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SPACE LAUNCH REPORT
by
Ed Kyle



Delta 2 Productive Years
Fourteenth in a Series Reviewing Thor Family History
by Ed Kyle, Updated 02/12/2017

d261xs.jpg (8776 bytes)Delta 261, a "Med Lite" Delta, Launches NASA's Deep Space One from Cape Canaveral in 1998

From 1989 through 2011, Delta 2 was the most often-flown, versatile, productive, and reliable U.S. launch vehicle.  Delta 2 returned the Thor family to three launch pads at two launch sites, and it became common to see multiple Deltas stacked simultaneously on those pads.  151 Delta 2 rockets would fly by the end of 2011, and 149 would succeed, making it one of the most successful orbital launchers in history.

Born to launch GPS satellites for the U.S. Air Force - it would orbit 48 in 49 attempts over the years - Delta 2 steadily expanded its "customer" base to include commercial satellites, non-U.S. government missions, and NASA satellites.  For NASA, Delta 2 eventually performed missions that no previous Delta or Thor had performed - flights far beyond Earth orbit into deep space and to Mars. 

Delta 2's 23 year run made it the longest-lived essentially unchanged U.S. launch vehicle model.  Incremental upgrades occurred during that time, but the basic propulsion and structure remained little changed.  Delta 2 ownership changed hands twice during its life, and its production and engineering sites moved twice, but its culture of success somehow remained unchanged. 


d210xs.jpg (14887 bytes)Mission Variety

Delta 210, one of the Final Castor 4A Boosted Extra Extended Long Tank Deltas, with a 10 Foot Diameter Metal Fairing

Delta 210, a 6920-10 with no third stage, returned Delta to NASA service after a three year hiatus by orbiting EUVE (Extreme UltraViolet Explorer) from Pad 17A on June 7, 1992.   The 3.275 tonne satellite, originally designed to be launched aboard Shuttle, entered a roughly 500 km x 28.4 deg orbit.  This was part of NASA's Medium Expendable Launch Vehicle Services (MELVS) contract with McDonnell Douglas for Delta 2 launch services.

Delta 212 was a landmark because it was the final 6925, the last Delta with Castor 4A strap on motors, or Thiokol Castor motors of any type - a relationship that began in 1964.  It launched Geotail, a 1,009 kg spinner built by Japan's ISAS designed to measure "fundamental magnetospheric processes", from LC 17A on July 24, 1992.  Geotail was boosted into a highly elliptical orbit, which was subsequently modified through the use of two lunar swingbys.  Geotail was still acquiring data as of 2005.
 

d2comps.jpg (14368 bytes)Delta 2 Model Comparison

After the final 6900 series rockets flew, Delta 7925, a 7000 core with an RS-27A engine boosted by nine GEM-40 Hercules Graphite Epoxy Motors topped by an Aerojet AJ10-118K ITIP (Improved Transtage Injector Program) powered second stage and a Star 48B spinning solid motor third stage, became the most common model.   7925 would fly 69 times by the end of 2011.  It was most often used to orbit GPS-2A, 2R, and 2RM satellites, Delta 2's most common payload.  Delta 7925 also launched communication and scientific satellites.

For GPS missions, Delta's pressure-fed hypergolic propellant second stage coasted in a parking orbit before restarting near the first (descending) or second (ascending) equator crossing.  The burn was followed by spin up and separation of the Star 48B third stage, which began its burn only a few minutes later.  The GPS satellite would then separate into a transfer orbit with a roughly 200 km perigee and 20,370 km apogee, and usually with a 40 deg inclination.   GPS 2A satellites weighed 1.816 tonnes at separation.  Upon reaching first apogee, the satellite would fire its own kick motor to circularize its orbit at roughly 20,200 km and to increase its inclination to 55 deg.  The GPS constellation steadily grew to and beyond its planned four satellites in each of six orbital planes.

d226xs.jpg (13926 bytes)Delta 226, a Standard 7925 GPS-Hauler with a 9.5 Foot Fairing

Delta 7925 orbited 15 GPS 2A satellites by the end of 1994.  It also performed nine geosynchronous transfer orbit (GTO) or highly elliptical orbit missions during the same period.  NATO 4A, ASC 2, and Satcom C5 were boosted to GTO by 7925 rockets during 1991.   Indonesia's Palapa B4, Satcom C4, and Germany's DFS Kopernikus 3 were likewise orbited in 1992.  GTO missions progressed in a similar fashion to GPS flights, except that the transfer orbit apogee was typically around 36,000 km or higher and the inclination was usually in the 20-28 degree range.  GTO perigees might be as low as 185 km but sometimes exceeded 1,000 km depending on the weight of the satellite, which typically ranged between 1.1 and 1.5 tonnes.  

