Whats the problem with The Unlimited land speed record?

[Blue]

They are expecting just over 2g accel and 3g decel in a 'perfect' run...

http://www.bloodhoundssc.com/project/adventure/breaking-record

This is where we need to go back to the basic physics.  a=F/m and d=-F/m

To accelerate and decelerate to a given speed on a shorter course or a higher speed on the same course, we need less weight.  Not more thrust, more engines, and more weight.  Less weight, period.  The weight required to do the ALSR is much less than assumed by many observers.  Rockets beat jets hands down because rockets lose more fuel weight than jets during the run and have less mass at top speed and less mass to decelerate.  Deep throttleable rocket engines in the thrust class required are available off the shelf at a TRL of 8+.  i.e. one level off the reliability of a production car.  The assumption that jets must be used with rockets is analogous to the use of both solid and liquid rockets on the space shuttle.  The disadvantages of each type limit the system.

Look at Blue Flame's original specs.  The engine design thrust was double what was actually used for the record runs.  Even with this handicap, Blue Flame hit the measured mile in a distance that allowed the driver to see the mile entrance from the launch line.  Heavy designs cannot do this no matter how much engineering is thrown at them.  The post run analysis showed that Blue Flame as designed would have topped out at 870-920 mph depending on the shock drag off the top of the exposed rear wheels (Mach 2.2 relative).  Blue Flame was light and simple.  It was built using 1960's state of the art steel space frame and aluminum skin.  Given today's rocket and carbon construction technology, the same car could be made with 50% greater thrust and Isp with 30% less launch mass.  We do the math from this point.  Heavy, blunt, and complex vehicles are not in the baseline.  When a program starts with a needlessly heavy, complex, and expensive concept it is at a severe disadvantage to a light, simple, and inexpensive design.

5.9 miles 0-1100-0 was our design point, with margin.  The analysis has shown the design to be lighter and faster than we have designed for.  4.2G launch, peak at 4.7G at 520 mph as mass is burned off, taper to 3.2G at 1100 mph due to wave drag.  Decel profile is symetrical over distance, this requires a multi-stage, fully redundant chute system with each stage capable of surviving the dynamic pressure of the chute two stages above it.  Peak G under decel should be under 5.5G.

We're going to hear a lot of howls about these G forces.  We interviewed three X-15 pilots and twelve race, aerobatic, and test pilots including Neil Armstrong.  Several were candidate drivers for the Fossett LSR.  Our G profile is a fraction of that experienced by most experimental test pilots, fighter pilots, and is laughable to unlimited aerobatic pilots.

The assumptions that have limited the understanding of the ALSR for 40 years need to be re-examined.  We can do it better, cheaper, faster, and simpler.  We just have to want to.

[DaveL]

I agree.
Your last paragraph and last sentence are the most telling.
I'm sure someday someone will come along and build just such a vehicle.
They may even simplify it further. How about a solid fueled vehicle with an even higher 'G' profile on an even shorter course.
Forget about any meaningful steering or driver input. The surface speed of the wheels will lag so far behind the vehicles speed it will effectively be a sled for the entire run profile. The run up to the traps will be measured in mere feet and the drivers job will be to simply press a button to initiate events. You could even test it unmanned prior to inserting 'the driver'. Nothing but the lack of will prevents this from reality and in my cynical opinion is, as the thread title suggests, '...the problem with the unlimited land speed record'.

[kiwi belly tank]

You've got my attention. I can't do the math but I can do the logic!
Do you have a design?
  Sid.

[manta22]

I agree.
Your last paragraph and last sentence are the most telling.
I'm sure someday someone will come along and build just such a vehicle.
They may even simplify it further. How about a solid fueled vehicle with an even higher 'G' profile on an even shorter course.
Forget about any meaningful steering or driver input. The surface speed of the wheels will lag so far behind the vehicles speed it will effectively be a sled for the entire run profile. The run up to the traps will be measured in mere feet and the drivers job will be to simply press a button to initiate events. You could even test it unmanned prior to inserting 'the driver'. Nothing but the lack of will prevents this from reality and in my cynical opinion is, as the thread title suggests, '...the problem with the unlimited land speed record'.

When a solid-fuel rocket is lit, it burns until the fuel is exhausted-- no way to shut it off or modulate the power.

Regards, Neil  Tucson, AZ

[tortoise]

When a solid-fuel rocket is lit, it burns until the fuel is exhausted-- no way to shut it off or modulate the power.

Regards, Neil  Tucson, AZ

In the extreme picture Mister L paints, things happen too fast for useful driver input. The question your post raises is whether a solid fuel rocket with the just right, reliably repeatable thrust profile is readily feasible.

[martine]

Blue:
I 'get' your earlier post - simple and light is good but...

If Blue Flame was theoretically capable of 900mph why did it stop at 600?

It would be good to get a Bloodhound engineer to answer but why do YOU think the UK team have gone the complicated/heavy route?  They are respected, experienced and are relatively well-resourced - I am sure they would have considered the simple/light way at an early stage.  I suspect they have some very good reasons to do with safety and flexibility in being able to run slow, faster, fastest runs without mass-redesign.

[Saltfever]

A liquid fueled rocket can be modulated, throttled, or shut off. A single tank of monopropellant (Hydrazine) is sprayed on a catalyst (Silver). Other scenarios exist. Don’t know the energy densities but solid propellant vs. liquid might have similar storage size. Of course a  monoprop would have throttle complexities.

[TrickyDicky]

If Blue Flame was theoretically capable of 900mph why did it stop at 600?

