Author Topic: RS-68  (Read 32711 times)

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 15391
    • Space Launch Report
  • Liked: 8565
  • Likes Given: 1356
Re: RS-68
« Reply #80 on: 06/27/2020 03:20 pm »
Which ends still with the open question: What are the stats of the BE-3U?
Blue Origin, at:
https://www.blueorigin.com/engines/be-3
only tells us that it will produce 710 kN (160,000 lbf) thrust in vacuum, but there is a nice image of the engine on the page that someone might be able to use to reverse-engineer it a bit.  Since it is expander bleed cycle, it should have lower ISP than RL-10 and Vinci (which are 460-465 sec), but more thrust.  On the other hand it should or could have higher ISP than J-2X (448 sec).  Then again, I'm not a combustion engineer, so I could be wrong!  There is a chance that BE-3U could end up being a more important engine in future decades than BE-4.

 - Ed Kyle
« Last Edit: 06/27/2020 03:33 pm by edkyle99 »

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10351
  • Everyplaceelse
  • Liked: 2430
  • Likes Given: 13606
Re: RS-68
« Reply #81 on: 06/27/2020 04:07 pm »
The Expander Bleed is a Gas Generator implementation on the expander cycle: you take a very small amount of propellant (say, 2%), get it as hot as your turbine's blades can take, and after passing them through the turbines you dump it. So, you still inject liquid fuel into the main combustion chamber.
So no actual gas generator involved.

That means that the combustion chamber pressure is not limited to a level that the drive turbine can generate from the heat extracted from the CC.

It also means no GG to generate, start or re-start. The lightest, cheapest parts are the ones that aren't there.

And that T/W ratio for an LH2 engine is phenomenal
« Last Edit: 06/27/2020 04:08 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Re: RS-68
« Reply #82 on: 06/27/2020 05:50 pm »
Which ends still with the open question: What are the stats of the BE-3U?
Blue Origin, at:
https://www.blueorigin.com/engines/be-3
only tells us that it will produce 710 kN (160,000 lbf) thrust in vacuum, but there is a nice image of the engine on the page that someone might be able to use to reverse-engineer it a bit.  Since it is expander bleed cycle, it should have lower ISP than RL-10 and Vinci (which are 460-465 sec), but more thrust.  On the other hand it should or could have higher ISP than J-2X (448 sec).  Then again, I'm not a combustion engineer, so I could be wrong!  There is a chance that BE-3U could end up being a more important engine in future decades than BE-4.

 - Ed Kyle

To my knowledge (maybe one of you more read up on China or India will correct me here), the only expander bleed upper stage engine in the world is the LE-5(A, B, B-2, and soon B-3) used on the H-II and soon the H3.

Rather than drop a list of specifications here, i'm just gonna add a screenshot of the chart on the LE-5 wiki page.

NOTE: The original LE-5 was gas generator, but all variants beyond it are expander-bleed.

What I find interesting, as a side note, is that between the A and B, they intentionally made changes that cost them 5 seconds of isp in order to increase thrust, make the engine more reliable, and cheaper to manufacture. That's very practical of MHI.
Wait, ∆V? This site will accept the ∆ symbol? How many times have I written out the word "delta" for no reason?

Offline baldusi

  • Senior Member
  • *****
  • Posts: 8356
  • Buenos Aires, Argentina
  • Liked: 2539
  • Likes Given: 8273
Re: RS-68
« Reply #83 on: 06/27/2020 07:56 pm »
The Expander Bleed is a Gas Generator implementation on the expander cycle: you take a very small amount of propellant (say, 2%), get it as hot as your turbine's blades can take, and after passing them through the turbines you dump it. So, you still inject liquid fuel into the main combustion chamber.
So no actual gas generator involved.

That means that the combustion chamber pressure is not limited to a level that the drive turbine can generate from the heat extracted from the CC.

It also means no GG to generate, start or re-start. The lightest, cheapest parts are the ones that aren't there.

And that T/W ratio for an LH2 engine is phenomenal

Yes it still is limited. In the closed-expander all the fuel is heated and passes through the turbine. In the bleed-expander, something like a 2% of fuel goes through the turbine. You can extract more work since you can extract more heat and have higher pressure losses. And you don't need the pump to push the pressure of all the fuel high enough that even after passing through the cooling channels and the turbines it still has main combustion chamber pressure. So you need less pump work. But you also use a lot less propellant.
As you go up in trust, you need more and more proportion of fuel (because it's heated less). Only that that relationship is a lot flatter than the closed case.

