SLEIGH secrets revealed!

Every December the SLEIGH (Super Light Exoatmospheric Intergalactic Gift Hauler) has precisely 24 hours to visit each child-containing home on Earth. A key to the success of this critical annual mission is the continuously evolving SLEIGH system. Though highly classified for many years, recent Freedom of Information Act (FOIA) decisions have made public details and performance specifications of the impressive SLEIGH system. The technological, physiological, and logistical requirements for this mission are significant and present myriad opportunities for lightweight, efficient and reliable solutions.

Other blogs may address the main SLEIGH interface, vehicle safety, infotainment and body control aspects of SLEIGH. This blog shall review select declassified technical aspects of the RPS (Reindeer Propulsion System). In particular, the Reindeer-Machine interface and how Texas Instruments power management products contribute to the performance and reliability of the RPS.

RPS Overview

The RPS is an assembly of eight similar and largely interchangeable RPUs (Reindeer Propulsion Units). Though typically arranged in a dual-series (2 x 4) configuration, a ninth guidance enhanced RUDOLPH (Red Ultra Directional Optical Laser Proboscis Homing) RPU is often attached fore to provide primary guidance and beacon functions during low visibility conditions. While originally viewed as a lab curiosity, the RUDOLPH RPU has proven its’ value and prevented disaster on many occasions.

The RPS attaches to the front of the SLEIGH body and when deployed with a nominal payload of [classified] kilotons, propels the SLEIGH at speeds in excess of [classified] mph. Each RPU has substantially similar support specifications, although the RPU lead pair (and RUDOLPH if deployed) includes enhanced radiation shielding, deicing, and guidance sensors whilst the trailing three pairs have enhanced space debris protection.

The RPS is comprised of four major electronic subsystems;

  • Life support
  • Telemetry
  • Navigation, guidance, and countermeasures
  • Power distribution and management   

Life Support

The RPS life support subsystem must provide a safe, comfortable, operating environment for each individual RPU. Composed primarily of Spandex and Kevlar, each RPU has a NICEFIT (Nearly Invisible, Custom Engineered, Fully Integrated Topcoat) with up to 4,096 sensors, both external and internal.

An RPU NICEFIT is required to have heating, cooling, hydration recirculation, fault protection/reporting, infotainment, and feeding systems for 24 hours of continuous deliveries from -70°C to +[classified]°C. A significant challenge has been maintaining critical system functionality during the extreme temperature gradients and ionization fields experienced while exiting and reentering the earth’s atmosphere.

Life support control, telemetry, and non-bulk power are handled thru a multi-port, Power-over-Ethernet (PoE) bus. PoE power management is used in conjunction with local RPU battery backup to maintain continued functionality of all telemetry, sensors, guidance, and control systems even if bulk power is temporarily lost.

TI Components in the RPU Life Support Subsystem:

  • TPS2379 PoE powered device– High power POE PD receives and manages 50W of power over PoE lines – one per NICEFIT, though may increase to two (100 W total) in 2015.
  • TPS2592A 12V, 5A eFuse- Protects the telemetry board sensor input. Clamps induced surge currents and spikes due to increased speed through ion clouds.
  • TPS2511 USB charge port controller Despite attempts by IT to standardize the use of personal devices, the RPUs insist upon BYOD (bring your own device). These devices require continuous charge throughout the mission.
  • TPS54361 3.5A, 60V Input Step-Down Converter with Eco-mode™.  Ideal for providing 5V USB power for multiple BYODs.  Low quiescent current reduces battery drain in RPS standby-mode.


Let no parameter go unmeasured! All 4,096 sensor slots per NICEFIT are used, many in redundant duties. For example, each NICEFIT hoof unit has 12 accelerometers to monitor G forces for each of the [classified] million surface landings during the mission. Cumulative impact forces in excess of RPU limits may trigger corrective actions such as reordering RPUs within the 2x4 RPS matrix, and/or adjustments to the intravenous feed mix.

