SpaceX Falcon 9 : Hispasat 30W-6 (1F) : March 6, 2018 - DISCUSSION

[drnscr]

Sir, I don’t wish to sound disrespectful, I really don’t.  However, most of your posts in SpaceX threads seem rather negative toward the company.  Now, maybe i’m reading your comments wrong, and if I am, I apologize.  But, what is the point of always sounding negative when you post in a SpaceX forum?

I am not "always negative".  It just seems that way to those who only see perfection in the company. 

It is a terrific, innovative company, but some of its hyperbole is too much.  It can't, for example, bring itself to say "subsynchronous", or to bother to tell us before-hand that the orbit would be less than geosynchronous, leaving most to assume it would be geo, or even super, synchronous). 

Maybe I'm just wistful for the days when such details were precisely communicated before and during launches.

 - Ed Kyle

Again, Mr. Kyle, I meant no disrespect.  Please don’t assume I only see perfection in SpaceX.  I just love spaceflight and have been following it for over 55 years.  I think what the company is doing is absolutely amazing, nothing more.  I thought shuttle was absolutely amazing and the same for Skylab, Apollo, Gemini and Mercury.

[Ben the Space Brit]

Two objects related to today's #Falcon9 launch tracked in a sub-GTO orbit
2018-023A: 184 x 22,261 km, 26.97°
2018-023C: 186 x 22,215 km, 26.92°

https://twitter.com/Spaceflight101/status/971074423108358144

But what’s 2018-023B?  Nothing else launched last night.  This could indicate a potential unknown ride share happened last night.

Random shot in the dark: A classified payload mini-sat of some sort. In that scenario 023B is almost certainly being tracked but will never be publicly listed.

[CorvusCorax]

I see my speculation back on 2/22 was pretty close...
https://forum.nasaspaceflight.com/index.php?topic=43435.msg1791886#msg1791886

Ed,
Maybe the assumed normal of GEO-1800m/s days from the Cape are over... and we just need to adjust to it...

As I implied back in the linked posting above...
The SpaceX price sheet is likely driving customers to make darn sure they stay under the ASDS recovery price cap...
They can do this by either getting under the weight limit stated... OR (as I have said many times before)
Agreeing to take a less energetic boost, and put more delta-v into their own payload boosting systems...

GS had indicated discussions along those lines with customers had happened, and it seems we just saw the first of maybe many, that fly out at less then the typical GEO-1800m/s on purpose... 

How does that plot out by means of delta-V and ISP? To optimize the lifetime of the Sat, is it better to spend satellite propellant to compensate for a less energetic launch? Or would it make more sense to make the sat lighter by taking less propellant and let the stage do its job?

I guess Falcon9 is a peculiar case, since the upper stage has a relatively low ISP (348s) compared to the hydrogen upper stages of ULA (centaur, 450.5 s), Ariane5 (ECA 446s) - then again most russian hypergolic stages have even less isp. On the other hand it likely has less dry mass than the hydrogen stages.

The sat - if it has chemical propulsion, usually has even worse ISP, but not much. (NTO+UDMH ... 320-330s ? ) but it doesn't need to drag around the upper stage's dry weight and residual/deorbit propellant anymore

If it has electric propulsion, ISP is a no brainer, but then again these sats are usually light enough to be placed in a supersync orbit anyway and the propellant is so light you wouldn't get any more deltaV from the upper stage by tanking less. I haven't ever heard of a GTO bird with literally tons of Xenon on board yet Issue here is more the time to service due to low thrust.

I guess it really boils down to the tradeoff between shed stage mass versus lower ISP. The lighter the sat and the more ISP it has, the more sense it would make to get rid of the stage and load more prop instead. If the sat has much more mass than the empty stage and low ISP, relying on the stage is more efficient. But tanking more propellant makes the sat heavier and as such the stage more efficient, taking less propellant makes the stage less efficient. So the sweet spot might be right somewhere in between, with the sats tank not completely full all the way, but yet still going a bit deliberately subsync...

