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Chrysaor

Two Stage Air Launched Rocket System

Space Vehicle Design Project

Professor Anderson

MAE 155A

Winter 2015

Torin Bowman

Garrett Onaga

Danny Shin

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Background

The development of air-launched vehicles began as early as the 1940’s with launches of

experimental aircraft. One such early air-launched system consisted of an M-21, a variant of the

A-12 which would later become the SR-71, modified to carry a D-21 drone. The idea of an air-

launched drone came about because of a treaty signed by the US to end flights of manned

vehicles over the Soviet Union, and the need for an unmanned reconnaissance vehicle

arose[1]. Instead of piloting SR-71s behind enemy lines, an M-21 would be piloted to the

enemy’s borders, and the D-21 would be launched autonomously across the enemy’s territory,

capturing images of nuclear silos, munitions factories, and troop movement. The D-21 would

then fly to a nearby ally territory and unload its film cartridge. However, launching the D-21

from the M-21 came to be a big problem for Lockheed’s Skunk Works as the M-21’s cruising

speed was Mach 3.3. At such great speeds, anything less than a perfect launch would result in a

catastrophic failure, as was the case when a D-21 failed to completely detach, hit one of the M-

21’s vertical stabilizers, and completely tore the aircraft apart.

Following the development of air-launched drones, the creation of air-launch to orbit

vehicles soon came into existence. The most famous of these vehicles is Orbital’s Pegasus, a

three-stage air-launched all-solid expendable launch system. The first Pegasus was successfully

launched on April 5, 1990[2]. It, along with 3 other successful Pegasus campaigns, was launched

from beneath a NASA B-52 aircraft. The Pegasus was then modified into the stretched and more

powerful Pegasus-XL, which was launched from a Lockheed L-1011 aircraft. The Pegasus was

and is still used to deploy small satellites weighing up to 1000lbs into low earth orbit. It is

carried to approximately 40,000ft where it is released and free-falls five seconds before igniting

its first stage rocket motor. In all, the Pegasus air-launch system has carried out 42 missions,

launching 86 satellites[3].

The three main advantages of an air-launched system over ground/sea based systems

include:

1. Avoiding the earliest part of a launch vehicle’s flight regime, where rockets suffer

significant performance degradation.

2. Avoiding unfavorable launch conditions.

3. And avoiding heavily populated areas.

In the earliest stages of their launch, ground/sea based vehicles suffer significant

performance degradation that an air-launched vehicle can avoid by starting with a higher initial

altitude and velocity. These performance losses are due for the most part to fighting against

Earth’s gravity, in addition to atmospheric drag losses caused by the denser atmosphere at lower

altitudes. The main losses of a ground-launched vehicle occur during the first 10 km of

ascent. According to NASA Spaceflight[4], “By the time the Space Shuttle had reached the

conditions of an air launched system, it had already burned 25 percent of its propellant, yet it had

only added 0.16 percent to its required kinetic energy.” By using air-launched systems,

propellant can be conserved because the air-breathing carrier aircraft can lift the rocket to

altitudes much more efficiently with engines that don’t require the onboard storage of an

oxidizer. This reduction in propellant mass allows for a larger payload mass, ultimately reducing

payload launch costs for customers.

In addition to avoiding the early stages of a ground/sea launch, air-launched systems also

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allow for fewer constraints to launch sites. This allows for avoidance of both bad weather

conditions and populated areas. In recent news, SpaceX had to delay a few of their cargo

resupply missions to the ISS due to unfavorable launch conditions regarding the weather. If the

area around the launch pad is too windy, for example, the wind may set the rocket off course,

possibly even aiming it inland. Because air-launched systems can be deployed over oceans,

launching payloads around heavily populated areas can be avoided, which can in turn save

thousands of lives in the case of a catastrophic failure. The advantage of reusability also comes

into play, as the carrier, technically the first stage, would be reusable. This is a great advantage

as it saves a great deal in not only funds, but also resources.

