Whats the problem with The Unlimited land speed record?

[Blue]

Just to be clear, we have designed for 5.9 miles of course 0-1100-0, both ways, through the same geographical timed mile (FIA legal) with a turn of under 30 minutes.

Everyone else considers this impossible.  We considered it a requirement.

[tallguy]

Since 1997, the (manned) land speed record is in excess of 763 mph.

Driver:  Andy Green
Owner:  Richard Noble
Name of Vehicle:   Thrust SSC

Tallguy
Northern California, USA

[martine]

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

Yes all good as an approximation but I'm not sure of the point you are making?

Bloodhound uses both jet engine and rocket as a combination to give optimum controllability and the power needed.  The jet engine will be used by itself to take the car up to around 400mph.  The Bloodhound team have concerns about Rosco's pure liquid-fuelled rocket...getting the mix right is very tricky and the acceleration is double Bloodhound's - it could all go wrong very, very quickly.

[TrickyDicky]

Just to be clear, we have designed for 5.9 miles of course 0-1100-0, both ways, through the same geographical timed mile (FIA legal) with a turn of under 30 minutes.

Everyone else considers this impossible.  We considered it a requirement.

I'm not qualified to join this debate, but . . . .

Where does '5.9' come from?  Others are planning to use courses 10-12 miles long.  Perhaps they consider designing for 5.9 miles as unnecessary rather than impossible?

Ditto for 30 minutes turnaround.  That's a generous 100% allowance for something to go wrong.  Although, as Thrust SSC found out, pushing the 60 minutes FIA requirement too close can cause you to miss out on an official record whilst running at record speed.

Glad to see you are designing for 1,100 mph though.  That takes the pressure off the build timetable, since the record you have to beat will be only a little over 1,000 mph.   

[TD]

Two points.

First, a look at the thrust required to accelerate to a given speed over a particular course length given an expected vehicle mass, in response to remarks that BH SSC would accelerate at 3g.  But really just an opportunity to fool around with equations of rectilinear motion again

Second, a casual look at the potential effects (mostly, on vehicle mass) of eliminating an air-breathing engine from a particular LSR design, in response to Blue's post of a representation of what looks like a rocket-powered ALSR/ULSR design concept.

If you have the resources to conduct O(60) runs then yes, one might put the ability to control thrust high on the requirements list.   Or maybe even if you may not have those resources.  McGlashan has recently posted that he's looking for ways to initially run at reduced thrust.

Hope that helps.

[martine]

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

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

[tortoise]

Just to be clear, we have designed for 5.9 miles of course 0-1100-0, both ways, through the same geographical timed mile (FIA legal) with a turn of under 30 minutes.

Everyone else considers this impossible.  We considered it a requirement.

Are they planning to run at Bonneville? How cool would that be?

[MAYOMAN]

Nice discussion on the consideration for weight and acceleration on the upcoming Bloodhound and Aussie Invader speed record attempts. Certainly thrust powered land speed record vehicles have some advantage here over wheel-driven vehicles. I just took a look back at the 1/4-mile runs we made with The Blue Flame in 1970 on the Bonneville Salt Flats. We were just beginning our first test series, recording a standing start elapsed time of 6.724 seconds, just under 2 Gs. Not too shabby, considering the "Standard 1320" top fuel dragster record at the time was 6.430 seconds. That was with our "detuned" rocket motor, since we were working with a 700mph maximum speed limit ordered by Goodyear, the tire supplier (and tire owner). Sounds like the new guys are working around a similar acceleration profile.

[F104A]

A couple reasons why we have not considered running at Bonneville, is the salt crust is to thin for a 14,000 lb vehicle on aluminum wheels (no rubber). The second reason was brought to the attention of racers by Richard Noble is the aluminum wheels on salt becomes to unstable at high speeds and allows the vehicle to yaw enough to get one into trouble. The third reason is (in our case) the salt is so corrosive and eblading to our aluminum fuselage that it would probably tear the aluminum panels off the vehicle. The dirt track, such as El Mirage, Edwards AFB, Alvord Desert and others will absorb the shock wave and reduce the lifting capacity created as you reach Mach 1 speeds. Our CFD analysis conducted by our aerodynamics team (these guys are pretty sharp) indicate we will have about 800 lbs of down force up to near 700 mph at which time we develop about 800 lbs lifting force above 710 mph. CFD similations at transonic speeds vary with such things as air density, temperature, surface rolling resistance, surface density and other factors. It's not easy is it!

[tortoise]

The dirt track, such as El Mirage, Edwards AFB, Alvord Desert and others will absorb the shock wave and reduce the lifting capacity created as you reach Mach 1 speeds.

El Mirage record is 308.605 mph. Could the Eagle do that in 1.3 miles?

[F104A]

We cannot get onto full throttle at the beginning of the run because we suck so much dirt into the inlets up to about 100 mph then I can roll it into full throttle then into afterburner. I have a 4 stage AB so I slip it into minimun AB and when I feel a good light, I slip the throttle all the way forward to full AB. That means I give up the first mile just getting into full power. In my runs last fall at the Alvord, I didn't go into full AB until the 2 mile. At the 4.5 mile I was at 450 Knots (515 MPH). At the 5 mile I pulled the throttle back to idle, deployed the speed brakes, fired one parachute then applied the magnetic brakes. I was fully stopped at 7.8 miles. This year, I'll go into full AB at the 1 mile then see what we can get out of it at the 5.

[martine]

We cannot get onto full throttle at the beginning of the run because we suck so much dirt into the inlets up to about 100 mph then I can roll it into full throttle then into afterburner. I have a 4 stage AB so I slip it into minimun AB and when I feel a good light, I slip the throttle all the way forward to full AB. That means I give up the first mile just getting into full power. In my runs last fall at the Alvord, I didn't go into full AB until the 2 mile. At the 4.5 mile I was at 450 Knots (515 MPH). At the 5 mile I pulled the throttle back to idle, deployed the speed brakes, fired one parachute then applied the magnetic brakes. I was fully stopped at 7.8 miles. This year, I'll go into full AB at the 1 mile then see what we can get out of it at the 5.

Don't you need the accel and decal to be symmetrical to be in the right position for the return run?

[tortoise]

Don't you need the accel and decal to be symmetrical to be in the right position for the return run?

I think they could stop slower if they needed to.

[martine]

Don't you need the accel and decal to be symmetrical to be in the right position for the return run?

I think they could stop slower if they needed to.

[F104A]

We don't need to be all that aggressive about stopping. We were conducting acceleration and deceleration tests to see how we fit into that two way window. Looks pretty good.