HydrogenHydrogen FuelledFuelled PrePre--CooledCooled JetJet EnginesEngines AA PresentationPresentation toto thethe RoyalRoyal AeronauticalAeronautical SocietySociety 33 JuneJune 20082008

Alan Bond, Managing Director Ltd Origins Early 1950s view of the route to space.

A fully reusable transport infrastructure. X-15 with B52 Mother ship.

199 flights between 1959 and 1968.

A fully reusable Spaceplane. Reusable launcher concepts of the late 1960s and early 1970s

..we thought we would have this .. But:- Can We Consider Single Stage Vehicles? Earth is marginally too big to admit an effective SSTO rocket with near term materials technology, discounting the use of ozone or fluorine.

Use must be made of the lower atmosphere for both its chemical potential and reaction mass.

(Nuclear propulsion is the subject of a different lecture!) Stagnation Temperature increases with Mach number

2 T = 220 1+ 0.2M N X-43A Scramjet Research Vehicle The LACE engine R.A. Jeffs & B.A. Beeton NGTE (1962) In the mid 1980s the UK returned to the higher-faster aircraft concept as a route to space …HOTOL

SKYLON 1990 The Spaceplane … the Phoenix of HOTOL

Skylon sculpture Festival of Britain 1951 Characteristics for Commercial Operations (1) • Reusability: reduced cost per flight by amortising production cost over 200 flights.

• Single-stage: reduced development and operating costs relative to multi-stage vehicles.

• Un-piloted: reduced mission control, relaxed safety during development, increased payload. dedicated accessory passenger module for payload bay. Characteristics for Commercial Operations (2) z Abort capability: abort to launch site with up to half engines failed. flight critical systems redundant to single point failure. z User friendly operations: simple ground handling and automatic checkout. low maintenance through robust TPS and long life engines. containerised payload system. z Re-entry cross-range: high hypersonic L/D to improve return opportunities to launch site. z Environmental impact: benign propellants, ‘low’ engine noise, no orbital debris.

Truss Structure of SKYLON Specific strength of advanced materials

Aero-shell composite Hypersonic wind tunnel tests at QinetiQ, Farnborough

SKYLON is a mature project study supported by extensive university and industry input.

Mn = 9.5 Courtesy of QinetiQ SKYLON

12 tonnes to LEO 10 tonnes to ISS 200m3 payload bay 4.6m diameter payload Abort Characteristics z Full return to base envelope for single point abortable failures. z Full take-off abort envelope. z Aerodynamically controllable with one nacelle inoperable in airbreathing ascent. z Mach 3 ramjet return cruise mode for early rocket abort. z ‘Once Around’ mode for late rocket abort. z Fully redundant RCS and OMS systems. Pre-Cooled Engines Precooled Engine Cycle

2nd Cycle

Air intake C o Cooler m Turbine b Compressor u s Thermodynamic Cycle t o Liquid r hydrogen Heat Sink

Some SABRE Parameters Area ratio 100 Airbreathing combustion pressure 102bar (nominal) Rocket combustion pressure 145bar (max) Cycle pressure ratio 4.5:1 Compressor pressure ratio 140 Equivalence ratio 2.8

Veff at Mach 5 16,000 m/s (cf. 46,000 ideal) Oxidiser cooled combustion chamber Pre-Cooler Construction Heat Exchanger Manufacturing Development

Brazed Joints

0.88mm x 30µm wall tube Supported by a DTI SMART Award Low Temperature Frost Control Testing

Matrix pressure drop

Test temperatures First Prototype Pre-cooler Module Low pressure-surface Heat Transfer Enhancement Pre-Cooled Gas Turbine Test

Objective

Demonstrate real heat exchanger construction and tube size on a test with 9% flow and area. Reaction Engines’ B9 Test Facility E-D Nozzle Test Program (STERN) (Joint program Uni. of Bristol and Airborne Engineering) Hypersonic Transport

LAPCAT Configuration A2

Take-off mass 400t Compliment 300 passengers Range 23,000km Speed Mach 5 Brussels-Sydney: Bering Straits route

Leg 2: Nome - Sydney 11,552 km Total journey 18,732 km

Leg 1: Brussels-Nome 4.7 hours @Mach 5 cruise (assuming (Alaska) 7176 km supersonic overflight of Bering straits) Scimitar Rev.1 Main Cycle Parameters at Mach5

3bar 2.4bar 1320K 635K 200bar

989K 853K

999K 200bar 2627K 861K 132bar

50.8bar 610K

843K 18bar 291K Scimitar Engine installation-nozzle view

Brazed Tube-Header of a Scimitar Module Scimitar Schematic Fan & hub turbine Core engine HX3 combustor Two spool compressor Precooler

Bypass He turbine combustor Preburner Experimental Contra-rotating Stator-less Turbine Installation Inlet Plenum & IGV Assembly

Rotors 1 & 3

Rotors 2 & 4 High Pressure Regenerator Research

Micro-channel plate assembly

50µm

Research press tool Silicon Carbide manufacturing research

Successful extrusion of rectangular strips 600mm long (or more). Relatively good control of channel dimensions and wall thickness. ‘Green’ extruded strips require drying mould to control profile. Removal process required for internal silicon beads that form during reaction bonding process. Some Scimitar Parameters Subsonic mode operation below Mach 2.5 Precooled above Mach 3 at inlet 635K

Mach 5 ER = 0.8, Veff = 44,000m/s

Mach 0.9 ER = 0.075, Veff = 96,000m/s Compressor pressure ratio 4 Fan pressure ratio 1.8 In Summary:- From the Von Braun Studies of the early 1950s, over half a Century has elapsed and a reusable space transportation system seems as remote as ever. 40 years have passed since Phil Bono of Douglas showed that a single stage to orbit low cross-range vehicle is credible, given high performance rocket engines and structures, which we now have. It is now 20+ years since British Aerospace and Rolls- Royce carried out the HOTOL study, indicating the possibility of realising a high cross-range single stage vehicle. In Summary:- Today the spacefaring nations of the World are planning a new generation of launchers based on ‘more of the same’. In addition the World is back to subsonic civil transport. The aerospace industry and the aerospace establishments are obsessed with Scramjets which will keep them in research funds for another generation. The precooled engine is virtually here. It is adequate to Mach 5 at which we can do a very great deal to advance the utility of space and the quality of life through improved transportation. Lets get on with it!