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General Rocket Engineering Q&A
by
Ben the Space Brit
on 10 Feb, 2012 11:27
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As a total amateur and non-professional, I am naturally ignorant of lots of aspects of building and operating a launch vehicle that a lot of the pros out there know intimately. This thread is for questions regarding the nuts-and-bolts of building, testing and launching an LV in general rather than any specific type.
I'll start off with a question that arose from a post over on the SpaceX threads:
Is it possible to store a fully-assembled liquid-fuelled rocket in a 'dry' state for long periods? With issues such as delamination of fuel tanks, insulation decay and metal fatigue in the engine parts, I would have thought that there is a 'shelf time', a period in which the vehicle must be used before environmental degradation makes it unsafe or impractical (high test/refurb costs) to do so.
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#1
by
Jim
on 10 Feb, 2012 13:16
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Is it possible to store a fully-assembled liquid-fuelled rocket in a 'dry' state for long periods? With issues such as delamination of fuel tanks, insulation decay and metal fatigue in the engine parts, I would have thought that there is a 'shelf time', a period in which the vehicle must be used before environmental degradation makes it unsafe or impractical (high test/refurb costs) to do so.
It depends how it is stored and what propellants are used. Fully fueled ICBM's were stored for years with periodic draining, inspections and upgrades. Solid vehicles even longer. Some Titan IV's sat on the pad for more than 16 months. Some Delta IV's had some long pad times.
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#2
by
edkyle99
on 10 Feb, 2012 13:29
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Is it possible to store a fully-assembled liquid-fuelled rocket in a 'dry' state for long periods? With issues such as delamination of fuel tanks, insulation decay and metal fatigue in the engine parts, I would have thought that there is a 'shelf time', a period in which the vehicle must be used before environmental degradation makes it unsafe or impractical (high test/refurb costs) to do so.
During the Apollo years, some Saturn stages were manufactured during the 1966-70 period and stored for years, with some finally flying during Skylab and ASTP in 1973-75. S-IVB and S-IB stages were, as I understand it, sealed up in temporary enclosures that were provided with conditioned air. I wonder, but don't know, if nitrogen may have been used for tanks and propellant lines, and if some type of liquid stabilizer may have been used to maintain moving parts.
Rocket parts lasted even longer. Most of the unflown S-IB stage H-1 engines were subsequently removed and re-assigned for use on Delta rockets (some unused LM descent engines were similarly reassigned to Delta upper stage use). The last of the "H-1" (RS-27) engines flew as late as 1989!
Jim mentioned Titan 2. Martin Marietta built 141 Titan 2 ICBMs between 1962 and 1967. Many were maintained on active duty until 1982, with some not being retired from their silos until 1987. A handful were reassigned for use as space boosters (Titan 23G). The final Titan 23G lifted off in 2003, probably 35 years or so after its construction. It had, of course, been refurbished and upgraded during that time, but the basic structure and propulsion system was original.
Similarly, some of the Thor missiles that had been manufactured before 1960 to stand duty in Great Britain ended up flying as space boosters well into the 1970s, with one launched as late as 1980. Some Atlas ICBMs had similar use, and today's Minotaur I and IV launch vehicles are using long-retired Minuteman and Peacekeeper missile stages. Russia's Dnepr and Rokot launchers use old missile stages too.
- Ed Kyle
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#3
by
Robotbeat
on 10 Feb, 2012 13:51
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Not to mention the warehouse full of NK-33 engines built in the early 1970s that are being used for Antares right now. 40 years!
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#4
by
Antares
on 10 Feb, 2012 16:07
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Metal is not really a concern for long-term storage if built and stored properly - a BIG if. Corrosion is the concern with long-term storage of metals. Corrosion ingredients include residual build stresses, humidity, electrical potential differences (even among constituent metals in an alloy or two different parts if there is electrical continuity), and time. Tiny levels of the first 3 that wouldn't be significant if stored for years can create problems when stored for decades. This is a concern for large structures, engines and metal piece parts in avionics and electrical systems.
Soft goods and non-metals are more of a concern that they can creep under load or degrade (material property changes) from age. Seals don't seal as well, both in fluid systems and hermetically sealed electronics boxes. Various parts get out of round or elongate.
