Quote from: wannamoonbase on 03/27/2018 06:31 pmQuote from: cppetrie on 03/27/2018 06:10 pmThe purpose of the winglets is adapt the aero profile across a variety of payload amounts and atmospheric conditions. Given that the tanker will always land under the same conditions (essentially empty and on earth) the winglets may not be needed. Or they may be fixed or different shaped. I assume there will be 1 mold line, one set of tooling and 1 way to do things. Right up to the point they decide if it's Cargo, Crew or Tanker.Tanker should be the easiest of all of them.Not expecting to see anything soon. Lots of development to be done. I'll entertain myself with the epic accomplishments of the Falcon family until then.We’ve already been told by Elon that the dedicated tanker will look “weird”. To me that means the dedicated tanker will probably not share the same OML as the ship and cargo versions. But the dedicated tanker will come (much) later. The early tankers will just be cargo versions with no cargo and so of course will have the same OML.
Quote from: cppetrie on 03/27/2018 06:10 pmThe purpose of the winglets is adapt the aero profile across a variety of payload amounts and atmospheric conditions. Given that the tanker will always land under the same conditions (essentially empty and on earth) the winglets may not be needed. Or they may be fixed or different shaped. I assume there will be 1 mold line, one set of tooling and 1 way to do things. Right up to the point they decide if it's Cargo, Crew or Tanker.Tanker should be the easiest of all of them.Not expecting to see anything soon. Lots of development to be done. I'll entertain myself with the epic accomplishments of the Falcon family until then.
The purpose of the winglets is adapt the aero profile across a variety of payload amounts and atmospheric conditions. Given that the tanker will always land under the same conditions (essentially empty and on earth) the winglets may not be needed. Or they may be fixed or different shaped.
Just speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)I'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.It would be very fluffy on reentry, with engine mass to the rear, and more reentry surface than a normal BFR. I would think that this would make up for any extra mass for a larger design by saving landing fuel from a softer landing.
Quote from: rakaydos on 03/29/2018 08:35 pmJust speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)I'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.It would be very fluffy on reentry, with engine mass to the rear, and more reentry surface than a normal BFR. I would think that this would make up for any extra mass for a larger design by saving landing fuel from a softer landing.The engines in the wings would not be thrusting through the centre of mass. Gimballing them through the centre would induce a backwards translation. I suppose if you're coming in from orbit, this might actually help do the flip upright and reduce forward velocity?
I'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.Quote from: rakaydos on 04/02/2018 05:41 pmThrusting throught the center of mass is done to avoid a rotation, which is nessisary for asymetric thrust. With symmetric thrusters, however, a tractor arrangement (skycrane?) should be reasonablePerhaps I'm misunderstanding you - are you suggesting 4 winglets instead of 2, with an engine in each wing (therefore symmetric thrust) or are you saying the wings should be moved to the centre of the cylinder so that you can have symmetric thust without a second set of wings? Otherwise I'm not following.
Thrusting throught the center of mass is done to avoid a rotation, which is nessisary for asymetric thrust. With symmetric thrusters, however, a tractor arrangement (skycrane?) should be reasonable
Just speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)
Quote from: rakaydos on 03/29/2018 08:35 pmI'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.Quote from: rakaydos on 04/02/2018 05:41 pmThrusting throught the center of mass is done to avoid a rotation, which is nessisary for asymetric thrust. With symmetric thrusters, however, a tractor arrangement (skycrane?) should be reasonablePerhaps I'm misunderstanding you - are you suggesting 4 winglets instead of 2, with an engine in each wing (therefore symmetric thrust) or are you saying the wings should be moved to the centre of the cylinder so that you can have symmetric thust without a second set of wings? Otherwise I'm not following.
I'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.
Quote from: rakaydos on 03/29/2018 08:35 pmJust speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)Makes absolutely no sense.Lifting weight of these engines and their tanks all the way to the orbit.Heat shielding the first stage tanks from the plume of these enginesAll the stability/control trouble of engines whose thrust vector is very far from the center of the gravity.Better to have more engines in the first stage instead - and oh, it already contains 31 of those.
As far as heat shielding... a properly expanded bell apparetly makes the exaust not so hot. Something about turning heat into movement.
Apologies for the multiple posts with messed up quotes. I'm not quite sure how that happened.
Quote from: rakaydos on 04/03/2018 03:57 pmAs far as heat shielding... a properly expanded bell apparetly makes the exaust not so hot. Something about turning heat into movement.Only with respect to the moving exhaust.If you place a thermometer moving along with the exhaust, it may read around 100C.If you place one sticking into the exhaust stationary, it will read about the same temperature as the combustion chamber.Plume interaction with structure can heat it a lot.Plus, if there is residual air, that gets heated lots by turbulence and impact from the jet.
