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Boeing's Delta 3/DM-F3 Launch
is Given Benefit of Doubt by Insurers

by David Todd

(Posted September 29, 2000)

At a presentation given by the Boeing to the London insurance market in Aldgate on 27th September, the recent Delta 3/DM-F3 flight analysis was disclosed to underwriters. The flight was declared a success by the company as the flight was just within the 3-sigma accuracy limits that were modelled on a previously failed commercial flight.


         
 

Since its maiden flight in August 1998 (see photos), Boeing's Delta 3 has flown three times with two obvious launch failures, resulting in insurance claims worth US$490 million.

While success was claimed on the third launch attempt - and unfortunately only the first to carry a test payload - doubts remains on the actual vehicle's performance.

Next Delta 3 flight is tentatively set for mid-2001
 

The Delta 3/DM-F3 rocket's apogee 3,396 km undershoot from its revised orbit target is believed to have been mainly caused by second stage under-performance when the liquid oxygen was depleted six seconds earlier than expected. After investigations, Boeing is adjusting fuel loading procedures and engine burn mixture ratios. The undershoot has caused various remedial corrections and weight reduction measures to be made in order to keep the rocket up to its advertised GTO performance capability.

The Boeing presentation was given to persuade underwriters that the performance shortfall was of a minor nature and that in insurance terms the flight would have been classed as a success had a live commercial satellite been flying as the payload. The mission was designed to mimic the failed Orion 3 flight and as such it used a close approximation to the Orion 3 flight's contract accuracy limits. The launch was just within the 3-sigma limits declared and as such Boeing able to declare the launch as a 'success'. The inclination achieved was exactly on the upper 3-sigma limit of the aimed-for inclination.

As such in satisfying the contract conditions no insurance loss would have been claimed for. Although there were a few dissenters the underwriters present were broadly in agreement that the flight just scraped into the acceptable limits. Some underwriters did express concerns about the size of the apogee 3-sigma range (circa +/-4,000 km) used for this mission even accounting for it being a low accuracy depletion shutdown flight. Depletion cut-off profiles are relatively rare when compared to the much more accurate commanded shutdown method which usually have apogee 3-sigma limits of less than +/-200 km. They also pointed out that for the target sub-synchronous transfer orbit that a significant amount of on-board fuel would have had to be used to make up the shortfall.

Boeing claimed that as with Orion 3, the operator and satellite designers of other satellites would normally use the 3-sigma limit for the reserve calculation and any extra fuel usage would have been within the contingency of the satellite. It would be dependent on each individual contract's definition of accuracy that would define whether an insurance loss would be paid. (Note that for some depletion cut-off flights satellite owners would use the 2-sigma limit in a contract instead to calculate its reserves for a depletion shut-down and in their case an insurance loss claim would probably have been made).

The final target and launch figures as revealed by Boeing are as follows:

Nominal prediction

Actual

+/- 3-sigma dispersion
 Apogee (km)

24,057

20,661

20,251 to 28,539
 Perigee (km)

183.9

183.7

180.9 to 186.9
 Inclination (deg)

27.53

27.63

27.43 to 27.63

COMMENT

There was much criticism of Boeing in the way that the target orbit appeared to have been 'altered' two or three times after the launch. Airclaims now accepts (after evidence was produced) that the target orbit declared was submitted before the launch. In future Boeing would be wise to declare its target orbit and dispersion range clearly to the public before a launch so that there is no ambiguity.

Airclaims' policy regards a commercial/contracted launch as a failure if the launch contract conditions are not complied with. For non-commercial/non contracted launches such as test flights (including dummy payloads) Airclaims currently uses the 3-sigma limit as the definition of successful flight.

Thus in the DM-F3 mission case, in the light of Boeing's detailed final submission with respect to the flight, Airclaims has now re-classed this as a successful flight with the event 'Satellite launched successfully' on the Airclaims SpaceTrak® database.

There remain serious doubts about the GTO payload performance of the Delta 3 rocket. Like most early flights of new launchers 'teething troubles' were to be expected. The DM-F3 shakedown flight has allowed them to 'tweak' their rocket so that with luck the next flight should be an unambiguous success.

Airclaims remains concerned about launch companies being tempted into 3-sigma limit 'inflation' for their test flights as it is usually the launch operator who works these 3-sigma limits out. Airclaims will remain vigilant with respect to this. If it is found to be happening, Airclaims will take measures to discourage this - for example be specifying a minimum percentage error in addition to the 3-sigma limit.

Where target orbit information is unavailable and it comes to Airclaims attention that there has been some kind of target orbit inaccuracy (usually indicated by extra on-board fuel being used to make a correction), we will NOT give a faulty launch the benefit of doubt. The flight will be declared as a partial failure. For example a Chang Zheng 3B flight of 1997 carrying Agila 2 was reported to have undershot its target orbit with extra satellite on-board fuel being used to correct the orbit. Although no insurance claim was made no detailed information on its target orbit or overshoot was released and as such it will remain classed as a partial failure.

David Todd is space analyst for Airclaims Ltd.

His columns appear as part of regular updates for subscribers to Airclaims' Spacetrack® database. Hyperlinks have been added to the original text.

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