Delta Rockets
Published on Jun 15, 2006 at 4:54 pm.
3 Comments.
Filed under rockets.
The first rockets used to launch satellites into space were basically ballistic missiles converted for the job. These rockets were essentially the same as their military cousins. Even the first rockets used to lift men into space were converted ballistic missiles. However, even in the earliest days of spaceflight, there was a recognized need for a dedicated booster — a rocket designed specifically to launch payloads into space. Out of this need grew the Air Force’s Delta rocket. The original Delta rocket was based on the technology of the Thor intermediate range ballistic missile, but the Delta was more than just a modified Thor. Over its more than four decade long operational life, the Delta rocket has undergone substantial modifications. Early modifications improved efficiency of the Delta. Later modifications involved various degrees of redesign. The current Delta IV rocket bears only very superficial resemblance to the early Delta rockets. With these redesigns and upgrades, the capabilities of the Delta have expanded from lifting a payload of 45 kg to low Earth orbit to the ability to lift nearly 13 metric tons to a geosynchronous orbit. With over 300 launches since inception, Delta rockets have better than a 95% success rate, one of the highest in the launch business. Delta rockets have launched from both the Cape Canaveral Air Force Station (Eastern Range) and from Vandenberg Air Force Base (Western Range), with both civilian and military payloads. Delta rockets have been a mainstay for NASA, launching many of the Explorer series of satellites, the Solar Max satellite, IRAS, ROSAT, Extreme Ultraviolet Explorer, CONTOUR, Deep Space 1, Mars Polar Lander, Mars Climate Observer, Mars Odyssey, the Mars Exploration Rovers, WMAP, Genesis, Gravity Probe B, SIRTIF, Messenger, FUSE, Stardust, Deep Impact, and many others. Delta rockets have launched GPS satellites, Iridium satellites, and a host of other navigaion, communication, and weather satellites. This is quite an impressive heritage!
The first Delta launch was May 13, 1960, designed to place the Echo 1 passive communication satellite into orbit. Unfortunately, this launch failed to achieve orbit. The second Delta launch, though, three months later successfully lifted Echo 1A into orbit. Delta launches continued into the 1980’s before temporarily ending in 1984 with the launch of the NATO-IIID satellite. There had been 177 Delta launches with about a 94% success rate. This was exemplary service, but the Air Force had declined to order any more Delta rockets. At this time, there was a feeling that the Delta had run its course. The Space Shuttle had entered routine service, and the Shuttles were supposed to be replacing the expendable launch vehicles. However, the Challenger explosion of 1986 changed all that. With the Shuttle fleet grounded, however, both the Air Force and NASA realized that there was a serious need for expendable rockets. This need was further apparent when President Reagan in 1986 issued an executive order that NASA was not to risk astronaut lives on manned space missions for launches that did not require manned flights, such as most satellite deployments. This was a public acknowledgement that space flight was inherently dangerous, and that some missions simply were not worth the risk to the lives of the astronauts. The Air Force quickly orderred more Delta rockets, and launches resumed later that year. However, though Delta rockets had proved their usefulness, they had limitations. An advantage of the Space Shuttle was that it could lift heavier and larger payloads than could Deltas. Satellites were getting larger. So, it was clear that a new, more powerful rocket was needed. Boeing rose to the challenge with the Delta II rockets. The last of the classic Delta rockets launched June 12, 1990.
Delta II rockets were originally designed to fill the gap in boosters to orbit left when the Shuttle became unavailable for most satellite deployments. The first Delta II rocket launched February 14, 1989, carrying NAVSTAR II-1 to orbit. Delta II rockets have proven to be fantastic launch vehicles, and they continue in service today.  Basically an improved version of the Delta, the Delta II rockets are launched from Launch Complex 17 (Pads A and B) at Cape Canaveral or from Launch Complex 2 at Vandenberg. These launch facilities were those used for Delta launches, and they were upgraded to accept the Delta II rockets. The first stage, as in the original Delta, is kerosine and liquid oxygen fueled. The second stage an hydrazine fueled AJ10-118K engine having a capability of being shut down and restarted. The third stage, if needed to achieve a geosynchronous orbit, employs a solid rocket motor. Delta II rockets come in several variants having different payload capabilities. The most obvious visual difference in these variants is a cluster of solid rocket boosters strapped onto the bottom of the rocket’s first stage. 3, 4, or 9 solid rockets can be fitted. Additionally, when 9 are fitted, different size strapons are available for different missions. Also, when 9 strapons are fitted, only 6 are lit at launch, with the remaining 3 kicking in during flight. Delta II rockets are able to lift up to 5.6 metric tons into low Earth orbit (depending upon configuration and orbital inclination), or 2.1 metric tons to geosynchronous orbit, or about 1.2 metric tons for an interplanetary mission.
