Quote from: the_other_Doug on 08/03/2016 03:07 pmNo one thinks that strapping together a total of 27 engines, in three different thrust structures and three discrete-but-interacting flight control systems, and igniting all of them for lift-off has any potential engineering challenges that might still be looking for hard solutions?No,a. They haven't have any issues for 9 engine starts for awhile. Doing 27, it isn't going to change muchb. They aren't 3 different, but two exactly the same,with the other similar. c. Flight control systems are any different. They are all slaved to the second stage until after separation, just like a single stick launch.
No one thinks that strapping together a total of 27 engines, in three different thrust structures and three discrete-but-interacting flight control systems, and igniting all of them for lift-off has any potential engineering challenges that might still be looking for hard solutions?
1. Obviously, the side boosters on each FH launch will have to be in very close agreement on their position, both via GPS and inertial, once their separate flight control systems take over upon separation.2. Also, the side cores will need to fly avoidance maneuvers to ensure no recontact with either the remaining center
Each stage is generating sonic booms, after all -- I wouldn't think you'd want them within a kilometer of each other when they each go subsonic. A little separation, please...?
2. Not really, they will be separated by solid motors and/or gas thrusters (just like other vehicles). Just as the single core booster doesn't do anything right after separation, neither will the side boosters. Aerodynamics will take over as the booster angle away and increase the separation.
Quote from: Jim on 08/03/2016 05:24 pm2. Not really, they will be separated by solid motors and/or gas thrusters (just like other vehicles). Just as the single core booster doesn't do anything right after separation, neither will the side boosters. Aerodynamics will take over as the booster angle away and increase the separation.Do we have any more info on this procedure? I think that SpaceX would use a hydraulic system initially for separation, and maybe couple it with the nitrogen thrusters for adding some distance after that.
Quote from: Dante80 on 08/03/2016 05:50 pmQuote from: Jim on 08/03/2016 05:24 pm2. Not really, they will be separated by solid motors and/or gas thrusters (just like other vehicles). Just as the single core booster doesn't do anything right after separation, neither will the side boosters. Aerodynamics will take over as the booster angle away and increase the separation.Do we have any more info on this procedure? I think that SpaceX would use a hydraulic system initially for separation, and maybe couple it with the nitrogen thrusters for adding some distance after that. Gas thrusters/gas pistons A large impulse is needed.
Quote from: Jim on 08/03/2016 05:53 pmQuote from: Dante80 on 08/03/2016 05:50 pmQuote from: Jim on 08/03/2016 05:24 pm2. Not really, they will be separated by solid motors and/or gas thrusters (just like other vehicles). Just as the single core booster doesn't do anything right after separation, neither will the side boosters. Aerodynamics will take over as the booster angle away and increase the separation.Do we have any more info on this procedure? I think that SpaceX would use a hydraulic system initially for separation, and maybe couple it with the nitrogen thrusters for adding some distance after that. Gas thrusters/gas pistons A large impulse is needed.Have side boosters (LRB or SRB) on any large rockets ever been jettisoned with anything except explosive bolts and solid-fuel separation motors?
Quote from: the_other_Doug on 08/03/2016 03:07 pmSo -- it's the consensus of all the engineering types around here that SpaceX is deliberately delaying FH for their own internal reasons, and not because they are still addressing potential engineering issues?No one thinks that strapping together a total of 27 engines, in three different thrust structures and three discrete-but-interacting flight control systems, and igniting all of them for lift-off has any potential engineering challenges that might still be looking for hard solutions?Just wonderin'... Not to mention the manpower/schedule challenge of trying to catch up on a severe F9 launch backlog...and getting crewed Dragon done, which has also been slipping, BTW...Their workload has been increasing at a rapid rate, and increasing staffing to match in an extremely demanding work environment like that can be very difficult to manage. Often the hiring lags behind the actual headcount need. We've already heard that 80-hour work weeks are common. It wouldn't surprise me if the delays in FH and crewed Dragon are simply the result of too few people trying to do too much work.
So -- it's the consensus of all the engineering types around here that SpaceX is deliberately delaying FH for their own internal reasons, and not because they are still addressing potential engineering issues?No one thinks that strapping together a total of 27 engines, in three different thrust structures and three discrete-but-interacting flight control systems, and igniting all of them for lift-off has any potential engineering challenges that might still be looking for hard solutions?Just wonderin'...
Quote from: su27k on 08/02/2016 11:10 amI remember seeing somewhere that range tracking system needs to be upgraded to support tracking multiple inbound boosters at the same time. Totally unconfirmed rumor, but makes certain amount of sense...Ah, that makes sense. Need someone to confirm that rumour then!
I remember seeing somewhere that range tracking system needs to be upgraded to support tracking multiple inbound boosters at the same time. Totally unconfirmed rumor, but makes certain amount of sense...
Shotwell on Falcon Heavy: “sorry we’re late” on it; harder problem to develop than we thought. #smallsat
Quote from: Shanuson on 08/09/2016 05:25 pmQuoteDavid Hurst@OrbitalDaveShotwell: 1st Falcon Heavy mission expected Q3 of 17 #smallsathttps://twitter.com/OrbitalDave/status/763060858528215040The guy posting from the conference on Reddit said that's the STP-2 mission in Q3 2017, which would be the second or third FH flight. Can't wait until they post a video of the talk so we don't have to rely on a bunch of possibly misleading tweets.
QuoteDavid Hurst@OrbitalDaveShotwell: 1st Falcon Heavy mission expected Q3 of 17 #smallsathttps://twitter.com/OrbitalDave/status/763060858528215040
David Hurst@OrbitalDaveShotwell: 1st Falcon Heavy mission expected Q3 of 17 #smallsat
Is it useful to create a FH with three cores that might not be the final design (how to jettison side boosters, flight software, thermal protection, etc.) to test out the GSE? Is there a benefit to getting a WDR done without waiting for the boosters and core to be complete?
I realized that, with latest improvements of M1D, FH would still have a good T/W at liftoff with a five engine center core.This would be 2000 kg dry mass reduction; not saying it is simple, but improving mass ratio on the center core would be a very good thing for reusability.
The lighter the core, the more overpowered the last part of the landing.
They can do it, but the benefit might be marginal compared to the job of designing a different stage.
It might also cost them engine out capabilty for much of the flight.
Quote from: Mike_1179 on 08/23/2016 05:38 pmIs it useful to create a FH with three cores that might not be the final design (how to jettison side boosters, flight software, thermal protection, etc.) to test out the GSE? Is there a benefit to getting a WDR done without waiting for the boosters and core to be complete?SpaceX adopted mantra "Test as you fly. Fly as you test." So no. Only if the use will gain them something very significant is the only exception. The only exception that comes to mind is that the M1D FTs are not yet the M1D maxFTs. M1D max FTs are to supposed start being used sometime after Oct on F9. But this is not to say that they will not tweak the designs once the FH starts flying either. Its just that intentionally not flying the current design is not likely to gain them anything. A BTW on the engines is that their impact if the non maxFT ones are used is use of different constants in the software and a smaller payload but not much else.
Direct GSO insertion of large sats needs expendable performance (and 2nd stage endurance). I know they have said they are working on the endurance, but don't think they have any direct GSO payloads manifested.