The huge heat shield that will protect the first Orion’s return from space has been installed on to the spacecraft. Exploration Flight Test -1 (EFT-) – set to launch at the end of this year – will provide an array of data on how the vehicle and heat shield perform during the speedy entry, which in turn will feed into the Critical Design Review (CDR) scheduled for next year.
The mission – involving two orbits to a high-apogee destination, allowing for a high-energy re-entry through Earth’s atmosphere on what is a multi-hour test – will provide critical re-entry flight performance data and demonstrate early integration capabilities of the spacecraft.
Although this EFT-1 mission will occur several years before a crew flies in the spacecraft, the test will provide valuable early data, that can be fed into Orion’s development, thus avoiding any “late” changes to the vehicle that could cause schedule impacts.
Unlike the Space Shuttle orbiters, the main business end of the heatshield – the blunt end of Orion – won’t be covered in tiles.
Instead it will use an ablative material, which was also used on the Apollo capsules.
NASA’s Orion Thermal Protection System Advanced Development Project considered eight different candidate materials, before downselecting to an Avcoat and Phenolic Impregnated Carbon Ablator – with a technical name of AVCO 5026-39 HCG (Filled Epoxy Novalac in Fiberglass-Phenolic Honeycomb).
Following its design review, the heat shield began to take shape via the mating of the “skin” onto the titanium support skeleton at Lockheed Martin’s Waterton Facility near Denver – which was also the site for a large amount of Orion testing on the Ground Test Article (GTA).
The heat shield was then shipped to Textron in Wilmington for the installation of its ablative protective coating.
The skin and skeleton will help give the spacecraft the strength to withstand its impact with the water’s surface upon landing in the Pacific Ocean, and provide the structure for the AVCOAT coating that will protect the vehicle and its crew from the huge temperatures that they would experience during a 27,000-mph return from Mars.
However, it was later revealed that a new heat shield would be required for returns from Mars. Orion’s current heat shield is only validated for lower entry energies, such as returning from Exploration Mission -2 (EM-2) around the Moon.
Following the Heat Shield’s arrival at the Shuttle Landing Facility (SLF) inside a Super Guppy aircraft, it was unloaded and transported to the Operations & Checkout (O&C), where the EFT-1 Orion has been undergoing outfitting tasks since its initial build at the Michoud Assembly Facility (MAF).
With the EFT-1 Orion continuing outfitting and initial power up operations, the heat shield was placed on to a fixture, prior to Orion being lowered down for mating operations.
Installation – and the lofting of the Orion with her heat shield in place – was conducted at the end of last week.
With the delay from a Summer to December 4 launch date, the team are well within their processing milestones ahead of flight.
Next up, the crew module and service module will mate together and will undergo functional testing. Then, the backshell tiles and forward bay cover will be installed onto the crew module.
The backshell will have several hundred tiles, exotically named as TUFI coated AETB-8 tiles, bonded to 10 panels of composite laminate facesheets on a titanium honeycomb core.
The first of these tiles were manufactured in February, 2012 – a historic milestone began with Tile 875-1 on Panel H of the backshell – as seen in this photo acquired by L2 in the EFT-1 Update Section.
Originally, the baseline for the backshell was a SLA-561V material with plasma sprayed aluminum coating for on-orbit thermal control. However, the AETB-8 tiles provide more mass-efficient MMOD (Micro-Meteoroid Orbital Debris) protection.
As such, panel tile thickness, substrate facesheet thickness, and core density are tailored for thermal and structural load, and MMOD requirements.
The tiles will be mechanically attached to the pressure vessel with thermal isolating brackets along their edges, a process which had already been practised on an entire C panel for the Orion Ground Test Article (GTA).
It is understood the backshell will also sport several tiles covered with a Catalytic Coating (CC), which has already enjoyed valuable entry data during shuttle Discovery’s final missions, which included a Catalytic Coating applied to two tiles in the turbulent heating wedge on the belly of the orbiter, appearing as two green stripes across the tiles.
A version of the coating was first flown on STS-2, 3 and 5, as part of a laminar/catalytic flight test effort. However, the documentation wasn’t maintained, leading to the Orion request for help from the flagship orbiter.
Several Detailed Test Objectives (DTOs) into understanding the entry heating performance of a fully catalytic (CC-2) coated tile located downstream of an in-built protuberance – designed for Mach 18 Boundary Layer Transition – were achieved by Discovery during the last few years of her service.
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Once the backshell tile installation is complete, the EFT-1 Orion will look like the spacecraft portrayed in mission videos for the test flight. The vehicle will then begin mating operations with the second stage of the Delta IV Heavy that will loft her into space for the first time.
This will be followed by the fuelling and serviced at the Kennedy Space Center Payload Hazardous Servicing Facility, ahead of ATK’s Launch Abort System (LAS) topping of the stack via mating operations.
The spacecraft will be prepped and transported to Launch Pad 37 where Lockheed Martin and United Launch Alliance will perform pad integration and launch operations.
“This team has done a great job keeping us on track for Orion’s first test flight,” said Cleon Lacefield, Lockheed Martin vice president and Orion program manager.
“That’s no easy task when you’re designing and building a unique vehicle for human exploration of deep space.”
(Images: Via NASA, Lockheed Martin and L2)
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