787 compared to Saturn V

Saturn V
First Stage

Boeing 787-9

ratio

Length

m

42

63

Top speed

m/s

2300

265

8.7

Max Range

km

560

15700

Max Altitude

km

112

13

Max Thrust

kN

34000

640

53

Takeoff accel

gee

1.3

0.26

5.0

Max accel

gee

4.0

0.26

15

Running time

sec

168

62000

Total Weight

tonnes

2800

251

11

Payload Weight

tonnes

500

63

7.9

includes fueled 2nd and 3rd stages + LEM + CM fuel

Dry Weight

tonnes

131

118

1.11

Fuel Weight

tonnes

490

70

O₂ Weight

tonnes

1680

0

Fuel+O₂ Weight

tonnes

2170

70

31

Fuel+O₂ rate

kg/s

13000

1.13

12000

Some people ask "why not make rockets reusable like airliners?" Then they don't wait around for the answer, because they want to keep repeating the "question", which is not a real question but a statement of belief.

Rockets are not airplanes. They have far different missions, go much faster, are subjected to far more stress, and guzzle far more fuel. If we want to improve cost/performance, we should focus on automated manufacturing, logistics, and reliability. Tankage and rocket bells costs can be driven towards raw materials cost. Perhaps we can work on recycling the returning stages as materials, perhaps even reusing the avionics, turbopumps, and thrust chambers after detailed inspection. But making the pop can holding the fuel reusable? We don't even do that for soda pop.

It might be possible to burn the tank aluminum for more thrust. The Isp approaches RP-1. I haven't a clue how to turn a tank into powder and burn it, though. Once in orbit, tank skin is usable as ballast mass for server sky thinsats.

MIR spent 5519 days in orbit, and travelled 2.27 billion miles. 747 cruising speed is 555mph, and 747s are retired before 130,000 hours. So MIR travelled 30 times farther in its lifetime than any 747 ever will. 787 long term durability is unknown - some fear the composites will delaminate sooner than aluminum fatigues. I hope 787s last much longer, but time will tell. Airlines buy 787s for fuel performance, not durability, and rocketeers should use the same metric.

Rockets are hard. We and the Soviets together spent 8 trillion dollars developing them. I think SpaceX will do better for less, but not a lot better. If getting to space with chemical energy was easy, the earth would have not retained an atmosphere for four billion years; both launch and atmospheric boiloff are subject to the same constraints. Humans got to space because we use staging, and are fiendishly clever; if we are airheads, we stay grounded.

[1] http://en.wikipedia.org/wiki/Boeing_787_Dreamliner [2] http://en.wikipedia.org/wiki/Saturn_V

787SV (last edited 2013-06-04 17:52:37 by KeithLofstrom)