I guess if we had both sat and stage ISP and drymass, we could calculate the curve

[deruch]

Two objects related to today's #Falcon9 launch tracked in a sub-GTO orbit
2018-023A: 184 x 22,261 km, 26.97°
2018-023C: 186 x 22,215 km, 26.92°

https://twitter.com/Spaceflight101/status/971074423108358144

From this I find about 320 m/s to raise apogee to GEO, then 1800 m/s to circularize.   Total about 2120 m/s to go.

So performance was typical for a block 4, and customer accepted less than GEO apogee.

Lou, does the 320 m/s to raise the apogee already include Oberth Effect benefits of doing the burn at perigee?

[LouScheffer]

Two objects related to today's #Falcon9 launch tracked in a sub-GTO orbit
2018-023A: 184 x 22,261 km, 26.97°
2018-023C: 186 x 22,215 km, 26.92°

https://twitter.com/Spaceflight101/status/971074423108358144

From this I find about 320 m/s to raise apogee to GEO, then 1800 m/s to circularize.   Total about 2120 m/s to go.

So performance was typical for a block 4, and customer accepted less than GEO apogee.

Lou, does the 320 m/s to raise the apogee already include Oberth Effect benefits of doing the burn at perigee?

Yes, this is assuming the burn is done at perigee, where it is most efficient.  The calculation goes like this:

(a) From the initial orbit, find the "semi-major axis", "a".  This is just the average of the apogee and perigee, but measured from the center of the Earth (so you need to add in an Earth radius, about 6371 km).

(b) Now you can find the speed at any altitude 'r', using v = sqrt(gm *(2/r - 1/a)).  "gm" is a constant that depends on the mass of the object you are orbiting.  For Earth it is 3.98600441E+14.  Plug in perigee altitude to get 9947 m/s at perigee.

(c) Now do the same for a 184x35800 (GEO apogee) orbit.  Bottom speed will be 10259 m/s.

(d) The difference between these two speeds is the delta-V you need, actually about 312 m/s.  (My original 320 m/s estimate was from plugging values into an existing spreadsheet that assumed a 250 perigee.  The real answer is slightly less, precisely because of the Oberth effect you mention.)

[acsawdey]

I see my speculation back on 2/22 was pretty close...
https://forum.nasaspaceflight.com/index.php?topic=43435.msg1791886#msg1791886

Ed,
Maybe the assumed normal of GEO-1800m/s days from the Cape are over... and we just need to adjust to it...

As I implied back in the linked posting above...
The SpaceX price sheet is likely driving customers to make darn sure they stay under the ASDS recovery price cap...
They can do this by either getting under the weight limit stated... OR (as I have said many times before)
Agreeing to take a less energetic boost, and put more delta-v into their own payload boosting systems...

GS had indicated discussions along those lines with customers had happened, and it seems we just saw the first of maybe many, that fly out at less then the typical GEO-1800m/s on purpose... 

How does that plot out by means of delta-V and ISP? To optimize the lifetime of the Sat, is it better to spend satellite propellant to compensate for a less energetic launch? Or would it make more sense to make the sat lighter by taking less propellant and let the stage do its job?

I guess Falcon9 is a peculiar case, since the upper stage has a relatively low ISP (348s) compared to the hydrogen upper stages of ULA (centaur, 450.5 s), Ariane5 (ECA 446s) - then again most russian hypergolic stages have even less isp. On the other hand it likely has less dry mass than the hydrogen stages.

The sat - if it has chemical propulsion, usually has even worse ISP, but not much. (NTO+UDMH ... 320-330s ? ) but it doesn't need to drag around the upper stage's dry weight and residual/deorbit propellant anymore

If it has electric propulsion, ISP is a no brainer, but then again these sats are usually light enough to be placed in a supersync orbit anyway and the propellant is so light you wouldn't get any more deltaV from the upper stage by tanking less. I haven't ever heard of a GTO bird with literally tons of Xenon on board yet Issue here is more the time to service due to low thrust.

I guess it really boils down to the tradeoff between shed stage mass versus lower ISP. The lighter the sat and the more ISP it has, the more sense it would make to get rid of the stage and load more prop instead. If the sat has much more mass than the empty stage and low ISP, relying on the stage is more efficient. But tanking more propellant makes the sat heavier and as such the stage more efficient, taking less propellant makes the stage less efficient. So the sweet spot might be right somewhere in between, with the sats tank not completely full all the way, but yet still going a bit deliberately subsync...

