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Author Topic: Whats the problem with The Unlimited land speed record?  (Read 28260 times)
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F104A
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« Reply #15 on: April 12, 2009, 11:44:37 PM »

If you have an hour or so to sit in front of your computer this coming Thursday you might
be interested in our webinar. If you go to our website, www.landspeed.com, you can sign
up for the online seminar. We talk a little about the vision that started this project and
some of the technology behind it all..............Ed
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Ed
healewis
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« Reply #16 on: July 14, 2010, 05:46:36 AM »

I've been sitting in the background on this site for a while now, and feel Confident to post, (there are some very clever members on here) And I Don't want to look to silly embarassed

I agree with ALL the replies to this thread.....From some very knowledgeable people

BUT....

without the dreamers we wouldn't have the likes of Seagreave,Cobb,Campbell,Breedlove,Gabelich,Noble and Green.

What I'm trying to say is Dreaming doesn't cost a penny, Do lots and lots of study, LISTEN to ALL that give advice to you, and you won't go far wrong.

Maybe just maybe you'll become a record breaker in time grin

Don't ever stop dreaming!

Here Here  grin nuff said
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wobblywalrus
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« Reply #17 on: July 14, 2010, 08:07:41 PM »

This forum has minimal censorship and there is a wide rage of opinions on most subjects.  Sure, there are some negative ones about the absolute record.  This is a sign of a healthy discussion.

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martine
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« Reply #18 on: August 01, 2014, 08:15:26 AM »

...Although I don't agree with his last two record breakers and his current design- he set the last two records.  QED, he knows what he is doing.  I do have strong opinions about how it should be done, referenced to the existing design database, and I am critical of efforts that ignore this. 
Sorry to resurrect a very old thread but...

What don't you like about Noble's last 2 cars and Bloodhound?
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Malcolm UK
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« Reply #19 on: August 02, 2014, 04:12:43 PM »

Just before Blue answers, might I suggest that any American will not like the two cars from Britain that have annexed the ALSR for over 30 years - (you had it for long enough in the sixties and seventies by the way) -  the latest BLOODHOUND SSC may achieve a 1000 mph two way average that will stop all of the remaining current record contenders. [A British view!  wink].

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Malcolm UK, Derby, England.
TD
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« Reply #20 on: August 02, 2014, 07:28:22 PM »

Wasn't it Adm Rickover who stated "Paper submarines work best?" Smiley

Seriously, I have little doubt that Bloodhound will go fast when it is finished.
« Last Edit: August 02, 2014, 07:32:34 PM by TD » Logged
Blue
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« Reply #21 on: August 18, 2014, 01:58:04 AM »

Wasn't it Adm Rickover who stated "Paper submarines work best?" Smiley

Seriously, I have little doubt that Bloodhound will go fast when it is finished.

I am very confident, in fact close to 100%, that Bloodhound will perform to the same level of speed vs. it's design goal as Thrust 2 and TSSC.  Dinner at the salt flats cafe to the first one to come up with the actual design goals of all three cars vs. their actual performance.  A bottle of good whiskey to the first who can go back through BSSC's  own web site and find out where their current drag and mass predictions put them vs. their original design goal. 

Now before anyone gets their nose out of joint over the fact that no car ever went as fast as its design, yes, that's my point.  Designs need margin:  weight margin, structural margin, drag margin, thrust margin.  In that order.  Think about it:  if we have weight to spare, ANYTHING else can be fixed.  If we don't, it gets very hard very quickly.  Next is structures:  speed does us little good if we turn into a debris field at that speed.  Drag may stop us from setting a record, it's not lethal to the car.  Higher than predicted drag can be fixed with more thrust, that requires more engine and more fuel which weigh more, which adds structural load which requires more weight, which requires more fuel to accelerate, which is more weight, etc.

