Author Topic: Delta IV Q&A  (Read 197540 times)

Offline kevin-rf

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8656
  • Overlooking the path Mary's little Lamb took..
  • Liked: 1125
  • Likes Given: 245
Re: Delta IV Q&A
« Reply #300 on: 01/25/2008 12:09 pm »
Tru Grit said something interesting over in one of the Ares-1 threads : http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=11584&start=61&posts=72

Quote
And finally... By the time the administrators successor gets around to begging from congressional money for the heavy booster ULA will have moved on to RL-60 and ACES. They'll also conveniently forget this speech when the same successor comes asking for support because NASA is stuck in LEO again.

Is ACES really moving foward at ULA and more interesting will it also replace Centuar on the ULA Atlas V?
If you're happy and you know it,
It's your med's!

Offline Big Al

  • Member
  • Posts: 97
  • Liked: 5
  • Likes Given: 0
Re: Delta IV Q&A
« Reply #301 on: 02/01/2008 11:55 pm »
I have some questions about the RS-68 start sequence. I was watching a movie of the last Delta IV flight. Since it was at night, you could see some interesting thing happening.

1)   The engine pump starts at T-15 seconds. This seems like along time before start up, my guess is that there is a chill sequence before start.
2)   The engine nozzles appear to be below the three holes in the flame chute. Does anyone have close up photos on how the rocket mounts on the pad? It would be interesting to see detail on this
3)   When the turbo pump starts it is only pumping hydrogen. The oxygen is shut off, I would be curious to see how they handle the O2 during that part of the startup. Most high-pressure pumps are very unhappy running with the flow shut off.
4)   At T-5 is when you get the fireball; I assume that is when the igniters are turned on.
5)   You notice also that the tapered aft end of the first stage allows the hydrogen to vent upward quickly

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32550
  • Cape Canaveral Spaceport
  • Liked: 11337
  • Likes Given: 334
Re: Delta IV Q&A
« Reply #302 on: 02/02/2008 12:11 am »
1.  It starts later than T-15,
2.Each CBC sits on 4 posts of the Launch Mate Unit which in turn sits on the launch table
http://www.ulalaunch.com/index_gallery.html
3.  It is pumping both LO2 and LH2 at the sametime
4.  No, that is caused by the burn off igniters (ROFIs) which are like the shuttle's and are lit at L-15
5.  Inconsequential.  That is just the aeroshell of the engine section.  The H2 is going to rise no matter what.

Will have more info on Monday.

Some of the real details will touch upon propriety and  ITAR issue.  

Offline Nick L.

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 3860
  • A unique little aerospace company
  • Liked: 4
  • Likes Given: 4
Re: Delta IV Q&A
« Reply #303 on: 02/02/2008 05:42 pm »
The pumps start about T-8.5 seconds (right about when the TCSR takes control of the vehicle), this can be seen as the smaller flames coming from the heat exchanger and roll control nozzles on either side of the aft cone. This is the gas generator exhaust and indicates that the gas generator has begun operating and producing gas to run the turbines.
The fuel rich exhaust from the turbopumps/gas generator is ignited by the radial outward-firing ignitors (ROFIs), which as Jim stated are lit off at T-15.
"Now you may leave here for four days in space, but when you return it's the same old place..."

Offline Big Al

  • Member
  • Posts: 97
  • Liked: 5
  • Likes Given: 0
Re: Delta IV Q&A
« Reply #304 on: 02/02/2008 06:55 pm »
Thanks for the great pictures!

Upon further review I realized that the RS-68 uses two turbo-pumps, this would give a lot more flexibility in the start sequence. I guess I was thinking of the Spacex Merlin with its single turbo-pump when I asked the question.


Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32550
  • Cape Canaveral Spaceport
  • Liked: 11337
  • Likes Given: 334
Re: Delta IV Q&A
« Reply #305 on: 02/02/2008 07:26 pm »
Quote
Big Al - 2/2/2008  2:55 PM

Thanks for the great pictures!

Upon further review I realized that the RS-68 uses two turbo-pumps, this would give a lot more flexibility in the start sequence. I guess I was thinking of the Spacex Merlin with its single turbo-pump when I asked the question.


