The impact of launch vehicle type and size on development cost

Acta Astrmmutica Vol. 8, No. 11-12, pp. 1195--1205, 1961 Printed in Great Britain

0094-5765/8 I/I I 1195--I 1502.00/0 Pergamon Press Ltd.

The impact of launch vehicle type and size on development costt

D I E T R I C H E. KOELLE~: MBB Space Division, Ottobrunn, F.R.G.

(Received 5 May 1981)

Abst~ct--The technical development trend of future launch vehicle systems is towards fully reusable systems, in order to reduce space transportation cost. However, different types of launch vehicles are feasible, as there are

--winged two-stage systems (WTS) --ballistic single-stage vehicles (BSS) --ballistic two-stage vehicles (BTS)

The performance of those systems is compared according to the present state of the art as well as the development cost, based on the "TRANSCOST-ModeI". The development costs are shown versus launch mass (GLOW) and pay-load for the three types of reusable systems mentioned above.

It is shown that performance optimization and cost minimization lead to different results. It is more economic to increase the vehicle size for achieving higher performance, instead of increasing technical complexity.

Finally it is described that due to the essentially lower launch cost of reusable vehicles it will be feasible to recover the development cost by an amortization charge on the launch cost. This possibility, however, would allow commercial funding of future launch vehicle developments.

1. Intreduction THE TECHNICAL development trend of future launch vehicle systems is towards fully reusable systems, in order to reduce the presently very high cost of space transportation with expendable vehicles.

However, different types of launch vehicles concepts are being considered as future candidates for Earth to LEO transportation as there are

• WINGED TWO-STAGE SYSTEMS (WTS) • BALLISTIC SINGLE-STAGE SYSTEMS (BSS) • BALLISTIC TWO-STAGE VEHICLES (BTS).

These systems have different performance, different flight operations cost and different development cost.

tPaper presented at the XXXlst Congress of the International Astronautical Federation, Tokyo, Japan, 22-27 September 1980 (Paper No. 80-IAA'35).

~;Dr.-lng., Head of Advanced Space Systems and Technology Development, Messerschmitt- BOlkow-Blohm GmbH (MBB) Space Division; Academy Member (Section 2).

1195

1196 D.E. Koelle

Development cost are important because they represent the hurdle to be overcome for any new vehicle development.

It is important to realize the magnitude and sensitivit~ of development cost with respect to size, respectively performance. This will be analyzed by a cost model based on statistical reference points.

2. The cost model structure The development cost analysis is based on the "TRANSCOST"-Model,

developed by MBB for ESA [1]. Figure 1 shows the structure of the model which is using specific CERs (Cost

estimation relationships) for vehicle stages and propulsion elements. The development cost are defined as such without the flight (test) vehicles and operations cost which are taken from special sub-models.

The complete program development cost are expressed as follows:

with Hs = development e fo r t for one stage system, HB = development effort for one engine type, CF =total fabrication cost of n flight test vehicles, and Co = total operations cost for n flight tests.

The factor 1.1 takes into account 10% additional cost for system engineering, integration and test of the complete vehicle.

The CERs are derived statistically by using realistic reference points. Figure 2 shows as an example the stage system specific development cost. The cost relationship for expendable stages H ~ - - 3 1 4 0 - M -°~ (MY) is based on the SATURN 5 stages, all developed at the same time with the same technology (M = net mass).

The cost unit used in this model is MY = Man Year, the equivalent to the total cost divided by productive manhours. The reason for using this unit is that it remains constant over time, independent from inflation and currency exchange factors. The cost of 1 MY 1981 are about 100,000 US$ or 72,000 AU.

For manned winged vehicles the only realistic reference point is the Shuttle Orbiter (without SSME development cost). The relevant CER has been defined such that it has the same trend vs size like the CER for the expendable stages, defined by a reference point 25% lower than the Orbiter cost. As the first of its kind the development costs are about 25% higher than consecutive systems. The resulting CER for the development cost is

Hu = 6500. M °'21 (MY)

indicating that the development costs for manned winged systems are higher by a factor 2 compared to expendable stages. This is confirmed by relevant cost estimates by Boeing for their HLLV concepts (see Fig. 2).

For unmanned ballistic reusable stages no reference point exists yet, therefore the assumption has been taken that it will be between the values for

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The impact of launch vehicle type and size on development cost 1199

expendable stages and manned winged systems, or about a factor 1.3 more expensive than expendable stages. In fact the costs will be higher than factor 1.3 or 2.0 for reusable systems of the same performance because of their higher net mass.

The net mass of the systems is highly important since all CERs are using the mass (in kg) as reference. Therefore, the CERs are related to the same and similar technology (neither very advanced nor intentionally simple or crude technology).

The complete CER is defined by

H = a . M x "f l "f2

with H = development effort in MY, a, x = specific values for each type of equipment or system (defining slope and level of the reference curve), M = the reference system mass in kg, f~ = influence of the technical development stan- dard, and f2 = technical quality factor, defined differently for each type of system.

The f~ influence factor is defined as follows:

--first generation system --second generation, but new

team/company --technology already proven - -same system as already built

by the same team/company

fl = 1.25

fl = 1.0 fl = 0.8--0.9

fl = 0 . 5 - 0 . 8 .

3. Launch vehicle performance characteristics

The cost model is using the net mass for reference, therefore, in a general comparison the net ma~s for different types of stage systems and sizes is required.

Figure 3 shows the result of the analysis based on existing and projected reference values [2].

