So once we’re flying that, all other rockets will probably be obsolete. <laughs>
Quote from: envy887 on 05/14/2017 02:21 pmHis examples about the Merlin have some interesting numbers:About 1000 lbs engine mass. Roughly 450 kg, which is a bit lower than the previous estimates I've seen.About 800 lbs/s propellant mass flow rate. That's about 360 kg/s, which is quite a bit higher than the 275 to 300 kg/s typically quoted for Merlin.About 10,500 ft/s exhaust velocity. He also says about Mach 10 exhaust velocity. Those are 3200 and 3400 m/s or 325/345 second ISP. These don't add up to the stated thrust of Falcon 9, which is 7606 kN. With those flow rates and velocities it would be 10000 kN or 11000 kN.But maybe Merlin is considerably more capable than we expected?It seemed like he was just pulling approximate numbers off the cuff. I would not read too much into that.
His examples about the Merlin have some interesting numbers:About 1000 lbs engine mass. Roughly 450 kg, which is a bit lower than the previous estimates I've seen.About 800 lbs/s propellant mass flow rate. That's about 360 kg/s, which is quite a bit higher than the 275 to 300 kg/s typically quoted for Merlin.About 10,500 ft/s exhaust velocity. He also says about Mach 10 exhaust velocity. Those are 3200 and 3400 m/s or 325/345 second ISP. These don't add up to the stated thrust of Falcon 9, which is 7606 kN. With those flow rates and velocities it would be 10000 kN or 11000 kN.But maybe Merlin is considerably more capable than we expected?
Quote from: Basto on 05/14/2017 03:36 pmQuote from: envy887 on 05/14/2017 02:21 pmHis examples about the Merlin have some interesting numbers:About 1000 lbs engine mass. Roughly 450 kg, which is a bit lower than the previous estimates I've seen.About 800 lbs/s propellant mass flow rate. That's about 360 kg/s, which is quite a bit higher than the 275 to 300 kg/s typically quoted for Merlin.About 10,500 ft/s exhaust velocity. He also says about Mach 10 exhaust velocity. Those are 3200 and 3400 m/s or 325/345 second ISP. These don't add up to the stated thrust of Falcon 9, which is 7606 kN. With those flow rates and velocities it would be 10000 kN or 11000 kN.But maybe Merlin is considerably more capable than we expected?It seemed like he was just pulling approximate numbers off the cuff. I would not read too much into that.He gave three significant digits for the exhaust velocity. If that was just making up numbers, I'd expect 10,000 not 10,500.
Quote from: butters on 05/14/2017 01:15 amRetractable landing gear must be intended for use with the landing pad robot (Roomba). Otherwise, erroneous retraction of landing gear while on the ground is a bad day which happens from time to time in aviation.Power fold was NOT indicated... Not my take anyway from Tom's statements... Manual unlatch and manual fold (I assume with some GSE involved) was hinted at... Key take away... is leaving the legs on to save in turn around time... Added quote from transcript...QuoteQuoteAnd it’s going to have a much better landing legs that just fold up and; just drop the rocket, fold the legs, ship it, fold the legs out when it lands. Making it turn very fast;
Retractable landing gear must be intended for use with the landing pad robot (Roomba). Otherwise, erroneous retraction of landing gear while on the ground is a bad day which happens from time to time in aviation.
QuoteAnd it’s going to have a much better landing legs that just fold up and; just drop the rocket, fold the legs, ship it, fold the legs out when it lands. Making it turn very fast;
And it’s going to have a much better landing legs that just fold up and; just drop the rocket, fold the legs, ship it, fold the legs out when it lands. Making it turn very fast;
QuoteSo once we’re flying that, all other rockets will probably be obsolete. <laughs>I bet Rogozin doesn't laugh
The Russians are saying they’re coming up with a rocket that can beat SpaceX, which is entertaining, <laughs> which is entertaining, because they’ve been working on their Angara rocket for 22 years, and launched it once. And suddenly they’re going to be coming up with a low-cost one.