One slightly thrilling moment occurred on November 6, 1992, when Delta 216 on Pad 17A with GPS 2A-7 reached the ignition point in the count, ignited its verniers, and shut down before igniting its main engine and solids.   A detector wire mounted at a vernier nozzle failed to burn through as designed, causing the shut down.  The abort pushed the launch back to November 22.  The resulting launch was the first of eight consecutive, successfully monotonous 7925 GPS flights that spanned the following 11 months.        

The GPS mission pattern was finally broken by Delta 224, yet another 7925, which boosted UK-built NATO 4B into GTO from Cape Canaveral LC 17A on December 8, 1993.

There were only three Delta 2 launches in 1994, making it the slowest year for Delta since 1988.  Much of the initial Block 2 GPS constellation had reached orbit by then.  All three were 7925 models, but all used different payload fairings. 


d225xs.jpg (8775 bytes)Delta 225 Suffered a Last Second Abort

Delta 225, with an 8 foot diameter fairing, carried Galaxy 1R2, a 1,397 kg Hughes 376 spinner, into GTO from LC 17B on February 19, 1994.  The launch occurred nine days after an on-pad abort that saw the first stage verniers start, then shut down.  The problem was traced to circuitry that monitored vernier combustion chamber pressure.

Delta 226, with the standard Delta 2 9.5 foot diameter fairing, orbited Navstar GPS 2A-15 from LC 17A on March 10.  The Small Expendable Deployer System (SEDS-2), a space tether experiment, was also deployed from Delta's second stage.  Ground observers could spot the 19 km long SEDS-2 tether (which broke away from the stage after several days) for weeks until it reentered. 

Delta 227, using a 10 foot diameter fairing, launched NASA's 1,250 kg WIND from LC 17B on November 1 toward an eventual Earth-Sun L1-point halo orbit (via. several lunar swingbys) to measure solar winds.  This was the 41st consecutive Delta 2 success and 49th consecutive Delta success, a new record for the launch vehicle that dated back to 1986.

d228xs.jpg (9307 bytes)First Failure

Delta 228 Liftoff

Nine months passed before the next Delta launch.  It was Delta 228, a 7925 that faltered during its flight with Koreasat 1 from LC 17B on August 5, 1995.  One of the three air-started solid motors failed to jettison, resulting in 1,464 kg Koreasat 1 being deposited in an orbit that was about 5,000 km short of its planned GTO apogee.  The satellite, a Lockheed Martin AS-3000 series 3-axis stabilized craft, had to use up 6 years worth of on-orbit propellant to make up the 325 m/sec delta-v deficiency, shortening Koreasat 1's life to about 4.5 years.   In the end, the satellite managed to function until December 2005, likely the result of extra-careful propellant management. 

The failure was attributed to an explosive transfer line (a type of detonation cord) possibly having been exposed to high temperatures.  This would have been caused by a failure of insulation protecting the rocket's booster separation circuits.  After 49 consecutive successes, it was the first Delta failure since 1986 and the first Delta 2 failure after 41 successes.  Delta would continue to carry 49 success stars on its decal until the mid-2000s.

d229xs.jpg (8154 bytes)West Coast Return 

Delta 229 Returned Delta to Vandenberg AFB

Three months after the Delta 228 failure, Delta 229, a 7920-10, successfully launched Radarsat 1 and Surfsat 1 into near polar orbits from Vandenberg AFB Space Launch Complex 2 West on November 4, 1995.   This first launch from SLC 2W since Delta 189 orbited COBE in 1989 followed a reconstruction of the pad for Delta 2.  It was also the first flight of a Delta 7920, the version without a Star 48B third stage.  7920 was typically used for LEO missions, usually from Vandenberg into near polar orbit, and would become the second most common Delta 2 model. 

Radarsat 1 was a 2,750 kg C-Band Synthetic Aperture Radar mapper largely built by Ball Aerospace for prime contractor Spar Aerospace for the Canadian Space Agency.  It was Canada's first remote-sensing satellite.  The big-antenna satellite was inserted into an 832 km x 98.6 deg sun synchronous orbit. 

