SpaceX Falcon 9 v1.1 - Jason 3 - SLC-4E Vandenberg - Jan 17, 2016 - DISCUSSION

[Robotbeat]

The issue has already been decided. V1.1 is a suitable substitute for V1.0, now that it's had a successful flight.

(And the engines are throttleable, you guys.)

[Lar]

The issue has already been decided. V1.1 is a suitable substitute for V1.0, now that it's had a successful flight.

(And the engines are throttleable, you guys.)

I thought the issue being discussed here was whether Jason was so extraordinarily light that extreme measures might be needed, beyond throttling (throttling has limits).... not the whole 1.1 substituted for 1.0 thing (which I for one would desperately like to see NOT reopened)

[Robotbeat]

The issue has already been decided. V1.1 is a suitable substitute for V1.0, now that it's had a successful flight.

(And the engines are throttleable, you guys.)

I thought the issue being discussed here was whether Jason was so extraordinarily light that extreme measures might be needed, beyond throttling (throttling has limits).... not the whole 1.1 substituted for 1.0 thing (which I for one would desperately like to see NOT reopened)

...well, if Jason is so dang light and if v1.1 has excess performance, it's not impossible for the stage to cut off with plenty of fuel still in the tank, which would reduce the peak acceleration, too. Otherwise, all you do is add some aluminum ballast or something. It really, really isn't a big deal.

[Joffan]

The issue has already been decided. V1.1 is a suitable substitute for V1.0, now that it's had a successful flight.

(And the engines are throttleable, you guys.)

I thought the issue being discussed here was whether Jason was so extraordinarily light that extreme measures might be needed, beyond throttling (throttling has limits).... not the whole 1.1 substituted for 1.0 thing (which I for one would desperately like to see NOT reopened)

...well, if Jason is so dang light and if v1.1 has excess performance, it's not impossible for the stage to cut off with plenty of fuel still in the tank, which would reduce the peak acceleration, too. Otherwise, all you do is add some aluminum ballast or something. It really, really isn't a big deal.

Yes - it's not like we're dealing with solids here. The engines can always be shut down. Realistically if you have reached a high g-force (and have also throttled down as far as possible) you have already given the payload a relatively large dV.

If in doubt, give the satellite itself a bigger fuel tank .

[Lars_J]

As others have mentioned, the v1.1 has more throttling capability than v1.0. If the v1.1 will provide too much acceleration for the payload, the v1.0 would have as well.

[faramund]

Don't they also, besides just throttling, also have the option of shutting down engines earlier than their 'standard' profile.

[guckyfan]

Don't they also, besides just throttling, also have the option of shutting down engines earlier than their 'standard' profile.

This is about the second stage with its single engine.

[Lars_J]

Don't they also, besides just throttling, also have the option of shutting down engines earlier than their 'standard' profile.

This is about the second stage with its single engine.

...and the M1Dvac can throttle deeper than the M1CVac, so the point still applies.

[guckyfan]

Don't they also, besides just throttling, also have the option of shutting down engines earlier than their 'standard' profile.

This is about the second stage with its single engine.

...and the M1Dvac can throttle deeper than the M1CVac, so the point still applies.

Switching engines off prematurely applies to the second stage? What do they use for propulsion after that?

[faramund]

Ok, fair point about there only being one engine on the second stage  . I didn't wade backwards far enough in the thread to get that context.

[Norm38]

This sounds like the perfect flight to test second stage recovery. How about instead of ballast they put a heat shield and super dracos on the second stage?  Isn't that the whole plan?  To get full reuse for super light payloads like this?

Why ballast when recovery can be tested?

[Lar]

This sounds like the perfect flight to test second stage recovery. How about instead of ballast they put a heat shield and super dracos on the second stage?  Isn't that the whole plan?  To get full reuse for super light payloads like this?

Why ballast when recovery can be tested?

And we come back around to what I was suggesting a few posts upthread too. Groupthink[1] says that 2014 is too early to see much, if any, second stage reuse testing, even preliminary things like trying to reenter an otherwise unmodified second stage and not have it tumble initially (till it melts, since it's unshielded), but maybe 2015?

Exciting times ahead

1 - see the current poll standings here http://forum.nasaspaceflight.com/index.php?topic=33826.0 ... as of this writing it is 140/195 (or about 72% of respondents) for no reuse work at all.

[MP99]

This sounds like the perfect flight to test second stage recovery. How about instead of ballast they put a heat shield and super dracos on the second stage?  Isn't that the whole plan?  To get full reuse for super light payloads like this?

Why ballast when recovery can be tested?