This is explained elsewhere, but in summary I think the key issues were:

• Whatever the design speed, in its 1970 configuration (especially the rocket) The Blue Flame's theoretical maximum speed was less than this.
• The tyres available were constrained to less than (something like) 700mph.
• The owners of the vehicle took their toys away.

I presume that the primary aim was to set the record.  Having achieved this, there would have been little perceived additional benefit in pushing their own record higher.

[Graham]

If Blue Flame was theoretically capable of 900mph why did it stop at 600?

This is explained elsewhere, but in summary I think the key issues were:

• Whatever the design speed, in its 1970 configuration (especially the rocket) The Blue Flame's theoretical maximum speed was less than this.
• The tyres available were constrained to less than (something like) 700mph.
• The owners of the vehicle took their toys away.

I presume that the primary aim was to set the record.  Having achieved this, there would have been little perceived additional benefit in pushing their own record higher.

After one of the original designers was kind enough to supply the blueprints (and apologies if he's reading, I still have them, in perfect condition, and you'll get them back!!) to a student of mine a couple of years ago, we examined the differences between the development-stage wind tunnel design and the as-built version that set the record, from an aero perspective, using modern tools and techniques. At Mach 1 and on a near-empty fuel load, we are pretty sure lift > weight. Fortunately we'll never really know what would've happened!

[Robin UK]

Eric (aka Blue) is clearly passionate about his design and may beg to differ but my view is that there is no such thing as the definitively correct, optimum LSR design since the rules allow you to take a variety of approaches towards achieving the same goal. And thank goodness for that. Whatever self imposed goals you set yourself, the only one that really matters is to beat the existing officially ratified record. So until he manages to successfully address all four major areas of any LSR project, then his design hypothesis based on the conclusions drawn from his research will be just another paper/computer only project. As he and many others before him have discovered, the project area marked “funding” is frequently the one that brings things to a halt. This is a shame because I personally would like to see more competition and a variety of approaches - not less - to add to those we already have.  If he can persuade the likes of a George Poteet to adopt and fund his design, that would be terrific.

But whatever he and others think of Richard’s designs, he is correct in saying that the results achieved by both Thrust teams prove that they knew what they were doing.  And I wouldn’t bet against his current team either - but then I would say that wouldn’t I? August 16th 2014 was 6149 days after TSSC set the second of Andy’s two records and thus it becomes the longest held outright record ever, beating John Cobb’s previous mark.  For those of you who prefer things in whole years and assuming Ed doesn’t up the mark in the meantime, you’ll have to wait until Oct 15th.  So – first record over 700mph at 714mph, biggest single increase ever in the history of the record, first supersonic record and now longest held record.  Oh, and it’s 31 years since anything other than a Richard Noble team held the record.  As Julius Caesar is purported to have said – Vini, Vidi, Vici.

The league table now reads:

ThrustSSC – 17 years
Napier Railton – 16 years
Thrust2 – 14 years
Blue Flame – 13 years

Get the right person in the right vehicle on the right surface backed up by the right amount of money and you too may get to join that list. But as Ron Ayers memorably said with tongue firmly in cheek, “others may go supersonic and beat our record but they will be tourists – we were the pioneers.”

Robin

[PorkPie]

Sorry, Robin,

but John Cobb and his Railton hold the record from 1939 to 1963.....and this is a little bit more than 16 years

[TrickyDicky]

Sorry, Robin,

but John Cobb and his Railton hold the record from 1939 to 1963.....and this is a little bit more than 16 years

Two records: 1939 to 1947 and 1947 to 1963.  Even though it is the same car and driver, Robin's clock resets in 1947.

[MAYOMAN]

WOW!
What a great discussion – just oozing creativity.
While Bloodhound continues to amaze us in its gestation, the Aussie Invader shows that ALSR speed attempts can be made without cubic money – at least at the beginning. Rosco has plunged into the race to 1,000mph on a shoestring budget. What he has shown, though, is that as a project becomes real – it attracts latecomers who prove the in-kind assistance necessary to achieve this lofty goal.

Following this thread, as these two project ramp up, requires an occasional fact correction – not a real big deal.

BLUE – While we built The Blue Flame using 1960s technology, the vehicle was largely a stressed skin monocoque structure (see photos). The spaced tube structure was only aft of the cockpit, to provide easy access to all the items needing continuing maintenance during the record runs.

TRICKY DICKY/MARTINE – Goodyear (who owned the tires) limited our maximum tire speed in 1970 to 700mph to avoid our making ‘banzai’ runs on our first trip to the Salt Flats. The tires and wheels had all been spun up to 850mph by Goodyear in anticipation of the later supersonic attempts. Pete and I wanted to return in 1971 to finish the job – but we had lost ownership of The Blue Flame vehicle and the AGA sponsor said “NO”.

GRAHAM – your student’s analysis using CFD techniques on The Blue Flame CAD solid model was very informative. Great job. However, he did not do an analysis that included the canard wings in the front of The Blue Flame, to trim the aerodynamics. That would also be interesting.

ROBIN UK – Your league table was accurate. But, interestingly, The Blue Flame did retain the kilometer record (the 1970 ALSR distance) for 27 years. Andy Green really smashed that one, didn’t he.

Hopefully, this animated discussion will encourage others to dedicate themselves to attempt the ALSR down the road.

[Robin UK]

Sorry, Robin,

but John Cobb and his Railton hold the record from 1939 to 1963.....and this is a little bit more than 16 years

PP - as TD has already pointed out I said longest held outright record rather than the person who had held the record longest. 

Robin

[Robin UK]

Dick,

it's such a shame that the AGA wouldn't fund another shot in 1971. On the other hand, if they had Richard might not have got his record 

Robin