I read that Angara 5 will carry a "payload simulator" on its first test flight tomorrow Dec. 23, 2014. But the Indian GSLV mk.III recently flew for the first time with a prototype of the ISRO crewed spacecraft as payload. And SLS is planned to carry an uncrewed Orion around the Moon on its premiere launch.

Why not always use a test launch to test some real payload? Or is a simulated payload just another name for doing precisely that?

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    $\begingroup$ See Boilerplate. ;) $\endgroup$
    – TildalWave
    Commented Dec 22, 2014 at 11:15
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    $\begingroup$ @Noordung Yes, but why send junk to space, instead of a more developed spacecraft prototype, or at least a bunch of student's cubesats? I've got the impression that there are many more prototype payloads around than there are launch opportunities. GSLV mk.III didn't even have a working upper stage, it still tested aspects of their crewed-to-be spaceship. Angara 5 first flight will carry a Briz-M upper stage, which is quite capable and expensive. So why just launch a boiler plate? If that is what "simulated payload" means. And Angara 5 is about as capable as the Delta IV Heavy, it could do alot $\endgroup$
    – LocalFluff
    Commented Dec 22, 2014 at 11:49

2 Answers 2


Launching on a risky booster, is risky.

You can define a risky booster as:

  • First launch of a new booster.
  • Return to flight after a failure.
  • Booster with record of failure

So you feeling lucky punk? How much development money are you willing to risk on any of those cases?

Why did ISRO take the risk on the GSLV launch and Angara5 won't? I would assume that ISRO wanted to launch that payload, their boosters are not cheap, their budget is not unlimited, and they needed a payload anyway to demonstrate it. If they do not demonstrate confidence in their own booster, who will be confident enough to use it?

The Russians launch often enough on so many different classes of vehicles that they are not lacking options for payloads. They may not have had some project that needed a cheap-to-free launch giveaway. Also Angara-5 is a fairly large payload booster (49,000 lbs to LEO), so to really test it out you need a fairly big payload. Big payloads are usually high value payloads.

At that point it becomes a better choice to literally launch a ball of steel, or container of water. Something cheap, with good sensors to characterize the details of the environment inside the launch fairing so customers know what to expect.

Now if you had say a propellant depot in orbit, and you had a tug, then it would have made a ton of sense to launch propellant for the depot. Value is low if lost, but nice freebie if it worked. But we don't.

As for SLS, it is so expensive, and will be launching so infrequently it almost cannot be 'wasted' on a test flight. That to me is a design flaw. It seems like a full up series of test flights before humans fly on it would be part of man-rating. Atlas V will have had 60 or 70 flights by the time a human flies in a CST-100. Falcon 9 will likely be at 20-30 flights before a human flies in a Dragon V2. Why is SLS going to do it on the second flight?

It will be interesting to see what SpaceX launches on Falcon Heavy as its first payload.

I personally would love to see Elon Musk's original goal, a greenhouse on Mars, as the first payload (Huge overkill since that was planned to be tiny, and F-H has a huge payload ability). That is the sort of 'waste' of money they could do as a publicity stunt for vaguely cheap inhouse if the booster needed a payload no one else would pay for.

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    $\begingroup$ Even a fuel depot would've been better than a dud. If it is on a free heavy launch, and the Russians surely have some fuel tanks lying around in storages. So I don't understand. Maybe a simulated payload is filled with instruments to measure the performance of the rocket, but 20+ tons of it? Thats a truck load. $\endgroup$
    – LocalFluff
    Commented Dec 22, 2014 at 12:19
  • $\begingroup$ @LocalFluff But there's nothing currently able to use a fuel depot in orbit, so launching an unusable fuel depot wouldn't be any more productive than launching a tank of water. $\endgroup$ Commented Dec 22, 2014 at 12:25
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    $\begingroup$ @LocalFluff What do you launch to this depot? LOX? Ok, gonna leak due to heat loss and boiling. LH2? Pretty hard stuff to keep in a depot. Keronsene? No one really uses that in an upper stage. So until there is a user or even a market, launching it would not be that helpful. $\endgroup$
    – geoffc
    Commented Dec 22, 2014 at 15:27
  • $\begingroup$ How about some supplies for ISS? $\endgroup$
    – vasin1987
    Commented Dec 22, 2014 at 21:09
  • $\begingroup$ @DavidRicherby If I understand yours and geoffc's point, it is basically that one needs to have a very specific purpose for a high risk test payload to be meaningful. And the Russians don't have that now. And maybe the Plesetsk launching site isn't making it more helpful. They haven't sent anything to any celestial body since over 30 years and have no plans to do it until next decade. And a bunch of cubesats which don't generate any real cash flow wouldn't be worth the trouble. $\endgroup$
    – LocalFluff
    Commented Dec 22, 2014 at 21:16

In my time in Aerospace, we used "mass simulators" (lead or brass weights or water) for the simple reason that the actual payload (a satellite) wasn't ready yet. We try to get the launch vehicle and the payload ready for launch around the same time, which means both things are in testing at the same time, typically at different facilities, and they never meet until the final launch vehicle is assembled. For testing launch vehicles, the answer above is absolutely correct (cheaper to blow up a bucket of water than a satellite) - but for most uses of mass simulators, it's because the actual device isn't available. You can be sure that "uncrewed Orion module" is mostly mass simulators.

  • $\begingroup$ Does that mean that the payload mass simulator on the Angara5 test launch tonight could partly consist of or "simulate" a lunar return probe or LEO crewed spacecraft or something like that? Along with a dud to make up for the full weight and balance and size and whatever which the launch itself needs to be tested for. $\endgroup$
    – LocalFluff
    Commented Dec 22, 2014 at 23:10
  • $\begingroup$ Yes absolutely. They will attempt to simulate the mass of the actual mission as closely as possible. Some of it will no doubt be instruments to measure conditions inside the craft, but all of the mass will need to be there. Ounces are important in rocketry, even at this scale. $\endgroup$
    – Jasmine
    Commented Dec 23, 2014 at 1:30

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