Figure (1.1): Ground-launched rocket performance losses (from NASA Spaceflight[4])

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Concept of Operation

Introduced and engineered to be a strategic bomber, North American’s XB-70’s speed

and large payload capacity (288,200lb) makes it a great aircraft to serve as an air-launch-rocket

carrier. The XB-70 will be acquired from the National Museum of the United States Air Force in

Dayton, Ohio[5]. It can take Chrysaor (156,224lb) to an altitude of over 65,000ft, while travelling

at a speed of over 1,800mph. The XB-70’s landing gear has a height of 8 feet 8 inches allowing a

foot of clearance between the ground and Chrysaor (diameter: 7 feet 8 inches) during takeoff. In

addition the width between the two rear landing gear structures (18 feet 3 inches) allows for

plenty of room for Chrysaor. As the carrier variant of the XB-70 will have no use for its weapons

bay, it will be converted to the hard point for Chrysaor. The current weapons bay will be gutted

and have its doors removed so that it can be retrofitted with an attachment structure for Chrysaor.

A lightweight structure comprised of titanium struts will be welded onto the bulkheads shown

visible in the weapons bay. A stainless steel skin, keeping the material consistency of the rest of

the vehicle’s fuselage, will act as an aerodynamic seal and cover the structure to blend it in with

the rest of the vehicle and effectively reduce its drag. Chrysaor will be launched by the pilot in

the same fashion as any conventional bomb the XB-70 was manufactured to drop, but instead of

descending, it will fire its first stage five seconds after deployment and ascend into orbit.

Chrysaor consists of two stages of motors and a wing attached to the second stage

structure. In the first stage, a Castor 120 solid-propellant motor is automatically ignited 5

seconds after Chrysaor is deployed from the bottom of the XB-70 carrier aircraft. During this

stage, elevators and a rudder on the rear fins of the vehicle are used to control its pitch and yaw,

keeping the flight path angle at 19° and flight path heading at 109.5°. In addition, a vector-able

nozzle on the Castor 120 engine allows for more control during the burn time. After the first

stage burns, it will be detached revealing a second set of fins on the rear of the second stage

structure. Chrysaor will then coast for 300 seconds with the help of the wing as it gains altitude

before igniting stage 2. In the second stage, a LCS III liquid-propellant motor designed for

ignition beyond an altitude of 85,000ft[6] will be used to accelerate Chrysaor into orbit. During

this stage, the will again control the pitch and yaw of the vehicle keeping the flight path angle

and heading at 0.02° and 75.0°, respectively. Once the second stage has been completely

burned, the LCS III motor along with the wing will be detached leaving only the payload

structure to coast into orbit. After about 800 seconds from the initial drop, the payload structure

will reach an altitude of 607,000ft where a control system will level out the flight path angle

back to 0°. The 5000lb payload will enter its orbit with a final velocity of just under 20,000mph

(8623m/s).

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Flight Profile

Chrysaor is a two stage air launched rocket system designed to put payloads of 5000lbs

into orbit. Graphs of the overall flight profile can be found in figures 2.1 and 2.2. The vehicle is

approximately 58ft long with a 92in diameter body and a wingspan of roughly 470in. The

payload compartment is just over 197ft3 and is incorporated into the front section and nose cone

of Chrysaor, exact vehicle dimensions can be found in table 3.3. Chrysaor is launched with an

initial weight of 156,226lbs from the XB-70 Valkyrie carrier aircraft and is designed for a 800s

(13min 20s) mission into space.

The launch sequence begins with the release of Chrysaor from the carrier aircraft at an

altitude of roughly 72,000ft (21.95km) and a speed of 1,863mph (Mach 2.8.) After

approximately 5 seconds and once Chrysaor has cleared the carrier aircraft, engine 1 is

automatically ignited. Specifications for engine 1 and engine 2 can be found in table 2.4. The

Castor 120 stage 1 engine begins burning providing approximately 379,000lbf of thrust and

Chrysaor begins climbing with a vertical flight path angle of 19° and a heading of 109.5°.

After 79.4 seconds of burn time engine 1 is ejected at an altitude of approximately 71km

and a velocity of 8,164mph (Mach 12.) After stage 1 separation the total weight of the vehicle is

roughly 50,470lbs. Chrysaor then coasts for a full 300 seconds (5 min) during which time it

descends to an altitude of just under 100 km while keeping a roughly constant velocity.

Once the mission time has reached 384.4 seconds stage 2 is ignited. Stage 2 consists of

the LCS III liquid propellant motor which produces 63,700lbf of thrust. As the LCS III motor is

ignited Chrysaor orientates itself to a vertical flight path angle of 0.02° and a heading of 75°.