It uses one (corection) gas generator.  Even, vehicles with two, like the shuttle, would start them at the same time.  An engine can not run unbalanced

Offline Big Al

  • Member
  • Posts: 97
  • Liked: 5
  • Likes Given: 0
Re: Delta IV Q&A
« Reply #306 on: 02/02/2008 07:37 pm »
I bet my timing was off too. I have been watching the video over at Spaceflight Now.com and as soon as The Fat Man Doing The Countdown (he looks just like me!) says “15” you see the red glow of hydrogen deep within the flame chute

Another comment on the taper of the aft end of the rocket is that the heat blankets on both the Delta and Atlas have a very tight fit. I’m sure this is good for aerodynamics, but I would think it would trap all the heat generated buy the upper part of the engine, but it does work and is widely used.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32550
  • Cape Canaveral Spaceport
  • Liked: 11337
  • Likes Given: 334
Re: Delta IV Q&A
« Reply #307 on: 02/02/2008 08:00 pm »
Quote
Big Al - 2/2/2008  3:37 PM

1.  I bet my timing was off too. I have been watching the video over at Spaceflight Now.com and as soon as The Fat Man Doing The Countdown (he looks just like me!) says “15” you see the red glow of hydrogen deep within the flame chute

2.  Another comment on the taper of the aft end of the rocket is that the heat blankets on both the Delta and Atlas have a very tight fit. I’m sure this is good for aerodynamics, but I would think it would trap all the heat generated buy the upper part of the engine, but it does work and is widely used.

1.  That is from the ROFI's

2.  If Spacex had such a structure,they are purged with conditioned air prelaunch, they wouldn't have had the corrosion on the first launch.   Most launch vehicles enclose the upper engine sections,  not just the EELV's.  Thor, Atlas I & II, Jupiter, Redstone, etc

Offline Big Al

  • Member
  • Posts: 97
  • Liked: 5
  • Likes Given: 0
Re: Delta IV Q&A
« Reply #308 on: 02/02/2008 10:09 pm »
Are you sure about the single turbo pump?
Wikipedia in their write up states that it has two pumps. Also over at Spaceandtech.com they have a very nice CAD rendering of the RS-68 with a good view of the top of the engine. It shows two pumps. Each pump exhausts on the opposite side of the engine. One of them, which I think is the hydrogen pump because it looks like it has bigger scroll housing, has a high pressure nozzle on it which I assume is used for roll control. The other pump looks like it uses a lower pressure exhaust system.
The over all design looks like a classical rocket engine…except it burns hydrogen….and its on the first stage of a rocket…..and it has an ablative lower nozzle…

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32550
  • Cape Canaveral Spaceport
  • Liked: 11337
  • Likes Given: 334
Re: Delta IV Q&A
« Reply #309 on: 02/02/2008 10:13 pm »
I corrected my post to single gas generator

Offline AnimatorRob

  • Member
  • Member
  • Posts: 98
  • Liked: 15
  • Likes Given: 20
Re: Delta IV Q&A
« Reply #310 on: 04/23/2008 08:07 pm »
Over on the Ares I TO thread it was mentioned that the RS-68 uses quite a lot of He and that was a potential problem due to the limited supply of He. Can someone explain exactly what the He is used for and why can't another inert gas be used, say N?

Offline nacnud

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2424
  • Liked: 648
  • Likes Given: 254
Re: Delta IV Q&A
« Reply #311 on: 04/23/2008 08:26 pm »
Well N freezes at LH temps while He stays a gas. So purging the system with cold He gas gets rid of all the air with might freeze just where you don't want it, but I'm no expert, best check with them.

Offline Rocket Rancher

  • Member
  • Full Member
  • *
  • Posts: 100
  • Space Coast, FL
  • Liked: 20
  • Likes Given: 13
Re: Delta IV Q&A
« Reply #312 on: 04/23/2008 08:40 pm »
Quote
nacnud - 23/4/2008  4:26 PM

Well N freezes at LH temps while He stays a gas. So purging the system with cold He gas gets rid of all the air with might freeze just where you don't want it, but I'm no expert, best check with them.

