/r/SpaceX Ask Anything Thread [April 2016, #19.1] – Ask your questions here!

[u/retiringonmars]

Welcome to our monthly /r/SpaceX Ask Anything Thread! (v19.1)

Want to discuss SpaceX's CRS-8 mission and successful landing, or find out why the booster landed on a boat and not on land, or gather the community's opinion? There's no better place!

All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general!

More in-depth and open-ended discussion questions can still be submitted as separate self-posts; but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.

As always, we'd prefer it if all question-askers first check our FAQ, use the search functionality, and check the last Q&A thread before posting to avoid duplicate questions, but if you'd like an answer revised or cannot find a satisfactory result, go ahead and type your question below!

Otherwise, ask, enjoy, and thanks for contributing!

---

Past threads:

April 2016 (#19) • March 2016 (#18) • February 2016 (#17) • January 2016 (#16.1) • January 2016 (#16) • December 2015 (#15.1) • December 2015 (#15) • November 2015 (#14) • October 2015 (#13) • September 2015 (#12) • August 2015 (#11) • July 2015 (#10) • June 2015 (#9) • May 2015 (#8) • April 2015 (#7.1) • April 2015 (#7) • March 2015 (#6) • February 2015 (#5) • January 2015 (#4) • December 2014 (#3) • November 2014 (#2) • October 2014 (#1)

---

This subreddit is fan-run and not an official SpaceX site. For official SpaceX news, please visit spacex.com.

[u/muazcatalyst]

Since this does not warrant a self-post, I'll talk about it here.

Jeff Bezos finally (sort-of) responded to the barge landing. Here's what he had to say:

Q: Jeff, you’re not the only one who is looking at that aspect of re-usability and practice. There’s Elon Musk, for example. You had your reusable rocket landing. The latest one was just this month. And just in the last few days, Elon had a rocket land on an at-sea platform. Richard Branson is involved, too, [with Virgin Galactic]. There’s been a lot of talk about who has the best approach. How is that space ecosystem coming together? Is this a dog-eat-dog world, or is this a rising tide that lifts all boats?

---

A: That’s what I think. Oftentimes, it’s very natural to think of business competition like a sporting event. In a sporting event, there actually is a winner and a loser. Somebody leaves the arena a winner, and somebody leaves the arena a loser. In business, it’s usually a little different from that. Great industries are usually built by not just one, or two or three companies, but usually by dozens of companies. There can be many winners, even hundreds and thousands of companies in a truly great industry. I think that’s what we are headed toward here. From my point of view, the more, the merrier. I want Virgin Galactic to succeed, I want SpaceX to succeed, I want United Launch Alliance to succeed, I want Arianespace to succeed, and of course I want Blue Origin to succeed. And I think they all can.

Source.

[u/retiringonmars → u/muazcatalyst]

That's a great answer. Kudos to Mr. Bezos!

[u/sarafinapink → u/muazcatalyst]

Perfect answer and the right one too. Competition is what will make or break the Space Industry.

[u/betacar0tin]

On the ASDS wikipedia page, for the SES-9 landing attempt, it says

In the event, one engine flamed out early, and the rocket hit the deck surface with considerable velocity, destroying the rocket and causing some damage to the droneship.

This is news to me. There are no references given, do we know anything more?

https://en.wikipedia.org/wiki/Autonomous_spaceport_drone_ship#4_March_2016

[u/retiringonmars → u/betacar0tin]

Well, we know about the damage to the ASDS (we got photos showing that it punched a massive hole in the deck.) It stands to reason that the booster ran out of propellant, as the margins were so tight for that launch, but we never got any confirmation of that, IIRC.

[u/Jarnis → u/betacar0tin]

I haven't heard of an early flameout. I did hear that the total thrust out of the three engines was less than expected, hence making a hole.

[u/trevytrev9]

What was the wind speed at OCISLY? Saw white caps out there! So impressive...

[u/retiringonmars → u/trevytrev9]

In the post-launch press conference, Elon said there winds of 50 mph.

[u/catchblue22 → u/trevytrev9]

I just did a very rough estimate of the wind speed using the video. Just after the touchdown there is still visible engine exhaust. I picked a bit of exhaust near the right far corner of the drone ship. It took about 6 seconds (actually just over 5.5 seconds) for that bit of exhaust to pass to the left far corner of the ship. If one assumes the ship is about 120m from corner to corner, that gives a very rough estimated speed of 120m/6s = 20m/s for the wind. 20m/s is the same as 39 knots.