Stage 2 burns for 133 seconds at the end of which it is ejected leaving only the payload which

will achieve the target orbital insertion parameters by the end of the 800 second (13 min 20 s)

mission time.

Under the starting conditions and the payload specified, Chrysaor will place the payload

into orbit with a final velocity of 19,290 mph (8623.41 m/s) at an altitude of 608,000ft (185,343

m). Furthermore it will achieve an orbital insertion point with a 28.277° inclination, a flight path

heading of 93.44° and a vertical flight path angle of 0.0138°. These values give an orbital

eccentricity of 0.224 along with a semi major axis of 525.68miles (846 km). Finally, it should be

noted that the simulated flight profile gives a final weight of 14,218.23lbs which is over the

desired 5,000lb payload capacity. This discrepancy represents the ability of Chrysaor to put

much heavier payloads into orbit if necessary. Exact mission parameters for each critical stage of

the flight can be found in table 2.3.

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Figure(2.1): Chrysaor Flight Profile 1 (Graphs made with MATLAB[7])

Figure(2.2): Chrysaor Flight Profile 2 (Graphs made with MATLAB[7])

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Table(2.3): Chrysaor Flight Profile Stage Values

Drop Point Post Stage 1 Start Stage 2 Post Stage 2 Final Position

Weight (lbf) 156,224 50,469.88 34,220.89 6,883.23 14,218.23

Velocity (m/s) 832.80 3649.7 3651.19 8337.24 8623.41

Altitude (km) 21.95 71.15 98.97 98.17 185.34

Heading (deg) 109.5 110.152 75 77.848 93.44

Flight Angle (deg) 19 19 0.02 0.02 0.01378

Mission Time (s) 5 85 385 515 800

Table(2.4): Chrysaor Motor Specifications

Diameter

(in) Length

(in) Burn

Time (s) Specific

Impulse (s) Average

Thrust (lbf) Total

Weight

(lbf)

Propellant

Weight (lbf) Structural

Ratio*

Castor 120 92 955 79.4 280 379,000 166,993 107,914 0.05

LCS III 92.1 164.5 133 300.3 63,730 31,307 28,278 0.05

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Vehicle Configuration Figure(3.1): Chrysaor attached to XB-70 Valkyrie Carrier Aircraft (Graphs made with Google SketchUp[8])

Figure(3.2): Dimensions and Key Components of Chrysaor (Graphs made with Google SketchUp[8])

Table(3.3): Chrysaor Spec Sheet

Units Diameter Length Wing Span Initial Weight Payload

Volume

Payload

Weight

English 92.1in 696.6875in 470.3in 156,226.15lbs 341158.7in3 5000lbs

English 7’ 8.1” 58’ 0.6875” 39’ 2.3” 156,226.15lbs 197.4298ft3 5000lbs

Metric 2.339m 17.69586m 11.946m 70,862.98922kg 5.59m3 5000lbs

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Environmental and Economic Impact

One of the advantages of a carrier launched system, when compared to a standard rocket

launch, involves the associated cost of reaching earth’s orbit. The carrier launched system

becomes more cost efficient by allowing propellant to be conserved because the air breathing

carrier aircraft lifts the rocket to altitude much more efficiently with the use of engines that do

not require on-board storage of an oxidizer. This allows the launch system to conserve a

significant amount of mass that would otherwise be reserved for fuel, reducing the overall size.

To put the mass of the propellant into perspective, the first stage of the Saturn V rocket had a dry

weight of about 289,000lbs and fully fueled at launch had a total weight of 5,100,000lbs,

meaning 94.33% of the first stage consisted of fuel. A larger fraction of the rocket mass can then

include payload, reducing payload launch costs.[8] Also, these carriers can also be used over and

over again, unlike booster rockets that are currently only single use. According to NASA, the

first stage of SpaceX’s Falcon 9 cost a whopping $701 million in 2010, and that was before tests

for the Falcon 9 Reusable started.[10] The XB-70, in comparison, costs $750 million and can be

reused multiple times, paying for itself in funds saved in less than two missions.

