Re: DART nearly a bullseye

Craig Fink <WeBeGood@xxxxxxxxx> wrote in
news:pan.2005.04.18.11.25.48.249406@xxxxxxxxx:

> On Mon, 18 Apr 2005 06:37:15 +0000, Jorge R. Frank wrote:
>
>> "Ray S" <rjs41@xxxxxxxxxxxxx> wrote in
>> news:h8i8e.4963$dT4.4766@xxxxxxxxxxxxxxxxxxxxxxxxxx:
>>
>>> Glad to hear that NASA's DART mission was a near 100% success. Now
>>> on to a full blown autonomous rendezvous and docking demo of two
>>> unmanned NASA spacecraft. Hope NASA can pull this off soon.
>>>
>>> The Soviets, of course, pioneered autonomous rendezvous (and
>>> docking) procedures and have used them to support their Salyut and
>>> Mir space stations.
>>
>> Not quite. The Soviets/Russians use *automated* rendezvous and
>> autonomous prox ops, while DART is fully autonomous in both
>> rendezvous and prox ops.
>>
>> The distinction? With the Russian system, prior to Kurs acquisition
>> the maneuver plan is generated in mission control, and the Russian
>> equivalent of the FDO uplinks burn solutions to the spacecraft, which
>> dutifully executes them. The spacecraft has no "big picture" of the
>> overall plan. Once given a target vector, DART internally generates
>> and executes its own maneuver plan. The Soviets/Russians have never
>> done anything like that.
>
> Ahhh, so the Russians use "automated" rendezvous and "autonomous" prox
> ops, while the DART uses "autonomous" rendezvous and "no" prox ops.
> Maybe the next one will have prox ops.

That's how it turned out. You know that wasn't the intent.

Like Ray said, the Soviet system didn't work right the first time, either.

> Prox Ops and Docking is one area were both the Russians and United
> States, and soon the Europeans won't have learned the lessons of the
> past. The first hand experience of the Russian, when the Progress
> slammed into Mir has essentially been ignored by the Russian. The US
> being a bit arrogant, thinking, "we would never do that".

I've read the accident reports. There are indeed a lot of stupid things the
Russians did that set up the Progress-Mir collision that we would never do,
period.

> At some point in the future it's going to take another accident for
> people to realize there are better ways to dock with large space
> structures like the Space Station. Tethered Capture seem to me to make
> more sense, and would vastly reduce the maneuvering
> capability/requirements of a delivery vehicle to the Space Station.
> The delivery vehicle could have fewer thrusters, use less fuel, and
> improve overall safety.

Nope. It's just moving the problem. For docking you have a set of contact
condition limits to engage the docking mechanism, and for tethering you
have a set of capture conditions to catch the tether. You still need
translational thrusters and all the rest in order to achieve those
conditions. And as TSS taught us, tethers can be very dynamic, even when
you try your best to keep then taut along the gravity gradient. The
visiting vehicle can wind up hosing prop chasing the tether. All you really
buy with this scheme is reduced RCS plume impingement on the station, while
buying into a whole bunch of other headaches.

--
JRF

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Relevant Pages

  • Re: DART nearly a bullseye
    ... Certainly the Russian R&D systems have evolved and matured since the late ... where "automated" refers to the absence of humans on either spacecraft. ... a problem with the Russian autonomous rendezvous and docking system. ... Moscow decided to repeat the test on 25 June 1997 with Progress ...
    (sci.space.shuttle)
  • Re: Progress problems.
    ... When I listened to the second docking attempt, I thought I heard the PAO ... I'm more worried about the Elektron (Russian O2 generators) ...
    (sci.space.station)
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