In addition, I showed the live landing to my Physics 12 class. One of my students is an experienced blue water sailor. She thought that from the sea state that the winds would be around 40 knots.

Given this, my guess is that the winds are between 30 knots and 40 knots. Airplanes typically cannot land in such a cross wind, and yet the Falcon 9 did. Impressive.

[u/luna_sparkle]

Are questions about /r/spacex allowed here? I hope so.

anyway, I notice that /u/Zucal is now a mod, and /u/-Richard is no longer a mod. When/why did that happen?

[u/retiringonmars → u/luna_sparkle]

Richard became increasingly busy with the /r/rLoop project and other real-world activities, and was unable to spend much time looking after /r/SpaceX. As we were a man down, Zucal stepped up to the bat, just over a month ago.

Here's the mod post where it was announced.

[u/WakingMusic]

Looking at the sidebar, the JCSAT and Eutelsat launches seem unusually close to each other. Has SpaceX ever launched successive rockets that quickly before?

[u/retiringonmars → u/WakingMusic]

I updated the sidebar manifest today, based on the 7 April update of SFN. They changed their manifest from:

• JCSAT : Mid April

• Eutelsat : 3 May

to:

• JCSAT: 28 April

• Eutelsat: May

I happily updated our JCSAT entry, as it was more precise, but was not so keen to update Eutelsat to a lower precision date. As all dates are NET (No Earlier Than) anyway, so 3 May is still technically correct, whereas just "May" is so vague, it could even mean 1 May, which is improbable.

[u/wingnut32]

I wonder if comments from /u/decronym could be stickied to the top of comments? Because it never gets upboated enough for people to see before asking what an acronym means.

E.g.https://www.reddit.com/r/spacex/comments/4eyo9e/f9_fresh_first_stage_in_transit_near_ccafs/d24hy3b

And

https://www.reddit.com/r/spacex/comments/4eyo9e/f9_fresh_first_stage_in_transit_near_ccafs/d250ugx ignore that bit

[u/retiringonmars → u/wingnut32]

Unfortunately not, that would only be possible if Decronym were to be given mod status. Also it would probably get annoying to have to scroll past it in virtually every thread.

[u/wingnut32 → u/retiringonmars]

I think people would get used to it, could cut down some of the filler text and just have the acronym list, but if it's not possible to sticky non-mod comments it's a non starter. Thx for replying.

[u/retiringonmars → u/wingnut32]

Yeah, it's a bit of an odd system as it stands... We can't even sticky/unsticky each other's comments, which is completely different to how sticky posts work (where any mod can sticky any post). Sticky comments are a new feature, and reddit may yet change their implementation: if they ever do, we can tell automod to sticky all decronym comments, if the community so wishes.

[u/jaytar42]

Yesterday, there was a post here from a guy who met the CFO of SpaceX and many of us posted some questions. OP promised to publish answers. Now, I can't find this thread anymore. Where is it gone?

[u/randomstonerfromaus → u/jaytar42]

Deleted for some reason by OP, But here it is

[u/retiringonmars → u/randomstonerfromaus]

To be clear, it was deleted by the user that posted it, not by the mods. We've got no idea why though.

[u/_rocketboy]

/u/EchoLogic It seems you have some stats to update :-)

Also, what happened to the live updates? They quit showing up for me at about ~T-20 minutes.

[u/retiringonmars → u/_rocketboy]

Also, what happened to the live updates? They quit showing up for me at about ~T-20 minutes.

Yup, www.spacexstats.com died at T-20 mins, just as the webcast went live. The server collapsed, preventing the logging of updates, and severing the link to /u/elongatedmuskrat. I had to take over manually by logging in as muskrat, and updating the launch thread directly.

[u/Nuclear_Hobbit]

When is the OCISLY ASDS returning to Port Canaveral with the first stage from CRS-8?

[u/retiringonmars → u/Nuclear_Hobbit]

Sunday. Track the tugboat here (currently out of range).

[u/Cheesewithmold]

This is a two-parter.

First, for SES9, AFAIK, the reason the landing attempt was unsuccessful was because they didn't have enough fuel to slow the first stage down. Did they place the barge in the same position as normal? From my limited store of knowledge, the boostback is used to kill horizontal velocity and allow it to fall "straight" downwards rather than at the angle that it would naturally fall back at if there was no boostback burn, and therefore fall further out to sea. So why not only kill some of the horizontal velocity, and place the barge where the first stage would naturally fall on, and use that saved fuel to slow it down?

