1. Economics of Separated Ascent Stage Launch Vehicles
By Chris Y. Taylor
42nd AIAA/ASME/SAE/ASEE Joint
Propulsion Conference
July 11, 2006

2. Separated Ascent Stage Launch Vehicles
Multiple vehicles launch separately but cooperate to put one of their number into orbit.
Examples:
FLOC/Flock
Black Horse Variation
Flock Space Launch Architecture
By Allan Goff, Novatia Labs, Folsom CA

3. c = R Γ c = specific cost ($/lb.) = Launch Cost/Payload Mass
R = structure - payload mass ratio
= Structure Mass/Payload Mass
Driven by Technology & Physics
Γ = structure cost ($/lb.)
= Launch Cost/Structure Mass
Driven by Management & Economics

4. + Γrisk + Γpropellant) + RD(Γnr/a)
c = R ( Γvehicle + Γops
+ Γrisk + Γpropellant) + RD(Γnr/a)
Recurring Cost
Γvehicle = Cost of Vehicle Hardware
Γops = Cost of Operations
Γrisk = Cost of Risk
Γpropellant = Cost of Propellant
Non-Recurring Cost
RD = Developed Structure–Payload Mass Ratio
Γnr = Non-recurring Structure Costs
a = Amortization Factor

5. Γvehicle= f Chardware $1100 < Γvehicle < $2300
f = fraction of vehicle expended
= 1 (completely expendable)
Chardware = cost of hardware ($/lb)
$1100 < Chardware <$2300
$1100 < Γvehicle < $2300

6. Γops = L Clabor $100 < Γops < $2000
L = labor intensity (manhours/lb)
= Total Labor Hours / Structure Mass
1 < L < 20 (for current launchers)
Clabor = cost of labor ($/manhour)
= $100
$100 < Γops < $2000

7. Γrisk ≈ Pfail[Cpayload/r +
(1-f) Chardware]
Pfail = probability of failure
0.02 < Pfail < 0.05
Cpayload = cost of payload ($/lb)
= payload cost/payload mass
≈ $10,000
r = 2, f = 1
$100 < Γrisk < $250
not including indirect costs

8. Γpropellant = q Cpropellant
q = Propellant Mass/Structure Mass
= r[η/(1-η)]
= 18 (assuming r=2, η=0.9)
$0.1 < Cpropellant <$0.25
$1.8 < Γpropellant <$4.5

9. Amortized Non-Recurring Cost
(Γ nr/a)
Γnr = non-recurring costs
$20,000 < Γnr < $120,000
(assuming R&D only)
a = amortization factor
 flight rate
= 27
(10 yr. payback, 4 yr. r&d , flight rate of 27/6 yr, 0% interest & inflation)
$750 < (Γ nr/a)< $4500

10. Current Structure Launch Cost Estimate

11. R and RD R = Structure – Payload Mass Ratio Typical Values:
Vehicle
r (to LEO)
Atlas V 400 2
Proton M
2.2
Ariane 5
5.2
Space Shuttle 12
Typical Values:
RD = Developed Structure – Payload Mass Ratio
= R (for entirely new launch vehicles)
Assumed R = RD = 2 for initial launch cost estimate.

12. Current Specific Launch Cost Estimate

13. R&D costs must be lowered!
Launch costs >$1000/lb. payload to LEO with current development & flight rate even if all recurring costs are zero!
How can RD(Γnr/a) be lowered? a
Γnr RD

14. Reduce Cost through Lean Operation and Good Management

15. Reduce Cost through Evolutionary Design
Griffen, M.D., “Heavy Lift Launch for Lunar Exploration”, presented U. of Wisconsin, April 11, 1999,

16. R&D costs must be lowered!
Launch costs >$1000/lb. payload to LEO with current development & flight rate even if all recurring costs are zero!
How can RD(Γnr/a) be lowered? a
Γnr RD

17. Using Identical Stages for Reduced Development Cost
With Identical stages RD < R
even for an entirely new launch vehicle.
Identical stages increases development cost (Γnr).
Bimese
Image from:
THE BIMESE CONCEPT: A STUDY OF MISSION AND ECONOMIC OPTIONS by Dr. John R. Olds and Jeffrey Tooley, 1999
Trimese

18. N-mese?
By Allan Goff, Novatia Labs, Folsom CA
Flock Space Launch Architecture
Separated ascent stages could allow a large number of identical stages with a simple vehicle configuration.

19. FLOC Weight Growth
Calculated Launch Vehicle Structure-Payload Mass Ratio vs. Structure Mass Fraction (Isp = 372)

20. Separated Ascent Stage Tradeoff
Large number of identical stages mean low RD.
Simple configuration allows low vehicle Γnr.
Flock flexibility might allow high flight rate and a.
Requires demonstration of safe, reliable mid-ascent rendezvous. This requires expensive and risky development effort. TANSTAAFL!

