Quote from: ugordan on 03/05/2010 04:16 pmQuote from: Kitspacer on 03/05/2010 02:56 pmWhat really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant: The first stage tanks are not made in the U.S. Using a liquid 2nd stage with an airstart AJ-26 would require new tankage. Would Orbital be making it? Do they have much experience with large liquid prop systems? Would it make the vehicle less than 51% "american" if a foreign contractor made it instead? Would it stretch-out the schedule even further?Questions, questions...If Dave Thompson is calling the schedule "busy and tight" in public, the reality is probably more like "frantic." Using a solid on S2 probably gives them the shortest critical path and the lowest schedule risk, I would guess.
Quote from: Kitspacer on 03/05/2010 02:56 pmWhat really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant: The first stage tanks are not made in the U.S. Using a liquid 2nd stage with an airstart AJ-26 would require new tankage. Would Orbital be making it? Do they have much experience with large liquid prop systems? Would it make the vehicle less than 51% "american" if a foreign contractor made it instead? Would it stretch-out the schedule even further?Questions, questions...
What really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant:
Quote from: Kabloona on 03/18/2010 02:12 amQuote from: ugordan on 03/05/2010 04:16 pmQuote from: Kitspacer on 03/05/2010 02:56 pmWhat really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant: The first stage tanks are not made in the U.S. Using a liquid 2nd stage with an airstart AJ-26 would require new tankage. Would Orbital be making it? Do they have much experience with large liquid prop systems? Would it make the vehicle less than 51% "american" if a foreign contractor made it instead? Would it stretch-out the schedule even further?Questions, questions...If Dave Thompson is calling the schedule "busy and tight" in public, the reality is probably more like "frantic." Using a solid on S2 probably gives them the shortest critical path and the lowest schedule risk, I would guess. If I were making decisions at Orbital, I'd be looking to fly initial Cygnus flights on the remaining white-tail Delta IIs. While expensive, it is the low-risk approach to keeping on track and meeting COTS commitments. Later, if T-II comes on line, switch, otherwise continue to fly on Atlas 5 401.
Quote from: HMXHMX on 03/18/2010 02:59 amQuote from: Kabloona on 03/18/2010 02:12 amQuote from: ugordan on 03/05/2010 04:16 pmQuote from: Kitspacer on 03/05/2010 02:56 pmWhat really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant: The first stage tanks are not made in the U.S. Using a liquid 2nd stage with an airstart AJ-26 would require new tankage. Would Orbital be making it? Do they have much experience with large liquid prop systems? Would it make the vehicle less than 51% "american" if a foreign contractor made it instead? Would it stretch-out the schedule even further?Questions, questions...If Dave Thompson is calling the schedule "busy and tight" in public, the reality is probably more like "frantic." Using a solid on S2 probably gives them the shortest critical path and the lowest schedule risk, I would guess. If I were making decisions at Orbital, I'd be looking to fly initial Cygnus flights on the remaining white-tail Delta IIs. While expensive, it is the low-risk approach to keeping on track and meeting COTS commitments. Later, if T-II comes on line, switch, otherwise continue to fly on Atlas 5 401.I'd keep that in the back of the mind, but not commit to it until after the full systems test is performed in the next 4 months. At this point, the engines are a known quality with hundreds of hours of testing under their belt.
I'm not concerned about the engines; I think they are fine. But there is much more to a LV than propulsion alone.
Quote from: HMXHMX on 03/18/2010 02:15 pmI'm not concerned about the engines; I think they are fine. But there is much more to a LV than propulsion alone.Perhaps, but Orbital has experience with those systems and the engines are the single hardest component.They'll be fine.
