Delta IV dodges upper level winds and launches with NROL-27 satellite

by William Graham

The United Launch Alliance (ULA) have launched their Delta IV rocket carrying a classified spacecraft for the United States National Reconnaissance Office on Friday. The mission, designated NRO Launch 27, lifted off from Cape Canaveral’s Space Launch Complex 37 at 6:38pm Eastern (23:38 UTC) – following a delayed T-0 due to unacceptable upper level wind data from weather balloons.

Delta IV Launch:

Delta 353, a Delta IV Medium+(4,2), was used to perform the launch. The M+(4,2) configuration consists of a single Common Booster Core first stage augmented by two GEM-60 solid rocket motors, with a four metre Delta Cryogenic Second Stage atop it. Both the first and second stages use cryogenic propellants; burning liquid hydrogen oxidised by liquid oxygen.

The Delta IV first flew in 2002, and is along with the Atlas V one of two Evolved Expendable Launch Vehicles in service with United Launch Alliance. The EELVs were developed as part of a programme initiated by the US Air Force to replace older rockets including the Atlas II and Titan IV. The launch marked the sixteenth flight of the Delta IV, and the seventh flight of the M+(4,2) configuration.

Whilst the path that will be taken by Delta 353 as it ascends to orbit was classified, a Launch Hazard Area published by the United States Air Force in order to warn mariners and pilots about the launch extends east from Cape Canaveral, across the Atlantic Ocean. It is consistent with a launch to a geosynchronous transfer orbit, from which the spacecraft will raise itself into a geostationary orbit. The NRO does not currently use any other low-inclination orbital regimes, and there would be few reasons for them to begin doing so.

The payload aboard Delta 353 is currently identified as NROL-27, and is the fifth NRO payload to be launched by a Delta IV. Whilst official details of the mission are classified, the combination of the type of rocket being used and the direction of the launch hazard area have revealed the identity of the spacecraft. NROL-27 is a communications satellite, which will form part of the Satellite Data System (SDS); a constellation of spacecraft used to relay data from other NRO satellites to the ground.

SDS satellites are the only medium-class NRO satellites operated in geosynchronous orbit. Much larger Mentor satellites, such as the USA-223 spacecraft which was launched last November, also operate in geosynchronous orbit; however they require a much larger rocket to place them into orbit. Additionally, the launch patch for NROL-27 includes the Latin phrase “nos suo caelum”, which roughly translates as “we connect the sky”.

Hidden ‘clues’ in mission patches are fairly common for NRO payloads, and the previous SDS launch also contained a similar Latin phrase indicating that it was a communications satellite. Another clue from the patches is the fact that the launch has been named “Gryphon”; traditionally rockets named after mythical creatures or constellations have deployed either SDS or NOSS satellites, and the trajectory that Delta 353 is to follow is not compatible with NOSS.

In its current, third generation, form SDS is a five-satellite constellation; consisting of two satellites in geostationary orbits, plus another three in highly elliptical molniya orbits. Earlier generation systems used less geostationary satellites, with none in the first generation constellation, and only one in the second generation system.

The first SDS satellite, OPS 7837, was launched in June 1976 atop a Titan III(34)B from Vandenberg. In total, seven first generation satellites were launched, all into Molniya orbits. Following the launch of OPS 7837, OPS 7940 was launched in August 1976, and with the August 1978 launch of OPS 7310, the initial constellation was complete.

Further satellites were launched to replace and augment those already in orbit; OPS 5805 in December 1980, USA-4 in August 1984, USA-9 in February 1985, and USA-21 in February 1987. First generation satellites were built by Hughes, and are believed to have been based on the HS-312 satellite bus, which was also used for Intelsat IV spacecraft. They had a mass of around 630 kilograms and each satellite could transmit and receive twelve UHF signals.

The first generation satellites were followed by four second generation, or SDS-2 satellites. The first satellite, USA-40, was deployed by Space Shuttle Columbia during the STS-28 mission in August 1989, with the aid of an Orbus-21S solid rocket motor.

The second spacecraft, USA-67 was deployed by Atlantis during STS-38 in November 1990. The first SDS satellite to be placed into geostationary orbit, it was initially identified as a Magnum signals intelligence satellite.

This misidentification was in part due to the fact that SDS satellites had not previously operated in geostationary orbit, and partly due to the deployment of a second satellite by the mission, which was not publically acknowledged and designed to avoid detection.

That spacecraft, Prowler, was also placed into a geosynchronous orbit, and also used a single kick motor. When the two motors were catalogued and the second payload was not, observers assumed that a two-stage kick motor had been used to deploy a single satellite; Magnum satellites were deployed using the two-stage Inertial Upper Stage.

After the launch of USA-67, two more molniya-orbit satellites were launched; Space Shuttle Discovery launched USA-87 in December 1992 during the STS-53 mission, and USA-125 was launched by a Titan IV(405)B in July 1996. The second generation satellites are believed to have been based on either the HS-381 or HS-389 bus.

Third generation satellites, which are also known as Quasar, followed the second generation spacecraft. The first, USA-137 or NROL-5, was launched by an Atlas IIA in January 1998, and subsequently placed into Molniya orbit.

