back to article NASA trying to stuff excess baggage into OSIRIS-REx after too-successful asteroid scoop

We’ve all been there: you go on holiday, find lots of fabulous stuff and when the time comes to return home, your suitcase just won’t close. And now that same problem appears to have befallen the OSIRIS-REx spacecraft after its visit to asteroid Bennu. Which is a good problem to have because despite being confident the craft …

  1. Chris G Silver badge

    Excess baggage

    The team can thank their lucky stars they are not trying to get a giant toy, stuffed donkey and a three foot diameter sombrero from Torremolinos, onto a Ryanair flight.

    The cost would mean leaving most of the sample at the departure gate.

    1. You aint sin me, roit Silver badge
      Trollface

      Not a fan of Ryanair, but...

      Anything that stops the trafficking of donkeys and sombreros would be doing civilization a favour!

  2. Pete 2 Silver badge

    Much too little and a little too much

    So the opposite problem to the Mars Insight lander's "mole" problem. One collects too much stuff and the other can't (literally) get stuck in.

  3. alain williams Silver badge

    Why only 2 oz ?

    Can anyone enlighten me as to why NASA would send an 880 kg space craft on a 7 year mission and only bring back 2.1 oz ? Would it really make much difference to the machine to have a bigger suitcase and so be able to give a sample to more labs when it gets back ?

    Maybe take samples from different places on Bennu.

    1. imanidiot Silver badge
      Boffin

      Re: Why only 2 oz ?

      The rocket equation is a harsh mistress.

      If you need to bring back mass, you need to change it's velocity, for which you need fuel. If you want to bring back more mass, you need more fuel. You also need more fuel to bring that extra fuel in the first place. And a bigger rocket to lift that extra fuel (that also needs to burn more fuel because of the extra fuel to move the added fuel). You also need a bigger return capsule, which adds mass, requiring more fuel (and a bigger rocket to bring that fuel)

      It's a basically a balancing act on how much mass you can bring back versus how much fuel you can stuff into your spacecraft and how big the rocket you have available to bring it to space is.

      1. Anonymous Coward
        Anonymous Coward

        Re: Why only 2 oz ?

        If you need to bring back mass, you need to change it's velocity, for which you need fuel. If you want to bring back more mass, you need more fuel. You also need more fuel to bring that extra fuel in the first place. And a bigger rocket to lift that extra fuel (that also needs to burn more fuel because of the extra fuel to move the added fuel). You also need a bigger return capsule, which adds mass, requiring more fuel (and a bigger rocket to bring that fuel)

        It's turtles fuel all the way down

    2. KarMann Silver badge
      Boffin

      Re: Why only 2 oz ?

      And that 2 oz/60 g figure is just the minimum they were hoping for, and if they'd gotten less than that, they might have gone back for more. What they were really hoping for was something around 1 kg. That would make rather more of a difference.

    3. UCAP Silver badge

      Re: Why only 2 oz ?

      It would make for a more complicated mission profile, which in turn would push up the costs enormously, as well as making the mass budget for the mission a whole lot more complicated.

      For example, it took NASA months to plan out this single sample collection. Adding additional samples would extend the planning process much longer, and would mean that the spacecraft would have to reposition itself and change its orbital profile a lot more. This would require a lot more fuel, and pushes the mission risk up significantly.

      Another example, in order to take multiple samples, the spacecraft would have to be fitted with multiple collector heads to ensure that sample cross-contamination does not occur. In addition the return capsule would have to be made larger to accommodate all of the samples which in turn would mean a larger landing system (i.e. bigger parachutes).

    4. Shadow Systems

      Re: Why only 2 oz ?

      It's simple. There was a boy robot & girl robot abord. The whole thing was designed to carry tons of stuff. The boy robot got a few ounces in which to carry the samples. The girl robot needed the rest for clothes, shoes, makeup, toiletries, fashion equipment (hair drier, curling tongs, blowdrier, etc), and a zillion other things no girl robot can do without. The boy robot was lucky to get what he did & wasn't left behind to make more room for her stuff.