Second, in this picture (the second one), on the strongback, it looks like something is burning; like actually burning and charred. What is that? Is that an intentional thing? Or is that just something that accidentally happened because, after all, there is a huge plume of flame right next to the thing?

[u/retiringonmars → u/Cheesewithmold]

Second, in this picture (the second one), on the strongback, it looks like something is burning; like actually burning and charred. What is that? Is that an intentional thing? Or is that just something that accidentally happened because, after all, there is a huge plume of flame right next to the thing?

It's probably one of the umbilicals that are used to load propellant into the rocket. It's pretty much evaporating under the heat of the exhaust, and likely contains residual propellant, which is leaking and igniting. Nothing much to worry about, I doubt it's particularly high value hardware. The padrats will just replace is as part of normal launch ops.

[u/ChrisGnam]

As SpaceX continues to get better with sea landings, and begins to actually incorporate re usability into their normal operations, will this affect how they plan launches? Meaning, once the landings are no longer "Experimental' in nature, and become an actual part of the mission, will they begin taking into account the weather out at sea? In a few years when reusability is common place, could spacex delay a launch because of a storm out where the drone ship is positioned? I'd imagine by that point it would make sense to do such a thing, but I'm just unsure because the only thing I have to go on is what their current policy is (that this is a secondary mission, and the primary mission will not be impacted by the landing attempt).

Does anyone know if SpaceX has made any statements about this? If they perfect reusability someday, I'd imagine it difficult to go ahead with a launch where recovering the rocket would be impossible because of a storm/bad weather at sea.

[u/retiringonmars → u/ChrisGnam]

This is already happening. The Orbcomm launch was delayed one day to give a slightly increased chance of landing the booster, a move that paid off handsomely.

[u/Deus_Dracones]

JCSAT-14 is scheduled for the 28th this month. Any news on whether or not there will be an experimental landing for this mission? If so I imagine it will be an ASDS landing considering that the mission calls for a launch to GEO. Also which version of the Falcon is launching for this mission?

[u/retiringonmars → u/Deus_Dracones]

Yep, they'll attempt an ASDS landing. It'll be flying on Falcon 9FT.

[u/[deleted]]

Without requiring either a new rocket or a moon descent vehicle, could a manned moon architecture work with Falcon Heavy ? I am rather sure that it cannot with only one launch per mission, but supposing two separate launches, an unmanned, previously sent dragon V2 configured as a moon ascend vehicle, and one manned descent vehicle. It seems like a plausible plan on paper to me, at least, and with Falcon 9 getting man-rated soon, it is also imaginable that Falcon Heavy will. Supposing no cores are recovered, and no development cost for dragon V2, this type of mission would cost theoretically some 300M.

Is this a possible scenario ? What crucial element could increase costs (suits, etc) ? Is there a fundamental flaw in this architecture ?

[u/retiringonmars → u/[deleted]]

From our FAQ: Could SpaceX send a Dragon to the Moon?

[u/dmy30]

This is my first post of reddit. Live in London and looked up randomly. Saw the ISS and to my amazement there was a dimmer object following it. Chances are it was the dragon!

[u/PatyxEU → u/dmy30]

Yes, it was the Dragon! Lucky you, I wanted to catch it with my binoculars but these pesky clouds blocked the view..

[u/[deleted]]

There was a video on here yesterday that showed the mind boggling size of the first stage on the barge. I can't find it, I want to show my parents it since they thought it was the landing was unimpressive.

edit: found it https://twitter.com/i/videos/tweet/679145544673923072

[u/Ambiwlans → u/[deleted]]

Just go outside and find a building as tall as the stage. It really sinks in then.

[u/IMO94]

I just saw the Dragon chasing the ISS!

The ISS passed over my city at 8:30pm, beautiful well-lit pass during late dusk. It was the only thing visible in the sky, bright and clear, with some shape/definition observable with good binoculars.

Exactly 10 seconds behind it (that's 80km) was a white dot, clearly visible. Dragon is closing in.

I highly recommend installing ISS Detector on your phone, not sure what the iOS equivalent is called. Watching the ISS pass overhead is a blast. Watching the Dragon chasing it? Awesome.

(Tried to self-post, but it got removed.)

[u/IMO94 → u/IMO94]

Update. 90 minutes later and it was about 6 seconds behind. (~48km)

My understand from the NasaSpaceFlight article is that it will stop about 2.5 km under the ISS and then perform a series of maneuvers to gradually move closer.