The Delta III variant was a short lived upgrade to the Delta II rockets. The two upper stages were replaced with a single high performance stage. The upper stage, though, was longer than the two stages of the Delta II, and so there were concerns about wind loading on the launch pad. To minimize these, the first stage was made shorter and wider. Only three Delta III flights were launched from 1998 to 2000, with the first two launches being failures. However, the Delta III was clearly not going to fulfill the demands for a heavy launch vehicle. This required a major revision of the Delta technology.
 The Delta IV is the latest in the Delta family of rockets. The Delta IV is, in fact, substantially different from the earlier Delta rockets. First of all, the first stage is replace with a Common Core Booster (CCB). The CCB departs from the kerosine/oxygen fuel of the earlier Delta rockets. Instead, it uses liquid hydrogen and oxygen as propellant, as does the second stage. Even with just the CCB and second stage, the Delta IV has far more lift capability than the earlier Delta rockets, with nearly double the capability of the Delta II rocket. Other variants include solid rockets strapped onto the sides of the bottom of the CCB for additional lift, nearly doubling the payload capability. The biggest Delta IV uses three of the Common Core Boosters strapped side by side as the first stage. This configuration again doubles the payload capability over the variant with one CCB and four solid rockets, for nearly four times the payload of the base model Delta IV. This version of the Delta IV, the Delta IV Heavy, has a payload capability of nearly 22 metric tons to low Earth orbit, almost 13 metric tons to geosynchronous orbit, or 8 metric tons to Mars. Planned Delta IV upgrades may be able to lift up to 50 metric tons into low Earth orbit, with proposed Delta IV derivatives perhaps able to double that payload. Delta IV rockets launch from Launch Complex 37 at Cape Canaveral, a site originally used for Saturn I-b Apollo test flights. The original pad structures were not maintained and were falling apart in the corrosive salty air of Cape Canaveral, so they were torn down in the 1970’s. Launch facilities for Delta IV were built from the ground up on the same site, making the new Launch Complex 37 the most modern launch facility in the country, and the only one built from the ground up in more than three decades. Delta IV rockets can also be launched at the upgraded Launch Complex 6 at Vandenberg.
Delta II rockets and Delta IV rockets continue the legacy of the original Delta rockets which began 46 years ago. It has been a wonderful run, and it shows no sign of ending any time soon.
-Astroprof
Astroprof’s Page » STEREO on the Sun on October 26, 2006 at 7:41 pm: 1
[…] Last night, October 25, a Delta II rocket lifted off from Pad 17B at the Cape Canaveral Air Force Station.  It was carrying twin NASA spacecraft on a mission to study our nearest star, the Sun.  The acronym selected for this mision is STEREO (standing for Solar Terrestrial Relations Observatory), and it is quite aprospos because these two craft will study the Sun from slightly different positions, permiting stereoscopic, or 3-D, studies of our star, the Sun. The spacecraft will achieve their stereoscopic views of the Sun by looking at it from two slightly different angles. Both will orbit the Sun about one Astronomical Unit out, close to Earth’s orbit. One will be ahead of the Earth along its orbit, and one trailing behind. To place them both into separate positions using one rocket, NASA fired them on a path that will eventually take them towards the Moon. They will be separate long before they get there, and the Moon will then sling one ahead of the Earth (Spacecraft A) and the other (Spacecraft B) trailing the Earth in our planet’s orbit around the Sun. This will give them the parallax needed to create three dimensional images of coronal mass ejections as they are hurled outward from the Sun.  The lunar flyby will be in about two months from now. […]
Astroprof’s Page » Delta rocket explosion on November 16, 2007 at 7:30 pm: 2
[…] This is a video that I found on YouTube about a Delta rocket exploding on launch. […]
nick on March 23, 2010 at 4:46 pm: 3
a delta exploded!?1? that’s horrible!!