Space-Based Force Application: A Technical View

Dr. Laura GregoUnion of Concerned Scientists

Outer Space & International Security: Options for the Future

29 October 2003

Case Study: Military Space Plane

Much of this analysis is relevant to space-basing generally.

MSP missions are closely related to DARPA’s Project Falcon (Force Application and Launch from the CONUS).

R&D for some of the key technologies conducted also

under Air Force, NASA

Funding is at a low level, however the program does have an impact on the perception of US intentions; Chinese press has much discussion of the US “space bomber.”

Case Study: Military Space Plane

• Missions – Prompt, global, precision strike capability– Rapid unpredictable reconnaissance– Spacelift for augmenting and reconstituting space assets– Space control (ASAT) and missile defense roles– Not designed to carry humans

• Desired capability: – Rapid, affordable, and on demand (within 5 to 12 hours) space-

launch capability – Ability to place a variety of payloads into LEO – Ability to deploy the Common Aero Vehicle (CAV)– Maneuverability in orbit

Desired Future Launch Vehicle

• Space Operation Vehicle (SOV)

• Goal is ability to place a 5-6 ton upper stage in LEO

• Lift capability is 1/3 that of Atlas 5 or Ariane 5

• Reusable, single-stage-to-orbit

• Goal is reduce costs, reduce time between launches

• Technology is probably 2 decades away

Space Maneuver Vehicle (SMV)

• Possible reusable upper stage of MSP

• Length ~ 10 m (Space Shuttle: 37 m)• Mass 6-8 tons (Space Shuttle: 94 tons)• Cargo bay 2-3 m (Space Shuttle: 18m)• Total V ~ 3-4 km/s (6 km/s with extra tanks) • Proposed to carry payload of 1-2 tons

(Space Shuttle payload ~ 20 tons in LEO)

• Could carry sensors, deploy satellites, deploy CAVs, etc.

• Expected to draw on technology of X-37 Orbital Vehicle planned for fight test in FY2006

• Development time unknown

• Conventional satellite buses currently provide similar maneuverability. However…

SMV Maneuvering is Limited• Total V = 3-4 km/s

• Some fuel is needed to de-orbit and return to earth (~1 km/s for 500 km altitude)

• Remaining V is only enough to:

– change inclination of orbital plane by 20-25o

– rotate orbital plane at constant inclination by 25-30o

• SMV could not change its orbit by more than this, so its role as “space bomber” or “maneuvering reconnaissance” would be limited

• SMV could not deploy satellites into orbits that differed by more than this, so launch of multiple SMVs would be required

• Would have significant capability to change orbital altitude in a given plane (changing altitude from 400 to 1000 km requires V = 0.32 km/s)

Common Aero Vehicle (CAV)

• Goals: – long-range non-nuclear attacks– launched in various ways (ballistic missile,

MSP, from orbit)– deliver many different payloads with high

accuracy

• Aerodynamic lift would give high maneuverability and lateral reach upon re-entry to atmosphere

• Conventional attacks require very high accuracy– Goal said to be CEP = 3 meters– Requires active guidance and very good control– Not currently feasible (CEP for ballistic missile

warheads 1-2 orders of magnitude larger than 3 m.)

• Basing in space does not make sense…

Space-based Delivery of CAVs (1)• Assume CAV in 500-km orbit (speed = 7.6 km/s, period = 94 min)

• Assume CAV can reach laterally 2000 km using lift on re-entry

• To give global coverage, use polar orbits:– 5 orbital planes with 1 satellite per plane will allow an attack of any

point on earth within about 100 minutes (5 total satellites)

– 5 orbital planes with 5 satellite per plane will allow an attack of any point on earth within about 30 minutes (25 total satellites)

• For no coverage above 50o latitude and longer revisit times near the equator, can use orbits inclined to about 50o:– Optimizes coverage between about 15o-50o

– Can cover the earth with 3 orbital planes (15 satellites for 30 minute response time)

Space-based Delivery of CAVs (2)

• Assuming V ~ 1.5-2 km/s is needed by CAV to de-orbit quickly, the fuel needed will roughly double the mass of the payload to be delivered

• In addition, a “garage” will be needed to house the CAV in space

• Total mass in orbit per ton of delivered payload is 2-2.5 tons (very conservative, assumes no mass for CAV itself)

global coverage capable of delivering 1 ton in 30 minutes to a target on earth would require 50-60 tons of material in orbit

Space-Based Delivery of CAVs

global coverage capable of delivering 1 ton in 30 minutes to a target on earth would require 50-60 tons of material in orbit

Comparison to Delivery by Ballistic Missile:

• A missile can put roughly half as much mass in orbit as it can put on an intercontinental trajectory

• As a result, for the same attack (mass on target, attack time) space-based delivery requires more than 100 times as much launch capacity as delivery by ballistic missile

These conclusions are easily generalized to other systems. In general, timely delivery from space is very inefficient compared to ground-based delivery.

CAV: Force Application MissionsMore particular to the MSP:The CAV is designed to deliver a 450 kg payload, which may include(1) An earth penetrator to attack hard/deeply buried objects(2) A kinetic energy weapon (destructs with force of impact)(3) Conventional ordnance/smart bombs (e.g., to attack mobile targets)

Technical issues with reentry (at ~7 km/s) into the atmosphere from orbit or from a ballistic trajectory:

• For (2) KEW require high speeds (at 3 km/s ~ to same mass of explosives) and very high accuracymanaging heat load and communication (radio communication very difficult until v<~4.5 km/s) technically difficult

• For (1) and (3), CAV to slow weapon in the upper atmosphere to avoid heating, permits communication and leaves time for maneuvering

• For (1) EPW effectiveness maxes out at ~1 km/s; higher vlower depth (10-15 meters max); no advantage to high entry speed

Conclusions

The force-application missions of the MSP could be carried out with ballistic missiles (forward-based or from the

CONUS) which would provide the global reach and timeliness required without the vulnerability and enormous additional expense of space-basing.

The technical challenges to CAV remain when deployed by ballistic missile.

The MSP concept combines accepted and potentially stabilizing space missions (e.g., deployment of reconnaissance satellites, rapid replenishment of space assets) which can be completed with existing technology with controversial activities (e.g., precision earth-directed weapons) which rely on technology yet to be developed. Unnecessarily threatening?