Surfsat 1 was the "Summer Undergraduate Research Fellowship Satellite", built by Caltech students with JPL involvement.  It consisted of two metal boxes bolted to Delta's second stage covered in solar cells to produce 15 Watts of power, filled with X-band, Ku-band, and Ka-band transponders, and fitted with omni directional antennas to test new NASA ground tracking systems.  The Delta second stage boosted itself and 55 kg Surfsat 1 into a 935 x 1495 km x 100.6 deg orbit after Radarsat 1 separated.  The stage and Surfsat were gravity gradient stabilized and there were no batteries.  The entire experiment cost $3 million.

RIFCA

Delta 230, another 7920-10, flew from Cape Canaveral LC 17A on December 30, 1995 with NASA's XTE (X-Ray Timing Explorer).   XTE, a 3,035 kg X-ray telescope (essentially), was boosted into a 565 x 585 km x 23 deg orbit where it scanned the cosmos until being decommissioned on January 5, 2012.   It is expected to reenter sometime during the next decade. 

Delta 230 was the first Delta controlled by a Redundant Inertial Flight Control Assembly (RIFCA).  RIFCA, built around six ring laser gyroscopes and six accelerometers, provided triple redundant guidance, flight control and mission sequencing functions.   Developed by AlliedSignal of New Jersey, RIFCA replaced the previous DRIMS guidance and control system that had been used since 1978.

d232xs.jpg (8239 bytes)Workhorse

Delta 232 Launched Asteroid Explorer NEAR in 1996

As 1995 ended, Delta's McDonnell Douglas team stood on the cusp of a real golden age - four years of launch-a-month business that would solidify the rocket's oft-used "workhorse" label.  Delta 2 would liftoff 43 times during the four year 1996-1999 period.  There would be more GPS launches, but also many "Little-LEO" launches and renewed NASA work as the Agency entered its "Better, Cheaper, Faster" era.  For the first time, the ancestor of the old Douglas Thunder God would head for Mars.

Delta 2 flew ten times in 1996. 

The first, Delta 231 (a 7925) boosted Koreasat 2 into GTO from Canaveral's LC 27B on January 14, 1996.  This was a successful repeat of the faulty Koreasat 1 mission.

Delta 232, a 7925-8 with an increasingly rare eight foot diameter fairing, boosted NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft into solar orbit from the same pad just over one month later, on February 17, 1996.  (Pad A was not used for launches for about six months during this period for restoration work.)  This was the first "Discovery Program" launch.  NEAR flew within 750 miles of asteroid 253 Mathilde on June 27, 1997, then topped that by entering orbit around asteroid Eros on February 14, 2000.  Then, on February 12, 2001, NEAR gently landed on Eros, snapping pictures down to the surface.  NEAR achieved several "firsts", including the first "orbiting and landing on a small, irregular body" and the "first use of the Internet for communicating with the public through Project Scientist Andy Cheng’s regular Science Updates".  NEAR really was a remarkable mission.

Delta 233, a 7925-10, launched NASA's Polar satellite from Vandenberg AFB SLC 2W on February 24, 1996.  Polar entered a highly elliptical polar orbit from which it studied the magnetosphere for more than a decade.

d235xs.jpg (11930 bytes)Delta 235 on a Rare Sunny Day at Vandenberg's SLC 2W

Delta 234 orbited GPS-2A-16 from Cape Canaveral LC 17B on March 27, 1996.  Deltas 237 and 238 orbited GPS 2A-17 and GPS 2A-18 from Cape Canaveral LC 17A on July 16 and September 12, 1996, respectfully.   These were the first launches from Pad 17A since its structures had been repainted from red to gray.

Delta 235 was a 7920-10 with a 10 foot diameter metal fairing.  It boosted Ballistic Missile Defense Organization's 2.7 tonne Midcourse Space Experiment (MSX) into a 900 km sun synchronous orbit from Vandenberg AFB SLC 2W on April 24, 1996.  MSX did missile tracking experiments, then turned its eyes upward to track GEO satellites until mid-2008.

Delta 236, a 7925, boosted 1.397 tonne Galaxy 9 into GTO from LC 17B on May 23, 1996.  Galaxy 9 was the last of the original model Hughes HS-376 spin stabilized satellites to be launched by a Delta - though a few HS-376HP types would yet fly.  Galaxy 9 was still in use as of 2008.  This was the last launch from Pad 17B before its umbilical and mobile service towers, too, were repainted from red to gray.