21. Mid-Ascent Rendezvous? Are You Serious?
“The idea of refueling an airplane in flight must have seemed bizarre to anyone witnessing the Wright Brother’s first flights. By the 1920s it had been demonstrated and today it is done routinely.”
- R.M. Zubrin
Black Horse Proposal: 6 min. of exo-atmospheric coasting, fuel transfer via. extendable boom needs 2
FLOC Proposal: Exo-atmospheric rendezvous, mating booster to orbiter instead of refueling, only 1 restart

22. Is Rocket Rendezvous Worthwhile?
Duration and cost of development program to demonstrate rocket mid-flight rendezvous unknown.
Novatia estimates specific cost of FLOC system at about $100 to $200 per pound to LEO.
Are Novatia’s cost estimates accurate?

23. FLOC Performance Estimates
Data taken from: Goff, A., “The Flock Booster Architecture – Low Cost Access to LEO via Sustained Fueling,” presented at the 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA , Ft. Lauderdale, FL, 2004.

24. RocketCost.xls (beta)

25. 32 Unit FLOC Baseline Cost Estimate
Rocket
Plane
Input
Value f
0.01 cH
$1000/lb L
0.1 cL
$100/hr
PFAIL 2%
cPL
$10,000/lb cP
$0.25/lb.
Γnr
$20,000/lb a 27
Result
Amortized Vehicle Development
$481/lb.
Vehicle Hardware
$209/lb.
Operations
Risk
$20/lb.
Propellant
$4/lb
TOTAL
$923/lb.
Input
Value f
0.01 cH
$500/lb L cL
$100/hr
PFAIL 2%
cPL
$10,000/lb cP
$0.25/lb.
Γnr
$9,500/lb a 27
Result
Amortized Vehicle Development
$229/lb.
Vehicle Hardware
$104/lb.
Operations
$21/lb.
Risk
$20/lb.
Propellant
$4/lb
TOTAL
$378/lb.

26. Is FLOC a Rocket or a Plane?
Rocket Specific Cost Estimate: $923/lb.
Plane Specific Cost Estimate: $378/lb.

27. Conclusions
Amortized development cost is really important for economical space access. Don’t spend $$$ to develop more than you have to.
Separated ascent stage launch systems can achieve low amortized vehicle development cost.
Keeping operations labor intensity low and reusability high would be key to realizing the cost savings of separated ascent stage launch systems.
The cost, duration, and risk of developing the mid-ascent rendezvous capability needed for separated ascent stage launch systems is unknown.
Do vehicle savings justify mid-ascent rendezvous development costs? I don’t know, but it is a serious question.

28. Selected Bibliography
Griffin, M. D., and Claybaugh, W. R., “The Cost of Access to Space,” JBIS, Vol. 47, 1994, pp
Claybaugh, W. R., AIAA Professional Study Series Course: Economics of Space Transportation, Oct , 2002, Houston TX.
Taylor, C.Y., “Propulsion Economic Considerations for Next Generation Space Launch,” presented at the 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA , Ft. Lauderdale, FL, 2004.
Griffin, M.D., “Heavy Lift Launch for Lunar Exploration,” presented at the U. of Wisconsin, Madison, WI, Nov. 9, 2001,
Chang, I.S., “Overview of World Space Launches,” Journal of Prop. and Power, Vol. 16, No. 5, 2000, pp
Isakowitz, S. J., Hopkins, J., and Hopkins, J. P., International Reference Guide to Space Launch Systems, 4th ed., AIAA, Reston, VA, 2004.
Clapp, M. B., and Zubrin, R. M., “Black Horse:One Stop to Orbit,” Analog Science Fiction and Fact, June 1995, pp
Goff, A., “FLOC Tradeoff Study – Minimizing Technical Risk with Zero-g Sustained Fueling,” presented at the 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA , Tuscon, AZ, 2005.
Goff, A., “The Flock Booster Architecture – Low Cost Access to LEO via Sustained Fueling,” presented at the 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA , Ft. Lauderdale, FL, 2004.
Dore, F. J., “Aircraft Design and Development Experience Related to Reusable Launch Vehicles,” Reducing the Cost of Space Transportation: Proceedings of the American Astronautical Society 7th Goddard Memorial Symposium, edited by George K. Chacko, American Astronautical Society, Washington, D.C., 1969.
Rocketcost.xls spreadsheet, Rev. K., Jupiter Research and Development, Houston, TX, 2006.