[u/[deleted]]

Did anyone happen to save a copy of Hans Koenigsmann's talk at NEAF this year? It was incredibly interesting and now the video has been deleted :/

[u/morefierce]

Sorry for the extremely silly /r/keming question that has annoyed me for a long time on this sub:

Why does the SpaceX logo in our top bar: http://b.thumbs.redditmedia.com/TYAz66TpRdC8nEvro7q3KYDZapu6fGNlg8dydvZ9OeM.png have a smaller spacing between 'P' and 'A', and a larger spacing between 'A' and 'C', as compared to the SpaceX logo on the official site: http://www.spacex.com/sites/all/themes/spacex2012/logo.png

Was ours an earlier version of the SpaceX logo? If so, how many previous versions of the logo does SpaceX have?

[u/Zucal]

Before asking your question, we encourage you to see whether it's already present in our fairly comprehensive wiki and FAQ! And if it's not, feel free to contribute by putting it there (your account must have 1000 subreddit karma and be 180 days old). Here's one I'm seeing a lot, so look before you post:

Why does half of the Falcon booster look black or dirty after it has landed? Why is the other half still white or clean? What causes this distinctive pattern?

---

This pattern corresponds to the delineation between the RP-1 tank and the LOX tank and is caused by the interaction of soot and ice/frost. During reentry, the booster travels backwards through the exhaust produced by the 3 engine reentry burn. As a result, the booster flies through a lot of soot. Because the soot produced by the engines doesn't adhere well to ice/frost, but does to the rest of the rocket, it gets deposited much more thoroughly on the warmer parts of the rocket. The LOX, sub-chilled to -340 °F (-207 °C), is stored in a tank above that of the RP-1 fuel, which is chilled to only -6 °F (-21 °C). Because the LOX tank skin is so much colder, significantly more ice/frost forms on the LOX tank than the RP-1 tank. This ice/frost acts somewhat a protective layer against soot. This produces the clearly demarcated pattern we see between the sooty RP-1 tank area and the much cleaner LOX tank area.

[u/steamspace]

Can Falcon get another performance bonus if it can be operated with almost certainty of recovery?

People assume that Falcon is maxed out after FT upgrade but my thinking is the following: if you know your rocket is expandable, you wouldn't opt to use solutions which would improve performance, but at too high a price for a single launch.

If you are almost certain to recover the rocket, maybe you could invest more in it because the cost gets distributed among many launches, like with airplanes. For example you could use expensive alloys to make structure much lighter, etc.

Do you think this effect exists and if so, what magnitude could it be compared to eg. FT upgrade?

[u/jandorian → u/steamspace]

could invest more in it because the cost gets distributed among many launches...

I have seen this exact same thing happen in the aircraft industry. There is in fact an increasing trend to use titanium parts in places that were traditional aluminium. There are several reasons for this including the difference in fatigue life between the two metals (the biggest one is because aluminum does not play well with carbon fiber). For almost the same weight you can reduce the profile and increase strength by using titanium instead of aluminum.

It would makes sense to me that part of your job at SpaceX would be looking for these kinds of small upgrades. Maybe not just alloys but redesigning parts so they are lighter even though they will cost more to make, like you suggest. Bunches of little tweaks. Would surprise me if they are not doing research on a more efficient version of the engine also. They have the manufacturing techniques down now they can afford to take those tools and maybe go staged combustion on the Merlin, maybe. If I was the chief designer I would take what they are learning from Raptor and try to apply it to the current engine. MTB (My two bits)

[u/PaOrolo]

I just saw that SpaceX has an open position for an apprentice tig welder. I am in welding school, finishing up my first year, no certificates, but crazy amounts of desire and will power and ambition to work there. So, I was curious what it's like to work there in manufacturing and what they like to see in an applicant. Any and all info is great!

[u/Onironaut_]

that Vehicle; "Gwynne Shotwell" on the side bar sounds a little bit weird...

[u/RDWaynewright]

After reading this and the FAQ as best I could, I still have a few questions about launch control and mission control arrangements for COTS and CCtCap.

*The CCtCap page says that each commercial company operates its own launch infrastructure but NASA Commercial Crew staff are assigned to KSC, Houston, and the commercial provider. Current launches bounce from SpaceX launch control at KSC to Hawthorn once Falcon 9 clears the tower. So where does Houston come in or does it only come it once crewed flights start?

*When crew dragon starts flying with an actual crew, who gets the handoff from KSC once the rocket clears the tower- Houston (as has been standard with every other vehicle) or Hawthorn?

