Quote from: edzieba on 11/08/2018 01:51 pmGood assumptions:- Non-destructive recovery... I don't believe this is a good assumption. I think this is a test vehicle. It's main purpose is to gather data for the real BFS.
Good assumptions:- Non-destructive recovery...
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing...
A test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing... My take is SpaceX wants to retire the question of "we can really control a BFS re-entering in this fashion and it will arrive at under Mach 1 and X altitude in one piece"... period. It will be a self funded research program with no customer payloads and no starlink either... Just use of a spare S1 which is recovered and reused...The test stage will then fly over a SpX research ship, downloading reams of data before crashing into the sea...May even be photographic assets on the same ship, taking hull pics for later review...No Recovery... no time wasted and @ low cost by June '19May even be a series of one a month for 6 months planned to make sure they can complete by time BFS get to that stage in it's test program... late '19/early 20'On edit... point is...They likely are thinking... we can build, fly and trash 6 mini's in 6 months for the cost of one BFS spare hull...The data is priceless... the possible time savings huge.... just do it...
Quote from: John Alan on 11/09/2018 12:01 amA test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing... That isn't quite true.There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.
Quote from: speedevil on 11/09/2018 12:04 amQuote from: John Alan on 11/09/2018 12:01 amA test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing... That isn't quite true.There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.The problem is they are using a very novel solution with 4 adjustable "fins" on a new vehicle flying in an environment that is not properly understood and is very difficult to simulate. The first one or two attempts could easily fail and failure with a prototype BFS would be more expensive than failure with a SFS by an order of magnitude.
Quote from: Slarty1080 on 11/09/2018 11:53 amQuote from: speedevil on 11/09/2018 12:04 amQuote from: John Alan on 11/09/2018 12:01 amA test vehicle with proper instrumentation and sensors embedded in the OML hull is all that is needed to verify the TPS works good enough to risk the full size BFS test article later in re-entry testing... That isn't quite true.There can be limited to no risk to the test article if you can refly the full scale BFS test article simply at gradually increasing heatloads, with adequate sensors.It would be very useful for 'no, this isn't going to work at all' determination in that it could shave time from exploring dead ends.The problem is they are using a very novel solution with 4 adjustable "fins" on a new vehicle flying in an environment that is not properly understood and is very difficult to simulate. The first one or two attempts could easily fail and failure with a prototype BFS would be more expensive than failure with a SFS by an order of magnitude.If your launch costs you $3M for BFS, then a really gradual campaign increasing heat loads by only a handful of percent a time is quite plausible.It would seriously risk the vehicle to go full orbital loads first.
They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.
Paying for just the testing by itself would be very un-SpaceX-like.
Existing materials will be used no composite tanks. IMO to keep things simple.
Quote from: Slarty1080 on 11/08/2018 05:00 pmExisting materials will be used no composite tanks. IMO to keep things simple.I think CF construction is a necessity of TPS tests. The TPS is not just the externally exposed material, but also the mounting hardware of that material to the vehicle itself (solid enough to hold it in place against significant force, insubstantial enough not to transmit heat through conduction). SpaceX already have tooling for F9 diameter CF composite cylinders (interstage) and a F9 diameter nosecone (F9H nosecones), so using the same tube-and-cap assembly method as BFR and BFS will use allows for existing tooling to produce the mini-BFS.
Quote from: lonestriker on 11/09/2018 09:07 amPaying for just the testing by itself would be very un-SpaceX-like. SpaceX paid plenty of tests by themselves: Grasshopper, F9R-Dev1/2, subscale Raptor (partially funded by USAF but majority is paid by SpaceX), first Falcon Heavy, recent fairing drop test with Mr. Steven.
Quote from: Slarty1080 on 11/09/2018 12:44 pm They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.Tackling the problem from both ends is of course the right solution here.Either end can be stretched if the data is slow in coming because you're having problems with that end.Being able to stretch all the way up to no external data needed for BFS is nice, but won't result in the fastest development.It is good for development security.
Mod to SpaceX tech tree build: The Falcon 9 second stage will be upgraded to be like a mini-BFR Ship
Mod to SpaceX tech tree build: Falcon 9 second stages will be upgraded to be like a mini-BFR Ship
Mod to SpaceX tech tree build: A Falcon 9 second stage will be upgraded to be like a mini-BFR Ship
Are MVacs even reusable, and if so, will they still be reusable after this type of reentry? They would still need regular S2s for BLEOs
Quote from: RoboGoofers on 11/09/2018 04:12 pmAre MVacs even reusable, and if so, will they still be reusable after this type of reentry? They would still need regular S2s for BLEOsMy guess is they will use a regular M1D on these S2 test objects... Used ones even...After all, it's just going to be crashed after the test, and data download phase, it's said... They really don't NEED an Mvac's ISP performance to accelerate the test item to orbit and then lightly brake burn it into setup for a max aero braking re-entry... do they?...
Quote from: speedevil on 11/09/2018 12:49 pmQuote from: Slarty1080 on 11/09/2018 12:44 pm They will tackle the problem from both "ends" at once to keep the time scale tight. The first BFR prototype will hop higher and higher and faster and faster up to perhaps to sub orbital supersonic speeds. Meanwhile the SFS will drop out of orbit to tackle the orbital and hypersonic / re-entry side of the flight.Tackling the problem from both ends is of course the right solution here.Either end can be stretched if the data is slow in coming because you're having problems with that end.Being able to stretch all the way up to no external data needed for BFS is nice, but won't result in the fastest development.It is good for development security.This is exactly what they did with Falcon first stage... Grasshopper from ground up and water landing boosters from top down. Recall that it was shortly after EM said 'we have all the pieces' that ASDS landing attempts began.
Flying missions for customers and then using the "free" S1/fairings to test recovery options is quintessential SpaceX. So it would be natural to extend this to S2.Assuming Elon meant minimal changes to S2, then if they're going to be sending S2 into orbit for testing, there's no reason not to throw Starlink satellites up at the same time.
Quote from: lonestriker on 11/09/2018 02:43 pmFlying missions for customers and then using the "free" S1/fairings to test recovery options is quintessential SpaceX. So it would be natural to extend this to S2.Assuming Elon meant minimal changes to S2, then if they're going to be sending S2 into orbit for testing, there's no reason not to throw Starlink satellites up at the same time.I don't think minimal changes to S2 was implied, else he would have said that. He would have said something like "We will be making incremental changes to S2 and perform re-entry experiments. But he specifically said "mini-BFR" not "modded S2".*snip*