Weight matters.  That's the first priority of the ALSR.  This is a problem of acceleration and deceleration regardless of drag.  The common denominator is weight.  F=ma or a=F/m and d=F/m  It's got to get up to speed and down from speed in the available course. 
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« Reply #22 on: August 18, 2014, 02:04:30 AM »

...Although I don't agree with his last two record breakers and his current design- he set the last two records.  QED, he knows what he is doing.  I do have strong opinions about how it should be done, referenced to the existing design database, and I am critical of efforts that ignore this.  
Sorry to resurrect a very old thread but...

What don't you like about Noble's last 2 cars and Bloodhound?
The things that can be directly traced to their actual vs. planned performance.  In order:
1. Heavy
2. No margins
3. Blunt
4. Complicated
5. Expensive

They're in that order because everything at the top of the list limits everything below, but not vice versa.

Try this:

This was rev 6, we're now on rev 8.4 which is significantly more advanced.  USAFA did the CFD, and we are under drag and completely stable through our design point.  I won't say how fast it is designed to go, it does have a 25% weight and a 50% drag margin at this point to make 1100 peak, 1050 average on a 5.9 mile course.  It would cost less than a couple of the last high dollar wheel driven cars have.  It is light, 4X structural margin, sleek, simple, and (relatively) cheap.  It is fully area ruled, which was much easier than anticipated.  At 70% definition, it is under weight by an additional 13% vs. goal, 38% vs. 1100.  Every time we touch the design, it gets simpler.  It is well within the financial resources of anyone like George Poteet.


* 100MEDIA95IMAG0570.jpg (17.76 KB, 640x480 - viewed 256 times.)
« Last Edit: August 18, 2014, 02:22:55 AM by Blue » Logged

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« Reply #23 on: August 18, 2014, 09:12:36 AM »

Well now that's very interesting.  A bit hard to tell from the picture but that doesn't appear to be an air-breather.  

To reach 1100 (about 491 m/s) in 6 miles (about 9656 m) requires acceleration of about 1.3g.  Not too much.  If 5.9 is the total length of the course then obviously the acceleration has got to be higher.

If your vehicle has a rest mass of 3000 kg (realistic?) you'll need 37 kN to accelerate at 1.3g, excluding drag.

With p = 1.225, A = 1.0 (Bloodhound state just under 2.0; so is 1.0 realistic?), Cd = 0.15 (Bloodhound state 1.32, so obviously something's wrong here), and V = 491 we have about 22 kN to overcome drag.

Total thrust of around 60 kN.

The Bloodhound site states 212 kN combined thrust, so either the rolling resistance is nontrivial (even discounting the greater mass of the car) and/or the frontal area and/or the CdA are way different.

I'd calculate the impulse but I don't know how...

Go for it! Smiley  But tell me where I'm going wrong first.  Thanks.


« Last Edit: August 18, 2014, 09:22:49 AM by TD » Logged
Seldom Seen Slim
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« Reply #24 on: August 18, 2014, 09:26:40 AM »

All:

Your maths are beyond me, but I think a bit of clarification will help one and all.  A few of you have described the course a 5.9 miles.  I wonder if that's the length of the course from one end to the other - or from one end to the end of the timed stretch at the other end.  It seems that accelerating to and braking from 1k mph in less than six miles is pretty danged unlikely, especially if we want car and driver to be viable for a return run.

What's the length of the entire course - from start line on one end to start line on the other end?
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« Reply #25 on: August 18, 2014, 10:12:12 AM »

Maybe that the majority here are into wheel driven, piston powered vehicles because we're hot rodders at heart. wink
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martine
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« Reply #26 on: August 18, 2014, 10:22:41 AM »

All:

Your maths are beyond me, but I think a bit of clarification will help one and all.  A few of you have described the course a 5.9 miles.  I wonder if that's the length of the course from one end to the other - or from one end to the end of the timed stretch at the other end.  It seems that accelerating to and braking from 1k mph in less than six miles is pretty danged unlikely, especially if we want car and driver to be viable for a return run.

