Total Members Voted: 504
Quote from: Lars-J on 10/06/2017 08:23 pmQuote from: Peter.Colin on 10/06/2017 08:20 pmQuote from: DJPledger on 10/06/2017 08:09 pmDue to the mass of Raptor's turbomachinery and plumbing. Pipes need to be a minimum thickness to withstand the operating pressures expected in Raptor. If Raptor could be made out of CNT then it's TWR could easily reach or exceed 600.And have you accounted for the fact that the plumbing is much shorter than Merlin 1D?How do *you* account for your T/W number of 600? It surely sounds like a number pulled out of thin air. M1D has record breaking T/W, so what - based on existing engines - makes it likely that somehow Raptor has bested that number by over 3 times? It just isn't credible.It’s mainly based on what was said by Elon, suppose he knows the number is 600, then he could easily say “same size engine as Merlin 1D, 3 times the thrust”. I don’t know any Raptor engine which is the same size and has 3 times the thrustThey are all bigger or have the same thrust. So why does he say that? Probably he meant by size, wheight, then it makes sense. Otherwise not
Quote from: Peter.Colin on 10/06/2017 08:20 pmQuote from: DJPledger on 10/06/2017 08:09 pmDue to the mass of Raptor's turbomachinery and plumbing. Pipes need to be a minimum thickness to withstand the operating pressures expected in Raptor. If Raptor could be made out of CNT then it's TWR could easily reach or exceed 600.And have you accounted for the fact that the plumbing is much shorter than Merlin 1D?How do *you* account for your T/W number of 600? It surely sounds like a number pulled out of thin air. M1D has record breaking T/W, so what - based on existing engines - makes it likely that somehow Raptor has bested that number by over 3 times? It just isn't credible.
Quote from: DJPledger on 10/06/2017 08:09 pmDue to the mass of Raptor's turbomachinery and plumbing. Pipes need to be a minimum thickness to withstand the operating pressures expected in Raptor. If Raptor could be made out of CNT then it's TWR could easily reach or exceed 600.And have you accounted for the fact that the plumbing is much shorter than Merlin 1D?
Due to the mass of Raptor's turbomachinery and plumbing. Pipes need to be a minimum thickness to withstand the operating pressures expected in Raptor. If Raptor could be made out of CNT then it's TWR could easily reach or exceed 600.
Really... we need to wait if or until SpaceX releases some specs at a later date TBD...That said...My guess of a mass of ~980kg (almost 1 metric ton) and a thrust stated at 170 to 190 metric tonsPuts Raptor in about the same thrust to weight ratio as Merlin 1D full thrust... 180 to 1I will add my thought of "Good Enough" to this... No real need to try and beat that...
200:1 is the planned 300 bar later version... in my opinion...
If Elon says at IAC 2016 on why such small engines? “similar engine size but 3 times the thrust” I asume T/W is around 600 because Merlin 1D is 200.
Quote from: Lars-J on 10/06/2017 08:23 pmQuote from: Peter.Colin on 10/06/2017 08:20 pmQuote from: DJPledger on 10/06/2017 08:09 pmDue to the mass of Raptor's turbomachinery and plumbing. Pipes need to be a minimum thickness to withstand the operating pressures expected in Raptor. If Raptor could be made out of CNT then it's TWR could easily reach or exceed 600.And have you accounted for the fact that the plumbing is much shorter than Merlin 1D?How do *you* account for your T/W number of 600? It surely sounds like a number pulled out of thin air. M1D has record breaking T/W, so what - based on existing engines - makes it likely that somehow Raptor has bested that number by over 3 times? It just isn't credible.It’s mainly based on what was said by Elon, suppose he knows the number is 600, then he could easily say “similar sized engine as Merlin 1D, 3 times the thrust”. I don’t know any Raptor engine which is the same size and has 3 times the thrust?They are all bigger or have the same thrust. So why does he say that? Probably he meant wheight instead of size, then it makes sense, otherwise not.But I dont know either, only that its “the highest TWR of any engine, of any kind”, so above 200.
I wonder if any of the Raptor plumbing is carbon fiber overwrapped. It sure saves a lot of mass in COPVs, and not all the fluid flows are high temp.
Quote from: envy887 on 10/06/2017 08:26 pmI wonder if any of the Raptor plumbing is carbon fiber overwrapped. It sure saves a lot of mass in COPVs, and not all the fluid flows are high temp.No chance, too much mismatch in thermal expansion coefficients, near impossible to do wrapping due to poor accessibility, potential fire danger around oxygen, and carbon fibre doesn't have the ability to handle more than about 200-250°C during reentry.
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: 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: 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: 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.
Raptor is on the path of needing to exceed LM ASC engine reliability. That's a tall order to fill. (If those point to point transport on Earth graphics are "real", likely engine reliability would have to approach commercial transport turbofan reliability, which is three orders plus of magnitude higher.) To prove this would require extreme testing/use/reuse.One could "concern troll" that if AJR/BO can't test to such, then SX couldn't ever do such, omitting the fact that they seem to be able to meet reliability margins above industry norms.
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: 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.
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?