RE: Bloodhound SSC - ?250k ONO
Discussion
dvs_dave said:
Sweating the details before the overall concept is given any proper consideration.....classic engineer’s downfall....and I say that as an engineer myself.
My big picture point is that modifying and improving upon an existing successful design with known performance characteristics is massively less work and cost than coming up with a clean sheet design and having to discover all of its foibles and failures all over again.
I’d be interested to know if this approach was ever given any serious thought and categorically ruled out as a non starter for solid engineering and/or commercial reasons?
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.My big picture point is that modifying and improving upon an existing successful design with known performance characteristics is massively less work and cost than coming up with a clean sheet design and having to discover all of its foibles and failures all over again.
I’d be interested to know if this approach was ever given any serious thought and categorically ruled out as a non starter for solid engineering and/or commercial reasons?
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
IN51GHT said:
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
Like I say, I’d be interested to know if this approach was considered and why it was ruled out. What were the show stoppers, engineering and/or commercially?
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen, supposedly insurmountable (yet not when a little thought is given to it) engineering detail.
dvs_dave said:
IN51GHT said:
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
Like I say, I’d be interested to know if this approach was considered and why it was ruled out. What were the show stoppers, engineering and/or commercially?
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen, supposedly insurmountable (yet not when a little thought is given to it) engineering detail.
IN51GHT said:
dvs_dave said:
IN51GHT said:
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
Like I say, I’d be interested to know if this approach was considered and why it was ruled out. What were the show stoppers, engineering and/or commercially?
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen, supposedly insurmountable (yet not when a little thought is given to it) engineering detail.
IN5IGHT, to my reading though, the exam question still goes unanswered. Elsewhere and on other threads and other posters, the question of clean sheet vs building on lessons learned design, keeps cropping up. Sure the maths is easy to see, and bridging 700-something mph to 1000mph isn’t a light endeavour, but what specifically makes all knowledge accrued from past LSR attempts seem less relevant when starting Bloodhound?
I get that no one would countenance sticking more bits on ThrustSSC like it was a Citroen Saxo, but, bluntly, Bloodhound looks like everyone started from scratch! Can you or someone break it down a bit as to what was behind the design thinking? Thanks.
Edited by tigerkoi on Tuesday 18th December 15:55
tigerkoi said:
IN51GHT said:
dvs_dave said:
IN51GHT said:
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
Like I say, I’d be interested to know if this approach was considered and why it was ruled out. What were the show stoppers, engineering and/or commercially?
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen, supposedly insurmountable (yet not when a little thought is given to it) engineering detail.
IN5IGHT, to my reading though, the exam question still goes unanswered. Elsewhere and on other threads and other posters, the question of clean sheet vs building on lessons learned design, keeps cropping up. Sure the maths is easy to see, and bridging 700-something mph to 1000mph isn’t a light endeavour, but what specifically makes all knowledge accrued from past LSR attempts seem less relevant when starting Bloodhound?
I get that no one would countenance sticking more bits on ThrustSSC like it was a Citroen Saxo, but, bluntly, Bloodhound looks like everyone started from scratch! Can you or someone break it down a bit as to what was behind the design thinking? Thanks.
Edited by tigerkoi on Tuesday 18th December 15:55
1. Thrust SSC weighed in at 10.5tonnes, too heavy to accelerate & stop in the distance given.
2. The twin engined configuration meant the works worst steering setup, lesson learnt to have simple, conventional steering.
3. The location of the engines meant that the eflux beat the rear of the car in submission.
4. The severity of the shockwave meant the ground was fluidised, vastly increasing wheel drag, the shockwave is as result of the shape of the car.
5. The car was within 11kph (from memory) of takeoff (or was that Thrust 2, I can't remember off the top of my head)
Edited by IN51GHT on Tuesday 18th December 16:11
IN51GHT said:
tigerkoi said:
IN51GHT said:
dvs_dave said:
IN51GHT said:
But it wasn't that driveable, look at the onboard footage, full LH lock at around 700mph, due to instability caused by the design, steering had zero feedback. Was likened to driving forklift truck.
There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.There were too many things wrong with that car to make it possible to redesign, was easier to start afresh
Like I say, I’d be interested to know if this approach was considered and why it was ruled out. What were the show stoppers, engineering and/or commercially?
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen, supposedly insurmountable (yet not when a little thought is given to it) engineering detail.
IN5IGHT, to my reading though, the exam question still goes unanswered. Elsewhere and on other threads and other posters, the question of clean sheet vs building on lessons learned design, keeps cropping up. Sure the maths is easy to see, and bridging 700-something mph to 1000mph isn’t a light endeavour, but what specifically makes all knowledge accrued from past LSR attempts seem less relevant when starting Bloodhound?