Offline sdsds

  • Senior Member
  • *****
  • Posts: 7201
  • “With peace and hope for all mankind.”
  • Seattle
  • Liked: 2050
  • Likes Given: 1962
Re: RS-68
« Reply #84 on: 04/13/2021 11:32 am »
World’s Most Powerful Hydrogen-Fueled Rocket Engine Completes Final Acceptance Test for ULA Delta IV Heavy Launch Vehicle

https://www.rocket.com/article/world%E2%80%99s-most-powerful-hydrogen-fueled-rocket-engine-completes-final-acceptance-test-ula

Quote
“We’ve continued to improve the RS-68 engine, which today remains the most powerful hydrogen-fueled rocket engine in the world,” said Jim Maser, Aerojet Rocketdyne senior vice president of Space. “This engine was developed entirely with company funds to be a very cost competitive and extremely reliable booster engine.”

This assertion from Maser (my emboldening above) caught me off guard.

Weren't the RS-68A improvements funded by the USAF?
— 𝐬𝐝𝐒𝐝𝐬 —

Offline spacenut

  • Senior Member
  • *****
  • Posts: 5181
  • East Alabama
  • Liked: 2587
  • Likes Given: 2895
Re: RS-68
« Reply #85 on: 04/13/2021 01:20 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?

Offline Alberto-Girardi

Re: RS-68
« Reply #86 on: 04/13/2021 07:42 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?

Maybe, but changing to a regeneratively cooled nozzle will be redesigning the engine, and SLS tank are built for RS-25, that uses staged combustion, unlicke the rs.68 that uses simpler and less efficent gas generator. Maybe even the proportion of fuel that the two engine need is different, given the different cycles. At the end you would need to re design and rebuilt the SLS.
Ad gloriam humanitatis - For the Glory of Humanity
I want to become an Aerospace Engineer!

Offline Hog

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
Re: RS-68
« Reply #87 on: 04/16/2021 05:13 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=EDIT make that 11,760,330 pounds of thrust (~52,313 kilonewtons) pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.
« Last Edit: 04/20/2021 11:55 pm by Hog »
Paul

Online ZachS09

  • Space Savant
  • Senior Member
  • *****
  • Posts: 8406
  • Roanoke, TX
  • Liked: 2344
  • Likes Given: 2060
Re: RS-68
« Reply #88 on: 04/17/2021 03:03 am »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=8,424,660 pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.

Actually, it's 11,760,330 pounds of thrust (~52,313 kilonewtons).
« Last Edit: 04/17/2021 03:03 am by ZachS09 »
Liftoff for St. Jude's! Go Dragon, Go Falcon, Godspeed Inspiration4!

Offline Hog

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
Re: RS-68
« Reply #89 on: 04/20/2021 02:35 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=8,424,660 pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.

Actually, it's 11,760,330 pounds of thrust (~52,313 kilonewtons).
Excellent, do you happen to have a quick breakdown of the core vs booster thrust?   I can't seem to find an off the pad/sea level thrust figure for the 5.5 segment boosters.

This read agrees with you stating 5306 tonnes/11,697,727 pounds/thrust/52,034kN.

""One Later Design - Six RS-68s and Two 5.5 SRBs

On June 23, 2008, NASA's Constellation Program Manager Jeff Hanley announced that the Ares V baseline design had grown larger and more powerful than previous designs.  The trans-lunar insertion (TLI) capability had risen to 71 tonnes, a 7 tonne increase.   The theoretical Low Earth Orbit (LEO) payload had grown to 145 tonnes or more from the previous 130-ish tonnes (see Table 1 for Details).

Planners added a sixth RS-68 engine to the core stage and specified a pair of five-and-a-half segment solid rocket boosters.  The previous design used five RS-68s and two five-segment boosters.  The core stage was lengthened.  The Earth Departure Stage (EDS) diameter had already been increased to 10 meters to match the core diameter during recent design iterations.  The payload fairing diameter also grew to 10 meters.  Overall height jumped to 116.16 meters, 5.56 meters taller than Saturn V.  Liftoff weight increased to 3,699.23 tonnes and liftoff thrust to an unprecedented 5,306 tonnes. """
https://www.spacelaunchreport.com/ares5.html
Paul

Online ZachS09

  • Space Savant
  • Senior Member
  • *****
  • Posts: 8406
  • Roanoke, TX
  • Liked: 2344
  • Likes Given: 2060
Re: RS-68
« Reply #90 on: 04/20/2021 07:45 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=8,424,660 pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.

Actually, it's 11,760,330 pounds of thrust (~52,313 kilonewtons).
Excellent, do you happen to have a quick breakdown of the core vs booster thrust?   I can't seem to find an off the pad/sea level thrust figure for the 5.5 segment boosters.

This read agrees with you stating 5306 tonnes/11,697,727 pounds/thrust/52,034kN.

""One Later Design - Six RS-68s and Two 5.5 SRBs

On June 23, 2008, NASA's Constellation Program Manager Jeff Hanley announced that the Ares V baseline design had grown larger and more powerful than previous designs.  The trans-lunar insertion (TLI) capability had risen to 71 tonnes, a 7 tonne increase.   The theoretical Low Earth Orbit (LEO) payload had grown to 145 tonnes or more from the previous 130-ish tonnes (see Table 1 for Details).