On October 7, 1996, the American Institute of Aeronautics and Astronautics (AIAA) awarded its prestigious George M. Low Space Transportation Award to the McDonnell Douglas Delta Launch Vehicle Team for their "unparalleled record of successful launches".

d240xs.jpg (17643 bytes)To Mars

Mars Pathfinder and Star 48B Third Stage Being Encapsulated by Fairing on Pad 17B

Delta 239 launched NASA's Mars Global Surveyor toward Mars from Cape Canaveral LC 17A on November 7, 1996.  Delta 240 did the same for Mars Pathfinder from LC 17B on December 4, 1996.  These were NASA Jet Propulsion Laboratory's (JPL) first "Mars Surveyor" program missions.   Delta 7925 rockets performed both launches.  These were essentially straight-up 7925 GPS-style rockets, but used to boost payloads on landmark missions to another planet. 

Mars Global Surveyor weighed 1,060 kilograms at launch.   It placed itself into orbit around Mars during September, 1997.  Mars Pathfinder weighed 990 kilograms at launch.  It consisted of a small cruise stage attached to an aeroshell and heat shield that housed parachutes, a folded-up lander protected by airbags, and a small 10 kilogram rover named "Sojourner".  The contraption deployed its parachute and airbags to "bounce down" onto Mars surface during July 1997.  Several days later, Sojourner drove off of the lander to begin exploring nearby rocks, capturing public interest as photographs streamed from the Red Planet to JPL, and then to the Internet, itself still a new public fascination.

Here was NASA's "Faster Better Cheaper" plan in full-bore action, starting the Agency on a startling decade of Delta-boosted Martian exploration.


d241xs.jpg (14869 bytes)The Big Bang 

Delta 241 Astonished Observers when it Exploded Violently Just Above its Pad

Delta 241, a McDonnell Douglas Delta 2-7925-9.5 lifted off from Cape Canaveral Launch Complex 17A at 16:28 UTC on January 14, 1997, carrying the first 2.03 tonne Block 2R Global Positioning System satellite, commonly identified as Navstar, or GPS, 2R-1.  This was the first Lockheed Martin AS4000 series GPS satellite.  The blue and white rocket flew for 12.6 seconds.   Then it exploded less than 500 meters above the pad, shocking launch crews, eyewitnesses, news reporters, and just about anyone hearing the news.  It was probably the biggest launch vehicle explosion near the ground at the Cape since Atlas Centaur AC-5 nearly 32 years earlier.

Delta 241 had nine GEM strap-on solid rocket motors, six ground start and three air-start, augmenting an RS-27A powered Extra Long Extended Tank (XLET) first stage.  The rocket was topped by a pressure fed, AJ-10-118K powered second stage and a Star 48B spin-stablized third stage.  Serial numbers were 20055 for the first stage, 20147 for the second stage, 20050 for the third stage, and 20381-20388 for the GEMs.

About 7.2 seconds after ignition, the casing of GEM No. 2 (Motor K-404) began to split.   The split grew from 28 cm to 100 cm in length within 5.4 seconds, when the motor "failed catastrophically", triggering the first stage automatic destruct system at T+12.581 seconds, which created the dramatic fireball less than 500 meters above the pad.   This occurred about 40 milliseconds after SRM No. 2 and No. 8 began to explode.  The upper stages and payload remained intact, drifting upward until the Flight Control Officer sent command destruct signals 22.3 seconds after liftoff.  The payload and fairing remained intact until they impacted the ground, causing the satellite propellants to exploded.

Solid motor fragments, and other debris, rained down on Launch Complex 17, trapping the 73 person launch crew for more than an hour in the blockhouse.  Conditions in the blockhouse deteriorated when smoke began entering via. a cable duct, but no one was injured or killed. About two dozen vehicles in the LC 17 parking lot were destroyed.  It would be the final Delta launch controlled from the Launch Complex blockhouse.

The exact trigger for the Automatic Destruct System was not determined.  It may have been a lanyard pulled due to engine section (boat tail) deformation.  It may have been sympathetic detonation due either to the shock or to high temperatures created by the SRM explosion.