      I'd get my coat but there wasn't room for it on this trip. =-)P

      *Runs away before all the womenfolk start setting me on fire for my insolence*

    5. I ain't Spartacus Gold badge

      Re: Why only 2 oz ?

      alain williams,

      To give you some numbers on the two above posts about fuel. I looked up the weight of the rocket that lifted the Mercury mission BepiColumbo. That's one big and one little orbiter to be taken to Mercury over 7 years. It's all rather silly/mad/impressive. See link to wiki here:

      Arianne 5 first stage is 189 tonnes of which 175t is fuel.

      2 x solid rocket boosters 277 tonnes each = 554t

      1 x second stage 16.1t - 14t fuel (this can get about 10t to GTO)

      Payload weight 4.1 tonnes - including 1.4t of fuel for an ion drive

      All to deliver 1,230kg Mercury Planetary Orbiter and the 255kg Mercury Magnetosphere Orbiter

      So that's a launch mass of about 763 tonnes

      Of which a bit under 700t is fuel of varying types.

      The solid rocket boosters last 30 seconds and then fall into the sea. The first stage of the rocket does a few minutes more, then does likewise. The upper stage of the rocket lights and takes the payload I'd imagine past geostationery transfer orbit and gives it as much velocity as it can - then drops off.

      Then the Mercury Transfer Module fires up with its special electric thrusters, powered by solar cells. That use much less fuel than chemical rockets. They're much slower, but are using tiny amounts of fuel so can burn continuously for years.

      But even that isn't nearly enough. It takes stupid amounts of power to decelerate enough to get close to the Sun, so it also has to do 1 Earth fly-by, after 1.5 years, to scrub off some speed. Followed by 2 Venus fly-bys and 6 Mercury fly-bys for a total flight of 7 years chucking away over 60 tonnes of spacecraft and about 700 tonnes of fuel in the process of getting those 2 craft massing a bit over 1.5 tonnes to Mercury orbit for a 1 year mission - though I'm sure they'll last longer than that.

      I admit that this is a special case, as Mercury is a right bastard to get to. But it's like going on holiday to the seaside in an articulated lorry, carrying a camper van to stay in and only getting home on a bike because you've had to throw the others away due to not being able to refuel them.

  4. Mage Silver badge
    Headmaster

    Ounces?

    NASA, get with metric. Imperial units are rubbish for engineering, which is why British Scientists refined the metric system.

    1. imanidiot Silver badge

      Re: Ounces?

      They actually are doing everything in metric, they're just putting everything in fantasy units for the press release, because apparently they get a lot of heat from the average public if they put it in proper units.

    2. Yet Another Anonymous coward Silver badge

      Re: Ounces?

      It'a American, I would have expected it to ask for 1/2 cup of rock

      1. HildyJ Silver badge
        Devil

        Re: Ounces?

        Only the British would ask for a half cuppa.

        Americans would want a full Venti. Or, given that Bennu is frozen, a Trenta.

  5. Anonymous Coward
    Anonymous Coward

    Lorryload of Hay

    Sounds a bit like a lorry full of hay bales heading down the motorway....

    Most will be deposited along the interstellar hyperspace bypass before it reaches the final destination.

    1. Roger Kynaston Silver badge

      Re: Lorryload of Hay

      s/interstellar/interplanetary/

      </pedant>

      1. Yet Another Anonymous coward Silver badge

        Re: Lorryload of Hay

        Strictly speak it is interstellar, just a lot closer to one stellar than another.

      2. Anonymous Coward
        Anonymous Coward

        Re: Lorryload of Hay

        s/interstellar/interplanetary/

        How quaintly parochial.

        Yours etc.,

        Freddled Gruntbuggly

        (3th Secretary, Galactic Hyperspace Planning Council)

        1. I ain't Spartacus Gold badge

          Re: Lorryload of Hay

          Oh Mr Gruntbuggly,

          How are your micturations today sir?

          1. Chris G Silver badge

            Re: Lorryload of Hay

            Mr NotSpartacus. Are you taking the p*ss?

  6. Mystic Megabyte
    Stop

    Derp!

    Where is Roger Wilco when you need him?

    1. I ain't Spartacus Gold badge
      Happy

      Re: Derp!

      He just left with Captain Over.

      And stop calling me Shirley!

  7. This post has been deleted by a moderator

  8. aregross
    Thumb Up

    Flippin Awesome

    "The Touch-and-Go Sample Acquisition Mechanism (TAGSAM)"

    That is awesome, people get paid good money to come up with that shit! I'd like that job!

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