Planners added a sixth RS-68 engine to the core stage and specified a pair of five-and-a-half segment solid rocket boosters.  The previous design used five RS-68s and two five-segment boosters.  The core stage was lengthened.  The Earth Departure Stage (EDS) diameter had already been increased to 10 meters to match the core diameter during recent design iterations.  The payload fairing diameter also grew to 10 meters.  Overall height jumped to 116.16 meters, 5.56 meters taller than Saturn V.  Liftoff weight increased to 3,699.23 tonnes and liftoff thrust to an unprecedented 5,306 tonnes. """
https://www.spacelaunchreport.com/ares5.html

That, I never thought of yet. And I honestly don’t know what the “off the pad/sea level thrust” thing means.
Liftoff for St. Jude's! Go Dragon, Go Falcon, Godspeed Inspiration4!

Offline Hog

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
Re: RS-68
« Reply #91 on: 04/20/2021 10:50 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=8,424,660 pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.

Actually, it's 11,760,330 pounds of thrust (~52,313 kilonewtons).
Excellent, do you happen to have a quick breakdown of the core vs booster thrust?   I can't seem to find an off the pad/sea level thrust figure for the 5.5 segment boosters.

This read agrees with you stating 5306 tonnes/11,697,727 pounds/thrust/52,034kN.

""One Later Design - Six RS-68s and Two 5.5 SRBs

On June 23, 2008, NASA's Constellation Program Manager Jeff Hanley announced that the Ares V baseline design had grown larger and more powerful than previous designs.  The trans-lunar insertion (TLI) capability had risen to 71 tonnes, a 7 tonne increase.   The theoretical Low Earth Orbit (LEO) payload had grown to 145 tonnes or more from the previous 130-ish tonnes (see Table 1 for Details).

Planners added a sixth RS-68 engine to the core stage and specified a pair of five-and-a-half segment solid rocket boosters.  The previous design used five RS-68s and two five-segment boosters.  The core stage was lengthened.  The Earth Departure Stage (EDS) diameter had already been increased to 10 meters to match the core diameter during recent design iterations.  The payload fairing diameter also grew to 10 meters.  Overall height jumped to 116.16 meters, 5.56 meters taller than Saturn V.  Liftoff weight increased to 3,699.23 tonnes and liftoff thrust to an unprecedented 5,306 tonnes. """
https://www.spacelaunchreport.com/ares5.html

That, I never thought of yet. And I honestly don’t know what the “off the pad/sea level thrust” thing means.
"Off the pad/sea level thrust" meaning the sea level rating of the 5.5 segment boosters vs their vacuum thrust rating.rating
Paul

Online ZachS09

  • Space Savant
  • Senior Member
  • *****
  • Posts: 8406
  • Roanoke, TX
  • Liked: 2344
  • Likes Given: 2060
Re: RS-68
« Reply #92 on: 04/20/2021 11:04 pm »
Okay. Using http://www.b14643.de/ as a source, here's the sea level/vacuum thrust rating of the Ares V 5.5 RSRMs.

Sea level average: 12,689.6 kN (~2,852,736 lbf)

Sea level maximum: 16,651 kN (~3,743,294 lbf)

Vacuum average: 14,000.5 kN (~3,147,438 lbf)

Vacuum maximum: 18,371.5 kN (~4,130,078 lbf)
Liftoff for St. Jude's! Go Dragon, Go Falcon, Godspeed Inspiration4!

Offline Hog

  • Senior Member
  • *****
  • Posts: 2846
  • Woodstock
  • Liked: 1700
  • Likes Given: 6866
Re: RS-68
« Reply #93 on: 04/20/2021 11:52 pm »
IF, big IF, they replaced the ablative nozzle on RS-68 and used 4 of them on SLS, wouldn't they have to have a larger upper stage?  This would be because the RS-68's would use more fuel than the RS-25's, right?  And IF they used a pair of BE-3U's on say a larger upper stage, wider anyway to leave room for cargo, what would be the SLS payload capability?
Remember the original 10 meter rocket, Ares-V?  6 RS-68 engines and dual 5.5 segment SRBs?

Core Stage
"The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum."  NSF David Harris
 4,212,330 million pounds thrust for the 6 core stage engines

5.5 segment SRBs
"Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned."  NSF David Harris

7,548,000 pounds thrust for the booster stage

Core Stage + Booster Stage= 4,212,330 + 7,548,000=8,424,660 pounds thrust off the pad.  Would have been a monster.  The N-1 moon rocket was 10,200,000 lbf/45,400 kN off the pad.

Actually, it's 11,760,330 pounds of thrust (~52,313 kilonewtons).
Jeez, I thought you were implying my input numbers were incorrect, when in fact it was my addition.

 It seems weird that the 5.5 segment SRBs don't perform better as when compared to the SLS 5 segment RSRMV, but I must remember that the  6 RS-68/5.5 segment iteration of ARES-V used SRBs that were reusable and were laden with parachutes and all the other recovery equipment. 
Paul

 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0