A sample of other monitored parameters (per RPU)

  1. External temp - 22 locations
  2. Internal temp - 2 locations
  3. Blood pressure – 8 locations
  4. Blood sugar and oxygen – 3 locations
  5. Heart rate – 6 sensors each 

TI Components in the RPU Telemetry:

  • TPS2592B – 5V, 5A eFuse for sensor port protection.
  • TPS7A8300 – Programmable 1% LDO keeps maintains clean and stable power to the sensor.
  • TPS53915 – High efficiency 18V Input, 12A  SWIFT™ DC/DC Converter with PMBus™ allows serial configuration of the converter to optimize power to each NICEFIT unit.

Navigation, guidance and countermeasures

Although the number of child-containing homes in the world keeps growing, the gift delivery window has not. Achieving more deliveries in the same period of time has driven average SLEIGH speeds up by 53.2% over the last eight years. This, in turn, has driven higher efficiency in the SANTA (Synthetic Aperture Natural Terrain Amplification) system, an accurate and high speed guidance system that is able to detect and track chimneys from great distances. To avoid false commercial targets the SANTA system has recently been upgraded with the HOHO ( Home On Home Only ) processor. Though still in evaluation, initial results show HOHO performance to be as advertised.

To support complete SLEIGHspace awareness, detection, and tracking each RPU NICEFIT has sixteen sensors: two each, top and bottom side,  at fore, aft, starboard and port. Each sensor pair is comprised of one [classified] terrapixel Infrared ( IR ) focal plane array and one ultraviolet ( UV ) array. These sensors communicate real time with multiple elements of the SANTA system to provide precision guidance to each targeted domicile. These sensors also provide real-time threat data to warning receivers and defensive countermeasure pods.

TI Components in the RPU Nav, Guidance, CM System:

  • TPS7A3501 – Active in line filters keep receiver front-end power ultra-clean with 42dB PSRR.  
  • TPS560200 – 17V, 500mA Synchronous-Step-Down SWIFT™ converter in 5 pin SOT2-3 improves power efficiency to the SANTA system from an intermediate bus voltage.

Power Management and Distribution

Each RPU has 3 kW of available power via the NICEFIT harness. This is delivered at a nominal 50 V, at up to 60 Amps. Typical loads are only 15% to 20% of maximum, but some conditions demand the full 3 kW. Examples include, but are not limited to, extreme cooling loads experienced during reentry, high power counter measure jammers to deflect inbound threats, and Blitzen blasting Crazy Train at level 11 on his infotainment sound system over Amsterdam.

NICEFIT power is continuously monitored and compared to standard profiles for each subsystem. Any mismatch triggers a fault alarm and, if necessary, corrective action.

SLEIGH power interface protocol requires hotswap capability between each NICEFIT and the central RPS harness to facilitate swift RPU swap out at any of the strategically located worldwide depots. This can take place up to [classified] times per mission so the exchange must be extremely swift to avoid delay.

TI Components in Power Distribution and Management System:

  • LM5066 – 80 V Hotswap protection switch controller and monitor provides overcurrent, overvoltage, inrush and short circuit protection, and PMBus power current voltage monitoring.
  • CSD13381F4 – 12V FemtoFET™ allows turn-off of unused NICEFIT down-stream circuitry in a 0402 form-factor with the lowest voltage drop in its size category.


The SLEIGH system has been, and will continue to be, a collection of technological accomplishments made possible by a team of talented elfineers and system integrators. By continuously adapting to environmental and social shifts and using leading edge components and systems, the SLEIGH team achieves the impossible each and every year.

Disclaimer:  In the spirit of the holiday, TI intends for the material contained in this blog to be technically inaccurate and likely wrought with errors or other mistakes.  TI assumes no liability for your use of this material or your subsequent product design based on this material.  But if you do build a rockin’ SLEIGH, please share your design with fellow elfineers in TI’s E2E Community.