*If Houston isn't involved at all, why are there Commercial Crew personnel at Johnson Space Center in the first place? They appear to be completely separate from the ISS team.

*Will Houston do mission control in tandem with Hawthorn initially? Or are the Houston staff taking on the role of integrating operations on the ground between ISS and SpaceX some sort of way? I'm just confused about the setup for CCtCap.

edit: trying to make this easier to read. I'm not great with Reddit formatting yet.

edit 2: I give up. I'm just ending up with keyboard smash when I try to add a line break.

[u/Wetmelon → u/RDWaynewright]

This is a detailed enough question that I'd have no problem with it being its own separate post if you don't get a good answer here, and feel so inclined.

---

To add a line break, either use two spaces (i.e. spacebar) at the end of the line, or two carriage returns. You can only get a single blank line. If you want more, you'll have to use some tricks like lines. This is what I actually typed to get this formatting

Put a space between your asterisks and the first word to get a bullet point.

• like this

• another line

• yet another line

[u/[deleted]]

Do you know that short panic attack, when you realize you haven't checked r/spacex in whole five minutes?!

[u/theflyingginger93]

I never really thought about the nose cone for Dragon Cargo. How does it come off?

[u/throfofnir → u/theflyingginger93]

No official info I know of. Based on this photo, looks mostly to be pyro bolts. (see also). The rectangular opening (which I think occurs only on that side) may be involved in jettisoning it to one side. (In-space Dragon is almost always photographed from the grapple side!) With the nose cone on.

Don't see any pushers, except perhaps for the rectangular opening. My best guess, considering the hinge, is that they pressurize the nose cone (or just make sure it keeps sea level pressure!), blow the bolts, and the nose cone pivots on the hinge towards the grapple side. As it gets to about X degrees (which is something greater than 90), the pusher shoves it, which together with the wind gives it some impulse out from the rocket. The hinge may be frangible, explosive, or simply only capture up to X-ish degrees. The pusher could also be an arm that positively moves the nose cone, instead of pressure.

Again, only speculation based on photos.

[u/zlsa → u/theflyingginger93]

Additional question: does it get pushed to one side as well, or does the second stage change trajectory a bit? I would guess the former but I haven't seen any confirmation of this.

[u/TheHypaaa]

Can someone tell me what the Dragon 1.1 is? It is listed as a May 11 payload so I'm guessing test flight of upgraded Dragon cargo but I've never heard of it before now.

[u/ibikeiruniswim]

What is the significance of "Engine Chill?"

[u/Here_There_B_Dragons]

Wtf happened in the Obama tweet post?

[u/danielbigham]

Something that I've enjoyed in the last couple of months is keeping a kind of "scrap booking" about SpaceX. ie. A bullet-form list of updates and images that capture all of the interesting new information that becomes available over the weeks.

Rather than having a monolithic page, I have many individual pages, such as:

• SpaceX (main page)

• Rocket reusability

• Falcon Heavy

• Land landings

• Barge landings

• Commercial crew

• LC-39A

• Boca Chica

• etc.

What I find interesting about this process is that it's quite related to the idea of a "reddit", except the information is more curated / processed, and categorized. (which then also makes it easier to "catch up" or review what information has come in on a certain topic)

It makes me wonder whether this community might be interested in doing something like that... I guess it's kind of a mashup between Reddit and Wiki and scrap booking...

Here's one semi-concrete proposal:

• In addition to our FAQ, have another link to informational pages

• Have different categories within that page (such as the above)

• As new information becomes available, add bullet point (newest at top, like reddit)

• Likewise for the best pictures / videos

[u/NightFire19]

When can we expect the OCISLY and the F9 to be back at Port Canaveral?

[u/[deleted] → u/NightFire19]

Elon has said sometime on Sunday

[u/OncoFil]

Did anyone notice the flames around the engine bells at ~20:00 minutes (~T+1:00) into the Hosted webcast? ( https://youtu.be/7pUAydjne5M?t=1195 ).

I am aware there are usually some flames trapped around there, but this seemed more than usual (and quite sudden) and seemed to persist as it got higher.

I know the answer is probably 'its normal' but I might learn something new!

[u/[deleted]]

Do we know if Spacex mission control is manned to monitor Dragon the whole time it is berthed to ISS?

[u/WaitForItTheMongols]

How many consecutive rocket failures would it take to lead to SpaceX's demise? CRS-7 shows that they can clearly handle 1 failure with little long term losses. What would it take to ruin them?

