« Reply #194 on: May 17, 2019, 02:10:48 PM »
NASA going back to the Moon.

http://www.youtube.com/watch?time_continue=151&v=NrlX7VsVZrs


Canada has announced being an international partner to NASA.  We are building CANADArm-3.

peace
Hog


The Spaceflight Thread
« Reply #196 on: September 30, 2019, 10:44:28 AM »
That is an amazing shot TAAROA!

Here is the Soyuz rocket and Soyuz capsule (i dislike teh way the Russians use the same name for their launch vehicles AND the spacecraft) on the way out to the "pad" at the Baikonur Cosmodrome Kazakhstan.


And the crew including the first Arab to visit ISS. The United Arab Emirates own Astronaut Hazzaa AlMansoori launched aboard the very last Soyuz-FG rocket carrying 3 crew inside the Soyuz MS-15 space vehicle that launched nominally on September 25/2019.  "To celebrate this event, pictures of the Soyuz launcher and of Hazza Al Mansouri are projected on Burj Khalifa, the tallest building in the world."
The Soyuz FG is a human-rated launch vehicle(rocket) in use since 2001.  The newer Soyuz-2.1a launch vehicle launched an uncrewed test vehicle MS-14 that brought supplies but no crew to the ISS during its August 22, 2019 test launch.

Here's a pic of the last Soyuz FG being erected at the Baikonur Site 1

where Yuri Gagarin first launched into orbit aboard a Vostok-1 rocket back on April 12/1961.  Here is a pic of the actual capsule he rode in. After re entry At about 7,000 metres (23,000 ft), Gagarin ejected from the descending capsule as planned and landed using a parachute. This "ejection" consisted of Gagarin opening the hatch and jumping out.
 This fact was NOT known until many years afterwards.

And liftoff


And here's another shot of the Soyuz 2nd stage


Once the United States gets their Commercial Crew program up and running the Boeing CST-100 "Starliner" launched upon a human-rated United Launch Alliance Atlas-V rocket and the Space Exploration Technologies Corporation Dragon-2 capsule launching atop a human rated Falcon-9 rocket will for the very first time since July 2011, have the ability to launch Americans into space, from United States soil, using United States hardware.

The Dragon-2/Falcon-9 vehicles will launch from Launch Complex 39-A at Kennedy SPace Center.  This is the launch facility that Space-X is leasing from NASA.  This is the same launch complex that some of the Apollo Moon missions and Space Shuttle missions launched from.

Here is the testing of the emergency egress systems at LC-39A.  Because the Falcon-9 rocket is much taller than the Shuttle access point was, the slidewire baskets had to be mounted higher than with Shuttle.  Back in the 80's Shuttle Commander and future NASA Administrator Major-General Charles  F Bolden was the only human to actually ride one of the slidewire baskets from the launch complex tower down to the ground. All other tests used simulated human weights.  At the end of teh slidewires, there will be an M-113 armoured personel carrier awaiting to take the astronauts to safety.


Here is the slidewires being released for the last time following the retirement of Space Shuttle in 2011. They are now currently located at the 265 foot level which is 70 feet higher than for Shuttle.  If you have to use these things, it's better NOT to look back as the world probably looks like it is ending at that point. Hopefully you get out of teh blast radius before you have "a bad day".


Here are NASA astronauts Shannon Walker, in front, and Bob Behnken(both assigned to the SPace-X portion of the NASA Commercial Crew Program) walking through a water deluge setup on the 265foot level of LC-39A.  Just in case they had to run through a hydrogen fire(which you cant see the flames) they walk through a water deluge to extinguish cool their Launch/Entry suits.  BTW  See the new Space-X Launch ENtry suits?


peace
Hog



The Spaceflight Thread
« Reply #197 on: September 30, 2019, 11:33:22 AM »
And here is the slidewire tests of the version that Boeing will employ at Cape Canaveral Air Force Station's Space Launch Complex-41 (SLC-41) where Boeing will be launching the Atlas-V rockets with the Boeing CST-100 Starliner capsule which will provide dual redundancy along with SPace Ex's Dragon-2 capsule/Falcon-9 rocket launching from Launch Complex-39A providing crew rotation for the International SPace Station.  No more paying teh Russians US$80 million per seat to get to and from the ISS.  Both the Starliner and Dragon-2 will stay on orbit docked to the ISS in case their respective crews need to quickly abandon the ISS during an emergency.