The comments from Mueller gives the impression that the M1D has hit all three items instead of just 2 in the cost, performance, reliability tradeoff. This is in itself very significant and also important for SpaceX. They have a very low cost engine with high performance and high reliability. Something that no one else in the US industry has even come close to. Which is why the Atlas V uses the low cost, high performance, high reliability RD-180 from Russia, the only other engine in use in the US that hits all three points.This goal of hitting all three for the Raptor is also encouraging. Using lessons learned and piling the difficulty into development to be able to make such an engine instead of compromising on operational costs to keep development costs down. Musk has it right. If your going to fly lots of them and want to lower operational costs have good or high performance and high reliability, don't push off doing the right things in development for reducing the development costs.
That rocket is going to be the real game-changer. I would say that the Falcon 9 is revolutionary, you know, a reusable rocket that greatly reduces the cost of access to space. Maybe we can achieve ten reduction in cost over, you know, like what ULA or the Russians or the Chinese are doing, with the Falcon. But we want like a hundred or more reduction in costs; and that’s what the Mars rocket’s gonna do. That’s going to be the revolutionary rocket.So once we’re flying that, all other rockets will probably be obsolete. <laughs>
Combustion efficiency is not actual energy-in (fuel chemical energy), energy-out (jet kinetic energy) efficiency. On that latter measure of efficiency, Raptor is 40-60% efficient.
These don't add up to the stated thrust of Falcon 9, which is 7606 kN. With those flow rates and velocities it would be 10000 kN or 11000 kN.But maybe Merlin is considerably more capable than we expected?
Quote from: Robotbeat on 05/14/2017 09:09 pmCombustion efficiency is not actual energy-in (fuel chemical energy), energy-out (jet kinetic energy) efficiency. On that latter measure of efficiency, Raptor is 40-60% efficient.So, what does the 99% efficiency refer to? ...fraction of hypothetical max. ISP achieved?
I get almost 61% efficiency for a 382s Isp, 3.8 oxidizer to fuel mass ratio, and 55.5MJ/kg specific energy for methane. Check my work..5*(382*9.80665m/s)^2/(55.5MJ/(4.8kg))http://tinyurl.com/kxc9so2
Quote from: Basto on 05/14/2017 03:36 pmQuote from: envy887 on 05/14/2017 02:21 pmHis examples about the Merlin have some interesting numbers:About 1000 lbs engine mass. Roughly 450 kg, which is a bit lower than the previous estimates I've seen.About 800 lbs/s propellant mass flow rate. That's about 360 kg/s, which is quite a bit higher than the 275 to 300 kg/s typically quoted for Merlin.About 10,500 ft/s exhaust velocity. He also says about Mach 10 exhaust velocity. Those are 3200 and 3400 m/s or 325/345 second ISP. These don't add up to the stated thrust of Falcon 9, which is 7606 kN. With those flow rates and velocities it would be 10000 kN or 11000 kN.But maybe Merlin is considerably more capable than we expected?It seemed like he was just pulling approximate numbers off the cuff. I would not read too much into that.TM breathes this stuff. I'd take him literally before believing our numbers to the slightest degree.
This interview is a gold mine of information. Not sure everybody realizes what *Tom* is presenting here. I'm working on a summary to be released shortly. This covers SpaceX, the SpaceX satellite business, Tesla and more. The whole idea that SpaceX is the "airline" to Mars and other companies will have to participate to have car rentals, hotels and other attractions is * AWESOME!*This is crazy!
The talk about nuclear thermal rockets isn't too surprising, either. We know already that SpaceX had been considering NTR at one point due to past presentations (most of them many years old, now). I feel this is a Mueller thing, as Mueller is maybe /the/ greatest propulsion engineer on the planet right now, and NTR is pretty tantalizing. I mean, we actually built them in the past and designed even better ones. (BTW, I think the conclusion is a good one: too expensive for what SpaceX wants to do now.) If you're a propulsion engineer that isn't super old, you might chafe a bit at the fact that you weren't around at the time when these things were being developed (potentially) for flight.
