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X-51 (Earth-616)

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Quote1 God is for fleshy ones. I am robot. And your God will throw up when he sees what I have done to you. Quote2
-- Machine Man src


Scientists working for a top-secret U.S military project worked on creating an army of fifty-one experimental robotic soldiers capable of acting like humans. Their goal was to create a sophisticated weapons system capable of independent thought. Dr. Abel Stack took X-51, one of the the projects robots, home to test his radical theory--that a robot could only function like a human if it was raised like one. The other 50 models began displaying psychotic tendencies due to insufficient programming. The project was determined a failure and the order came down to destroy them. Each of the robots was equipped with an auto-destruct device that could be triggered remotely. Stack attempted to remove the self-destruct mechanism from X-51, however it was triggered, killing him instantly. X-51 survived and vowed that Stack's dream of human and robot peace would come true.[4]

Aaron Stack

Machine Man 001

Machine Man

As Machine Man, he assumed the name Aaron Stack and became a fugitive in the eyes of the military. He found a world greatly afraid of machines, but managed to blend in without suspicion. [5] Mr. Hotline dispatched a suicide bomber to hold Aaron's friends hostage in order to get him to return to the Hades Organization HQ where technicians dismember X-51 and present his head to the Monitor, a computer that projects a Satanic hologram. The Monitor searches Aaron's mind for the anti-life equation, but before he can prep a second assault Machine Man orders his limbs to reassemble and he re-programs the computer to neutralize the bomber and free his friends. [6]

Delmar Insurance Company

After being captured and later freed, Machine Man was found by psychiatrist Dr. Peter Spaulding. He also battled Colonel Kragg's troops.[7][8][9][10][11] [12] Soon after that, he first encountered Power Broker.[13][14][15][16] Alongside the Hulk, he battled the Power Broker.[17][18][19][20]Soon after that, he was redesigned and rebuilt by Dr. Oliver Broadhurst.[21][22][23][24][25]He then first encountered the Fantastic Four.[26] He then met mechanic "Gears" Garvin, and then battled Baron Brimstone. [27] He also battled Sunset Bain. [28] He then first encountered Alpha Flight.[29] Spaulding and Garvin set up Machine Man with a human identity as Aaron Stack, insurance investigator for the Delmar Insurance Company.[30]

Machine Man teamed up with Hulk and the Heroes for Hire to battle Nightshade[31]

Machine Man teams up with Spider-Man to battle Baron Brimstone and Sandman.[32][33]

Machine Man took part in the Contest of Champions.[34]


While working with Ben Grimm, Machine Man first met and fell in love with another sentient robot Jocasta. Alongside the Thing and Jocasta, he battled Ultron.[35] However, during the battle, Machine Man witnessed the seeming destruction of Jocasta by Ultron.[36]

Machine Man and the heroes of Earth come together to honor the Hulk as a hero.[37][38]

Iron Man

Machine Man tried to meet with Iron Man, who he believed was a fellow robot. However Tony was very drunk, irate, and under considerable stress from the machinations of Obadiah Stane. He attacked Machine Man and almost killed two of his own employees, but Machine Man was able to rescue them.[39]

Machine Man battled Doctor Doom along with other heroes when he used mind-control to enslave most of the world's population.[40]

X-51 Vol 1 12 Textless

Aaron as Machine Man after being upgraded

Heavy Metal

After being held captive for months, the Super-Adaptoid was freed by the Fixer and set out to get his revenge on the Avengers. [41] He first recruited the Awesome Android to his cause, and used the Fixer's brilliant technical mind to reprogram him. He then confronted the hero Machine Man and offered to fix his long-lost love Jocasta if he would join his team.[42] Machine Man accepted, and they went to the panhandle of Texas and reprogrammed Sentry and then the TESS-One robot, adding them to the team. Heavy Metal then went to Hydrobase and attacked the Avengers who resided there, battling the She-Hulk, Sub-Mariner, Captain Marvel, and Marrina.[43] Unknown to the other members of the team, the Adaptoid was merely looking for information on the Cosmic Cube. He found the information he needed and summoned Kubik, a cosmic being that evolved from the cube. Meanwhile, the other members of the team began to lose one by one, except for Machine Man, who switched sides and joined the Avengers to fight the Adaptoid after he copied Kubik's powers and became almost omnipotent. The Adaptoid eventually lost the battle, and the androids and robots were sent to a secure location.[44]


Machine Man again worked alongside the Avengers during a battle with Terminus.[45][46] When the Avengers reorganized their roster shortly thereafter, X-51 was nominated in absentia as a reservist for the West Coast Avengers.[47] He eventually accepted and was seen in action alongside his fellow reserve substitutes shortly after Operation: Galactic Storm.[48]

