Kryten
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Posts posted by Kryten
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36 minutes ago, radonek said:
I don't think any warhead used that technique ever. Blunt-body capsule was invented for Mercury, when ICBM's were already well established.
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Only a few early missile warheads used capsule-esque 'blunt body' designs-they're vulnerable to interception because they come down so slowly, and they're particularly visible to radar. Even scud warheads come in 'pointy end down'.
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13 minutes ago, tater said:
EDIT: I honestly had not been aware how thin the nozzle extension was, most is apparently ~0.3mm thick (!?) according to one of the pages I found.
It's a niobium-based alloy, so it's still going to be pretty expensive. Not so much from raw materials cost, but from manufacturing costs.
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Ejection seats would also have been used if they ended up re-entering over land, given absence of any kind of shock cushioning features on gemini.
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1 hour ago, TheEpicSquared said:
Didn't China once experiment with using wood for heat shields? I haven't read up fully on that (and I have no idea if it would be successful) but that's an idea...
Their early FSW sats used oak impregnated with an ablative treatment. Not very efficient in terms of mass, but it worked.
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2 hours ago, sevenperforce said:
Oh, right. Good catch. There was definitely a parachute on Vostok; it just wasn't enough to keep the person alive so they would eject once the altitude was low enough.
I'm pretty sure the flights with dogs didn't involve ejection, and they turned out fine. Most likely it would just be a very unpleasant landing like Soyuz 5, not a fatal one.
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There's no way this is happening. Sorry to be so pessimistic about it, but the last however many years or ARCA activities leaves no other plausible option.
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If you take out crewed spaceflight and associated support stuff, my gut feeling is it won't average more than a couple tons. I'll have a look through last year's launches and tot something up when I've got time.
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4 minutes ago, sevenperforce said:
Yeah, it gets complicated. In cases where the government subsidizes the launch, that subsidy isn't available to every potential customer. For example, I doubt a US-based comsat company with a 3.5 tonne LEO bird would be able to get the $15M price for a Polar Satellite launch.
That's not how launch subsidies generally work. Usually it's a subsidy that applies to all launches (to get increased launch rate) or to the pad work and maintenance; which means all customers benefit, commercial or otherwise. This was the case with Delta II, and is the case for Ariane.
PSLV in particular doesn't have subsidies, it just has at-cost launches for gov. customers and for-profit launches for commercial ones. ISRO cost and pricing has come up repeatedly in Indian parliament Q and A, which has ended up with it being the most open pricing of any current launch provider; the figures have been collated here.
NB: that $15 million is either made up or very old, it's below cost for even the cheapest PSLV variant.
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23 minutes ago, Veeltch said:
Here's something I have found on reddit:
Most of the numbers are dodgy. According to that Soyuz FG can't lift the Soyuz spacecraft, and Ariane can't lift ATV.
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1 hour ago, Benjamin Kerman said:
PAF is probobly payload attached fairing?
Payload attach fitting. Can be part of the fairing system (and is on F9), but not always.
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2 hours ago, Benjamin Kerman said:
Thought: have a heat shield on the front of the stage where the payload sits, so it reenters forward...
They need a standard PAF on the front to count for USAF cert.
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11 minutes ago, sevenperforce said:
The payload fairing on the Falcon 9 is wide enough to loft ISS modules. It's also large enough to launch a folded Canadarm. The ISS could have been assembled using repeated Falcon 9 launches (alternating crewed and uncrewed) more rapidly and more cheaply than it was with the Shuttle. And that's if it was being flown expendable. Flying reusable, the cost savings would be astronomical.
None of the US modules were capable of maneuvering in space or attaching autonomously.
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7 hours ago, munlander1 said:
Once the iss is decommissioned, what are they going to do with it?
The plan for is to deorbit it into the south Pacific using a pair of Progress' or one of the new Russian TGK PGcargo vehicles. Some bits will probably come down intact, but you'll have a hard time finding and recovering them.
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And this the spacecraft itself will need checks and maintenance.
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48 minutes ago, CatastrophicFailure said:
Yup, @DMagic's right. In fact, SpaceX had been quietly developing a new system to automatically blow up their own crappy broken rockets with the specific aim of speeding turnaround time at the Cape. ULA, et al, would get a similar thing too. SX and the Air Force have said it might eventually make two launches in a day possible.
It's not a SpaceX system, it's an air force system. The first gen was flying in shadow mode on some of Orbital's rockets around the time SpaceX was founded. It's been a long time coming.
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1 hour ago, sevenperforce said:
Is the distinction between "suborbital sounding-rocket class" and "orbital-class first stage" meaningful? I mean, I suppose you could call New Shepard orbital class. It's notionally possible to launch a payload to LEO from a starting velocity of 1.3 km/s and a stage+payload mass of 4.5 tonnes, but you're cutting it pretty close. Falcon 1 staged a similarly-sized payload at twice the velocity of New Shepard.
There are entire orbital rockets that are less than 4.5 tonnes; it's not ultimately that hard in terms of total energy or impulse. You only have a hard distinction between 'orbital class' and 'suborbital class' if you're talking small rockets, up to maybe two tons.
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So when I'm in here in three years or so saying F9 barely counts as reusable because it's not in the same class as NG, you'll be fine with it?
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11 minutes ago, sevenperforce said:
You can also look at it in terms of payload. On escape, the Aerojet Rocketdyne CCE-SRM develops 70,000 lbs of thrust, accelerating the BO crew capsule at a peak of 7 gees. Thus, the crew capsule masses around 10,000 lbs or 4.5 tonnes. So the New Shepard propulsion module delivers 1.3 km/s to a 4.5 tonne payload. In contrast, the Falcon 9 first stage on GTO missions delivers nearly twice that velocity to a 120+ tonne payload.
But that's still more than enough energy to be 'orbital class'. Heck, NS is in the same size class as, and likely has more total impulse than Falcon 1. If SX had recovered one of them, would you be here saying that didn't count?
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9 hours ago, CoreI said:
Also, one of the key factors in BO's ability to reuse New Shepard five times was that the heating from reentry was much less intense than what the Falcon 9 has to endure.
A returning falcon 9 won't receive much more heating in practice than what NS receives, because of the entry burn. Otherwise falcon would need a complete TPS covering, rather than a coating in a few areas like NS has.
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3 hours ago, Steel said:
Yes, but those engine were not used at launch, they were glorified (and highly complicated) RCS thrusters. My point was that to launch the shuttle again you have to build a new fuel tank, to launch a F9 again you do not.
Grasshopper never got above a kilometre altitude.
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Shuttle contained the fuel tanks and engines for orbital insertion, so even by your definition it was a reused stage.
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2 hours ago, Veeltch said:
So when is the reused stage flight? By the end of March?
Not likely. There's a Delta and an Atlas from the cape after the next falcon, and they're all jostling for position.
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7 minutes ago, Mitchz95 said:
I wonder if they'll have a camera on board and livestream it plummeting into the ocean.
There's no boat out there for this attempt, so they couldn't get the signal out.
Blue Origin Thread (merged)
in Science & Spaceflight
Posted
There was an ESA concept for a capsule on Ariane that would use an LES under a special quick-release fairing. SNC probably aren't doing that with DC, but it is possible.