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Author Topic: Why is the Bloodhound Car using Turbine & Rocket? Why not Rocket only?  (Read 3464 times)
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Dynoroom
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« Reply #15 on: May 13, 2016, 07:31:00 PM »

Not to mention they have been successful twice before. Some might say 4 times...
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« Reply #16 on: May 13, 2016, 08:01:07 PM »

It is an admirable effort.
Well, sure. But complexity is not intrinsically more admirable than simplicity.
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J79
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« Reply #17 on: May 13, 2016, 09:39:35 PM »

Here are Andy Greens diaries from the Bloodhound website. Looks like one per month April 16 2016-July 2009, around 80 of them. http://www.bloodhoundssc.com/andygreen?page=6 Instead of me reading each one of them, which is very time consuming, do you know which one describes why Bloodhound has chosen to run a Turbine and a Rocket versus Rocket only or why they have made that choice?

Does anyone know the answer to the question?

J79 - you are clearly interested in thrust driven vehicles so let me help here in terms of engaging with the people on this forum.

First, most are well aware of the BloodhoundSSC project (even if their primary interest is wheel driven vehicles) so the links you've posted have already been covered and are old news. There is a thread elsewhere where any new stuff from them is referenced.

Second, the question you ask about why they've chosen a mixed power plant design is answered on their own website. Poke around a bit more and you'll find the answer - think it's in one of Andy's updates. As to the simpler jet or rocket designs you mention, well that's the beauty of having rules that encourage a multitude of solutions. There is no right or wrong way, only your way based on the your view of how best to solve the problem of going fast. And the only way of testing the validity of your solution is to build and run the vehicle and beat an existing record. If you hold a record, then that's the right way. Until somebody else comes along and beats it with a different solution.

The rotational effect you mention does exist and it did indeed cause Art some issues because he was a jet car pioneer so the extra forces exerted on wheel bearings, tyres and so on weren't fully understood back then by everybody. But other jet cars ran successfully and by now designers are well aware of it and know how to cater for it - hence Ed's succinct response.

Finally, most people here would use the word Turbine to describe an engine with a drive shaft attached to it. Yes they work on pretty much the same principles as a pure jet engine, but the exhaust gas driven output shaft connected to something makes it a turbine. the Turbinator team hold the current wheel driven record with a turbine engine. Sid knows a bit about this.  cool BloodhoundSSC and its predecessors Thrust2 and ThrustSSC use pure jets so Jet is the description they and most others would use.

Hope this helps.

Robin


« Last Edit: May 13, 2016, 11:28:23 PM by J79 » Logged

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« Reply #18 on: May 14, 2016, 08:11:53 AM »

..............if you ask when (and where).....6th April 1988....Hampton Court.....................

there is also an answer to why...... grin



Here are Andy Greens diaries from the Bloodhound website. Looks like one per month April 16 2016-July 2009, around 80 of them. http://www.bloodhoundssc.com/andygreen?page=6 Instead of me reading each one of them, which is very time consuming, do you know which one describes why Bloodhound has chosen to run a Turbine and a Rocket versus Rocket only or why they have made that choice?

Does anyone know the answer to the question?


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« Reply #19 on: May 14, 2016, 08:40:05 AM »

In the very early stages of the Project, BLOODHOUND SSC was intended to be purely rocket-powered. While this offered certain performance advantages, rockets are not as easy to control as jets, so it was decided to combine both powerplants to gain power and control.
 
In order to accelerate the car to 1000mph, each Nammo hybrid rocket will provide a thrust of 30kN (6,000 lbs). This will be combined with the thrust from the EJ200 jet to generate about 212kN (47,700lbs) - that's eight times more power than all the cars on a Formula 1 starting grid combined.

The Nammo rocket will be used instead of the Falcon Project rocket which proved the concept of using a hybrid rocket in BLOODHOUND. The design of the Nammo rocket is still being finalised, but it is likely to have a cluster of four or five motors rather than a single large combustion chamber.