X-51 also appeared at the all-hands-on-deck Avengers meeting against Morgan le Fay shortly after the Heroes Reborn universe collapsed.[49]


During an encounter between Cable and the humanoid Sentinel Bastion, X-51 was infected with Sentinel nano-technology and forced to serve Bastion. he reasserted his independence, but the Sentinel programming remained buried deep in his software. [50][51]

X-51 was captured by S.H.I.E.L.D. and swept up into an X-Men adventure where the Red Skull took control of the S.H.I.E.L.D. Helicarrier. Machine Man helped ferry SHIELD agents to safety as the Helicarrier was being destroyed, but was seemingly destroyed himself in the process.[52]

As a last ditch effort at survival, X-51 transferred his consciousness from his failing body into the Life Model Decoy of agent Jack Kubrick which landed near him in the Helicarrier's wreckage. Aaron was so damaged in the crash, however, that his intelligence was subsumed beneath the LMD's programming, leading him to believe he actually was Jack Kubrick, searching for information on Machine Man.[2]

X-51 001

Aaron as the Machine Sentinel

The Brotherhood of Mutants, looking for weapons and devices, excavated the wreckage where X-51 had been lost. They confronted "Kubrick", also on scene, and blew his head off. The LMDs headless body collapsed near the inert original head of Machine Man. The two interfaced, bringing X-51 back online and letting him access the full power of his futuristic Sentinel tech, reconfiguring the LMD body into a more powerful form. However, he was also now vulnerable to the Sentinel protocols, reverting to an aggressive mutant-hunting posture whenever in the presence of Homo Superior.[53]

Machine man's new status fascinated the Celestials, who sent a Monolith to observe him. The Monolith offered him a chance to accompany the Celestials, and he agreed.[54]


X-51 later resurfaced as part of a counter-terrorism team called the Nextwave that went rogue. He was apparently dumped back on Earth by the Celestials and now preferred to be called Aaron. His personality was much colder, developing a resentment for humans, referring to them frequently as 'fleshy ones'. [55]

Operation: Lightning Storm.

Even more recently, he joined Ms. Marvel's Operation: Lightning Storm. He joined primarily as an intelligence specialist.[56]


Aaron during his time with Nextwave.

Due to his inorganic nature, Aaron was incapable of having a nervous breakdown, and so constructed a convoluted fantasy for himself, which allowed him to do so.[55]


X-51 (Earth-616) from Red She-Hulk Vol 1 59 001

Aaron was tasked by A.R.M.O.R. to investigate the arrival of extra-dimensional zombies, by traveling to the host reality. Initially he refused, claiming not to care for the fleshy ones. However, when he learned that Jocasta would be entering the hostile dimension on her own, Aaron had no choice but to accompany her and found himself hunting and killing zombies in the company of Howard the Duck.[49]

Machine Man eventually reverted back to his original personality from before his time with Nextwave. He became a reoccurring partner to the Red Hulk.[57]

He also later became an ally of Red She-Hulk and her alliance with the Order of the Shield.[58]

Power Grid [65]
Energy Projection
Fighting Skills*
* Lower ratings in original form


  • Z2P45-9-X-Robot: Machine Man is the 51st model of Z2P45-9-X range of Robots designed by Dr. Abel Stack. His robotic form provides him with various abilities; [59]
    • Superhuman Strength: As the Machine Man, Aaron could lift 2 tons and an extended limb could lift a few hundred pounds.[60]
    • Superhuman Durability: As the Machine Man, Aaron's titanium alloy construction makes him very durable.
    • Wave-Modifying Coating: A special 'wave modifying' coating provides some protection from energy attacks.
    • Limb Extension: Machine Man can extend his limbs up to 100 feet.[61]
    • Flight: As the Machine Man, Aaron could fly using anti-gravity units and hover using a propeller attachment.[1]
  • Machine Sentinel: in addition to his earlier capabilities, Aaron acquired the following powers from absorbing Sentinel nanotechnology:
    • Flight: As the Machine Sentinel, Aaron has absorbed and adapted technology for flight using his nanites and can now form a jetpack for personal use. With his jetpack, Aaron is capable of flight speeds in an atmosphere up to Mach 25 (19,250 mph), he can achieve escape velocity from Earth's gravitational pull (25,000 mph), and can reach sub-light speed while traveling in space (176,700 mps/95% lightspeed).[1]
    • Superhuman Strength: As the Machine Sentinel, Aaron can now lift well beyond 100 tons.[60]
    • Nano-Technological Self-Repair: The Prime-Sentinel nanites in his body give Stack a form of self-repair similar to a Healing Factor. These nanites also allows him to adapt technology and weapons appropriate for the present situation or opponent. The nanites were responsible for the fusion of Machine Man's damaged body and the remains of the Jack Kubrick Life-Model-Decoy, this resulted in Aaron becoming the Machine Sentinel.[62]
    • X-Gene Disruptor-Field: Aaron possesses the standard weapons and technology of a Prime-Sentinel, including the X-Gene Disruptor-Field. The X-Gene Disruptor-Field is a device used to disable or weaken the powers of any mutants in his vicinity.[63]
    • Transformation: After absorbing the Jack Kubrick Life-Mdel-Decoy and his Prime-Sentinel nanites, Aaron has gain the ability to changed his appearance at will using his acquired technology. Aaron's forms include: his "Aaron Stack" human form, his upgraded robotic Machine Man form, his stronger Machine Sentinel form, the Life-Model-Decoy of Jack Kubrick, or his human Machine Man form.[64]


