Author Topic: CEV HLV Upper Stage Engine  (Read 15845 times)

Offline Andy L

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RE: CEV HLV Upper Stage Engine
« Reply #20 on: 12/28/2005 04:46 pm »
But isn't a single SSME being used for the Lunar transit? I don't like the word unreliable.

Offline AndyMc

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RE: CEV HLV Upper Stage Engine
« Reply #21 on: 12/28/2005 07:26 pm »
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Andy L - 28/12/2005  11:46 AM

But isn't a single SSME being used for the Lunar transit? I don't like the word unreliable.

No. The EDS -  Earth Departure Stage has 2 J2-S Engines - a simplified version of the J2 engine that powered the Saturn V 2nd and 3rd stages.

The 'Stick' that launches the CEV uses a single SSME for its second stage. It is started at altitude, something that has been tested I believe. It is only has to be fired once before disposal.

Using a single SSME for the EDS would mean it had to be re-started - after initially placing the LSAM in LEO. Its this process of re-start, which involves chill-down and purging etc that would be a problem. It can probably done, by why bother when you have the J2 already designed. The J2 is also a much simpler engine than the SSME. Building a re-start capability into the SSME could introduce unreliability as well as additional costs.

Offline braddock

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RE: CEV HLV Upper Stage Engine
« Reply #22 on: 12/28/2005 10:37 pm »
What is the cost of a SSME?  It wasn't exactly designed to be disposable, was it?

Interesting note from Astronautix on the J-2S ( http://www.astronautix.com/engines/j2s.htm ):

"It was estimated by ATK Thiokol in 2005 that restarting the J-2S program, including engine fabrication, design and reliability verification, certification, and production, would require four years."



Offline Stardust9906

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RE: CEV HLV Upper Stage Engine
« Reply #23 on: 12/29/2005 09:30 am »
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braddock - 28/12/2005  11:37 PM

What is the cost of a SSME?  It wasn't exactly designed to be disposable, was it?

They are planning a new single use version that will be cheaper than the Shuttle version since it doesn't have to be engineered to be reusable.

Offline braddock

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RE: CEV HLV Upper Stage Engine
« Reply #24 on: 12/29/2005 11:46 am »
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Stardust9906 - 29/12/2005  5:30 AM

Quote
braddock - 28/12/2005  11:37 PM

What is the cost of a SSME?  It wasn't exactly designed to be disposable, was it?

They are planning a new single use version that will be cheaper than the Shuttle version since it doesn't have to be engineered to be reusable.

What types of things would they change on the SSME?  It doesn't seem like the type of thing that has a lot of non-essential parts.

Are there removable parts and connectors that can be eliminated because it won't have to go through an overhaul?
Could it just use a design revision based on 25 years experience?
All of the above?

Offline Stardust9906

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RE: CEV HLV Upper Stage Engine
« Reply #25 on: 12/30/2005 07:36 pm »
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braddock - 29/12/2005  12:46 PM

Quote
Stardust9906 - 29/12/2005  5:30 AM

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braddock - 28/12/2005  11:37 PM

What is the cost of a SSME?  It wasn't exactly designed to be disposable, was it?

They are planning a new single use version that will be cheaper than the Shuttle version since it doesn't have to be engineered to be reusable.

What types of things would they change on the SSME?  It doesn't seem like the type of thing that has a lot of non-essential parts.

Are there removable parts and connectors that can be eliminated because it won't have to go through an overhaul?
Could it just use a design revision based on 25 years experience?
All of the above?

I read somewhere that they plan to make changes to the nozzle and throat among other things and hope to get a cost reduction of 15-20%.  Can't vouch for the accuracy of that though.

There's also a thread over at the SDC Forum http://uplink.space.com/showflat.php?Cat=&Board=missions&Number=346913&page=20&view=collapsed&sb=5&o=0&fpart=1&vc=1 which you might want to take a look at for more information on this subject.

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