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Quote from: Space Ghost 1962 on 10/07/2017 10:54 pmQuote from: RedLineTrain on 10/07/2017 10:01 pmWhat are the industry norms on development testing? Was the SSME Block III proposal especially gold-plated? Or do some substitute testing of production engines for development testing -- i.e., like I assume SpaceX did with Merlin 1D?Some things to educate yourself with:Test and Evaluation Guideline for Liquid Rocket EnginesLiquid Rocket Engine Flight CertificationIn general, look at the acceptance criteria of contracts for vehicles engines.Very interesting, thanks. One thing I picked up is "Testing should demonstrate margin on maximum specified operating life." If you read that literally and simplistically, then all the claims for BFR booster design life imply an extremely long test program.
Quote from: RedLineTrain on 10/07/2017 10:01 pmWhat are the industry norms on development testing? Was the SSME Block III proposal especially gold-plated? Or do some substitute testing of production engines for development testing -- i.e., like I assume SpaceX did with Merlin 1D?Some things to educate yourself with:Test and Evaluation Guideline for Liquid Rocket EnginesLiquid Rocket Engine Flight CertificationIn general, look at the acceptance criteria of contracts for vehicles engines.
What are the industry norms on development testing? Was the SSME Block III proposal especially gold-plated? Or do some substitute testing of production engines for development testing -- i.e., like I assume SpaceX did with Merlin 1D?
Quote from: Peter.Colin on 10/08/2017 07:36 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?What’s the Block 5 Merlin ?Is it Merlin 1E ?Is it 145% more heavy?The latest version of Merlin (M-1D) is a standard engine with upgrades for human rating the Falcon 9. It is basically the same mass engine AFAIK. The test to 145% power was a validation of margin, I believe, not a new rating for the engine or even a planned operating 'option.'
Quote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?What’s the Block 5 Merlin ?Is it Merlin 1E ?Is it 145% more heavy?
Question for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?
Quote from: AncientU on 10/08/2017 01:50 pmQuote from: Peter.Colin on 10/08/2017 07:36 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?What’s the Block 5 Merlin ?Is it Merlin 1E ?Is it 145% more heavy?The latest version of Merlin (M-1D) is a standard engine with upgrades for human rating the Falcon 9. It is basically the same mass engine AFAIK. The test to 145% power was a validation of margin, I believe, not a new rating for the engine or even a planned operating 'option.'A long life engine will experience "plastic creep" of its hot and highly stressed parts. (turbines, combustion chamber coolant passages). Running engines at higher than rated temperatures, pressures and speeds greatly reduces life. Running at these conditions during development testing shows margin and provides information about plastic creep and other failure modes. John
Quote from: livingjw on 10/08/2017 03:13 pmQuote from: AncientU on 10/08/2017 01:50 pmQuote from: Peter.Colin on 10/08/2017 07:36 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?What’s the Block 5 Merlin ?Is it Merlin 1E ?Is it 145% more heavy?The latest version of Merlin (M-1D) is a standard engine with upgrades for human rating the Falcon 9. It is basically the same mass engine AFAIK. The test to 145% power was a validation of margin, I believe, not a new rating for the engine or even a planned operating 'option.'A long life engine will experience "plastic creep" of its hot and highly stressed parts. (turbines, combustion chamber coolant passages). Running engines at higher than rated temperatures, pressures and speeds greatly reduces life. Running at these conditions during development testing shows margin and provides information about plastic creep and other failure modes. JohnUnderstood, but the original question was asking for the BFS Abort system thread. While running engines at higher than rated values greatly reduces the life of the engine, I am asking whether it may, in a dramatic situation, contribute to an increase in the life of the payload, given what we know about expansion ratios and TWR. :p
Very nice drawing I like it!How high T/W? why is it not made public?
Quote from: rakaydos on 10/08/2017 05:43 pmQuote from: livingjw on 10/08/2017 03:13 pmQuote from: AncientU on 10/08/2017 01:50 pmQuote from: Peter.Colin on 10/08/2017 07:36 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?What’s the Block 5 Merlin ?Is it Merlin 1E ?Is it 145% more heavy?The latest version of Merlin (M-1D) is a standard engine with upgrades for human rating the Falcon 9. It is basically the same mass engine AFAIK. The test to 145% power was a validation of margin, I believe, not a new rating for the engine or even a planned operating 'option.'A long life engine will experience "plastic creep" of its hot and highly stressed parts. (turbines, combustion chamber coolant passages). Running engines at higher than rated temperatures, pressures and speeds greatly reduces life. Running at these conditions during development testing shows margin and provides information about plastic creep and other failure modes. JohnUnderstood, but the original question was asking for the BFS Abort system thread. While running engines at higher than rated values greatly reduces the life of the engine, I am asking whether it may, in a dramatic situation, contribute to an increase in the life of the payload, given what we know about expansion ratios and TWR. :pFalcon 9 Block 5 will have higher thrust than Falcon 9 Full Thrust. We don’t know if the 145%, is higher than planned operation. Since we don’t know how much more thrust the Fuller than Full thrust will be...
