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#11
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Rocket Racing League First Exhibition Race August 1st and August 2nd, 2008
On Tue, 1 Jul 2008 14:55:40 -0700 (PDT), BobR wrote:
Not sure why everyone keeps making the comment about dead stick landings. Rutan demonstrated the rocket plane at Oshkosh a couple of years back with the full ability to start, stop, and restart the engines. When Rutan flew, he was the only plane up there. When he hit the "go" button, all he was expected to do was fly around the airport at least once, then land. He could keep some fuel back in case he had to go around, or "blip" the rocket to correct for an undershoot. In contrast, of course, the RRL pilots will be busy flying the invisible course and keeping from running into up to nine other rocket planes. It's a little different problem.... According to the RRL web page, they're going to stagger the takeoffs, so that should reduce the chances for simultaneous deadsticks. However, it's going to be interesting if (for instance) a landing gear collapses and the plane stops on the runway. I'm sure they'll have a backup runway, but the guys aloft may have to scramble a bit. Trouble is, unless there's a second backup runway, racing will have to stop until they get the primary cleared. I surfed around the RRL web page, and found some technical data that I hadn't noticed the last time I checked, several months back. "...1,500 pound thrust rocket engine burning liquid oxygen (LOX) and kerosene... Each X-Racer will be a single-pilot vehicle with an empty weight of roughly 1,000 lbs and a propellant weight of 1,000 lbs..." Lox/Kerosene has a Specific Impulse of about 300 seconds, so this comes out to 200 seconds of engine run time (web page says 4 minutes of intermittent powered flight, so that ties in). Ten minutes of glide time, Pit times are listed as 5-10 minutes. So that makes less than four minutes of powered flight per aircraft every twenty to twenty-five minutes. "...the Rocket Racing League will feature multiple races pitting up to 10 Rocket Racers going head to head in a 4-lap, multiple elimination heat format on a 5-mile "Formula One"-like closed circuit raceway in the sky." It's a twenty-mile course (five miles around, four laps). The planes should be able to complete the course WITHOUT a pit stop...the plane has to average just 80 MPH during that 15-minute flight. However, the web page says they have to pit after "3-4 laps." They may be requiring some sort of fuel reserve. But it seems weird to plan for a 5-10 minute pit stop when the plane could practically *coast* around the course for that last lap. My guess is that the "pit stops" are more to get planes ready quickly for the next heat before the spectators wander away. Still didn't' find anything on the web page about flight altitudes. It might be something they leave up to the teams to decide...either go up high and coast downhill at high speeds, or stay low and run the engine in short blips. Ron Wanttaja |
#12
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Rocket Racing League First Exhibition Race August 1st and August 2nd, 2008
"Ron Wanttaja" wrote in message ... On Mon, 30 Jun 2008 07:06:27 -0700 (PDT), Harry K wrote: ... of course a plane just out of the pits will be a lot slower and have less acceleration than those already aloft (due to still carrying a heavy fuel load). Reduced acceleration yes, but a heavier aircraft has a faster best L/D, (all else being equal) which is why competition gliders often fly with water ballast. If you take the time to think about it, the optimum Fuel Consumption vs Gross Weight vs Altitude vs Speed vs Flight Duration vs Range strategy for these birds gets more and more complicated. Vaughn |
#13
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Rocket Racing League First Exhibition Race August 1st and August 2nd, 2008
"Ron Wanttaja" wrote in message
... Still didn't' find anything on the web page about flight altitudes. It might be something they leave up to the teams to decide...either go up high and coast downhill at high speeds, or stay low and run the engine in short blips. Something I saw indicated the course would be 3-D. They would have "gates" with upper, lower, left and right boundaries. So, they would have to climb, dive, left and right maneuvers. Only the vectors between the gates would be left up to the pilots, as well as the use of power. The racers wouldn't be aiming for the same gate. The computer would have gates for each racer, perhaps laid out side-by-side (with spacing for safety), so the planes would appear to be racing but in reality flying parallel courses. I think that was on a TV spot or perhaps an animated internet movie clip. Rich S. |
#14
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Rocket Racing League First Exhibition Race August 1st and August 2nd, 2008
On Wed, 02 Jul 2008 11:44:03 GMT, "Vaughn Simon"