The above is a quote from the Bloodhound web site.

I have heard Ron Ayers explaining the design concept several times, but cannot remember all the details. In no particular order, the following are factors:

  • Jet is more controllable
  • Several EJ200s that were at the end of their flying life became available at no or low cost
  • The team had no previous experience of rocket propulsion
  • There was no off-the-shelf rocket solution
  • At very high speeds, aerodynamic forces dwarf all others
  • Bloodhound is not required to go round corners, so what appears to be a high c of g is not a big disadvantage (as long as you can keep the pointy end at the front)

As with many things in life, it's a compromise. Others are going down the rocket-only route but I don't think they will be ready to break the current record before Bloodhound SSC.

J79, you are still referring to Turbine instead of Jet. This suggests you are not reading and understanding other posts. In particular, Robin UK provided some sage advice on how to engage with members of this forum. 
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« Reply #20 on: May 14, 2016, 08:53:01 AM »

Not to mention they have been successful twice before. Some might say 4 times...

OK, I bite. Thrust 2 set the record on one occasion and Thrust SSC twice. Why might some say 4 times?
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« Reply #21 on: May 14, 2016, 09:02:04 AM »

Don't I remember that there was a set of runs that set record speeds - but the team took just a minute or so over the 1 hour - - so all was for naught?

Would that the #4?
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« Reply #22 on: May 14, 2016, 09:13:10 AM »

Don't I remember that there was a set of runs that set record speeds - but the team took just a minute or so over the 1 hour - - so all was for naught?

Would that the #4?

Ah, yes. You are correct Jon. Two days before the official supersonic record they made a pair of runs at 760+ mph, but the time between them was 49.6 seconds over the permitted hour (it says here).
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« Reply #23 on: May 14, 2016, 09:28:58 AM »

Been there & done that on FIA records before, man does rip your feet out from under you! cry
  Sid.
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« Reply #24 on: May 14, 2016, 11:42:59 AM »

TrickyDicky.....

"J79, you are still referring to Turbine instead of Jet. This suggests you are not reading and understanding other posts. In particular, Robin UK provided some sage advice on how to engage with members of this forum.  "

The General Electric J79 is an axial-flow turbojet engine..do you have a different definition of a jet engine?

Bill
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« Reply #25 on: May 14, 2016, 10:31:59 PM »

Slim gets it...  Wink
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Michael LeFevers
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« Reply #26 on: May 15, 2016, 01:01:51 AM »

Awesome video, Kiwi.  Thanks for providing it.  I have been "following" the
absolute land speed record for decades, and knew about these cars and
teams, but hadn't seen that particular video yet.  It was informative.

tallguy
(in northern California)
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« Reply #27 on: May 15, 2016, 03:56:52 AM »

TrickyDicky.....

"J79, you are still referring to Turbine instead of Jet. This suggests you are not reading and understanding other posts. In particular, Robin UK provided some sage advice on how to engage with members of this forum.  "

The General Electric J79 is an axial-flow turbojet engine..do you have a different definition of a jet engine?

Bill

Bill,

I think we have a misunderstanding. I was referring to J79 the poster who started this thread and has asked several further questions.

On definitions, I was going with Robin UK's input, i.e. a General Electric J79 might be referred to as a "jet"when providing thrust but a "turbine" when configured to provide drive through the wheels.
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« Reply #28 on: September 28, 2016, 04:29:07 PM »

At the risk of resurrecting an old post..... The EJ200 jet engine Bloodhound is using has counter rotating blades to ensure there are no undue forces affecting the car.

The jet engine is easily throttleable and enables the team to conduct much of the low speed testing - up to 600mph without the need or expense of the rocket (oxidizer can be pricey stuff at high concentration).

The EJ200 is the most power dense jet ever, it weighs just one tonne so it's positioning in the car is less crucial than the position of the cluster of hybrid rockets.

JT


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