No Scarcity of Desires: Star-Raker (1978)

Elsewhere on this weblog, I’ve described the Nineteen Seventies joint NASA/Division of Vitality Photo voltaic Energy Satellite tv for pc (SPS) research (see “Extra Info” beneath). Had even a single SPS been assembled, it could have been by far the most important human development mission in area; it could have weighed greater than 100 instances as a lot because the 420-metric-ton (460-U.S.-ton) Worldwide House Station. The SPS research envisioned meeting of two such satellites per 12 months between 2000 and 2030, bringing the entire quantity within the SPS constellation to sixty. 

NASA envisioned boosting SPS parts to low-Earth orbit (LEO) within the payload bays of huge reusable launch automobiles. One such launcher, Boeing’s winged, two-stage House Freighter, would have weighed about 11,000 metric tons (12,125 U.S. tons) at liftoff and delivered about 420 metric tons (463 U.S. tons) to LEO. For comparability, the two-stage Saturn V rocket used to put 77-metric-ton (85-U.S.-ton) Skylab into LEO weighed about 2800 metric tons (3086 U.S. tons) at liftoff.

The House Freighter would have risen vertically from a launch pad and pointed itself usually towards the east. As its first stage, the Booster, expended its propellants, it could have separated. The second stage, the Orbiter, would then have ignited its engines to finish its climb to LEO. In orbit, it could have maneuvered to rendezvous and dock with a big area station designed particularly for dealing with SPS cargo modules.

The House Freighter Booster would have been a completely reusable winged automobile carefully resembling the House Freighter Orbiter. After House Freighter Orbiter separation, the House Freighter Booster would have turned, deployed jet engines, and flown to an extended, large runway at its launch web site. 

To start return to Earth, the House Freighter Orbiter in LEO would have separated from the cargo-handling area station, then would have turned its tail ahead and ignited rocket motors to decelerate, decreasing its orbit in order that it intersected Earth’s ambiance. Following a fiery reentry, it could have landed on the runway close to its launch pad. 

After launch pad, Orbiter, and Booster refurbishment, the 2 House Freighter phases would have been hoisted vertical. After the Orbiter was positioned atop the Booster’s nostril, a cargo module would have been loaded into its payload bay. The House Freighter would then have been moved to a launch pad to start one other flight. Launching components for 2 SPS into LEO in a 12 months would have required about 240 House Freighter launches, or about one launch each 36 hours.

In October 1977, a crew of 14 Rockwell Worldwide engineers studied a House Freighter various. The Star-Raker area aircraft, 103 meters (310 ft) lengthy with a wing span of about 93 meters (280 ft), would have carried a most of 89.2 metric tons (98.3 U.S. tons) of cargo into LEO. Greater than 1100 flights would have been required annually to assist the SPS program, or about one launch each eight hours.

In its totally developed kind, nonetheless, Star-Raker would have had necessary benefits over House Freighter which could have made its required excessive flight fee possible. For instance, it could have begun its flights to LEO by taking off horizontally from a standard 2670-to-4670-meter-long (8000-to-14,000-foot-long) runway at nearly any civilian or army airport able to supporting 747 or C-5A Galaxy cargo planes. No specialised launch and touchdown web site would have been required.

Each bit as necessary, Star-Raker would have been able to flying routinely between such airports. The Rockwell crew defined that this could “scale back the variety of operations required to move materials and tools from their place of manufacture on Earth to [LEO].” For instance, rolls of photo voltaic cell blankets wouldn’t should be shipped by prepare, barge, or aircraft to a specialised launch and touchdown web site; they might, doubtlessly, want solely be transported to a neighborhood airport for Star-Raker pickup.

Although the 1977-1978 Star-Raker examine centered on its attainable use within the Division of Vitality/NASA Photo voltaic Energy Satellite tv for pc program, Star-Raker would have had potential as a general-purpose area cargo aircraft. Within the picture above, three Star-Rakers, their nostril sections hinged again to reveal their cargo bays, tackle payloads sure for locations starting from low-Earth orbit to deep area. Picture credit score: M. Alvarez/Rockwell Worldwide.

David Reed, an engineer at North American Rockwell (NAR), as the corporate was then identified, originated the Star-Raker idea in 1968, as NASA started earnest efforts to develop a reusable House Shuttle. Key components of the idea had been proposed — and rejected — earlier within the Nineteen Sixties decade. These included wings full of light-weight structurally integral tanks holding liquid hydrogen gasoline and liquid oxygen oxidizer and a posh jet engine/rocket engine propulsion system.

