Quote from: edkyle99 on 02/20/2009 02:26 amStage 2Gross Mass: ~46 tonnesPropellant Mass: ~43 tonnesThrust: 48.99 tonnes vacuumISP: ~340 sec vacuumI just read the F9 User manual that the 2nd stage burns for 345 seconds. With an ISP of 340 and a thrust of 49 tons, that means that the propellant *consumed* during the burn must be > 49 tons. Since your gross mass for the stage is 46 tons, something is off here.Not to mention setting aside some 500 kg for residual prop.
Stage 2Gross Mass: ~46 tonnesPropellant Mass: ~43 tonnesThrust: 48.99 tonnes vacuumISP: ~340 sec vacuum
49 tons of thrust when the tanks were nearing empty would be a hell of a ride. I suspect they'll throttle down a tad.
Quote from: mlorrey on 02/20/2009 06:23 pmQuote from: Danderman on 02/20/2009 04:50 pmGiven that SeaLaunch's original capacity to GTO was 5 tons, launched on a Saturn class, 3 stage vehicle sitting on the Equator, its hard to imagine that a 2 stage vehicle with lower ISP, launched from Florida, would provide 4.5 tons to GTO. These numbers just don't make sense.Its about the mass ratio of the vehicle. PRECISELY! Zenit might be considered a heavy NASCAR racer. Falcon 9, by comparison, would be a lightweight Formula 1 race car. The Zenit first stage was originally designed to be a strap-on booster for Energia, so it likely had robust margin built into the design. Both Zenit stages use separate tanks - and the second stage uses a torodial tank around the engine. Zenit is built from aluminum, presumably aircraft grade aluminum. The rocket has aluminum interstages and an aluminum thrust section, to the best of my knowledge. Falcon 9 is built from Aluminum-Lithium and carbon composites. It has common bulkhead tanks. While one RD-180 weighs 5.4 tonnes, nine Merlin 1C engines only weigh 4.22 tonnes all together - and produce more thrust. When SpaceX lifted the Falcon 9 "run tank" onto the test stand in Texas, the company's web site said that the tanks and engine section (minus engines) weighed only 4.1 tonnes combined during the lift. I'm still not sure I believe that number, but regardless it hints that the thing really is light. This is the revolutionary evolution that Falcon 9 seems to represent. Using the latest materials and the lightest weight structural design methods, SpaceX is aiming to do things with a two-stage kerosene rocket that no one else has done since the Space Age began. If the company pulls it off, and it is an "if", it will be the equivalent of the emergence of lightweight aluminum monoplanes just before World War II. They had engines and wings like their predecessors, but they weighed less while being stronger, and were faster than anything that had flown before. Each piece of the puzzle was an evolutionary change, but when the puzzle was assembled, a revolution happened. - Ed Kyle
Quote from: Danderman on 02/20/2009 04:50 pmGiven that SeaLaunch's original capacity to GTO was 5 tons, launched on a Saturn class, 3 stage vehicle sitting on the Equator, its hard to imagine that a 2 stage vehicle with lower ISP, launched from Florida, would provide 4.5 tons to GTO. These numbers just don't make sense.Its about the mass ratio of the vehicle.
Given that SeaLaunch's original capacity to GTO was 5 tons, launched on a Saturn class, 3 stage vehicle sitting on the Equator, its hard to imagine that a 2 stage vehicle with lower ISP, launched from Florida, would provide 4.5 tons to GTO. These numbers just don't make sense.
Quote from: Danderman on 02/20/2009 11:12 pmI just read the F9 User manual that the 2nd stage burns for 345 seconds. With an ISP of 340 and a thrust of 49 tons, that means that the propellant *consumed* during the burn must be > 49 tons. Since your gross mass for the stage is 46 tons, something is off here.Yes, your assumption that the engine runs at full throttle the whole time is off.