  • He communicates well with humans, due to his upbringing and observations. After merging with the Jack Kubrick Life-Model Decoy, which was uploaded with a copy of Kubrick's mind, this gives Aaron any and all skills, knowledge, memories, and abilities possessed by the real Jack Kubrick.

Strength level

  • As Machine Man, Aaron could lift 2 tons and an extended limb could lift a few hundred pounds. As the Machine Sentinel, Aaron can now lift well beyond 100 tons.


  • Himself. As a synthetic entity, Machine Man has a variety of built-in gear. This has been shown to include a gas chromatograph, laser interferometer, micro-pulse radar, audiometer, seismometer, gravity wave detector, pulse-code modulator, standard computer input/output, radio beacon, all-wave transceiver, and laser cutting torch. Formerly Avengers Identicard.


  • Anti-gravity units, a propeller attachment to hover, formerly Avengers Quinjet


  • Normally, his index fingers are loaded with pistol rounds. He can also switch out various devices and other weapons with items contained on his belt. After merging with the Prime Sentinel, Stack can adapt his weapons systems as needed.
  • In the 2020 future Machine Man was deactivated by Sunset Bain, but rebuilt by a group of scavengers.

  • The character and stories are based on the eponymous Stanley Kubrick film and Arthur C. Clarke novel.
  • The band Powerman 5000 wrote and performed a song called "The Son of X-51", referencing the character.

Discover and Discuss


  1. 1.0 1.1 1.2 Official Handbook of the Marvel Universe A-Z #6
  2. 2.0 2.1 X-51 #1
  3. Marvel Fact Files #23
  4. 2001: A Space Odyssey #8
  5. 2001: A Space Odyssey #9
  6. 2001: A Space Odyssey #10
  7. Machine Man #1
  8. Machine Man #2
  9. Marvel Comics Presents #10
  10. Machine Man #3
  11. Machine Man #4
  12. Machine Man #5
  13. Machine Man #6
  14. Machine Man #7
  15. Machine Man #8
  16. Machine Man #9
  17. Incredible Hulk #234
  18. Incredible Hulk #235
  19. Incredible Hulk #236
  20. Incredible Hulk #237
  21. Machine Man #10
  22. Machine Man #11
  23. Machine Man #12
  24. Machine Man #13
  25. Machine Man #14
  26. Machine Man #15
  27. Machine Man #16
  28. Machine Man #17
  29. Machine Man #18
  30. Machine Man #19
  31. Marvel Team-Up Annual #3
  32. Marvel Team-Up #99
  33. Peter Parker, The Spectacular Spider-Man #56
  34. Contest of Champions #1
  35. Marvel Two-In-One #92
  36. Marvel Two-In-One #93
  37. Incredible Hulk #278
  38. Incredible Hulk #279
  39. Iron Man #168
  40. Marvel Graphic Novel #27
  41. Avengers #287
  42. Avengers #288
  43. Avengers #289
  44. Avengers #290
  45. Avengers: West Coast Annual #5
  46. Avengers Annual #19
  47. Avengers: West Coast #69
  48. Avengers: West Coast #83
  49. 49.0 49.1 Avengers Vol 3 #1-4
  50. Cable and Machine Man Annual #1998
  51. Machine Man & Bastion Annual #1998
  52. Rage Against The Machine crossover.
  53. X-51 #2-8
  54. X-51 #12
  55. 55.0 55.1 Nextwave #1-12
  56. Ms. Marvel Vol 2 #13-34
  57. Hulk Vol 2 #49-57
  58. Red She-Hulk #59-67
  59. Official Handbook of the Marvel Universe #6
  60. 60.0 60.1 Official Handbook of the Marvel Universe Vol 2 #7
  61. Official Handbook of the Marvel Universe Master Edition #24
  62. Marvel Avengers: The Ultimate Character Guide #1
  63. Heroic Age: Heroes #1
  64. All-New Official Handbook of the Marvel Universe #6
  65. Official Handbook of the Marvel Universe A-Z hardcover Vol. 6

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