The next two launches occurred in December 2000 and October 2001 using Atlas IIAS rockets, and saw the USA-155 (NROL-10) and USA-162 (NROL-12) satellites placed into geostationary orbits. These satellites are located respectively at 10 and 144 degrees west of the Greenwich meridian, and it is expected that NROL-27 will replace one of them.

Two more third generation satellites have since been placed into Molniya orbits; USA-179 or NROL-1 was launched on the final flight of the Atlas IIAS in August 2004, and USA-198 or NROL-24 was launched by an Atlas V 401 in December 2007. Little is known about the third generation satellites. Once in orbit, NROL-27 will receive a USA designation; USA-227 is the next sequential designation and as such the most likely candidate, although the designations have not always been assigned sequentially, and the designation USA-163 still remains unassigned.

Assuming that Friday’s launch meant one of the geostationary SDS satellites is at the end of its operational life, then it will establish that SDS-3 satellites are designed to operate for around ten years. It is logical to assume that the other geostationary must also be approaching the end of its design life, and that USA-137 is overdue replacement.

It is therefore likely that two more SDS launches will occur in the next few years. NROL-33 and 38 have been identified as likely candidates from their configurations and launch sites, however not enough information is currently known about them to establish their identities with any degree of certainty.

Whilst it is known that Delta 353 flew east from Cape Canaveral, the exact profile for its ascent has not been announced. Assuming that Delta 353 will place NROL-27 directly into geosynchronous transfer orbit, then it will probably follow a similar mission profile to that published in United Launch Alliance’s Payload Planners Guide, and those used for previous launches to geosynchronous transfer orbits; such as flights carrying GOES weather satellites.

Five and a half seconds before launch, the RS-68 engine of the first stage started, and begin throttling up to full thrust. At T-0, the twin solid rocket motors ignited, and Delta 353 lifted off. Around 50 seconds after launch, the rocket travelling at Mach 1, the speed of sound. Shortly afterwards, it passed through the area of maximum dynamic pressure; max-Q, around a minute into the flight.

The solid rocket motors burned for 100 seconds, before burning out and separating from the first stage. About 210 seconds after launch the RS-68 throttled down to limit the loads on the rocket caused by acceleration. Fifty seven seconds later, the engine cut off. Six seconds after cutoff, the first stage separated, and the extendable nozzle on the second stage’s RL10B-2 engine deployed. The RL10 ignited around fourteen to nineteen seconds after staging, and ten to fourteen seconds later the payload fairing separated from around the spacecraft.

At this point in the flight, all official coverage of the launch ended. The first burn of the second stage engine will probably last around eleven and a half minutes. It will then be followed by a coast phase lasting about seven and a half minutes, and then a second burn lasting about four minutes and twenty seconds. After the second burn, there will be another short coast phase, and then the spacecraft will separate.

Delta 353 will be the twenty-first rocket to be launched from Cape Canaveral’s Space Launch Complex 37B (SLC-37B). The complex was built in the 1960s and initially used as a backup launch site for Saturn I and IB rockets, with eight launches being conducted between 1964 and 1968, culminating in the Apollo 5 mission which tested the Apollo Lunar Module in low Earth orbit. The complex was mothballed once Apollo launches switched to the Saturn V, however it was expected to be used again during the Apollo Applications programme, which was planned for the 1970s.

When most of Apollo Applications was cancelled, Saturn IB launches were moved to Launch Complex 39 to reduce infrastructure, and eliminate the need to reactivate the older Saturn I complexes. LC-37 was subsequently demolished, and rebuilt in the 1990s for the Delta IV programme. This will be the thirteenth launch from the complex since it was reactivated in 2002.

Delta 353 is the third EELV and second Delta IV to launch in 2011. The previous Delta IV launch, conducted on 20 January, deployed USA-224; a KH-11 electro-optical imaging satellite, in a launch from Vandenberg. An Atlas V launch last week deployed USA-226; the first flight of the second X-37B spaceplane. A further six EELV launches are planned this year; four Atlas Vs and two Delta IVs, with the next scheduled launch being that of an Atlas V 411 with NROL-34. That launch is currently planned for 12 April; the fiftieth anniversary of Yuri Gagarin’s launch on the first manned spaceflight, Vostok 1.

The next Delta IV launch is scheduled for 23 June, carrying the GPS IIF SV-5 satellite. Before this, the older Delta II rocket is expected to launch the Argentine SAC-D satellite. The Delta II launch, which will mark the final flight of the 7320 configuration, is currently scheduled to occur no earlier than 9 June. Two further Delta II launches are planned this year, and whilst United Launch Alliance have the parts to produce five more Delta II Heavy rockets and are attempting to sell the rockets, it is expected that the Delta II will be retired from service this year.

This was the twelfth orbital launch attempt of 2011. Of the previous eleven launches, nine have been successful. The two failures were of a Russian Rokot/Briz-KM rocket, which placed a Geo-IK-2 satellite, since redesignated Kosmos 2470, into an unusable orbit, and of an Orbital Sciences Taurus-XL which failed to place NASA’s Glory satellite and three CubeSats into orbit after its payload fairing failed to separate.

(Images: ULA, Boeing and L2 Historical Mission Database Hi Res Images)

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