The ADS did several things.  It fired linear shaped destruct charges that cut open the sides of the first stage LOX and RP tanks and that simultaneously opened up each SRM - except for SRMs 2 and 8 which broke away prior to ADS detonation.  The ADS also fired frangible nuts to separate the SRMs (except for SRMs 2 and 8 ). 


d241ys.jpg (33184 bytes)Damage in LC 17 Parking Lot

The launch vehicle broke up into about 2,100 fragments and more then 2,000 "firebrands" from the SRMs.  Debris landed on and around LC17, LC18, and LC26 (the Space Museum).  Damage included 26 destroyed vehicles (including a tractor trailer), 46 damaged vehicles, four destroyed modular trailers, seven damaged modular trailers, and damage to the Titan 1 and Thor IRBM displays at the Museum. 

An Air Force Accident Investigation Board determined that the motor’s outer composite layers had been damaged prior to the launch.  The cause of the damage was never determined, but possible causes included hydrostatic proof testing operations and damage during launch processing.  Significant attention focused on the possibility that a new ground handling traveling trunnion device might have been involved in the damage.  

In the end, the Air Force investigation report focused most of its attention on the ATK hydrostatic proof test procedure, which was found to expose some motors to 95% of their ultimate strength capability.  SRM 2's carbon composite case may thus have been damaged slightly, but not catastrophically, during the test, setting it up for its final failure a few seconds after its ignition.   The investigation recommended improving case strength design margins, adding ultrasonic inspections, and modifying the hydroproof testing procedures.

Alliant manufacturing and test procedures were altered, ground processing procedures were modified, ultrasonic inspection steps were added, and no GEM failures subsequently occurred.

Delta 241 served as a kind of harbinger of ugly things to come outside the program.  Five additional Cape Canaveral launch failures would occur during the next 2.5 years, but none of those failures were by Delta 2 rockets.  Delta 2, in fact, was about to embark on the longest success streak by any U.S. rocket - 96 launches spanning 13 years.

d242xs.jpg (6597 bytes)Little LEO Era

First Iridium Launch

With the Delta 241 investigation complete, McDonnell Douglas returned Delta 2 to service less than four months after the failure on May 5, 1997, when Delta 242 launched the very first Iridium mission (Iridium MS-1) from Vandenberg AFB SLC 2W.  A Delta 7920-10C, equipped with the first 10 foot diameter composite payload fairing, lifted five 689 kilogram Iridium satellites into 667 km 667 km, 86.4 insertion orbits.  It was the first of ten successful Delta 2 launches before year's end.

The Delta 242/Iridium MS-1 mission was a near miss, because the rocket's second stage cold gas attitude control system ran out of nitrogen gas after the fourth satellite was released but before the fifth was released.   The stage was just entering a slow tumble when the fifth and final satellite separated.  The problem prevented the second stage from performing the usual post separation maneuvers.

Motorola's Iridium plan called for a constellation of 66 satellites in low earth orbit, called a "Little LEO" constellation, to route cellular type phone calls.  The idea was that it would be cheaper to orbit satellites than to build 40,000 cell phone towers.

Five more Iridium mission launches took place in 1997, all from SLC 2W.  Some of the launches were only spaced five weeks apart.  This would be the busiest year for SLC 2W.

Delta 243, a 7925, boosted Thor 2 into GTO from Cape Canaveral Launch Complex 17A on May 24, 1997.  Norway's Thor 2 was a 1.4 metric ton Hughes HS-376HP spinner with 15 Ku band direct to home TV transponders.   Only four months earlier structures at this pad had been damaged by the Delta 241 explosion. 

Boeing Takes Over

Delta 245 and 246 bracketed a historic change in the U.S. aerospace industry. 

Delta 245, a 7925, orbited GPS 2R-2 from LC 17A on July 23, 1997.  This was the first successful "2R" series launch, and the first from LC 17A since the Delta 241 explosion.  It would be the last Delta rocket adorned with a "McDonnell Douglas" decal.  McDonnell Douglas would soon - on August 4, 1997 - vanish in a merger with Boeing, it's long time corporate nemesis. 