wrote: ... of course a plane just out of the pits will be a lot slower and have less acceleration than those already aloft (due to still carrying a heavy fuel load). Reduced acceleration yes, but a heavier aircraft has a faster best L/D, (all else being equal) which is why competition gliders often fly with water ballast. If you take the time to think about it, the optimum Fuel Consumption vs Gross Weight vs Altitude vs Speed vs Flight Duration vs Range strategy for these birds gets more and more complicated. You're right, of course. As an engineer, it's a problem that really tickles my fancy. However, we're right back to considering how interesting the races will be (e.g., how willing they are to pay for another) to the average spectator. A spectator at a NASCAR race or at Reno can easily judge how their favorite racer is doing...e.g., if he's passing a lot of other vehicles, he's probably a front-runner. Not the case with the RRL. For one thing, the planes stagger their takeoffs...they don't start at the same time. So unless the course length differs for each aircraft (which is a really, REALLY thorny problem in fuel planning), the order they cross the "finish line" has nothing to do with their standings. Plus, EVERY plane will be getting passed by the other planes in the first half of their flight, and passing more and more of the other planes as their tanks go dry and their acceleration increases (a RRL plane has about a 0.75G capability at takeoff, but is able to accelerate at 1.5Gs just prior to running out of fuel). I'm sure the NASCAR and Reno events are complicated enough that to truly understand how each competitor is doing, the spectator must consult the scoreboard. But if a guy is a Rare Bear fan, he can probably tell pretty well how the plane is doing just by watching it. Not so in the RRL. It doesn't mean a thing if their favorite is passing other racers; it just means the aircraft has burned more fuel. It doesn't mean a thing if a racer crosses the finish line in front of others; it may have taken off minutes before they did. So the spectator's eyes gravitate towards the video monitors. By the end of the day, he'll probably come to the conclusion that he could have followed the race better from his computer at home. The discussion on this thread started when Harry asked if the racers were just racing against the clock. I corrected him... but the more I think about it, the more I think he had it right. The rockets are aloft at the same time, but each is racing against an individual clock. Ron Wanttaja |
#15
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Rocket Racing League First Exhibition Race August 1st and August 2nd, 2008
In article ,
Ron Wanttaja wrote: On Wed, 02 Jul 2008 11:44:03 GMT, "Vaughn Simon" wrote: ... of course a plane just out of the pits will be a lot slower and have less acceleration than those already aloft (due to still carrying a heavy fuel load). Reduced acceleration yes, but a heavier aircraft has a faster best L/D, (all else being equal) which is why competition gliders often fly with water ballast. If you take the time to think about it, the optimum Fuel Consumption vs Gross Weight vs Altitude vs Speed vs Flight Duration vs Range strategy for these birds gets more and more complicated. You're right, of course. As an engineer, it's a problem that really tickles my fancy. However, we're right back to considering how interesting the races will be (e.g., how willing they are to pay for another) to the average spectator. A spectator at a NASCAR race or at Reno can easily judge how their favorite racer is doing...e.g., if he's passing a lot of other vehicles, he's probably a front-runner. Not the case with the RRL. For one thing, the planes stagger their takeoffs...they don't start at the same time. So unless the course length differs for each aircraft (which is a really, REALLY thorny problem in fuel planning), the order they cross the "finish line" has nothing to do with their standings. Plus, EVERY plane will be getting passed by the other planes in the first half of their flight, and passing more and more of the other planes as their tanks go dry and their acceleration increases (a RRL plane has about a 0.75G capability at takeoff, but is able to accelerate at 1.5Gs just prior to running out of fuel). I'm sure the NASCAR and Reno events are complicated enough that to truly understand how each competitor is doing, the spectator must consult the scoreboard. But if a guy is a Rare Bear fan, he can probably tell pretty well how the plane is doing just by watching it. Not so in the RRL. It doesn't mean a thing if their favorite is passing other racers; it just means the aircraft has burned more fuel. It doesn't mean a thing if a racer crosses the finish line in front of others; it may have taken off minutes before they did. So the spectator's eyes gravitate towards the video monitors. By the end of the day, he'll probably come to the conclusion that he could have followed the race better from his computer at home. The discussion on this thread started when Harry asked if the racers were just racing against the clock. I corrected him... but the more I think about it, the more I think he had it right. The rockets are aloft at the same time, but each is racing against an individual clock. It's beginning to sound more and more like a bicycle time trial. If it's done right, it could be pretty compelling (look at cycle racing fans in europe), or it could end up being good for insomniacs. |
#16
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Rocket Racing League First Exhibition Race August 1st and August2nd, 2008
Ron Wanttaja wrote:
The discussion on this thread started when Harry asked if the racers were just racing against the clock. I corrected him... but the more I think about it, the more I think he had it right. The rockets are aloft at the same time, but each is racing against an individual clock. Ron Wanttaja It's beginning to sound more like a made for TV stunt. |
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