Space X has completed an orbital test that docked to the ISS and returned back to Earth.  The first orbital test of Crew Dragon 2 was an uncrewed mission, designated SpX-DM1 launched March 2, 2019 remained docked until March 8, 2019, then conducted the full re-entry, splashdown and recovery steps to qualify for a crewed mission.

That very same Dragon-2 capsule later exploded during an engine test on a test stand in Florida on April 20/2019. This has caused delays with the Space X Commercial Crew Flight Test schedule.

Here is the leaked cell phone camera video of the test from the test blockhouse. Obviously a serious issue to the crews to be inside these capsules.


And here is Scott Manley describing what happened.



Both the Boeing and Space-X capsules next step is to complete full on crewed orbital flight tests.
NASA Astronauts Bob Behnken and Douglas Hurley were announced as the crew on 3 August 2018 for the upcoming crewed orbital test.
First test crew - Boe-CFT: Michael Fincke, Christopher Ferguson, Nicole Aunapu Mann will crew the first Boeing Starliner Crewed Flight Test on orbit to the ISS.  It should be noted that Chris Ferguson is employed as a Test Pilot/Commander of the mission, he is no longer a NASA Astronaut.  IOW He is making a shitload more money being a Boeing Astronaut, than a NASA astronaut sitting in the seat beside him. This test flight will be Ferguson's 4th visit to space. He was an F-14 test pilot in his Navy days and Commanded the last Space Shuttle Mission-STS-135 back in July 2011.

Boeing Crew-CST-100 Starliner mockup and the astronauts initially selected for the first two missions, from left to right: Sunita Williams, Josh Cassada, Eric Boe, Nicole Mann, and Christopher Ferguson.


peace
Hog

The Spaceflight Thread
« Reply #198 on: October 10, 2019, 06:52:26 PM »
The first RS-25 engine is now being installed onto the first SLS rocket.  Main engine #2056 which last flew on STS-121, or the 2nd Return To Flight mission that Discovery flew to ISS.

Here are the rest of the engine assignments for the Artemis 1 through 4 missions.

EM-1 ME-2045, ME-2056, ME-2058, ME-2060

EM-2 ME-2047, ME-2059, ME-2062, ME-2063

EM-3 ME-2048, ME-2054, ME-2057, ME-2061

EM-4 ME-2044, ME-2050, EM-2051, EM-2052


We're going to the Moon yo!


peace
Hog

The Spaceflight Thread
« Reply #199 on: October 11, 2019, 12:31:05 AM »
The first RS-25 engine is now being installed onto the first SLS rocket.  Main engine #2056 which last flew on STS-121, or the 2nd Return To Flight mission that Discovery flew to ISS.

Here are the rest of the engine assignments for the Artemis 1 through 4 missions.

EM-1 ME-2045, ME-2056, ME-2058, ME-2060

EM-2 ME-2047, ME-2059, ME-2062, ME-2063

EM-3 ME-2048, ME-2054, ME-2057, ME-2061

EM-4 ME-2044, ME-2050, EM-2051, EM-2052


We're going to the Moon yo!


peace
Hog

Its about fucking time!

The Spaceflight Thread
« Reply #200 on: October 11, 2019, 04:28:28 AM »
Its about fucking time!

What, no video?

The Spaceflight Thread
« Reply #201 on: October 11, 2019, 07:21:55 AM »
What, no video?

Even before I clicked on this post I knew it would be this. I think maybe youre losing your edge.


The Spaceflight Thread
« Reply #202 on: October 11, 2019, 09:04:12 AM »
 https://podcasts.google.com/?feed=aHR0cHM6Ly9yc3MuYXJ0MTkuY29tL2dvbmU&episode=YjdlMzgzZDQtZDYwNS0xMWU4LTgyMzYtYzNmMTljZjkyMDc3

Interesting podcast about the long rumored lost Soviet cosmonauts from early in the space race.  I had a colleague when I worked at NASA, a ham radio operator, who had once met the brothers who allegedly picked up the transmissions from the doomed cosmonauts.

