Tuesday, September 11, 2007

Really good news...

The vehicle is 100% hardware complete.

We weighed it and we are at least 10% under our target weight!!!!!!!

I'm not going to publish the weight until I can repeat the measurement, with a better calibrated scale,but this gives us significant performance margin for reaching 180 seconds!

More details:
The target weight with payload was 326 lbs.
The target empty weight was 271 lbs
The actual empty weight 230 Lbs.
My actual empty weight is 15% under Budget!!!

In order to do the 180 seconds I need a realized in flight ISP of ~152
As John Carmack rightly points out it won't be as high as I expect or wish.
The theoretical ISP for the pressures and fuel combination I'm using is 227
So I need to realize 66% of theoretical.

This is with tanks 90% full.
If I go to tanks 97% full I need an ISP of 145


Anonymous said...


One of the hardest parts to come up next: getting reliable and simultaneous ignition for all engines and stable hovering...

We've seen the possible difficulties from Mastens updates.

Best of luck, and hope to see you competing in XPC!

A picture of the complete vehicle would be nice...

(I hope/guess you'll be doing the flight tests on a tether... :)

John Carmack said...

Just a warning -- your in-flight Isp isn't going to be what you think it will be...

John Carmack