A consequence of launching payloads into orbit arises in the form of environmental

impacts. Interestingly, spacecraft contribute very little to the global ozone problem. In a recent

paper on the topic, researcher Martin Ross and three co-authors estimated that rocket launches

are responsible for roughly only 1 percent of the total ozone depletion that can be attributed to

human causes. The exhaust from space-ship engines does add several kilotons of carbon dioxide

to the atmosphere every year. But that's just a smidgen compared with the several hundred

kilotons produced by aircraft, as Ross and his co-authors point out. Aircraft, in turn, are

responsible for just 2 percent to 5 percent of the world's CO2 emissions.[11] These negative

contributions to the environment such as CO2, although seemingly large, are relatively negligible

when compared to the car industry’s contribution of 30% of CO2 emissions in the United

States.[12]

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Risk and Regulatory Assessment

With the utilization of the XB-70, Chrysaor can be launched from virtually anywhere in

the world, reducing the risk of safety should it drift off course. Regulatory procedures for

launching Chrysaor will require it to be ignited overseas. This will greatly reduce the expected

number of casualties in the event of a catastrophic failure considering that Chrysaor will not be

launched over any populated areas, or any habitable areas for that matter. However, should

Chrysaor sense any anomalies during its mission, it will self-destruct. For example, if the

onboard angular rate gyroscopes, accelerometers, or magnetometers sense any drift in its flight

path that is too difficult to overcome, Chrysaor will self-destruct, preventing it from potentially

becoming a ballistic missile aimed towards a populated area. In addition, since the XB-70’s very

high cruising altitude allows for the launch to be initiated beyond 20 kilometers, there is a

significant time allowed for Chrysaor to abort once it is dropped.

One of the largest risks of Chrysaor’s mission is the initial drop from the XB-70 because

it is launched at such a high velocity (Mach 2.8). For example, the M-21 proved to have

difficulties launching the D-21 drone at similar speeds as discussed earlier; however, the drone

was launched from the top of the M-21. In contrast to the D-21 drone, Chrysaor is dropped from

below the XB-70 aircraft and allows for 5 seconds before its first stage is ignited. This allows

the military high performance bomber plenty of time to change its course away from Chrysaor’s

flight path. Since such a high risk comes with the initial drop, regulatory assessment and

maintenance will be required on the retrofitted structure that attaches Chrysaor to the XB-

70. This structure will be made specifically for Chrysaor and therefore perfected. Another

possibility of risk occurs with the use of multiple stages. Utilizing multiple stages increases the

possibility of error because the number of variables in the mission increases. For example, the

first stage may ignite, but the second stage may not, or may even ignite before it detaches from

the first stage. These problems will be averted through the strenuous testing and optimization of

the controls and systems onboard Chrysaor. The use of Castor and LCS motors that have been

flight proven (Castor 120) and qualified at simulated altitude (LCS III) also increases the

reliability of the propulsion system.

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References:

1Kucher, P. R. “M-21 Blackbird,” SR-71 Online, An Online Aircraft Museum [online

database], URL: http://www.sr-71.org/blackbird/m-21.php [cited 1 February 2015].

2Brown, S. F., “Winging It Into Space,” Popular Science, May 1989, pp. 126-128.

3“Pegasus,” Orbital Science Corporation, URL:

http://www.orbital.com/LaunchSystems/SpaceLaunchVehicles/Pegasus/ [cited 1 Fevruary 2015].

4Bergin, C. and Graham W., “Commercial Space Flight Shows Reignited Interest in the

Air Launch System,” Nasa Spaceflight, 13 July 2012, URL:

http://www.nasaspaceflight.com/2012/07/commercial-shows-reignited-interest-air-launch-

system/ [cited 1 February 2015].

5“North American XB-70 Valkryie,” National Museum of the United States Air Force

[online database], URL: http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=592

[cited 1 February 2015].

6“ATK Space Propulsion Products Catalog,” ATK, 7 August 2012, pp. 29-33.

7MATLAB, Software Package, Student 2014a, The MathWorks, Inc., Natick, MA, 2015.

8Google SketchUp, Software Package, 2013, Google, Mountain View, CA, 2015.

9Duncan, John. "The Saturn V." The Saturn V. N.p., 8 July 1999. Web. 1 Feb. 2015.

10Falcon 9 Launch Vehicle (n.d.): n. pag. NASA.gov. NASA, Aug. 2011. Web. 1 Feb.

2015.

11Rastogi, Nina. "What Impact Do Rockets Have on the Environment?"Slate.com. Slate,

17 Nov. 2009. Web. 01 Feb. 2015.

12"Car Emissions and Global Warming." Union of Concerned Scientists. Union of

Concerned Scientists, n.d. Web. 1 Feb. 2015.