According to the Wikipedia article about Elon Musk's Tesla Roadster now in Heliocentric orbit:

Traditionally, concrete or steel blocks are used as ballast in risky test flights. SpaceX wanted to demonstrate that their new rocket could carry a payload as far as the orbit of Mars. They reportedly had offered NASA to carry a scientific payload, but these plans did not come to fruition.

Are any of those "concrete or steel blocks" still in Earth orbit or beyond?

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    $\begingroup$ full disclosure: I want to make a website called aconcreteblockin.space so I can get rich and retire ;-) $\endgroup$
    – uhoh
    Commented Feb 27, 2018 at 15:13
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    $\begingroup$ Usually they reenter, I imagine. So vaporized or at the bottom of the ocean. $\endgroup$
    – geoffc
    Commented Feb 27, 2018 at 16:20
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    $\begingroup$ @geoffc well "usually" goes without saying, but you've gone and said it anyway. But I've asked about exceptions in the last sentence. You see while the story about a sponge who lives in a pineapple at the bottom of the sea is a big money maker, my character the concrete (or steel) block is not likely to be so interesting there. So I need her to be in space. $\endgroup$
    – uhoh
    Commented Feb 27, 2018 at 16:58
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    $\begingroup$ I think most missions that test like this, do not boost out of Earth orbit. Then to be good citizens, they clean up after themselves. I look forward to seeing possible answers. $\endgroup$
    – geoffc
    Commented Feb 27, 2018 at 16:59
  • $\begingroup$ @geoffc indeed! And so the secret title to my question is "Is the FH 2nd stage the first case where a static payload for a first test of a launch vehicle has remained in space, rather than re-entered the atmosphere?" But don't tell anybody, or they'll make me change it! $\endgroup$
    – uhoh
    Commented Feb 27, 2018 at 17:05

2 Answers 2


I have collected a list of orbital mass simulator launches and their fates:

  • Antares A-ONE, mass simulator
    • Orbit: approximately 150 by 160 miles (240 km x 260 km) with an inclination of 51.6 degrees
    • Fate: Burned up in atmosphere
  • Falcon 9, Dragon Spacecraft Qualification Unit (basically a mass simulator)
    • 249.5 kilometers (155.0 mi) x 252.5 kilometers (156.9 mi) with an inclination of 34.5 degrees
    • Fate: Burned up in atmosphere
  • Strela test launch, Kondor mass simulator
  • Falcon 1, Ratsat (mass simulator)
    • 617 kilometers (383 mi) x 635 kilometers (395 mi) with an inclination of 9.35 degrees
    • Status: in orbit
  • Zenit-2, Tselina-2 mass simulator
    • Orbit: 840.7 km x 869.3 km with an inclination of 71.0 degrees
    • Fate: in orbit
    • There were a ton of Zenit-2 launches with mass simulators, check them out here, they all seem to be a similar orbit, some burned up.
  • Delta III (Delta Flight 280), mass simulator
    • Orbit: 170.0 km x 13,740.6 km with an inclination of 27.3 degrees
    • Fate: in orbit
  • Angara A5, mass simulator
    • Orbit: 36,160.5 km x 39,099.3 km with an inclination of 2.8 degrees
    • Fate: in orbit
  • Long March 2C, 2 mass simulators
    • Orbit: 616.1 km x 624.4 km with an inclination of 86.3 degrees
    • Fate: both in orbit
  • Falcon Heavy, Tesla Roadster
    • 0.98614 au x 1.6639 au with an inclination of 1.078 degrees (Heliocentric)
    • Fate: in orbit (or here, I don't know of a website that gives a good visualization of objects in Heliocentric orbit)
  • Saturn 1 (SA-5), mass simulator
    • Orbit: 258 kilometers (160 mi) x 741 kilometers (460 mi) with an inclination of 31.4 degrees
    • Fate: Burned up in atmosphere
    • There were 2 more boilerplate (mass simulator) launches (AS-102/AS-103) by the Saturn 1

If you know of any other mass simulator launches let me know, I am looking at orbital launches only here, there were plenty more suborbital mass simulator launches but this question is dealing with orbital space junk.

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    $\begingroup$ Some of the early Saturn launches carried large amounts of water as payload mass - en.wikipedia.org/wiki/Project_Highwater $\endgroup$ Commented Feb 28, 2018 at 19:44
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    $\begingroup$ Wow, what an amazing list, this must have taken quite a bit of work, thanks! $\endgroup$
    – uhoh
    Commented Mar 1, 2018 at 0:24
  • $\begingroup$ @OrganicMarble it looks like Project Highwater was not an orbital mass simulator launch, very cool though $\endgroup$
    – Mark Omo
    Commented Mar 1, 2018 at 20:37
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    $\begingroup$ It may have been spun as an experiment, but I'm pretty sure it was test mass in actuality. $\endgroup$ Commented Mar 1, 2018 at 21:06
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    $\begingroup$ @OrganicMarble I definitely agree that it falls under the category of test launches, however, I am only collecting orbital launches, Highwater was Sub-Orbital $\endgroup$
    – Mark Omo
    Commented Mar 1, 2018 at 21:08

I only have a partial answer, but here is what I was able to dig up:

That same Wikipedia page you link contains this:

Tommy Sanford, director of the Commercial Spaceflight Federation, opined that the car and its rocket stage are no more "space junk" than the mundane material usually launched on other test flights. Mass simulators are often deliberately placed in a graveyard orbit or sent on a deep space trajectory, where they are not a hazard.

Clicking through to the source of that quote, here, does indeed have his exact words.

"People could always argue about debris and define it as debris, but when they do those early launches with dummy payload, they make sure they put the dummy payload into a graveyard or inoperable orbit that is not of value to the space community and something that won’t be a threat to future activities in space," said Sanford.

So it would appear that at least some past mass simulators are in a graveyard orbit around either the Earth or the Sun.

Your linked Wikipedia page also has a reference to the boilerplate page, which lists many missions that were considered "boiler plate," but the list lacks information on the fate of the mission hardware. Perhaps more specific research on a case-by-case basis would yield where some of them are. Searching Wikipedia for "mass simulator" redirects to the boilerplate page, so that's no help. I don't have a source confirming what Tommy Sanford said in the above quote, nor anything more specific about it.

  • $\begingroup$ Thanks, this is a great start! Both I and others assumed in comments below the question that these would all likely be at the bottom of the ocean (or at least for concrete, possibly vaporized or dispersed upon reentry) but you show that the situation is far more interesting! $\endgroup$
    – uhoh
    Commented Feb 28, 2018 at 4:58

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