The Spaceflight Thread
« Reply #203 on: November 01, 2019, 11:48:36 PM »
I guess they're not bothered by the light either?

https://twitter.com/LVaughanJones/status/1189718599952470016

The Spaceflight Thread
« Reply #204 on: November 01, 2019, 11:57:49 PM »

The Spaceflight Thread
« Reply #205 on: November 09, 2019, 11:54:36 AM »
I guess they're not bothered by the light either?

https://twitter.com/LVaughanJones/status/1189718599952470016
The lights were switched on for those pics.

You can see Judy Resnick on the bottom at the end.  So obviously a mission before Jan 28/1986 when STS-51-L/Challenger broke up 73 seconds into flight.



peace
Hog

The Spaceflight Thread
« Reply #206 on: November 09, 2019, 01:30:31 PM »
And the last RS-25 "Adaptation" engine was bolted up to the first Core Stage of the SLS program.  This Core Stage will fire those 4 RS25 engines at 109% of their Rated Power Level from the pad to just over 17,000mph in under 9 minutes.  The 2 now 5 segment Solid Rocket Boosters(SRB-the Shuttle Program used 2(two) 4(four) segment SRBs making about 3 million pounds thrust).  The newer SLS 5 segment SRBs will make just under 4 million pounds of thrust. 
The RS25 engines begin to fire up 6.6 seconds before liftoff to allow them to come up from a dead standstill, up to 100% RPL within those few seconds, once the flight computers detect that the RS25s have indeed started an come up to 100% thrust, at T minus zero seconds, the igniters at the top of each SRB get their "fire" signals and the 4 explosive nuts that are tightened onto 4 bolts at the base of each SRB get their "fire" signals and each of the 8 nuts total are split in two, thus allowing the bolts to drop down into specifically designed "bolt catchers"(in order to prevent the bolts from becoming projectiles.  Then the entire SLS stack will rise up off of the Mobile Launcher(ML) and as the rockets clears the tower, the Main Engines throttle up from 100% RPL up to the never before used 109% RPL (during an actual flight-Shuttle COULD have used 109% but only in a do or die emergency as such a high throttle was VERY hard on the engines and hurt their reuse-ability, but since the SLS main engine will be dropped into the ocean, the impacts on reuse-ability are moot)perform its "roll maneuver" which "points" the rocket into the correct orientation and for the first approx 122 seconds, all 4 liquid propellant and the 2 solid propellant engines work in concert providing upwards of 10 million pounds of thrust.  As with Shuttle, both the 4 Core Stage engines AND the 2 SRBs will throttle down just before hitting the area of maximum dynamic pressure to ease the vehicle through that area, then once through that area and now supersonic, the SRBs "throttle up" to 100% and the RS25 core stage engines throttle up from approx 70% RPL back up to its 109%RPL levels.

Then after approx. 122 seconds, the pressure within the SRBs is less than 50psi and explosive charges at the top and bottom of each SRB are fired, then separation motors fire at both the top and the bottom of the SRBs to push them away from teh ciore stage, you do NOT want them recontacting the Core Stage. Something similar occurred last year(October 11, 2018) when the Soyuz rocket carrying the Soyuz capsule MS-10 with Russian commander Aleksey Ovchinin  and USA space virgin Nick Hague.  During staging one of the 4 boosters failed to separate correctly and recontacted the core stage.  This caused an immediate abort rocketing the crew capsule away from the failing booster.

Here is a good video of the abort.  As you can see, the Launch Escape Tower was jettisoned just prior to staging(just as it should) then the 4 boosters separate which from the ground makes a cross appearing shape, called Korolev's Cross(Koroloev was the Soviet rocket guy, akin to the USA Operation Paperclip -rocket engineer Werner Von Braun. He died before the unsuccessful Soviet Moon shots).  If he had lived, who knows how the Moon shots would have turned out?
Well the usual Soyuz rockets Korloevs Cross was mis-shaped as on eof the boosters jettisoned incorrectly.  Since the Launch Escape Tower was already gone, the secondary mode of escape was used by the firing of the engines of the Soyuz and got the crew capsule safely away from the failing rocket.  The abort occurred at a height of 50km and the crew capsule stopped going higher at about the 93 km/58 mile mark then started its fall downwards until the parachutes deployed allowing the crew capsule to land SAFELY 19 minutes 41 seconds after launch.