I'm not sure about a 2,000 ton fuel depot, but the idea of what could take advantage of a replenishable, available BFS tank rigged for long term use has to be going through a lot of minds. Or single use tankers rigged for non SpaceX users. NASA or commercial, it would enable entirely new architectures.
Quote from: Nomadd on 04/03/2018 11:40 pm I'm not sure about a 2,000 ton fuel depot, but the idea of what could take advantage of a replenishable, available BFS tank rigged for long term use has to be going through a lot of minds. Or single use tankers rigged for non SpaceX users. NASA or commercial, it would enable entirely new architectures.SpaceX is basically going to define the Industry Standard Cryomethane refueling interface. I hope they are planning around future designs being backward compatable.
And then no one else will use it, even though it's clearly better. Instead, they'll develop much larger interfaces that cost more and can't transfer fuel as quickly...
Quote from: octavo on 04/03/2018 07:12 amQuote from: rakaydos on 03/29/2018 08:35 pmI'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.Quote from: rakaydos on 04/02/2018 05:41 pmThrusting throught the center of mass is done to avoid a rotation, which is nessisary for asymetric thrust. With symmetric thrusters, however, a tractor arrangement (skycrane?) should be reasonablePerhaps I'm misunderstanding you - are you suggesting 4 winglets instead of 2, with an engine in each wing (therefore symmetric thrust) or are you saying the wings should be moved to the centre of the cylinder so that you can have symmetric thust without a second set of wings? Otherwise I'm not following.Moving the wings to parallel the axis of thrust- sorry I thought that was imlied by putting things in them. I was unclear.Quote from: hkultala on 04/03/2018 07:33 amQuote from: rakaydos on 03/29/2018 08:35 pmJust speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)Makes absolutely no sense.Lifting weight of these engines and their tanks all the way to the orbit.Heat shielding the first stage tanks from the plume of these enginesAll the stability/control trouble of engines whose thrust vector is very far from the center of the gravity.Better to have more engines in the first stage instead - and oh, it already contains 31 of those.In case you didnt notice, the upper stage already includes sea level engines for landing purposes. Moving them to the wings to be used on ascent doesnt actually add mass. Tanks do, but we're adding tanks because it's a tanker.As far as heat shielding... a properly expanded bell apparetly makes the exaust not so hot. Something about turning heat into movement.
Quote from: rakaydos on 04/03/2018 03:57 pmQuote from: octavo on 04/03/2018 07:12 amQuote from: rakaydos on 03/29/2018 08:35 pmI'm thinking a rounded diamond or arrowhead shape, outboard SL engines in the "wings" for landing, Vac engines in the circular interface with Stage 1, (up to 7 R-vac with no gimbal, but probably not that many) and the rest of the internal volume is fuel. Exact size is iterated based on how much fuel the rocket can lift to a reference orbit.Quote from: rakaydos on 04/02/2018 05:41 pmThrusting throught the center of mass is done to avoid a rotation, which is nessisary for asymetric thrust. With symmetric thrusters, however, a tractor arrangement (skycrane?) should be reasonablePerhaps I'm misunderstanding you - are you suggesting 4 winglets instead of 2, with an engine in each wing (therefore symmetric thrust) or are you saying the wings should be moved to the centre of the cylinder so that you can have symmetric thust without a second set of wings? Otherwise I'm not following.Moving the wings to parallel the axis of thrust- sorry I thought that was imlied by putting things in them. I was unclear.Quote from: hkultala on 04/03/2018 07:33 amQuote from: rakaydos on 03/29/2018 08:35 pmJust speculating here...I like the idea mentioned of improving payload to orbit by having outward gimbaled sea level engines outboard on the second stage, to improve liftoff TWR. Possibly with some aerospike-like effects as the plume interacts with the body, if you have enough balls to design it that way. (note: this very dangerous if not designed correctly)Makes absolutely no sense.Lifting weight of these engines and their tanks all the way to the orbit.Heat shielding the first stage tanks from the plume of these enginesAll the stability/control trouble of engines whose thrust vector is very far from the center of the gravity.Better to have more engines in the first stage instead - and oh, it already contains 31 of those.In case you didnt notice, the upper stage already includes sea level engines for landing purposes. Moving them to the wings to be used on ascent doesnt actually add mass. Tanks do, but we're adding tanks because it's a tanker.As far as heat shielding... a properly expanded bell apparetly makes the exaust not so hot. Something about turning heat into movement.Moving them to the wings would mean they could not be used for landing.So, makes no sense.