I get that no one would countenance sticking more bits on ThrustSSC like it was a Citroen Saxo, but, bluntly, Bloodhound looks like everyone started from scratch! Can you or someone break it down a bit as to what was behind the design thinking? Thanks.
Edited by tigerkoi on Tuesday 18th December 15:55
1. Thrust SSC weighed in at 10.5tonnes, too heavy to accelerate & stop in the distance given.
2. The twin engined configuration meant the works worst steering setup, lesson learnt to have simple, conventional steering.
3. The location of the engines meant that the eflux beat the rear of the car in submission.
4. The severity of the shockwave meant the ground was fluidised, vastly increasing wheel drag, the shockwave is as result of the shape of the car.
5. The car was within 11kph (from memory) of takeoff (or was that Thrust 2, I can't remember off the top of my head)
Edited by IN51GHT on Tuesday 18th December 16:11
Appreciated
dvs_dave said:
I just find it very hard to believe that the best approach for “a bit more supersonic than the last one” is to completely bin that design and start afresh rather than developing and refining an already proven design.
Mach 1.4 is not just "a bit more supersonic than the last one"dvs_dave said:
Seems the only response I’m getting to this big picture question is essentially “just because” and then backing it up with some randomly chosen,
Installed thrust, drag, and stability, are hardly "randomly chosen" given the context of a LSR car.dvs_dave said:
supposedly insurmountable
I don't think anyone has said it's insurmountable
dvs_dave said:
(yet not when a little thought is given to it) engineering detail.
So whats your solution to 10 tonnes of extra drag / less thrust on one side when one of your SRBs shuts down before the other? You seem to imply you've already got a solution after only the smallest consideration...Mave said:
So whats your solution to 10 tonnes of extra drag / less thrust on one side when one of your SRBs shuts down before the other? You seem to imply you've already got a solution after only the smallest consideration...
Getting into the weeds again....I don’t personally have the solution, but it’s no different a problem than one of the jet engines shutting down unexpectedly creating massive asymmetric thrust and likely catastrophic failure. That risk was obviously seemed acceptable, and is arguably much more likely given the complexity of a jet engine over an SRB, which is essentially a glorified firework. In addition, the SRB’s could be very quickly (explosively) jettisoned in the event of one of them beginning to fail and significant asymmetric thrust being sensed. Such systems work very well with spacecraft, so not sure why it couldn’t be deployed here. No need to reinvent the wheel.
I thin the reasons here were simple.
The team knew they could not go THAT much faster with one engine, they had to use either something small and flighty like Sonic Arrow, or use a hybrid system.
They were using Spey's in SSC, they were very powerful, though not the best jet engine in the world, the F4 was always a better plane with J79's in it. Noble also had another pair of more powerful Speys on site should they have been needed, and some of them team even wanted to push and try and go faster, but the car was knackered.
This new vehicle uses the clever idea of rockets too, that is the way forward. I don't know the weight of the new car, but SSC was very heavy and still was close to its limit aerodynamically and mechanically. This car is completely different. To me it looks too high, and not very sleek, are they replying on brute force? Possibly.
And they did a lot of work in CAD and rocket sleds etc on SSC to make sure it would be safe.
I would imagine the research gone into this is monumentally more, therefore it must have the potential to be just as safe or they wouldn't bother. Noble. Ackroyd et al have a re coed of building safe LSR cars, and I see no reason to doubt them again.
The team knew they could not go THAT much faster with one engine, they had to use either something small and flighty like Sonic Arrow, or use a hybrid system.
They were using Spey's in SSC, they were very powerful, though not the best jet engine in the world, the F4 was always a better plane with J79's in it. Noble also had another pair of more powerful Speys on site should they have been needed, and some of them team even wanted to push and try and go faster, but the car was knackered.
This new vehicle uses the clever idea of rockets too, that is the way forward. I don't know the weight of the new car, but SSC was very heavy and still was close to its limit aerodynamically and mechanically. This car is completely different. To me it looks too high, and not very sleek, are they replying on brute force? Possibly.
And they did a lot of work in CAD and rocket sleds etc on SSC to make sure it would be safe.
I would imagine the research gone into this is monumentally more, therefore it must have the potential to be just as safe or they wouldn't bother. Noble. Ackroyd et al have a re coed of building safe LSR cars, and I see no reason to doubt them again.
dvs_dave said:
Getting into the weeds again....