After the SRBs separate away from the SLS core stage after the SRBs have helped the Core Stage attain an altitude of approx. 28 miles at velocities of approx. 3000mph.(these are approx. values as the SLS ascent parameters havent been released yet).  The 4 RS-25s continue to fire at 109% until enough liquid hydrogen(LH2) and liquid oxygen(LOX) have burned away making the core stage light enough that the acceleration of the vehicle approaches 3 g's of acceleration. That's quite a push into ones seat.  I weight about 230 pounds, so at an acceleration of 3g's would make my seat experience a force of 690 pounds in the opposite direction of the engines thrust.  Falkie's seat would experience approx. 1300 pounds of force.lol
Once 3 g's of acceleration have been reached, in order to maintain crew comfort and utility, the 4 RS-25 engines will begin to pull its throttles back from 109% down to 70%-80% to maintain that 3 g of acceleration force all the way to Main Engine Cut Off(MECO). Now travelling at just over 17,000mph/28,000km/hr the Core Stage and the ICPS(Interim Cryogenic Propulsion Stage which is basically a modified Delta -4 upper stage) separate and since orbital velocity of 17,500 mph was NOT yet reached the Core Stage drops into the Indian or Pacific Ocean.  The ICPS then firse it's engines(2) and the ICPS/Orion Capsule and the European built orion Service Module continue on the way to orbit and beyond.
The ICPS will be used for the first 3 flights when it will be replaced with teh much more capable Exploration Upper Stage which has tanks for propellant to feed the 4 RL10C-3 with each engine making just under 25,000 pounds of thrust each, for a total thrust for the stage at just under 100,000 pounds of thrust.

Here is the 4 RS-25's installed(first attachment), finishing last Wednesday night, on the first Core Stage to be produced. This rocket will be used during Artemis-1 which will travel from Earth out passed the Moon and come back.  It;s a test flight and while it will carry an Orion Capsule and Orion Service Module, there will be no astronauts on board.  Humans are to fly on Artemis-2 in 2022.

This is on the same property where the Apollo programs Saturn-V rockets were assembled. The Michoud Assembly Facility in Louisiana.

After a mountain of testing, the Artemis-1 Core Stage will be loaded into the Pegasus barge and taken to the Stennis Space Center where it will be loaded into the B1/2 test stand where they will fire all 4 of the hydrogen/oxygen RS-25s at once.  EXACTLY what occurs in this video of the same B-1/2 test stand.  That's what 7.5 million pounds of thrust looks like.(yet is right around the same thrust that the 2 Space Launch Systems SRBs will output.  That's 2 rocket engines burning solid propellant providing just under 8 million pounds of thrust.


After the Artemis-1 Core Stage is finished its "Green Run" testing at Stennis, again the Pegasus barge will take the core stage to Kennedy Space Center in Florida where it will be taken to the Vehicle Assembly Building, erected to vertical, and stacked onto the 2 5 segment SRBs atop Mobile Launcher-1 which was MLP-3(Mobile LAuncher Platform-they added the word Platform forshuttle use for some reason) for Shuttle which was also Mobile Launcher-1 or ML-1 used for Apollo/Saturn-V Moon launches.  One of the Crawler Transporters that carry the Mobile Launchers was upgraded from a max capacity of 12 million pounds up to 18 million pounds.  Those SRBs are VERY heavy and weigh 1.6 million pounds each and these SLS boosters do NOT have the recovery parachutes that the Shuttle era 4 segment SRBs used.  The Shuttle ear 4 segment boosters weighed about 1.3 million pounds.

pics
1) 4 rs25 engines installed on Core Stage 1
2) Core Stage-1 with a single RS-25 installed
3) Same shot but from the 1960's where you can see multiple Saturn-V rockets with their 5 Rocketdyne kerosene/LOX powered F-1 rocket engines.  Each F-1 produces over 1.5 million pounds of thrust.





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