What's the length of the entire course - from start line on one end to start line on the other end?
Sorry - not sure if you're talking about the course in South Africa that is going to be used for Bloodhound...if you are it is 12 miles and Bloodhound is designed to accelerate to 1000mph in 5.5m, through the measured mile and then decelerate in another 5.5.  There is no safety overrun!  When I queried this they said they will know from building the speeds up during the 40-50 runs they are expecting to do, if the car (and driver!) are performing the way they expect so it's not quite a risky as it sounds.  It does mean though that when they are going for a max. run there is little margin for error.

Circa 2-3g accel and decel seems to be the plan.  Rosco in Aussie Invader is planning on double that...gulp.
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Robin UK
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« Reply #27 on: August 18, 2014, 10:37:59 AM »

For those reading this thread who are new to the outright LSR, the following statement from one of Blue's earlier posts is wrong and needs correcting.

  More people have died attempting it than have held it, although this includes a lot of pre-war fatalities.

Parry Thomas was the first fatality in 1927 by which time the record had been increased over 30 times by more than 20 drivers. Early records were the subject of some confusion before proper two way runs were sanctioned over the same measured mile or kilo but even so those numbers immediately invalidate his statement. Frank Lockhart also died while Lee Bible killed himself and an unfortunate photographer. Post war Metvelev driving the word's first jet LSR car in 1954 either died or was badly injured depending on which sources are correct about his accident. Then there were Glenn Leasher and Athol Graham. Again, depending on which records you include from the early days and allowing for a slight overlap when thrust power finally took over from wheel driven for the outright LSR, the record has changed hands over 60 times with relatively few fatalities. It's the water speed record that is statistically really dangerous although even then the fatality rate is around 25% - bad to be sure nowhere near "more dying attempting it than holding it".

Robin
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TD
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« Reply #28 on: August 18, 2014, 02:02:28 PM »

Another go.

Bloodhound state a fully-fueled mass of 7868 kg.  They further quote 90 kN thrust for the EJ-200.

Way back in 1687 Newton came up with F=ma.  So, from rest, running on jet power only, a fully-fueled 7868 kg Bloodhound will accelerate at not more than a = F/m or 90,000 N / 7868 kg = 11.44 m/s**2, or about 1.17g.

The web site quotes 6227 kg dry with driver.  So, if both the rocket and the EJ-200 are running at maximum thrust of 212 kN, just before the fuel runs out (ignoring aero drag!) the acceleration cannot be more than 3.47g.

At peak speed, using the BH SSC tech data (Cda = 1.3, V = 469 m/s), overcoming drag will consume 142 kN.  That leaves about 70 kN left over to accelerate the 6227 kg.  Again, a = F/m or a = ~11.3 m/s**2 or about 1.15g.

If you look at the mass breakdown, the EJ200 weighs 1200 kg (or 20% of the dry weight).   The jet fuel tank, fuel, and intake structure weigh about 550 kg.   So if you toss the jet overboard you've reduced your fully-fueled mass by at least 1750 kg, or 22%.  If you then substitute a gas pressurization system for the "APU" (and the associated APU cooling system) you might shed a further 360 kg or so, leaving you at 5700 kg rather than 7800+.  

Currently, the rocket propellant is specified as about 200 kg and HTP mass is nearly 1000 kg.  So add some mass back in to increase the fuel burn beyond 20 seconds... to get it to 40 seconds, presumably you'd double that.  So you are back up to 6500 kg or so, assuming some modest reduction elsewhere.

But what do I know?  I'm a telecom guy and web forum lurker... but this stuff is cool Smiley
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« Reply #29 on: August 18, 2014, 08:36:35 PM »

http://en.wikipedia.org/wiki/Land_speed_record_for_railed_vehicles


The unmanned absolute land speed record is an interesting 6,400 mph.  Manned it is a mere 632 mph ...
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