There are probably more, but those are the first that come to mind.
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#5
by
Danderman
on 21 Apr, 2012 19:24
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I can't believe there isn't a SpaceX Q&A topic.
Anyway, I noticed in the Falcon 1 user guide that the main computer is a PC/104 based system. Is that the same PC/104 board that CubeSATs use?
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#6
by
kevin-rf
on 23 Apr, 2012 13:38
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I can't believe there isn't a SpaceX Q&A topic.
Anyway, I noticed in the Falcon 1 user guide that the main computer is a PC/104 based system. Is that the same PC/104 board that CubeSATs use?
PC/104 is a standard, there are more manufactures and flavors of PC/104 than you can shake a stick at. So your question should be, does spaceX use the same PC/104 vendor as say a particular cube sat.
http://www.pc104.org/http://en.wikipedia.org/wiki/PC/104
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#7
by
CitabriaFlyer
on 10 Jun, 2012 23:58
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Which rockets would provide the most benign launch environment for a new space telescope if one were to be constructed out of the mirrors recently donated to NASA. Is one EELV more benign than the other with respect to loads and vibrations imparted on the payload? How do they compare to shuttle of SLS?
Thanks
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#8
by
Jim
on 11 Jun, 2012 00:26
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Which rockets would provide the most benign launch environment for a new space telescope if one were to be constructed out of the mirrors recently donated to NASA. Is one EELV more benign than the other with respect to loads and vibrations imparted on the payload? How do they compare to shuttle of SLS?
Thanks
The ones without solids. Shuttle had lower gloads but high dynamic loads
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#9
by
wolfpack
on 11 Jun, 2012 00:37
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I would think that with slight pressurization with N2, liquid stages would last a long time.
With solids you have to worry about the propellant drying out and internal cracks forming which, when exposed during the burn, may cause overpressure and explosion.
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#10
by
go4mars
on 08 Nov, 2012 02:42
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Are elliptical tanks instead of cylindrical ones a possibility (especially for tanks where a lot of the strength comes from internal tubes and wires like the SpaceX tanks)?
Thinking in terms of SLS liquid boosters being limited to whatever can fit through the VAB.
Also thinking in terms of road transport where low bridges/wires/trees/signs impact height far more than width.
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#11
by
Jim
on 08 Nov, 2012 12:01
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Are elliptical tanks instead of cylindrical ones a possibility (especially for tanks where a lot of the strength comes from internal tubes and wires like the SpaceX tanks)?
Huh? Spacex tanks are not internally braced (don't understand the tube and wire reference). They like any other rocket, monocoque.
Elliptical tanks are not viable. They would be heavy.
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#12
by
Fequalsma
on 11 Nov, 2012 11:37
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Many, if not most, rocket structures are semi-monocoque (stiffened skin). Examples include the ET LH2 tank barrel, S-IC, S-II, and S-IVB tank barrels, ET and Saturn V intertanks and interstages, etc. The ET LO2 tank aft dome has seven or eight circumferential ring-stiffeners, so it is also semi-monocoque.
Some rocket structures are pure monocoque where the skins carry all loads. Examples include the ET LH2 tank domes, and the ET LO2 tank barrel and ogive.
The S-II and S-IVB common bulkheads are honeycomb sandwich structures, where the skins carry the in-plane loads loads, and the honeycomb provides depth to resist bending and buckling.
F=ma
They like any other rocket, monocoque.
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#13
by
Jim
on 11 Nov, 2012 12:55
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Many, if not most, rocket structures are semi-monocoque (stiffened skin). Examples include the ET LH2 tank barrel, S-IC, S-II, and S-IVB tank barrels, ET and Saturn V intertanks and interstages, etc. The ET LO2 tank aft dome has seven or eight circumferential ring-stiffeners, so it is also semi-monocoque.
Some rocket structures are pure monocoque where the skins carry all loads. Examples include the ET LH2 tank domes, and the ET LO2 tank barrel and ogive.
The S-II and S-IVB common bulkheads are honeycomb sandwich structures, where the skins carry the in-plane loads loads, and the honeycomb provides depth to resist bending and buckling.
F=ma
They like any other rocket, monocoque.
Thanks for the correction.