I guess if we had both sat and stage ISP and drymass, we could calculate the curve

One other piece of this ... at ~ $100/lb the price of hydrazine/NTO propellant might be expensive enough to figure into the calculation too. By comparison kerolox is practically free.

[speedevil]

One other piece of this ... at ~ $100/lb the price of hydrazine/NTO propellant might be expensive enough to figure into the calculation too. By comparison kerolox is practically free.

The most obvious point is that unless you're mass limited, you're not paying for the kerosene in any way, but the whole rocket price.
Secondly - once you start this trade - you can't forget the dry mass.
If you've got (say) a 4 ton satellite with a two ton fuel tank, the ISP is more-or-less a wash, comparing Merlin with hypergolic.
But, you're now pushing 6 tons of nonpropellant mass, not four, if you use kerosene.

Considering the last 20 tons of mass, you either have:
4 ton satellite with 0 ton fuel, 2 ton S2, 14 tons fuel -> 4.1km/s.
4 ton satellite with 2 tons fuel, 2 ton S2, 12 tons fuel -> 3.75km/s + 1.4km/s = 5.15km/s.

In order to get to 5.1km/s with the first case, you need to drop the satellite mass to 2.4 tons.
So, adding 2 tons of fuel to your satellite actually almost doubles the actual payload the rocket can deliver.

[Steven Pietrobon]

Two objects related to today's #Falcon9 launch tracked in a sub-GTO orbit
2018-023A: 184 x 22,261 km, 26.97°
2018-023C: 186 x 22,215 km, 26.92°

https://twitter.com/Spaceflight101/status/971074423108358144

From this I find about 320 m/s to raise apogee to GEO, then 1800 m/s to circularize.   Total about 2120 m/s to go.

My delta-V program gives a total delta-V of 2113.4 m/s. This has a small plane change of 0.22 degrees at perigee. This saves 2.3 m/s.

Enter initial perigee (km): 184
Enter initial apogee (km): 22261
Enter initial inclination (deg): 26.97

theta1 =  0.00 deg, dv1 =  312.6 m/s
theta2 = 26.97 deg, dv2 = 1803.1 m/s
dv = 2115.7 m/s

theta1 =  0.22 deg, dv1 =  315.0 m/s
theta2 = 26.75 deg, dv2 = 1798.4 m/s
dv = 2113.4 m/s

[speedevil]

A slight rotation of the entire stack will help with separation if the release mechanism doesn't give its normal push, perhaps?

If you look carefully at the separation, you can see that though the stage and satellite are rotating, the spin axis seems to be aligned with the centre of the satellite.
So, no aid to separation.
Plus, the separation looks to be around 1m/s, which would have taken quite a rapid spin to equal.

From falcon payload document.

[Elthiryel]

From updates thread:

Object B now identified as Podsat, presumably what's described here:
https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3363&context=smallsat

From the linked document:

PODSat is intended for launch on a to-be-determined expendable launch vehicle in 2017. (...) the initial HPA would be hosted on a geostationary communications satellite, with the PODSat deployment occuring in a subsynchronous geostationary transfer orbit.

The document is dated August 2016. There aren't many launches to sub-GTO, is it possible that the PODSat operator was targeting this particular launch back then? Contract between Hispasat and SpaceX was publicly announced in September 2015 (http://www.spacex.com/press/2015/09/14/spacex-signs-new-commercial-launch-contracts). It may possibly mean that they were planning to go to sub-GTO from the very beginning. It impacts the satellite design, as when going to sub-GTO more fuel is required to reach the same operational lifetime compared to GTO/SSTO.

[Lars-J]

Do we know what the final orbit is for the Podsat? A GTO orbit with this low perigee is not going to be long lived.

[russianhalo117]

Do we know what the final orbit is for the Podsat? A GTO orbit with this low perigee is not going to be long lived.

PODSAT (DARPA HPA project) as planned was separated from the host sat (Hispasat 30W-6) before Hispasat 30W-6 performs its orbit raising sequence. As for deployment orbit information: PODSAT   2018-023B      387.19min    27.00deg   22250km   188km

PODSAT Background info:
PODSAT (Payload Orbital Delivery Satellite) is the third mission by NovaWurks to demonstrate the satlets technology.