The 1968-1969 examine decided that, because it burned the propellants in its wings and maneuvered by way of ascent from subsonic velocity to Mach 6 (six instances the velocity of sound), aerodynamic strain on its construction would turn into extreme. This led NAR to look at wing designs developed in 1970 for the proposed (and subsequently deserted) U.S. Supersonic Transport program. 

A “tridelta flying wing” design appeared to resolve the strain drawback; by then, nonetheless, NASA had narrowed its Shuttle design necessities, excluding Star-Raker from consideration. NAR continued Shuttle research and have become Shuttle prime contractor in July 1972. 

Rockwell revived examine of the tridelta flying wing Star-Raker as SPS research ramped up in 1976. The Star-Raker examine that started in October 1977, led by Reed and carried out for NASA Marshall House Flight Heart (MSFC) in Huntsville, Alabama, continued into late 1978, yielding the design described on this submit.  

The 1977-1978 examine benefited from laptop modeling that enabled Rockwell to additional refine Star-Raker wing form and flight profile. It additionally allowed Reed’s crew to take extra totally under consideration the advantages of propellant-saving “lifting ascent.” 

Star-Raker’s propellants, liquid hydrogen and liquid oxygen, weren’t sometimes discovered at airports in 1977-1978; this stays true in 2020. The Star-Raker examine crew may need assumed that airports would evolve to supply them by the point SPS cargo flights started in 2000. This might, maybe, not have been an unreasonable assumption, provided that the 30-year SPS program was anticipated to create a profitable new trade spanning the continental United States. 

One Star-Raker takes off as one other undergoes airport servicing. With its touchdown gear prolonged, Star-Raker floor clearance would have been 1.52 meters (5 ft). Picture credit score: M. Alvarez/Rockwell Worldwide.

For the 1977-1978 examine, nonetheless, they hedged their bets by assuming that liquid hydrogen gasoline could be obtainable at airports solely in ample portions for airport-to-airport subsonic air-breathing jet engine Star-Raker flights. Liquid oxygen would, in fact, not have been required. Flights to LEO, which might have wanted each propellants in massive portions, would have begun on a runway at NASA’s Kennedy House Heart (KSC) in Florida, at Vandenberg Air Drive Base, California, or at every other launch websites the U.S. may need deigned to determine. 

The propellant tanks in Star-Raker’s wings would have been roughly conical in form. They’d have prolonged from the area aircraft’s physique to its wing suggestions and been designed to strengthen the wings with minimal weight penalty. They’d have been bolstered with frequently spaced “cell internet” partitions. Foam-filled glass-fiber honeycomb would have surrounded the tanks, defining Star-Raker’s form.

The Rockwell crew described intimately a Star-Raker flight from KSC to 556-kilometer-high (345-mile-high) LEO and again to a U.S. airport. It could have begun with arrival at KSC of a Star-Raker area aircraft loaded with cargo sure for LEO on the finish of a subsonic flight from a standard airport. 

Following a restricted airplane-type checkout, crews would have put in three units of jettisonable orbital-takeoff fundamental touchdown gear, every with eight wheels, and pumped liquid hydrogen and liquid oxygen propellants into Star-Raker’s tanks. Absolutely loaded with propellants and cargo and with its orbital-takeoff gear hooked up, Star-Raker would have weighed about 1935 metric tons (2130 U.S. tons). 

Star-Raker would have lifted off from the runway at a velocity of 415 kilometers per hour (260 miles per hour) underneath “supercharged afterburner” energy from its 10 multicycle jet engines. The Rockwell crew defined that it had consulted with main jet engine producers to reach at its jet engine design; these included Basic Electrical, Pratt & Whitney, Aerojet, Marquardt, and Rocketdyne. The ensuing engine was extra a want listing than a agency design, although it was an knowledgeable want listing. 

The Rockwell crew envisioned 4 operational cycles for its jet engine starting from typical turbofan to ramjet. Liquid hydrogen would have been used to chill the engine after which burned as gasoline. Massive, slot-shaped inlets on the underside of Star-Raker’s wings, organized in two teams of 5 on both facet of the area aircraft’s physique, would have funneled air to the engines, which might have been mounted on the wing trailing edge. The inlets would have been outfitted with “ramp” doorways that might shut partially or totally to average or halt airflow.

Shortly after leaving the bottom, the area aircraft’s crew would have dropped the three units of orbital-takeoff touchdown gear (they might have lowered to the bottom on parachutes for restoration and reuse), then would have retracted its nostril and fundamental touchdown gear. The area aircraft would then have switched its jet engines to turbofan energy, climbed to 6100-meter (20,000-foot) cruise altitude, and elevated its velocity to Mach 0.85. It could have turned due south and, over the following hour and fifty minutes, flown on to Earth’s equator.

