Project ICARUS: the NASA Interim Crew Transfer Vehicle
In the immediate aftermath of the Columbia disaster, it became clear to NASA that further funding for the Space Shuttle would not be forthcoming. Sure enough, the Bush administration announced that the Shuttle programme would be ended once construction of the ISS was completed. This left NASA planners in a perilous position: without the Shuttle, they would be unable to operate crew transfer and resupply missions to the ISS. Although Bush instigated Project Constellation for a long-term lunar and Martian expedition programme, it would be many years from completion.
Following a comprehensive review process throughout the second half of 2003, it was determined that the short-term needs would have to be met by expendable boosters and craft. On The decision was made to approach US aerospace companies for proposals to modify existing equipment into low-cost resupply drones, to be cheaper than the ESA Automated Transfer Vehicle but more capable than the Russian Progress. To meet the crew transfer needs, NASA released a proposal for what became known as the Interim Crew Transfer Vehicle in early 2004.
The proposed specification was put to the US aerospace industry, specifying that the craft be able to carry a minimum of three crew, remain docked for over six months and that the descent module should be reusable. While most of the big companies showed interest, as did new boys SpaceX and Sierra Nevada Corporation, the tight timescale specified by NASA quickly whittled the proposed craft down to two bidders: Boeing and McDonnell Douglas.
Boeing’s proposal borrowed heavily from the Project Constellation’s Orion command module, fitting a smaller version of that capsule to a new service module. McDonnell Douglas, meanwhile, was in the middle of fighting off a renewed bid by Boeing to buy out the company and saw the ICTV as another way of reassuring its shareholders to not sell their stock. Submitting a cost proposal that was on a par with Northrop Grumman and Orbital Sciences’ bid for the Cygnus cargo drone, McDD proposed to re-engineer the old Apollo design to modern standards, utilising new lithium-aluminium alloys to further save weight.
Part of the appeal of McDonnell Douglas’s proposal was that the company would crew-rate its new Delta IV launch vehicle to carry the ICTV. Cost was a primary factor, as shown when Project Constellation was scrapped along with its projected Aries I and Aries V launch vehicles in August 2006. Newcomers like SpaceX were trying to take a bigger stake in government-funded space operations and while NASA was still looking at Orion, now part of the less-costly Project Artemis, in the long-term for crewed space flight, a cheaper interim option was still needed. Consequently, on 12 September 2006 McDonnell Douglas was announced as the winner of the ICTV programme, by now given the name Icarus – a name explained as a backronym for Interim Crew And Resource Utility System.
Icarus, as mentioned previously, was heavily based on the Apollo Command & Service Modules. It took the basic CM design of 1960s vintage and stripped out the flight control systems, replacing them with lighter, 21st Century equipment. A new heat shield, made of next-generation AVCOAT, was planned to allow the capsule to be reused and would not leave enormous scars down the sides. This heat shield would be jettisoned immediately before touchdown, exposing the Soyuz-style battery of landing rockets since the ICTV was intended to land at the White Sands missile range rather than splashing down into the ocean. The SM was truncated compared to the original, since less fuel was required for an Earth orbital mission. The fuel cell electrical system was replaced with solar panels to further save weight.
Six capsules were ordered, which were intended to be reused up to ten times each. The Delta IV Medium began trials for crew-certification from early 2007, carrying boilerplate versions of the return capsule. Similar full-scale capsules were dropped from a C-17 over Edwards Air Force Base, testing the parachute and landing rocket control systems. Launch escape tests were conducted at Cape Canaveral throughout July and August of 2008.
By the time the Shuttle was retired in 2011, ICTV was almost ready to fly. The unmanned proving flight of the first operational-standard capsule, OC-101, was carried out from 3-6 December 2011. In this flight the capsule rendezvoused with the ISS, made a dummy docking manoeuvre and then deorbited and made a perfect soft-landing at White Sands missile test range in New Mexico. The stage was set for the first launch with a crew.
Icarus-1, consisting of Capsule OC-102 (which had been named Intrepid in a ceremony before launch), was launched to ISS with a crew of three on 14 April 2012. The spacecraft remained docked to the ISS for three months before separating and returning to Earth. Intrepid would make a second flight two years later, marking the first time a non-Space Shuttle manned spacecraft had been reused in this way.
Upon launch, Icarus is provisioned for 45 man-days of independent flight. It can remain docked to the ISS for up to 200 days. Launches are carried out from Kennedy Space Center, Cape Canaveral, Florida, utilising a Delta IV (Crew) Medium+ (4,2) expendable launch vehicle and Aerojet-designed launch escape tower originally developed for the larger Orion.