Quote from: rakaydos on 10/07/2017 02:44 pmQuote from: Kaputnik on 10/07/2017 01:16 pmQuote from: DJPledger on 10/07/2017 11:44 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?Raptor vac. could be designed with a detachable nozzle extension which can be jettisoned in an emergency abort situation. This would allow it to operate at SL along with an emergency thrust reserve to push the ship safely away in an emergency.Given it is a full regen nozzle, you'd need to set up the plumbing to allow this (upper and lower circuits?) and have valves that shut off in an emergency- otherwise you'll be spewing unburned fuel into the exhaust, within the relatively enclosed interstage area. I'd imagine the base heating would ramp up extremely quickly in this scenario, limiting how long you could burn the RapVacs.Keep in mind spewing unburnt fuel isnt exactly a drawback when you're struggling to raise your TWR as quickly as possible.But it wouldn't contribute to thrust, it would be ejected from the severed regen channels and burn somewhere behind the vehicle.It would also cut off cooling to the remaining part of the nozzle and the chamber, leading to very rapid engine failure.So any sort of jettisonable nozzle is going to have to address this anyway by redirecting the coolant pathway.Edited to add: simply chopping off the nozzle would actually lower T:W because all that fuel is lost rather than going to the combustion chamber. So I would assert that even if it is only for use in dire emergencies, it is essential that any sort of nozzle jettison capability must be accompanied by a redirect of the regen pathway. Not impossible, I'm sure, just an added complication.
Quote from: Kaputnik on 10/07/2017 01:16 pmQuote from: DJPledger on 10/07/2017 11:44 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?Raptor vac. could be designed with a detachable nozzle extension which can be jettisoned in an emergency abort situation. This would allow it to operate at SL along with an emergency thrust reserve to push the ship safely away in an emergency.Given it is a full regen nozzle, you'd need to set up the plumbing to allow this (upper and lower circuits?) and have valves that shut off in an emergency- otherwise you'll be spewing unburned fuel into the exhaust, within the relatively enclosed interstage area. I'd imagine the base heating would ramp up extremely quickly in this scenario, limiting how long you could burn the RapVacs.Keep in mind spewing unburnt fuel isnt exactly a drawback when you're struggling to raise your TWR as quickly as possible.
Quote from: DJPledger on 10/07/2017 11:44 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?Raptor vac. could be designed with a detachable nozzle extension which can be jettisoned in an emergency abort situation. This would allow it to operate at SL along with an emergency thrust reserve to push the ship safely away in an emergency.Given it is a full regen nozzle, you'd need to set up the plumbing to allow this (upper and lower circuits?) and have valves that shut off in an emergency- otherwise you'll be spewing unburned fuel into the exhaust, within the relatively enclosed interstage area. I'd imagine the base heating would ramp up extremely quickly in this scenario, limiting how long you could burn the RapVacs.
Quote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?Raptor vac. could be designed with a detachable nozzle extension which can be jettisoned in an emergency abort situation. This would allow it to operate at SL along with an emergency thrust reserve to push the ship safely away in an emergency.