It is evident that expendable stages with high-density propellants have the lowest net mass fraction. It is higher for LH2/LO2 stages and about 45% more for reusable stages. Another increase of 65% or more than factor 2 compared to expendable stages is valid for winged manned systems with LH2/LO2 propulsion.

A similar analytical model is shown in Fig. 4 for the overall LEO payload as percentage of GLOW (Gross Liftoff Weight).

There is a general trend of increasing payload share with vehicle size. This is due to the partially constant masses in each vehicle (independent of size) and to the improved volume efficiency.

The Shuttle system has only a payload of 1.5%, while SATURN V (two- stage) provided 4.4% as an expendable system. The same applies for a Shuttle- derived cargo vehicle (SDV-LRB) with a medium-energy first stage.

The use of LH2/LO2 propellants also in the first stage greatly increases the performance to 6% (Europa III D-Concept) or 7--8% for larger vehicles.

1200 D.E. Koelle

Reusable systems have a lower payload generally because the return pro- visions are a mass penalty. The difference is larger, however, for smaller vehicles and decreases with size.

The reusable two-stage system (BTS) provides about twice the payload of a single-stager (BSS) in the 1000 Mg class, but about 15% less payload than a two-stage expendable system (ETS).

The two performance diagrams provide the basis for a general comparison of development cost for different vehicle types and sizes.

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1 2 0 2 D . E . Koelle

4. Development cost trends vs vehicle launch mass and payload The computation of the development cost for WTS, BSS and BTS-type

launch vehicles using the net mass and the engine types required leads to the cost survey of Fig. 5.

The two-stage ballistic requires almost twice the development cost compared to a single-stage vehicle for the same GLOW, independent from the fact that the two stages are much smaller than the SSTO. However, two different engine types are required and contribute to the overall cost, as well as the system interface between the two stages.

The winged manned system is 30-35% more expensive than the ballistic one, which is explained by the more complex structure and the pilots cabin, support and safety systems.

The picture changes somewhat if we do not use the total launch mass but the (same) payload capability for comparison: In this case the two-stage ballistic system improves relatively because of its superior performance. It is only about 50% more expensive than an SSTO (BSS), and requires only half the development cost of a winged system (WTS) (Fig. 6).

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Fig. 6. System development cost vs L E O payload capability.

The winged system is by far the most expensive one to develop, in fact it requires 300% of the minimum cost solution--an SSTO (BST).

A WTS-system with about 400 Mg payload capability has a GLOW of some 11,000 Mg (Fig. 4). It requires 250,000 MY development effort or 25 billion US$ (1981 value).

A BTS-System with the same payloads has only 5500 Mg GLOW (Fig. 4) and costs only 150,000 MY or 15 billion US$ to develop.

The BST (SSTO) system requires a launch mass of 8700 Mg and development cost of 100,000 MY or 10 billion US$ (81).

$. Amortization of development cost

In the past development cost for launch vehicles have always been funded by the Government. It has not been tried to recover these costs because the cost per launch for expendable vehicles are already extremely high.

In case of fully reusable vehicles the situation is different. The cost per flight will be less than 10% compared to expendable vehicles. Therefore, it would be possible to amortize the development cost by an additional charge.

A simplified model, not taking into account interest and inflation factors, is shown in Fig. 7: With a ratio of about 1:300 or 0.3% of launch cost to development cost, valid for reusable systems, it is shown that a little over 300 launches with a development cost amortization charge equal to the launch cost (= 100%) would recover the full development cost.

1204 D.E . Koelle

AMORTIZATION CHARGE IN % OF LAUNCH COST 1000

500

200

100

50

20

10

\

~Ik~ ~ ~ L a~ch C~$1~evelopment Co$t - -

_ _

1 200 400 600 800 1000 1200 1400 1600 1800 2000 TOTAL NUMBER OF LAUNCHES

Fig. 7. Amortization charge vs number of launches for full recovery of development cost.

For Europe, by example, with an average launch rate of 10 over 15 years (1993-2007) a new reusable launcher development could be amortized by adding 200% charge to the cost per launch of some 8 MAU, resulting in 24 MAU per launch, which still would be only 60% of an equivalent expendable launcher. Or, in other words, during the above mentioned period, no less than 2.4 billion AU could be saved by the investment into a fully reusable launcher.

For the USA, by example, in case of a new launch vehicle for a Space Power Station Program (SPS) with a launch rate of 300 per year the new launch vehicle development would already be amortized after 6 years with only 20% surplus charge on launch cost.

6. Conclusions The launch system with the highest performance is not necessarily the most

economic one. Minimum cost and not maximum performance should be the design goal for the future. A larger payload is much cheaper to realize with a larger vehicle of minimum complexity. As Fig. 6 shows the vehicle payload capability can be doubled for only 15-20% increase in development cost.

The development cost as such, however, are not the only criteria for the selection of a launch system. The operations cost, by example, may be more important for a system with high launch rates. However, also in this case the most simple system also will result in the lowest operations cost.


Due to the greatly reduced cost per launch the deve lopment cost for fully reusable launch vehicles can be amort ized by a surplus change on the launch cost , thus enabling the commerc ia l funding of such a vehicle in the future.

References 1. Koelle D. E. Cost model for space transportation systems and operations (TRANSCOST). Rep.

MBB-TN-RX 1-328 (1980). 2. Koelle D. E. The next generation of space transportation systems. J. BIS 34, 201-204 (1981). 3. MBB-Rep. URV-119(80): Future Space Transportation Systems for Europe (ESA-Study), Oct.

1980.

Documents

The impact of launch vehicle type and size on development cost