Project ORCHID

The SPARTAN-IV Augmentation Program is the formal name for the biochemical and surgical augmentation procedures performed on the SPARTAN-IV supersoldiers.

Background
Like the augmentations performed for the SPARTAN-IIs and the improved procedures utilized in the subsequent SPARTAN-III program, the SPARTAN-IVs underwent a series of procedures to enhance their physical capabilities. Unlike the Spartan-III augmentations, which were almost entirely based upon chemical injections, the SPARTAN-IV augmentations combine chemicals and surgical procedures like those pioneered by Dr. Catherine Halsey in the SPARTAN-II program. The technology used in the two preceding SPARTAN programs necessitated that the candidates meet exceedingly strict genetic qualifications as well as the application of the enhancements on preteens, to avoid the catastrophic failure rates produced by the augmentation of adult subjects in the ORION Project. By the time of the initiation of the SPARTAN-IV program, the technology had advanced to the point that many of the previously dangerous procedures could be performed on adults seemingly without major risk.

Augmentations
While the enhancements have not been described in detail, they incorporate technologies originating from the prior SPARTAN programs as well as completely new additions. However, the neural augmentation utilized in the previous programs, which provided the SPARTAN-IIs and SPARTAN-IIIs their superhuman reaction times, is absent due to the GEN2 MJOLNIR armor compensating for it.

Experimental phase
A series of additional augmentations were included in the earliest, prototypical phase of the program. These enhancements would have made the Spartans significantly stronger and more resistant to injury, the goal being that they could operate without MJOLNIR armor. However, these procedures proved to have an unacceptable casualty rate, killing or crippling nine of the ten initial candidates; the sole survivor, Ilsa Zane, was rendered mentally unstable. Demonstrating the effectiveness of these experimental enhancements, Zane was able to engage a MJOLNIR-armored Sarah Palmer in hand-to-hand combat without the use of any protective equipment, and survived Palmer violently driving her head into a metal bulkhead face-first, as well as her subsequent prolonged exposure to the vacuum of space.

Procedure
The SPARTAN-IV augmentation procedures take three weeks to perform, with recovery and subsequent training usually lasting several months. It took about two days for the Spartans to relearn how to walk again following their augmentations; additionally, significant disorientation was in evidence during their initial training exercises.

Effects
The synthetic cardiac weave allegedly allows a SPARTAN-IV to "outrun a horse"; this would imply speeds of up to, or over, 50 km/h. This would also imply that the substance coated on the IV's muscular system increases the IV's strength by a factor of 3. The enhancements performed on the lungs potentially allow a SPARTAN-IV to breathe methane for around an hour.

However, the decision to augment adults as opposed to preteens comes at the cost of performance: the SPARTAN-IVs' physical augmentations are not as effective as those of the preceding generations. To compensate for this shortcoming, the GEN2 MJOLNIR armor worn by the SPARTAN-IVs is designed to multiply the wearer's strength and speed significantly more than the first-generation MJOLNIR, although this still leaves the SPARTAN-IVs' weaker than their predecessors out of armor.

SPARTAN-IVs must follow a rigid set of guidelines to maintain their physical fitness and health. These include undergoing regular medical examinations, including physiological scans, reviews and treatment before and after each mission. A SPARTAN-IV is expected to perform at optimum capacity with a minimum of two-and-one-half hours of sleep per a 48-hour cycle; for cryosleep, standard UNSC practices apply. They are also instructed to follow standard UNSC physical training practices. Due to their augmented physiques, however, they are provided their own, custom-built gym equipment. Official meals are specifically prepared to meet the caloric, nutritional and medicinal needs of each individual Spartan. These personal needs are measured based on activity data recorded by the Spartan's individual physiometer. Ancillary medications may be provided to ensure the Spartan's well-being and to reduce risk of potential implant rejections.

Performance
Training performance of the initial SPARTAN-IV batch in 2553 was decidedly underwhelming, something that was acknowledged by their recruiter, SPARTAN-III supersoldier Jun-A266. Part of this may be attributed to their still-ongoing acclimatization to their enhancements, as well as the group not having worked together before, although all of them did possess a military background. The majority of the first batch of SPARTAN-IVs were incapacitated by their baseline human Marine training opponents, and their lack of coordination resulted in SPARTAN-IV program head, Commander Musa-096, personally chastising them about the importance of teamwork (a lesson the SPARTAN-IIs learned in their first days of training at the age of six). The SPARTAN-IVs' post-augmentation performance also stands in stark contrast to the SPARTAN-IIs, whose teamwork and resourcefulness could be described in nigh-mystical terms, with their trainers forced to wear special protective equipment only to prevent the Spartans from accidentally killing them. However, several SPARTAN-IVs of this group later distinguished themselves in live combat during the New Colonial Alliance's attempted takeover of.

Later combat performance also shows marked improvement to the training sessions of the initial group. Spartan Gabriel Thorne was able to fight five Sangheili in close-quarters combat and successfully kill them, before being subdued by two other Sangheili during the Second Battle of Requiem. Thorne also took on a battle-seasoned Sangheili, Gek 'Lhar, in hand-to-hand combat and had the upper hand for a majority of the brawl, before having a boulder smashed on his chest and unprotected head, dazing him. Later on during the Requiem campaign, Spartan Paul DeMarco was able to defeat multiple Sangheili and a Promethean Knight in close-quarters combat. Many other Spartan teams have also displayed equally or more impressive feats of prowess, particularly in the Requiem theater.

List of appearances

 * Halo 4
 * Infinity Briefing Packet
 * Halo: Initiation