Ideals are much greater than that.The specific strength of aluminum lithium is about 200MPa/(g/cc). The specific strength of the best available carbon fiber, Toray T1100G (which is very hard to get, by the way), is 3900MPa/(g/cc). That's at the fiber level. If you make a unidirectional composite, it's closer to 2000GPa/(g/cc), still a factor of 10 better. Of course, that's with tensile-dominated structures. Quasi isotropic is less, more like 500-700MPa/(g/cc), but if you're very clever with design, you can utilize unidirectional properties.So the >30% weight reduction is /after/ "non-ideals."
Quote from: Robotbeat on 07/28/2017 11:50 amIdeals are much greater than that.The specific strength of aluminum lithium is about 200MPa/(g/cc). The specific strength of the best available carbon fiber, Toray T1100G (which is very hard to get, by the way), is 3900MPa/(g/cc). That's at the fiber level. If you make a unidirectional composite, it's closer to 2000GPa/(g/cc), still a factor of 10 better. Of course, that's with tensile-dominated structures. Quasi isotropic is less, more like 500-700MPa/(g/cc), but if you're very clever with design, you can utilize unidirectional properties.So the >30% weight reduction is /after/ "non-ideals."You have tension in two directions. It cannot be unidirectional.John
Did you make that? I'd love to see the 9m compared to the shuttle.
The very wide shape of the 9m ITS spaceship might require new type ofmultiple satellite holders?
So, starting at the lower engine count (19) what would be the approximate length of the 9M first stage? Can we assume a common bulkhead? If it could fit within Pegasus, SpaceX could just lease it for the first few years of development. AND if 12 meters proves too large, they could think about a 9 meter core version that could handle three Falcon 9 side boosters.
Quote from: lamontagne on 07/29/2017 03:53 pmThe very wide shape of the 9m ITS spaceship might require new type ofmultiple satellite holders?You mean an active dispenser, some kind of carousel which moves sets of satellites into a dispensing position under the door opening?
Quote from: Norm38 on 07/29/2017 02:10 pmDid you make that? I'd love to see the 9m compared to the shuttle.Yes, here it is. I checked the wingspan, all seems correct.
Quote from: lamontagne on 07/29/2017 03:40 pmQuote from: Norm38 on 07/29/2017 02:10 pmDid you make that? I'd love to see the 9m compared to the shuttle.Yes, here it is. I checked the wingspan, all seems correct.I like it.I am increasingly of the opinion that the most comparable vehicle to BFS is Shuttle. Shuttle used drop tanks and landed horizontally, but otherwise quite similar.
If they can get the 9m from the factory to the port. Ships and barges can get it to the Cape. If they only made 4 per year, that is only one per quarter. It could move at night or on a weekend. They could spend a little to get all overhead utilities out of the way so the transfers would be quicker and neater. I think they have to go wide to get the 100 tons of cargo to space and not have an overly tall rocket.
The specific strength of the best available carbon fiber, Toray T1100G (which is very hard to get, by the way), is 3900MPa/(g/cc).
Quote from: spacenut on 07/28/2017 12:58 amIf they can get the 9m from the factory to the port. Ships and barges can get it to the Cape. If they only made 4 per year, that is only one per quarter. It could move at night or on a weekend. They could spend a little to get all overhead utilities out of the way so the transfers would be quicker and neater. I think they have to go wide to get the 100 tons of cargo to space and not have an overly tall rocket. Why on earth would they want to make 4 per year? If the booster turns out to be as reusable as Elon hopes, one will last decades.One booster every few years could slowly build up a sizeable fleet.
This is not as pretty but clearer.The very wide shape of the 9m ITS spaceship might require new type ofmultiple satellite holders?
SpaceX sure won't go to multiple core designs again after all the trouble with FH. 9m ITS system will stay single core. If they want a bigger ITS system in the future they will go with a larger dia. core.