Satlets are a new low-cost, modular satellite architecture that can scale almost infinitely. Satlets are small modules that incorporate multiple essential satellite functions and share data, power and thermal management capabilities. Satlets physically aggregate in different combinations that would provide capabilities to accomplish diverse missions.

The Payload Orbital Delivery system Satellite (PODSat) is a four-HISat PAC nearing the start of assembly, integration, and test. PODSat was integrated with the SSL built Hispasat 30W-6 satellite. PODSat is designed to be the free-flying element of the DARPA-funded Hosted POD Assembly (HPA), which seeks to provide a platform (the POD) and a separation mechanism for it be deployed by a host spacecraft. Conceived to take advantage of under-utilized launch vehicle payload mass and reliable, frequent launch opportunities, the initial HPA would be hosted on a geostationary communications satellite, with the PODSat deployment occurring in a subsynchronous geostationary transfer orbit.

PODSat would provide a demonstration of the ability of cellular architecture to incorporate a structural element, the POD chassis, into a PAC. Similar to the way app-based software architectures allow easy integration of new software, celluar architectures could offer that same feature to a variety of hardware options.

The PODSat experiment would also provide valuable in-orbit data on an orbit environmental regime outside of the first two experiments.

[CJ]

FutureSpaceTourist posted the blow in the updates thread a couple of days ago, and I was hoping that someone could comment on it.
The object seems to come from the pad area. If it's dense (say, a piece of the flame trench) that could pose a danger to the LV. However, due to where it's at, I was wondering if it's a piece of foil.

Anyone have any ideas what kind of a thing it is?

[leetdan]

Looks like a pair of calipers to me.

[jcm]

Do we know what the final orbit is for the Podsat? A GTO orbit with this low perigee is not going to be long lived.

PODSAT (DARPA HPA project) as planned was separated from the host sat (Hispasat 30W-6) before Hispasat 30W-6 performs its orbit raising sequence. As for deployment orbit information: PODSAT   2018-023B      387.19min    27.00deg   22250km   188km

PODSAT Background info:
PODSAT (Payload Orbital Delivery Satellite) is the third mission by NovaWurks to demonstrate the satlets technology.

Satlets are a new low-cost, modular satellite architecture that can scale almost infinitely. Satlets are small modules that incorporate multiple essential satellite functions and share data, power and thermal management capabilities. Satlets physically aggregate in different combinations that would provide capabilities to accomplish diverse missions.

The Payload Orbital Delivery system Satellite (PODSat) is a four-HISat PAC nearing the start of assembly, integration, and test. PODSat was integrated with the SSL built Hispasat 30W-6 satellite. PODSat is designed to be the free-flying element of the DARPA-funded Hosted POD Assembly (HPA), which seeks to provide a platform (the POD) and a separation mechanism for it be deployed by a host spacecraft. Conceived to take advantage of under-utilized launch vehicle payload mass and reliable, frequent launch opportunities, the initial HPA would be hosted on a geostationary communications satellite, with the PODSat deployment occurring in a subsynchronous geostationary transfer orbit.

PODSat would provide a demonstration of the ability of cellular architecture to incorporate a structural element, the POD chassis, into a PAC. Similar to the way app-based software architectures allow easy integration of new software, celluar architectures could offer that same feature to a variety of hardware options.

The PODSat experiment would also provide valuable in-orbit data on an orbit environmental regime outside of the first two experiments.

Do you mind sharing your source for the above? There's also a whole bunch of PODSAT stuff on the SSLMDA site that
doesn't mention NovaWurks so I am wondering if there are two separate DARPA PODSAT contractors
https://sslmda.com/pods/index.html

[russianhalo117]

Do we know what the final orbit is for the Podsat? A GTO orbit with this low perigee is not going to be long lived.

PODSAT (DARPA HPA project) as planned was separated from the host sat (Hispasat 30W-6) before Hispasat 30W-6 performs its orbit raising sequence. As for deployment orbit information: PODSAT   2018-023B      387.19min    27.00deg   22250km   188km

PODSAT Background info:
PODSAT (Payload Orbital Delivery Satellite) is the third mission by NovaWurks to demonstrate the satlets technology.