I just read the F9 User manual that the 2nd stage burns for 345 seconds. With an ISP of 340 and a thrust of 49 tons, that means that the propellant *consumed* during the burn must be > 49 tons. Since your gross mass for the stage is 46 tons, something is off here.
Side question: what is the limiting factor for maximum allowed acceleration on crewed flights: human endurance or the construction of the rocket?
What I don't know if this is simply a throttle down prior to shutoff, or a more useful, gradual throttle capability.
FWIW, the Falcon 1 upper stage almost meets the mass fraction requirements needed to make the "magic" Falcon 9 numbers work. And it uses a pressure-fed engine. Not saying that a ~95% propellant fraction is easy, just saying it isn't impossible either. ~Jon
Question: does the interstage section mass count against the first stage or second stage mass fraction?
As I recall, the Long Tank Thor had a 0.95 propellant mass fraction, and that was nearly fifty years ago.
FWIW, I just noticed Falcon 9 User's Guide appeared on the SpaceX site.
Quote from: HMXHMX on 02/20/2009 11:29 pmAs I recall, the Long Tank Thor had a 0.95 propellant mass fraction, and that was nearly fifty years ago.Yes, but that launch vehicle didn't have all of the "puzzle pieces" in place. Thor, designed as an IRBM, was a smaller than ideal starting point for a GTO launcher. It was topped by a hypergolic second stage, which was adapted from another launch vehicle (Vanguard), and so, even though an impressive engineering achievement, was a compromise. Solid upper stages and solid strap-on boosters were required to provide sufficient performance. It worked, and worked very well for many years, but it wasn't the revolution.It is too early to say for sure if Falcon 9 will be a Brewster Buffalo or a Grumman Wildcat - a Boeing 247 or a Douglas DC-3 - whether it will be a near miss or a turning point in space history. - Ed Kyle
Quote from: ugordan on 02/20/2009 10:19 pmFWIW, I just noticed Falcon 9 User's Guide appeared on the SpaceX site.Foremost is the revelation that the Block 2 LEO payload is now given as only 10,454 kg to 200 km x 28.5 deg! The GTO x 28.5 deg payload is given as 4,536 kg.
Foremost is the revelation that the Block 2 LEO payload is now given as only 10,454 kg to 200 km x 28.5 deg! The GTO x 28.5 deg payload is given as 4,536 kg.
-pg 46 - Payload will be vertically integrated to the payload adapter, then rotated horizontal and encapsulated by fairing off site (does not say where, but I assume at a 3rd party clean room, because to my knowledge SpaceX will not have a full clean room any closer than California). I will then be shipped to the launch site and integrated to Falcon 9's 2nd stage.
2. "Connectivity between the payload EGSE, located in the Instrumentation Bay below the launch pad, and the payload is provided by an electrical umbilical. This umbilical is routed up theerector and mates to the payload‐dedicated electrical connector on the second stage umbilical plate."So if the EGSE is at the pad, how can:"Once inside the hangar at the launch complex, the encapsulated payload assembly is mechanically mated to the launch vehicle.Electrical umbilicals between the second stage and the payload are mated and the payload is connected to electrical ground support equipment (if required)"happen.Figure 5‐14 says this happens at the pad
1. A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads. This goes against the rest of the vehicle design for weight efficiency
Quote from: Jim on 02/21/2009 04:25 pm1. A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads. This goes against the rest of the vehicle design for weight efficiencyIs it that the fairing is supporting the weight of the payload, or that the payload adapter serves as the mounting for the fairing?
Quote from: iamlucky13 on 02/21/2009 06:03 pmQuote from: Jim on 02/21/2009 04:25 pm1. A fairing that can support the weight of the payload during ground ops would be "overbuilt" for flight loads. This goes against the rest of the vehicle design for weight efficiencyIs it that the fairing is supporting the weight of the payload, or that the payload adapter serves as the mounting for the fairing?It supports the second stage, and that in turn supports the payload adaptor, payload and fairing. Pretty conventional layout; we all use the same approach.