I don’t personally have the solution,
You said it was not insurmountable when a little thought was given to it - kinda sets the expectation that you do have a solution!I don’t personally have the solution,
dvs_dave said:
but it’s no different a problem than one of the jet engines shutting down unexpectedly creating massive asymmetric thrust and likely catastrophic failure. That risk was obviously seemed acceptable, and is arguably much more likely given the complexity of a jet engine over an SRB, which is essentially a glorified firework.
Sorry, but I disagree. The rate of failures of gas turbines is much better than SRBs, and SSC didn't deliberately jettison it's engines during a high speed part of the run per your proposal.dvs_dave said:
In addition, the SRB’s could be very quickly (explosively) jettisoned in the event of one of them beginning to fail and significant asymmetric thrust being sensed.
So now you've got an additional safety critical system to design and verify which also introduces the hazard it's supposed to mitigate if it operates inadvertently when not needed!dvs_dave said:
Such systems work very well with spacecraft, so not sure why it couldn’t be deployed here. No need to reinvent the wheel.
Because spacecraft have the relative luxury of space and time to react, not (at a guess) a few 10s of milliseconds and a foot or so.
You must be cross with yourself all the time. IN51GHT said:
The reasons are too numerous to fully cover, but here's an idea of a few.
1. Thrust SSC weighed in at 10.5tonnes, too heavy to accelerate & stop in the distance given.
2. The twin engined configuration meant the works worst steering setup, lesson learnt to have simple, conventional steering.
3. The location of the engines meant that the eflux beat the rear of the car in submission.
4. The severity of the shockwave meant the ground was fluidised, vastly increasing wheel drag, the shockwave is as result of the shape of the car.
5. The car was within 11kph (from memory) of takeoff (or was that Thrust 2, I can't remember off the top of my head.
There we go. Took a fair bit of cajoling but those are are good set of reasons. 1. Thrust SSC weighed in at 10.5tonnes, too heavy to accelerate & stop in the distance given.
2. The twin engined configuration meant the works worst steering setup, lesson learnt to have simple, conventional steering.
3. The location of the engines meant that the eflux beat the rear of the car in submission.
4. The severity of the shockwave meant the ground was fluidised, vastly increasing wheel drag, the shockwave is as result of the shape of the car.
5. The car was within 11kph (from memory) of takeoff (or was that Thrust 2, I can't remember off the top of my head.
Although it begs the question why SSC was designed the way it was as in hindsight some of these problems seem as though they should have revealed themselves at prototype modeling and analysis stages. Wonky steering, improperly fixed bodywork, unexpected shockwave behavior and it’s infuence on the running surface. How much in the way of FEA resources did the SSC team have back then?
Then again it satisfied its purpose and nothing more, so it’s academic if it needed to be improved anywhere. As is this discussion....which is the point many seem to also be missing.
Mave said:
dvs_dave said:
Getting into the weeds again....
I don’t personally have the solution,
You said it was not insurmountable when a little thought was given to it - kinda sets the expectation that you do have a solution!I don’t personally have the solution,
dvs_dave said:
but it’s no different a problem than one of the jet engines shutting down unexpectedly creating massive asymmetric thrust and likely catastrophic failure. That risk was obviously seemed acceptable, and is arguably much more likely given the complexity of a jet engine over an SRB, which is essentially a glorified firework.
Sorry, but I disagree. The rate of failures of gas turbines is much better than SRBs, and SSC didn't deliberately jettison it's engines during a high speed part of the run per your proposal.dvs_dave said:
In addition, the SRB’s could be very quickly (explosively) jettisoned in the event of one of them beginning to fail and significant asymmetric thrust being sensed.
So now you've got an additional safety critical system to design and verify which also introduces the hazard it's supposed to mitigate if it operates inadvertently when not needed!dvs_dave said:
Such systems work very well with spacecraft, so not sure why it couldn’t be deployed here. No need to reinvent the wheel.
Because spacecraft have the relative luxury of space and time to react, not (at a guess) a few 10s of milliseconds and a foot or so.
dvs_dave said:
Mave said:
Most of those reasons have already recently been highlighted!
I suppose if you call 2 out of 5 (steering, eflux) “most” then you’re correct. However most others would disagree.Edited by Mave on Tuesday 18th December 22:11
mcdjl said:
Mave said:
dvs_dave said:
Uh huh. I think it’s fair to say that you’re not a solutions guy.
Quite the opposite. But I like to work out what problems I'm trying to fix first.Gassing Station | General Gassing | Top of Page | What's New | My Stuff