And we come back around to what I was suggesting a few posts upthread too. Groupthink[1] says that 2014 is too early to see much, if any, second stage reuse testing, even preliminary things like trying to reenter an otherwise unmodified second stage and not have it tumble initially (till it melts, since it's unshielded), but maybe 2015?

Exciting times ahead

1 - see the current poll standings here http://forum.nasaspaceflight.com/index.php?topic=33826.0 ... as of this writing it is 140/195 (or about 72% of respondents) for no reuse work at all.

They have done secondary burns after payload release before.

I could see them doing this as a de-orbit burn after a LEO mission (seems very little additional effort), but nevertheless voted in the poll that this would not count as a recovery event.

Cheers, Martin

[slavim]

This sounds like the perfect flight to test second stage recovery. How about instead of ballast they put a heat shield and super dracos on the second stage?  Isn't that the whole plan?  To get full reuse for super light payloads like this?

Why ballast when recovery can be tested?

And we come back around to what I was suggesting a few posts upthread too. Groupthink[1] says that 2014 is too early to see much, if any, second stage reuse testing, even preliminary things like trying to reenter an otherwise unmodified second stage and not have it tumble initially (till it melts, since it's unshielded), but maybe 2015?

Exciting times ahead

1 - see the current poll standings here http://forum.nasaspaceflight.com/index.php?topic=33826.0 ... as of this writing it is 140/195 (or about 72% of respondents) for no reuse work at all.

They have done secondary burns after payload release before.

I could see them doing this as a de-orbit burn after a LEO mission (seems very little additional effort), but nevertheless voted in the poll that this would not count as a recovery event.

Cheers, Martin

Moreover, the second stage won't require as much R&D for re-use as the first one. It should be possible to accurately simulate the required heat shield and reentry characteristics and you'd only need the landing algorithms and sequence (which based on Morpheus, it's tougher than it looks. But they got it going finally).

For the first stage, you'd need to calculate max reentry speed and a lot of aerodynamic forces. It's definitely uncharted territory.

I think after dragon 2, they can get a reusable second stage fairly quickly.

[Danderman]

Edit: I was reminded via PM that launch vehicles are not typically ballasted but rather are throttled back or engines shut down if g loads need adjusting.

Delta II GPS launches required 1,000 lbs of ballast.

[kevin-rf]

I thought those weights where there to despin the satellite after the solid spin stabilized third stage burned out.

and are you sure it was 1000lbs, I thought it was three 75 lb weights.

[sdsds]

Groupthink[1] says that 2014 is too early to see much, if any, second stage reuse testing, even preliminary things like trying to reenter an otherwise unmodified second stage and not have it tumble initially (till it melts, since it's unshielded), but maybe 2015?

This seems like good thinking. As for 2014 being too early, I voted that way but ... for Jason 3 and indeed for recovery of any second stage that was tasked with a two-burn mission profile (i.e. GTO) the first step of stage recovery would likely involve a third burn, i.e. a second restart much later in the mission. I could see SpaceX doing early trials of just that step in 2014, even if there wasn't sufficient residual propellant to send the stage immediately into the atmosphere.

[Galactic Penguin SST]

Looks like NOAA is pressing to move up this satellite's launch to 1Q 2015 due to cancellation pressures from the CNES side if Jason-3 doesn't launches by then: http://www.spacenews.com/article/civil-space/39937noaa-seeks-boost-for-sat-programs-great-and-small-in-2015-budget

[Prober]

Looks like NOAA is pressing to move up this satellite's launch to 1Q 2015 due to cancellation pressures from the CNES side if Jason-3 doesn't launches by then: http://www.spacenews.com/article/civil-space/39937noaa-seeks-boost-for-sat-programs-great-and-small-in-2015-budget

Looks like agencies were unhappy with this launch.

"NOAA said its European partners on Jason-3 threatened to cancel their participation if the agency could not guarantee the launch by next spring. NOAA had previously scheduled the launch by the end of next year."

So the question becomes;  If the SpaceX launch schedule moved another 2 weeks cause of CRS-3, did the Jason launch also move 2 weeks more?    Can that time be made up?

[Ben the Space Brit]

So the question becomes;  If the SpaceX launch schedule moved another 2 weeks cause of CRS-3, did the Jason launch also move 2 weeks more?    Can that time be made up?

As it's a Vandenberg launch, at least hypothetically, you could make up quite a bit of time as there is no issue of recycling SLC-40 from the previous launch. So long as the LV can be delivered on time, then you could hypothetically launch it the day after an east coast launch (although I don't know what SpaceX's 2015 manifest is like or whether MCC-X at Hawthorne could be recycled that fast).