Delta 246 was Boeing's first.  It launched five more Iridium satellites (22-26) from Vandenberg AFB SLC 2W on August 21, 1997.  Boeing Launch Services, essentially just a renamed McDonnell Douglas Space Systems Company at the time, handled the launch service.   This was Delta's "MS-3" mission for Iridium.

d247xs.jpg (7089 bytes)Delta 247 on Pad 17A After Service Tower Rollback

Delta 247, a 7920-8, launched NASA's ACE (Advanced Composition Explorer) from Canaveral LC 17A on August 25, 1997.  ACE was a 785 kg spin-stabilized solar observatory built at JHU/APL, which was sent to an L-1 halo orbit.  ACE was still out there operating as of 2012, and had enough propellant to maintain its orbit until 2024.  This may have been the first Delta to carry an "in memory of" decal, a practice that appears to have begun during the post McDonnell Douglas era.

Delta 249 launched Navstar 2A-19, the last 2A model built by Rockwell, from Cape Canaveral LC 17A on November 6, 1997.

1998 would be the busiest ever year for Delta 2, with 12 launches, all successful.  (There was also one unsuccessful Delta 3 launch.)  Four of the launches would be performed by a new "Med-Lite" Delta 2 variant.

Delta 252, a 7925, started the year on January 9 by boosting Britain's Skynet 4D into GTO from Cape Canaveral Launch Complex 17B.  This was the first launch from "B" in more than a year, and you could see the effects of the modifications made to the pad during that time, when it was rebuilt to handle Delta 3 and its bigger GEM-46 solids.   Louvers at the top of the new box-style flame duct forced exhaust upward so that it wrapped around the rocket.  Pad "A" was never modified this way, so a post modification "B" launches can be identified in photographs by the smoke wrap.

Skynet 4D was a 1.5 tonne 3-axis British Aerospace built satellite with a Star 30E apogee kick motor.  It was the last Skynet launched by a U.S. launch vehicle.

dlites.jpg (12576 bytes)Med-Lite and "Delta Lite"

Comparison of Delta 2 7325 and Delta Lite

Delta 253, the first 7420-10C with only four strap-on solid motors, launched from LC 17A on February 14, 1998 with the first four Globalstar satellites.  These 450 kg SS/Loral LS-400 satellites were inserted into 1,400 km x 52 deg orbits.  A second Globalstar launch with four more satellites took place from the same pad on April 24. 

Delta 261, a 7326 with only three strap on motors and with a smaller, Star 37FM third stage.  It launched NASA's Deep Space 1 and SEDSat from Cape Canaveral's just-renamed "Space Launch Complex" 17A on October 10, 1998.  It was the first Delta with only three strap on motors since 1974.    Deep Space 1 was a New Millennium technology demonstration mission that flew a xenon gas ion engine into heliocentric orbit.  It weighed 486.3 kg at launch.  DS-1 flew by Asteroid 9962 Braille in July 1999 and comet 19P/Borrelly in September 2001.  SEDSat was a microsatellite that deployed from Delta's second stage, after DS-1/Star 30FM separated and the stage performed a depletion burn, into a 547 1,079 km x 31.4 orbit.  

Delta 264, a 7425 model with only four strap on motors but with the standard Star 48B third stage, launched NASA's ill-fated 338 kg Mars Climate Orbiter from SLC 17A on December 11, 1998.  MCO failed at Mars due to a targeting error that plunged it destructively through the upper Martian atmosphere just before it was to fire its main engine to enter orbit.  The error was caused by contractor software programmed to use non-metric units rather than the metric units specified by NASA-JPL. 

d253xs.jpg (13393 bytes)Delta 253, the First 7420

These were the first "Med-Lite" type Delta 2 rockets.  The type was originally offered by McDonnell Douglas in response to NASA's December 1994 request for bids for a Medium Light Expendable Launch Vehicle Services (Med-Lite) contract.  The goal was to create a rocket that could lift about half as much to orbit as a standard Delta 2, preferably for half as much money. 

A 7320/7326 series Delta could lift 2.8 tonnes to LEO or 0.629 tonnes to escape velocity.  A Delta 7420/25 could handle 3.2 tonnes to LEO or 0.806 tonnes to escape.  This compared with 5.1 tonnes and 1.284 tonnes, respectfully, for Delta 7920/25.    

McDonnell Douglas and Orbital Sciences teamed to win the contract in March 1995.  Orbital's Taurus would handle the lightest payloads (up to 1.5 tonnes to LEO) in the class while Delta 2 rockets with three or four strap on motors would handle the heaviest.  For "in-between" payloads, McDonnell Douglas proposed development of a new "Delta-Lite" variant. 