Satlets are a new low-cost, modular satellite architecture that can scale almost infinitely. Satlets are small modules that incorporate multiple essential satellite functions and share data, power and thermal management capabilities. Satlets physically aggregate in different combinations that would provide capabilities to accomplish diverse missions.

The Payload Orbital Delivery system Satellite (PODSat) is a four-HISat PAC nearing the start of assembly, integration, and test. PODSat was integrated with the SSL built Hispasat 30W-6 satellite. PODSat is designed to be the free-flying element of the DARPA-funded Hosted POD Assembly (HPA), which seeks to provide a platform (the POD) and a separation mechanism for it be deployed by a host spacecraft. Conceived to take advantage of under-utilized launch vehicle payload mass and reliable, frequent launch opportunities, the initial HPA would be hosted on a geostationary communications satellite, with the PODSat deployment occurring in a subsynchronous geostationary transfer orbit.

PODSat would provide a demonstration of the ability of cellular architecture to incorporate a structural element, the POD chassis, into a PAC. Similar to the way app-based software architectures allow easy integration of new software, celluar architectures could offer that same feature to a variety of hardware options.

The PODSat experiment would also provide valuable in-orbit data on an orbit environmental regime outside of the first two experiments.

Do you mind sharing your source for the above? There's also a whole bunch of PODSAT stuff on the SSLMDA site that
doesn't mention NovaWurks so I am wondering if there are two separate DARPA PODSAT contractors
https://sslmda.com/pods/index.html

Both companies are partners in the same DARPA-funded Hosted POD Assembly (HPA) project.

http://space.skyrocket.de/doc_sdat/podsat.htm
NovaWurks PODSat was what was deployed from SSLMDA host satellite that provided the rideshare. DARPA is what funded the technology and the carrier was developed jointly by NovaWurks and SSLMDA but NovaWurks AFAIU actually built the carrier..

[georgegassaway]

I get a ~380 m/s difference between the two orbits [expendable vs recovery]

This makes excellent sense, and is a better way to look at it than percentage (which can vary a lot by mission, since the rocket equation is very non-linear).

To have enough fuel for recovery, SpaceX needs to save about 9 seconds of fuel (this is 81 engine-seconds, of which they use about 20x3 = 60 for re-entry, and about 21 for landing with 3 engines (30 if they use single engine)).  At the end of the first stage burn, the rocket is accelerating at 4-5 Gs.   4.5 Gs x 9 seconds is about 395 m/s, very close to your value.

Re-entry burn is 1-3-1. Center ignites first for about 1 second, then the outer two for most of the burn, the outer two shut down, then about one second later the center engine shuts down. So if a re-entry burn lasted exactly 20 seconds,  then that'd be more like 56 engine-seconds (20 + 18 + 18).   

Doing a quick look at the FH video for comparison, Center core aiming at an ASDS landing, does seem to have been about 20 seconds for re-entry burn.   Side booster re-entry burns, those were about 12 seconds, which would be about 32 engine-seconds (of course those had a different incoming profile for RTLS after the Boostback burn, than for an ASDS profile).

In any case, you make a nice point.

Just wanted to note that if anyone wanted to do a more detailed work (not ballpark) along those lines, they'd need to account for when there is only one engine burning, then when all three are burning, for a specific re-entry profile.   Also..... the issue of how much fuel is used for say the first two seconds when an engine ignites.  I would not assume it would use the same amount of fuel for the first two seconds as for the next two seconds, I would expect it to be less (especially fuel use  for the first second). 

[speedevil]

Ride-share confirmed.

What are the approvals required for such a ride-share?
Is it just 'get the approval of your host'?

Do these satellites have to be separately approved, or are they buried in the not-revealed applications paperwork, and only the main satellite reported publically?

[deruch]

From falcon payload document.

Just to be clear, that (spin about the X-axis) wasn't the type of rotation imparted to this satellite.

[speedevil]

From falcon payload document.

Just to be clear, that (spin about the X-axis) wasn't the type of rotation imparted to this satellite.

I may have been misremembering - but I thought it was.
The cameras that are pointed not along the axis of the stage show it rotating confusingly, but the payload deploy makes it clear - the satellite is departing along the spin axis, which makes the spin axis the X axis.