As a surveying engineer at sigma3D, you travel all over the world and see many different job sites, but even our colleagues rarely come across one quite like this.
Two of our colleagues had the opportunity to work at the European spaceport. Read here about their experiences and the challenges they faced in the middle of the jungle.
This knowledge of the on-site conditions presented the measurement team with challenges that, while familiar, cannot be planned for.
Climatic conditions with temperatures exceeding 30 °C and humidity levels of up to 90% not only made work difficult for the sigma3D staff on site but also put a strain on the equipment. The extreme temperature fluctuations during the 10-hour work shifts had to be countered with appropriate controls and compensation strategies. Equally problematic were the sudden tropical rainstorms, which repeatedly interrupted the measurements despite protective measures. In addition to the climatic conditions, the jungle also presents its own share of animal companions. When working on the ground, one must watch out for tarantulas and snakes, while during nighttime measurements, insect repellent and as little light as possible were used to ward off mosquitoes and moths.
Measuring the Booster Pallets
Top view of the Ariane 5 launch pad
View from below of the Ariane 6 launch pad
Transport of the booster rockets
Anyone familiar with the aerospace industry has likely heard about the construction of the new Ariane 6 launch vehicle and its launch complex in Kourou, French Guiana.
Ariane 6 is now set to build on the reliability and endurance of Ariane 4 and 5. To ensure that the modern launch vehicle fits the launch complex optimally in the future, the retaining devices must be constructed and calibrated accordingly.
sigma3D GmbH was commissioned by OHB Digital Connect, formerly MT Mechatronis, to measure the booster and sacrificial pallets at the manufacturer’s site and to perform the corresponding verification measurements in Kourou. Likewise, the alignment of the landing plates for the booster pallets on the launch pad had to be installed with the highest precision.
The Ariane 5 rocket launch observed at the start of the project—which the sigma3D team had the opportunity to witness—also made it clear that, upon successful completion of the project, their work would help keep the European space program competitive.
When measuring the sacrificial pallets, the distances between the three support points—in terms of flatness and pitch—had to be determined.
To this end, the local plates were positioned in the same manner as during the preliminary measurement at the manufacturer’s facility. The measurements were carried out at night to ensure the most stable and consistent environmental conditions possible. Difficulties arose here in determining the measurement points, as the underside of the pallet had to be measured, and it was supported by only three points, standing approximately 40 cm above the ground. The makeshift gravel area, which served as a material storage area, also had unevenness and is, compared to a warehouse, rather unsuitable for such a measurement.
The solution involved a steel plate and two ropes, which were used to pull the plate—along with its magnetic base—across the ground and position it directly beneath the pallet to be measured. To link the measurement point beneath the pallet with the one on top of it, corresponding reference points—so-called “nests”—were affixed for the laser tracker.
Thanks to PolyWorks’ multi-part functionality, the analysis for each measurement could be neatly processed. Without any further issues, all pallets were measured on-site during the night shift, and the required dimensions were determined.
To ensure that the Ariane 6 boosters were in the correct position, the sacrificial pallets had to be positioned.
As part of the preparatory work, the sigma3D employees calibrated themselves to the launch pad’s coordinate system. The end customer’s previously defined coordinate system was stabilized with an additional level measurement. The challenge was to account for the table’s drift caused by solar radiation. The sigma3D team determined and accounted for this by extrapolating the expected material expansion based on the temperature curve measured the previous day.
The surveying work could then be carried out within sigma3D’s own, highly precise reference system.
For the assembly and alignment of the sacrificial pallets, steel plates were first mounted and positioned to accommodate them.
For each pallet, one fixed bearing and two sliding bearings were adjusted. These were cold-welded using a special two-component adhesive. The advantage of this method was that it eliminated the need for conventional welding. With conventional welding, there is a risk that the pallets could warp. What made the cold welding process unique was the curing time of just 15 minutes after mixing. This meant that the steel plates, each weighing several metric tons, had to be adjusted to tolerances of one-tenth of a millimeter within a short period of time using grub screws and a hammer.
When the schedule was changed at short notice later in the project, the measurements of the support plates could not be carried out only at night as planned; instead, measurements also had to be taken during the day. Here, the influence of temperature was accounted for through appropriate temperature compensation.
Thanks to the fast and precise work, the control measurements revealed no significant differences in measurement accuracy between daytime and nighttime measurements.
The experienced team from sigma3D was always able to answer any metrological questions that arose on site and adapt flexibly to the installation process. For example, they were able to immediately verify whether the guide rails for the sacrificial pallets were parallel and at the same height. The real-time display of adjustment values was a great help here, as it allowed the on-site adjustment team to immediately see whether the achieved settings were within specification.
All in all, despite the on-site challenges, the assembly was successfully completed as planned, and we are grateful for the trust placed in us and the opportunity to continue this project.
The sigma3D team is also looking forward to eagerly following the upcoming launch of Ariane 6 and seeing the fruits of our joint labor disappear into space.