Delta Lite would have consisted of two Castor 120 motors stacked as Stage 1 and 2, topped by an Aerojet AJ10-118K powered Delta 2 ITIP stage and payload fairing.  A standard RIFCA would have controlled the rocket's flight.  It would have lifted 1.985 tonnes to LEO, 1.51 tonnes to polar LEO, or 0.66 tonnes to GTO.  A growth version with two Castor 4B motors strapped to the first stage would have lifted 2.61 tonnes, 2.03 tonnes, or 0.86 tonnes to the same orbits - almost as much as a Delta 7320/26 series "Med Lite" Delta. 

NASA's FUSE satellite was slated to be the first to ride the new rocket in 1998, but after almost a year of negotiation with NASA, McDonnell Douglas decided not to develop Delta Lite.  It determined that NASA was not offering sufficient payloads in the class to makes its development worthwhile.  Payloads that might have flown on Delta Lite ended up flying on Delta 7300 series rockets instead. 

In the end, "Med-Lite" saved NASA money, but not as much as it had originally hoped.

Delta Model Numbering System         

Table 1 lists the Delta model number designations used prior to and during the Extra Extended Long Tank era.

Table 1:  Delta Model Numbers

First Digit:  First Stage and Strap on Motor Types

0:  Long Tank, MB-3-3 engine, Castor 2 motors (1968)
1:  Extended Long Tank, MB-3-3 engine, Castor 2 motors (1972)
2:  Extended Long Tank, RS-27 engine, Castor 2 motors (1974)
3:  Extended Long Tank, RS-27 engine, Castor 4 motors (1975)
4:  Extended Long Tank, MB-3-3 engine, Castor 4A motors (1989)
5:  Extended Long Tank, RS-27 engine, Castor 4A motors (1989)
6:  Extra Extended Long Tank, RS-27 engine, Castor 4A motors (1989)
7:  Extra Extended Long Tank, RS-27A engine, GEM-40 motors (1990)
8:  Delta 3 First Stage, RS-27A engine, GEM-46 motors (1998)

Second Digit:  Number of Strap on Motors

Third Digit:  Second Stage Type

0:  AJ10-118F (Aerojet Transtage derivative, 1972)
1:  TR-201 (TRW LM Descent Engine derivative, 1972)
2:  AJ10-118K (Aerojet ITIP engine, 1982)
3:  Delta Cryogenic Second Stage (1998)

Fourth Digit:  Third Stage Type

0:  No third stage
3:  Star 37D (TE-364-3, 1968)
4:  Star 37E (TE-364-4, 1972)
5:  Star 48B (TE-M-799, 1989)
6:  Star 37FM (1998)

"H" Designation

7920/7925 Series Delta with GEM-46 motors (1998)

 

Table 2:  Delta Launch Vehicle Performance, 1990-2011

Vehicle 185kmx28.5 deg 185kmx90 deg GTOx28.7 deg C3=0
Delta Lite
(not developed)
1.985 tonnes 1.510 tonnes 0.660 tonnes ~0.444 t
Delta Lite w/SRM
(not developed)
2.610 t 2.030 t 0.860 t ~0.579 t
Delta 7320/7326 2.865 t 2.095 t 0.950 t 0.629 t
Delta 7420/7425 3.200 t 2.460 t 1.140 t 0.806 t
Delta 7920/7925 5.045 t 3.830 t 1.820 t 1.284 t
Delta 7920H/7925H 6.140 t n/a 2.190 t 1.508 t
Delta 8930 8.290 t n/a 3.800 t 2.720 t


References

"Defining Aerospace Policy: Essays in Honor of Francis T. Hoban", Edited by Kenneth John Button, Francis T. Hoban, Julianne Lammersen-Baum, Roger Stough, Ashgate Publishing, 2004.

"Delta - A Progress Report on Latest Developments", J.F. Meyers, McDonnell Douglas Aerospace, AIAA 1995 Space Programs and Technologies Conference, AIAA 95-3773.

Boeing/McDonnell Douglas Merger Agreement Announcement, 12-15-1996.

"Boeing Delta 2 Heavy Lift Rocket Developed for NASA Payload", Boeing, 8-31-1999.

Press Releases and Mission Press Kits by NASA, McDonnell Douglas, Boeing, and United Launch Alliance.

Photos by NASA, USAF, McDonnell Douglas, Boeing, United Launch Alliance

 

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