Quote from: Kaputnik on 10/07/2017 02:53 pmQuote from: rakaydos on 10/07/2017 02:44 pmQuote from: Kaputnik on 10/07/2017 01:16 pmQuote from: DJPledger on 10/07/2017 11:44 amQuote from: rakaydos on 10/07/2017 04:14 amQuestion for the thread: I know the Block 5 merlin has been tested to 145% thrust without issue- assuming the raptor had an equivilant level of engineered reserve, Given the expansion ratio of the Raptor vac, could you use the RaptorVacs to get useful emergency thrust during a near-sea level Abort scenerio?Raptor vac. could be designed with a detachable nozzle extension which can be jettisoned in an emergency abort situation. This would allow it to operate at SL along with an emergency thrust reserve to push the ship safely away in an emergency.Given it is a full regen nozzle, you'd need to set up the plumbing to allow this (upper and lower circuits?) and have valves that shut off in an emergency- otherwise you'll be spewing unburned fuel into the exhaust, within the relatively enclosed interstage area. I'd imagine the base heating would ramp up extremely quickly in this scenario, limiting how long you could burn the RapVacs.Keep in mind spewing unburnt fuel isnt exactly a drawback when you're struggling to raise your TWR as quickly as possible.But it wouldn't contribute to thrust, it would be ejected from the severed regen channels and burn somewhere behind the vehicle.It would also cut off cooling to the remaining part of the nozzle and the chamber, leading to very rapid engine failure.So any sort of jettisonable nozzle is going to have to address this anyway by redirecting the coolant pathway.Edited to add: simply chopping off the nozzle would actually lower T:W because all that fuel is lost rather than going to the combustion chamber. So I would assert that even if it is only for use in dire emergencies, it is essential that any sort of nozzle jettison capability must be accompanied by a redirect of the regen pathway. Not impossible, I'm sure, just an added complication.Does the extension skirt actually need active cooling, or is it radiatively cooled? I'd expect the exhaust to be rather cold when it has expanded 30 times or so...
Will be full regen cooled all the way out to the 3 meter (10 ft) nozzle diameter. Heat flux is nuts & radiative view factor is low.
Historically rocket builders have frequently launched extremely expensive engine development programs in search of larger engines. Were they wrong to do so?
Quote from: DreamyPickle on 10/04/2017 07:30 pmHistorically rocket builders have frequently launched extremely expensive engine development programs in search of larger engines. Were they wrong to do so?Probably not. Historically, rockets used analog computers to control the engines. More engines increase complexity more than linearly, which means both heavier and more difficult to design avionics. Think N1 KORD as an extreme and failed example.Miniaturized digital computers you can program, optical cables, etc, diminish the mass and complexity of such systems significantly, allowing more engines to be used economically. So, probably since the 90s, multiple engine rockets became more viable.
Future BFR’s with 200 or much more engines really wouldn’t surprise me at all.
The flight engine design is much lighter and tighter, and is extremely focused on reliability. The objective is to meet or exceed passenger airline levels of safety. If our engine is even close to a jet engine in reliability, has a flak shield to protect against a rapid unscheduled disassembly and we have more engines than the typical two of most airliners, then exceeding airline safety should be possible.
Q: Will the BFS methalox control thrusters be derived from Raptor or from SuperDraco engines?A: The control thrusters will be closer in design to the Raptor main chamber than SuperDraco and will be pressure-fed to enable lowest possible impulse bit (no turbopump spin delay).
Quote from: EM AMAThe flight engine design is much lighter and tighter, and is extremely focused on reliability. The objective is to meet or exceed passenger airline levels of safety. If our engine is even close to a jet engine in reliability, has a flak shield to protect against a rapid unscheduled disassembly and we have more engines than the typical two of most airliners, then exceeding airline safety should be possible.The NASA/Richards document continues to be golden. Thanks again, Space Ghost. It shows a jet fighter engine qualification requirement to be 150 hours (540,000 seconds), or roughly two orders of magnitude more than the original SSME qualification requirement.The 150 hour requirement also appears to be replicated in the FAA type certification requirements for endurance testing. Perhaps because Raptor only fires for a short time compared to jet engines, the qualification requirements arrived at for Raptor may be less, at least in duration.Edit: Reliability for modern jet engines seems pretty extreme. GE's G90 powerplant (used on the Boeing 777) is said to have an in-flight shutdown rate of one per million engine flight hours.
QuoteQ: Will the BFS methalox control thrusters be derived from Raptor or from SuperDraco engines?A: The control thrusters will be closer in design to the Raptor main chamber than SuperDraco and will be pressure-fed to enable lowest possible impulse bit (no turbopump spin delay).I'm curious what kind of ignition these will use. I would think even sparker ignition might be too slow. Could they have a hot ignition coil in the combustion chamber that stays heated when it is anticipated that they might need to be fired?
Quote from: yokem55 on 10/15/2017 10:40 pmQuoteQ: Will the BFS methalox control thrusters be derived from Raptor or from SuperDraco engines?A: The control thrusters will be closer in design to the Raptor main chamber than SuperDraco and will be pressure-fed to enable lowest possible impulse bit (no turbopump spin delay).I'm curious what kind of ignition these will use. I would think even sparker ignition might be too slow. Could they have a hot ignition coil in the combustion chamber that stays heated when it is anticipated that they might need to be fired?I don't have any inside information, but I would bet they will use normal spark torch igniters. I have worked with them before, and they have a pretty fast response time that should be more than adequate for an RCS system.