Star-Raker would have flown to the equator and turned east in order that it may get a lift from Earth’s rotational velocity, which at our planet’s midriff can, in idea, add about 1600 kilometers (1000 miles) per hour to the orbital velocity of ascending launch automobiles. 

As well as, and extra importantly, the turbofan flight to the equator would have amounted to a plane-change maneuver; that’s, it could have enabled Star-Raker to succeed in equatorial LEO with out performing the rocket-propelled plane-change maneuver in LEO required if Star-Raker flew on to orbit from a non-equatorial launch web site, corresponding to KSC. The Rockwell crew hoped that this could save propellants, enabling a rise in cargo weight.

Following the eastward flip, the area aircraft would have climbed to 13,710 meters (45,000 ft) underneath supercharged afterburner energy, then would have begun a shallow dive to 11,280 meters (37,000 ft). Through the powered dive, a propellant-saving maneuver, Earth’s gravity would have helped it to interrupt the sound barrier and speed up to Mach 1.2. 

Go for orbit: the Star-Raker area aircraft design included 10 multicycle air-breathing jet engines, three high-pressure rocket engines akin to the House Shuttle Predominant Engine, and two superior Orbital Maneuvering System rocket engines. Within the picture above, the ten jet engines are throttling as much as start the transition to supersonic flight. Picture credit score: M. Alvarez/Rockwell Worldwide.

Star-Raker would then have begun ascent to orbit in earnest, with a supersonic climb to 29 kilometers (18 miles). Throughout this section, the area aircraft’s jet engines would have throttled as much as “full ramjet” energy, accelerating it to Mach 6.2. All through its climb to orbit, Star-Raker would have maneuvered to place to good use elevate offered by its wings. 

Upon reaching Mach 6.2, the three rocket motors in Star-Raker’s tail would have ignited, including rocket energy to ramjet energy. The three engines, with a mixed thrust of 1.45 million kilograms (3.2 million kilos), would have drawn liquid hydrogen from a sturdy tank positioned on the aft finish of the lengthy, slender Star-Raker cargo bay. The tank, to which the engines would have been mounted, would have served because the load path that will have distributed their thrust to the area aircraft’s construction.

At Mach 7.2, Star-Raker would have switched to full rocket energy. Because it throttled up the rocket motors to full thrust, it could have shut down the jet engines and closed fully their air inlet doorways. 

When Star-Raker reached a 51-kilometer-by-556-kilometer (32-mile-by-345-mile) equatorial orbit, the principle rocket motors would have shut down. At apogee, the excessive level in its orbit, the crew would have ignited the dual superior Orbital Maneuvering System (OMS) engines on the base of its tail to lift its perigee (orbit low level) and circularize its orbit. Upon attainment of round equatorial orbit, Star-Raker would have used the OMS to maneuver to a rendezvous with the SPS cargo-handling area station.

Star-Raker in low-Earth orbit. Picture credit score: M. Alvarez/Rockwell Worldwide.

The load of cargo Star-Raker may carry would rely upon its mission profile. For the profile described right here, cargo weight delivered to orbit would have amounted to solely about 48.6 metric tons (53.6 U.S. tons). The aerodynamic flight to the equator underneath jet energy, meant to steal a number of the Earth’s rotational vitality and keep away from a aircraft change maneuver in LEO, had underneath shut examination turned out to be costly. 

The Rockwell crew proposed enhancing the equatorial profile’s payload efficiency by loading liquid oxygen on the equator, both throughout flight utilizing a new-design tanker plane, or after a touchdown at an equatorial facility with an ample runway, orbital-takeoff gear attachment and restoration functionality, and skill to supply liquid oxygen. Both method would, nonetheless, have difficult Star-Raker operations.

To unload cargo, Star-Raker would have swung its nostril, which might have contained its crew compartment, sideways out of the way in which, exposing one finish of its six-meter-high-by-six-meter-wide-by-43-meter-long (20-foot-high-by-20-foot-wide-by-141.5-foot-long) cargo bay. The bay’s arched ceiling would have made it a degree of structural power, not weak spot, within the Star-Raker design.

The crew would have moved to the rear of the crew compartment to help with cargo switch. Home windows on the rear of the two-deck crew compartment would have offered a 121° discipline of visibility. 

The Rockwell crew didn’t describe its cargo switch system in any element, although it’s clear that Star-Raker wouldn’t have docked within the typical sense. Temporary point out was made from a switch rail system within the cargo bay that will have linked to equal rails on the area station.

Return to Earth would have begun with cargo bay closure. After shifting away from the area station, the crew would have turned Star-Raker in order that its tail confronted in its course of orbital movement, then would have fired its OMS engines to decelerate. 