You very correct on that description. Frozen air in the RL-10 was the cause of 2 failures for the Atlas II program back in the late 80's.
"In God We Trust ... All Others Bring Data"

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32550
  • Cape Canaveral Spaceport
  • Liked: 11337
  • Likes Given: 334
Re: Delta IV Q&A
« Reply #313 on: 04/23/2008 08:42 pm »
Quote
Rocket Rancher - 23/4/2008  4:40 PM

Quote
nacnud - 23/4/2008  4:26 PM

Well N freezes at LH temps while He stays a gas. So purging the system with cold He gas gets rid of all the air with might freeze just where you don't want it, but I'm no expert, best check with them.

You very correct on that description. Frozen air in the RL-10 was the cause of 2 failures for the Atlas II program back in the late 80's.

early 90's

Offline Ronsmytheiii

  • Moderator
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 22559
  • Liked: 910
  • Likes Given: 332
Re: Delta IV Q&A
« Reply #314 on: 04/23/2008 10:43 pm »
This may not be as sophisticated as the other questions, but what is a good book as an overview of the Delta IV system and its development? And if any other books of other launchers if know.

Offline Analyst

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 2
  • Likes Given: 8
Re: Delta IV Q&A
« Reply #315 on: 04/24/2008 06:13 am »
Quote
Jim - 23/4/2008  10:42 PM

Quote
Rocket Rancher - 23/4/2008  4:40 PM

Quote
nacnud - 23/4/2008  4:26 PM

Well N freezes at LH temps while He stays a gas. So purging the system with cold He gas gets rid of all the air with might freeze just where you don't want it, but I'm no expert, best check with them.

You very correct on that description. Frozen air in the RL-10 was the cause of 2 failures for the Atlas II program back in the late 80's.

early 90's

Atlas II never failed. It has been Atlas I.

Analyst

Offline Antares

  • ABO^2
  • Senior Member
  • *****
  • Posts: 5202
  • Done arguing with amateurs
  • Liked: 368
  • Likes Given: 226
Re: Delta IV Q&A
« Reply #316 on: 04/24/2008 03:40 pm »
Quote
Ronsmytheiii - 23/4/2008  5:43 PM
This may not be as sophisticated as the other questions, but what is a good book as an overview of the Delta IV system and its development? And if any other books of other launchers if know.
Rocketdyne had an internal and PR magazine called Threshold.  There was one called "First Flight Edition" for RS-68 that gave a very good overview of the development of the engine.  I can't find it on Google.  Maybe a request to Canoga to get a soft copy of it.

Doubtful there's a book on this, exactly.  I suggest looking at AIAA papers over the 1997-2004 and more recent time period.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline Analyst

  • Senior Member
  • *****
  • Posts: 3337
  • Liked: 2
  • Likes Given: 8
Re: Delta IV Q&A
« Reply #317 on: 04/24/2008 03:51 pm »
Quote
Antares - 24/4/2008  5:40 PM

Doubtful there's a book on this, exactly.  I suggest looking at AIAA papers over the 1997-2004 and more recent time period.

These papers are extremly expensive. Sadly its very often this way in academics and engineering. $30 for a pdf with 15 pages - while I am interested in this stuff, I have to pay my bills too.

Analyst

Offline Antares

  • ABO^2
  • Senior Member
  • *****
  • Posts: 5202
  • Done arguing with amateurs
  • Liked: 368
  • Likes Given: 226
Re: Delta IV Q&A
« Reply #318 on: 04/24/2008 08:00 pm »
Libraries, anyone?  Many companies, agencies and universities have subscriptions to pdf-dot-aiaa-dot-org.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline Nick L.

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 3860
  • A unique little aerospace company
  • Liked: 4
  • Likes Given: 4
Re: Delta IV Q&A
« Reply #319 on: 04/27/2008 07:11 am »
There is an interesting Word document and PowerPoint about the RS-68 and its design philosophy and development here:
http://www.engineeringatboeing.com/data.htm

Look for "Propulsion For the 21st Century"

HTH,
Nick
"Now you may leave here for four days in space, but when you return it's the same old place..."

Tags: