|December 8, 2007 Taurus II Article|
In early December 2007, Orbital Sciences Corporation provided an initial glimpse of its plans for a new medium-class launch vehicle named Taurus II. According to a description on the company's web site at
Orbital is targeting the 98% reliability number achieved by the United Launch Alliance Delta II.
Delta II faces imminent retirement because the U.S. Air Force will soon move its GPS launches to the EELV program. The move will slow Delta II production, driving up costs for NASA and commercial customers. If Delta II is retired, NASA will have to launch its "medium" class payloads on more expensive EELVs.
Twin Kuznetsov NK33 engines, modified by Aerojet, may power the Taurus first stage. During the 1990s, Aerojet acquired rights to import about 46 of the engines from ND Kuznetsov Joint Stock Company Scientific-Technical Complex of Samara Russia. The engines were originally developed for the Soviet Union's N1 launch vehicle. More than 50 more NK33s are reported to remain in storage in Samara. Aerojet also negotiated a license to produce new copies in the U.S., but such production would require several years to initiate. Each staged combustion cycle kerosene/liquid oxygen NK33 develops nearly 153 tonnes of sea level thrust and 167 tonnes in vacuum. The engines are highly efficient, with specific impulse ratings of 297 seconds at sea level and 331 seconds in vacuum.
The high thrust provided by two NK33 engines means that Orbital can develop a simplified launch vehicle that can efficiently be prepared for launch. Since Delta II's RS-27A engine only develops 90.7 tonnes of thrust at sea level, strap-on solid boosters must augment the first stage thrust. Taurus II will not need strap-on boosters to match Delta II performance, but such boosters could presumably be added to increase performance in the future.
In its October 18, 2007 report of third quarter earnings, Orbital Sciences disclosed that Taurus II development could cost $40-45 million in 2008, but could also increase corporate revenue by as much as $25 million. The report stated that the company planned to announce whether it intended to proceed with Taurus II or not in early 2008.
Orbital Sciences did not initially provide details of the Taurus II upper stage or stages, but a profile sketch of the rocket provided at
The following is educated guesswork and could very well be misinformed, incorrect, off-base, erroneous, or dead-wrong!
Based on the Orbital Sciences drawing, a 3.9 meter diameter assumption (based on
In the past, Orbital Sciences has used solid motor upper stages topped by a liquid propellant "trim" stage called "HAPS" (Hydrazine Auxiliary Propulsion System). Such an arrangement is plausible for Taurus II, although the trim stage would need to be more powerful, and carry more propellant, than the Pegasus HAPS stage.
For geosynchronous transfer orbit missions, Taurus II could conceivably use a solid propellant kick motor like Star 48. A Star 48 on top of a Taurus II should be able to match or beat the 1.84 tonne Delta II-7925 GTO capability.
If Taurus II is developed, Cape Canaveral's former Atlas Centaur Space Launch Complex 36 could host launches beginning no earlier than mid-2010.
Orbital Sciences has examined Taurus II designs before. A Taurus II design studied during the early 1990s used two Castor 120 motors stacked in series topped by a new bi-propellant liquid stage. As many as eight Castor IVA strap-on boosters could augment the core stage. The most powerful variant would have matched Delta II capability.
|January 28, 2008 Taurus II Update|
In January, ATK provided some details of its competing COTS Demonstration Launch Vehicle that could also provide a new clue about Taurus II. The ATK Launch Vehicle, described in the January 2008 Launch Report, was said to use a new Castor 30 third stage motor. If Taurus II is being designed to also use Castor 30, the second stage could weigh less than originally postulated in the original article here.
In the past, the Castor motor identificatification system used numbers to indicate propellant weight. Castor 120 was a motor that was roughly planned to be in the 120,000 lb (54.4 tonne) weight range (it ended up carrying 107,154 lbs of (48.596 tonnes) of propellant). A "Castor 30" should, under this naming system, be loaded with about 30,000 lbs (13.61 tonnes) of propellant, and might weigh 32,300-32,500 lbs (14.65-14.74 tonnes) altogether.
Since the original writeup was published, additional details of the Taurus II third stage have also been provided. The stage, equipped with a bipropellant hypergolic pressure-fed propulsion system similar to equipment used by Orbital's Star2bus satellites, has been called an Orbit Raising Kit (ORK). Its design could very well be influenced by the configuration of the guidance and control section used by Orbital Science's Minotaur IV launch vehicle. Minotaur IV is a retired three-stage Peacekeeper missile topped by an Orion 38 fourth stage. The Orion 38 solid motor is mounted to an "Avionics Assembly" that provides attitude control before, during, and after the fourth stage motor burn. On Taurus II, the Castor 30 second stage motor could be mounted in a similar fashion to the ORK third stage. After its burn, the Castor 30 motor could be jettisonned from the ORK, allowing the third stage to provide the final orbit insertion burn and/or orbit raising maneuvers.
It has also become apparant that Orbital Sciences, a company that has not developed a large liquid propellant stage in the past, may be partnering with another company for first stage development. The company's Taurus II web page said that the "design adapts .... hardware from one of the world’s leading launch vehicle integrators". The only kerosene launch vehicle in the world that currently uses a 3.9 meter diameter structure is the Ukrainian-Russian Zenit 2/3 series. The Yuzhnoe Design Bureau of Dniepropetrovsk, Ukraine builds the Zenit tank structure and integrates the overall launch vehicle. It would be accurate to call Yuzhnoe, a company that has probably built and assembled more liquid launch vehicles any other company in the world save one (TsSKB Progress), "one of the world's leading launch vehicle integrators".
Although the original article, reproduced below, mentioned Cape Canaveral's Complex 36 as a possible launch site, it is worth considering (albeit speculatively on my part) that Orbital Sciences has performed a pair of Minotaur I launches from Wallops Island, Virginia, in recent years. Wallops Island, due to its higher latitude, would be a slightly better site to conduct International Space Station launches from than Cape Canaveral. In addition, Wallops Island offers flight azimuths that allow sun synchronous orbit launches - a capability not available at Cape Canaveral. It goes without saying that if only one launch pad could fulfill the needs of the launch program rather than the usual two (one at Canaveral and one at Vandenberg AFB), Taurus II could have lower infrastructure costs.
Finally, since the original article was written, it has become known that Orbital Sciences is one of the final four bidders for NASA's COTS (Commercial Orbital Transportation Services) program. Other bidders include Andrews Space, PlanetSpace, and Spacehab. It is reasonable to assume that Taurus II is part of the Orbital Sciences proposal.
"Были когда-то и мы рысаками!!!"