Most deceleration through the unhurried shallow-angle reentry would have reached not more than 2.3 gravities. Star-Raker would, generally, have skilled reentry temperatures decrease than the House Shuttle Orbiter, although nostril and wing modern temperatures have been anticipated be considerably increased. The upper modern temperature was attributable to its comparatively blunt form. 

The Rockwell crew proposed two varieties of reusable Thermal Safety System (TPS) for Star-Raker. Each would have been mounted on an outer going through sheet overlaying a honeycomb layer. The honeycomb layer would in flip have been hooked up to an inside going through sheet overlaying the honeycomb core that surrounded the propellant tanks.

The primary TPS design carefully resembled that baselined for the House Shuttle Orbiter. Ceramic tiles individually molded and milled to match Star-Raker’s curves would have been glued to material strain-isolator pads affixed to the outer going through sheet. 

The second TPS design, much like one developed for the B-1 Bomber, was extra complicated. Metallic panels — titanium-aluminum for low-temperature areas and “superalloy” for high-temperature areas — would have been hooked up to the outer going through sheet utilizing versatile standoffs. The standoffs would have permitted the overlapping panel edges to slip over one another as they grew sizzling and expanded or cooled and contracted. Foil-wrapped thermal insulation blankets affixed to the outer going through sheet would have offered extra thermal safety.

Each TPS designs would have included a system for detecting breaches within the TPS. The Rockwell crew offered no particulars of its design and didn’t describe what the crew would possibly do if a breach have been detected.

Star-Raker on method. Picture credit score: M. Alvarez/Rockwell Worldwide.

When Star-Raker slowed to Mach 6, it could have begun cross-range maneuvers designed to shed vitality and sluggish it to Mach 0.85. The crew would then have opened the inlet ramps and began “some” of its jet engines. 

The Rockwell crew offered the area aircraft with sufficient liquid hydrogen to allow a 556-kilometer (345-mile) subsonic cruise and two powered touchdown makes an attempt. Touchdown velocity would have been about 215 kilometers per hour (135 miles per hour). At wheels cease at an airport able to supporting a cargo 747 or a C-5A Galaxy, Star-Raker would have weighed about 281 metric tons (310 U.S. tons).

Star-Raker weights given on this flight description are primarily based on information the Rockwell crew generated within the interval spanning December 1977-January 1978. In February-March 1978, NASA MSFC and NASA Langley Analysis Heart (LaRC) in Hampton, Virginia, reviewed the Rockwell crew’s Star-Raker weight numbers. 

The NASA facilities discovered that Rockwell’s estimates have been low if “regular” expertise have been assumed and excessive if “acceleration” (superior) expertise have been assumed. Whereas Rockwell had positioned Star-Raker’s “dry” weight with orbital-takeoff gear at 293.5 metric tons (323.5 U.S. tons), MSFC/LaRC decided that, with regular expertise and a ten% cushion for weight progress throughout growth, Star-Raker would weigh 407.6 metric tons (449.3 U.S. tons) with out propellants; with superior expertise and the cushion, it could weigh solely 257.6 metric tons (284 U.S. tons). 

The Rockwell crew and NASA MSFC engineers met in Might 1978 to attempt to reconcile the load estimates. They made one necessary change in Star-Raker’s flight profile: they deserted the subsonic flight to the equator in favor of a KSC launch and direct climb to a 556-kilometer (345-mile) LEO inclined 28.5° relative to Earth’s equator (that’s, the latitude of KSC). 

The NASA and Rockwell groups settled on a Star-Raker weight with out propellants (however with orbital-takeoff gear and 10% cushion) of 330.4 metric tons (364.2 U.S. tons). Because it started ascent to orbit on a KSC runway, the area aircraft would have weighed 2280.5 metric tons (2514 U.S. tons). Of this, Star-Raker’s most weight, 89.2 metric tons (98.3 U.S. tons) would have comprised cargo for the SPS mission.

Sources

Unbiased Analysis and Improvement Information Sheet, Challenge Title: Earth-to-LEO Transportation System for SPS, Rockwell Worldwide, 15 December 1978.

“Star-Raker: An Airbreather/Rocket-Powered, Horizontal Takeoff Tridelta Flying Wing, Single-Stage-to-Orbit Transportation System,” SSD 79-0082, D. Reed, H. Ikawa, and J. Sadunas, North American Rockwell House Methods Division; paper offered on the American Institute of Aeronautics & Astronautics Convention on Superior Know-how for Future House Methods in Hampton, Virginia, 8-11 Might 1979.

Extra Info

Electrical energy from House: The Nineteen Seventies DOE/NASA Photo voltaic Energy Satellite tv for pc Research

NASA Johnson House Heart’s Shuttle II (1988)