Quote from: ugordan on 03/05/2010 04:16 pmQuote from: Kitspacer on 03/05/2010 02:56 pmWhat really surprised me is OSC using a low Isp Solid 2nd Stage. Rather nullifies the efficiency of the 26. The engine is also available with a high-altitude/vacuo nozzle- the NK-43/??? variant: The first stage tanks are not made in the U.S. Using a liquid 2nd stage with an airstart AJ-26 would require new tankage. Would Orbital be making it? Do they have much experience with large liquid prop systems? Would it make the vehicle less than 51% "american" if a foreign contractor made it instead? Would it stretch-out the schedule even further?Questions, questions...If Dave Thompson is calling the schedule "busy and tight" in public, the reality is probably more like "frantic."
Using a solid on S2 probably gives them the shortest critical path and the lowest schedule risk, I would guess.
Quote from: wannamoonbase on 03/18/2010 10:32 pmQuote from: HMXHMX on 03/18/2010 02:15 pmI'm not concerned about the engines; I think they are fine. But there is much more to a LV than propulsion alone.Perhaps, but Orbital has experience with those systems and the engines are the single hardest component.They'll be fine.I agree - I wouldn't say the engines are the hardest component, certainly not these engines - but they are, though, the newest component considering Orbital's previous launch vehicle experience. They just dissasembled the engine that was test-fired last week at flight thrust levels for two times mission duration+qual test (straight out of the box, after 30+ years in storage!!!) and the bearings and everything else look just fine.The single hardest component of the whole program, IMHO, is the integration of the entire LV. There's where previous experience, albeit with solids and smaller vehicles, helps.
Right on target. As for using the NK-43 for the second stage, it's a very good engine with great ISP (346 s) and great T/W (120+). Unfortunately, it's about 5 times too big (about 400,000 lbf thrust vs. 80,000 lbf for the Castor 30). There are better Lox-kerosene engines for the Taurus II second stage from the thrust matching standpoint with equal or better Isp and good enough T/W (e.g. RD-0124 at 66,000 lbf thrust, Isp = 359 s, T/W = 63 with TVC and controller)
Quote from: antonioe on 03/19/2010 03:55 pmRight on target. As for using the NK-43 for the second stage, it's a very good engine with great ISP (346 s) and great T/W (120+). Unfortunately, it's about 5 times too big (about 400,000 lbf thrust vs. 80,000 lbf for the Castor 30). There are better Lox-kerosene engines for the Taurus II second stage from the thrust matching standpoint with equal or better Isp and good enough T/W (e.g. RD-0124 at 66,000 lbf thrust, Isp = 359 s, T/W = 63 with TVC and controller)NK-31/39. May be?
Dmitry, since you live in Samara, can you say if you work at the plant? I've been looking for an answer to how many NK-33 and 43 complete and partial engines are still available there. I have heard numbers from a "a few" to "dozens". Care to shed light on the true count?
Quote from: HMXHMX on 03/21/2010 04:37 pmDmitry, since you live in Samara, can you say if you work at the plant? I've been looking for an answer to how many NK-33 and 43 complete and partial engines are still available there. I have heard numbers from a "a few" to "dozens". Care to shed light on the true count?I do not live for a long time already in Samara and did not work in SNTK (I worked in Volga branch RKK "Energia"). But I can tell that now on SNTK 54 engines NK-33 from which 46 engines can be prepared for commodity deliveries remain.The total of engines NK-33/43/39/31, including engines in Aerojet, does not exceed 150.
Quote from: Dmitry_V_home on 03/21/2010 08:51 pmQuote from: HMXHMX on 03/21/2010 04:37 pmDmitry, since you live in Samara, can you say if you work at the plant? I've been looking for an answer to how many NK-33 and 43 complete and partial engines are still available there. I have heard numbers from a "a few" to "dozens". Care to shed light on the true count?I do not live for a long time already in Samara and did not work in SNTK (I worked in Volga branch RKK "Energia"). But I can tell that now on SNTK 54 engines NK-33 from which 46 engines can be prepared for commodity deliveries remain.The total of engines NK-33/43/39/31, including engines in Aerojet, does not exceed 150.What are the plans for new production?
What are the plans for new production?