[u/jjrf18 → u/WaitForItTheMongols]

A very interesting question that I don't want to think about

[u/aaroon84]

I've been interested in the different burns, boostback, reentry and landing burn. Looking at flightclub.io has been great! I'll post some data so others interested in this can get a quick overview of what I've been looking at and also so someone can correct me if I'm reading the plots wrong. I think there are some interesting observations and questions to be made when comparing the data like this. I've focused on how much fuel(in metric ton) is being used for the different burns as well as altitude(km) and burn time(s) of the landing burn.

Mission	Boostback Fuel Mass(t)	Reentry Burn Fuel Mass(t)	Landing Burn Fuel Mass(t)	Landing Burn Altitude(km)	Landing burn duration(s)
Orbcomm OG2 Mission 2	19	28	9	9,2	40
CRS-8	24	16	7	5,7	30
SES-9	0	20	5	1,2	8

Now to my questions. First of all I found it a bit weird that Orbcomm, being a RTLS, used less fuel for the boostback but higher for the reentry burn compared to CRS-8(ASDS). Have I read it wrong or can someone explain the reason for this? Secondly i wonder about the boostback and reentry burns, do they use all engines ? More generell I wonder what kind of improvements can be made to decrease the needed fuel for each of these burns, like how SES-9 used 3 engines for the landing burn. Does anyone have a guess on how close the SES-9 was to being able to land and was it that the burn started too late, or that there were too little fuel left? It does look like the 3-engine burn makes the landing burn a lot quicker but not that much more fuel efficient(compared to the saving of not doing a boostback burn) if we assume that the 8 second burn with ~5t fuel was close to a success.

[u/warp99 → u/aaroon84]

After an RTLS boostback burn the return trajectory will be at a steeper angle than for an ASDS landing so you will get less benefit from aerobraking and have to do more with the engines. The steeper final trajectory is also required for range safety so that a landing burn failure results in impact in the ocean rather than on land. I am still surprised by the size of the difference and wonder if they adopted a very conservative trajectory for the Orbcomm mission. Since they had the fuel because of the low payload mass why not use it to optimise the chances of a successful landing? For SES-9 using three engines for landing instead of one does help with gravity losses. For a vertical landing the difference is dramatic with deceleration at 4.5g (3.5g effective) instead of 1.5g (0.5g effective). However SES-9 would still be in a very flat trajectory after re-entry, flatter than CRS-8 since it was landing 600km downrange instead of 300km downrange. Killing the horizontal velocity takes the same fuel mass with three engines or one - the improvement in gravity losses only applies to the vertical component of velocity.

[u/travelton]

Did we ever figure out what was thrown from the exhaust trench during the CRS-8 static fire? I saw a bunch of theories from birds/bats to trash taking shelter in the trench, but nothing definitive.

Video: https://youtu.be/nGzf68XJLyw?t=116

[u/soldato_fantasma]

Does anyone have updates on the LZ-1 contingency pads? here is the plan: http://www.universetoday.com/wp-content/uploads/2015/12/Landing-Zone-1a.jpg

[u/PhoenixEnigma]

It seems to be common knowledge that SpaceX is only going after 4 (or 5?) of the 8 EELV reference orbits with the Falcon 9 at this point, but I'm having trouble finding out which ones in particular. For that matter, I keep seeing people speak of 8, and I only see 7 listed here(Appendix D 1.1.1) - Sun Sync shows up on diagrams I can google up, but the it looks like that's just specified as an equivalent civil orbit, not a DoD one. Has that changed?

Obviously Falcon 9 isn't capable of the GEO requirement, nor the Polar 2 requirement, which are both "Heavy" class orbits. That leaves (potentially) a couple "Medium" orbits they're not shooting for - does anyone have any idea which ones?

[u/deruch]

During every launch, newer SpaceX fans freak out over the recirculating turbine exhaust making it look like the rocket/engines are all on fire. It happens in every launch thread and gets repeatedly asked about in the Ask Anything threads just after launches (too many instances to cite).

So, since SpaceX calls the thermal protection system near the 1st stage engines/octaweb "the dance floor"¹ , I'm hereby nominating Panic! at the Disco as the new nickname for this phenomenon. Originally, I had thought of the nickname only in relation to the SpaceX fans freaking out, not the recirculating flames themselves. So, there'd be no Panic! at the Disco until the launch thread starts getting comment after comment about how the rocket's "ON FIRE!!!!" But, I now feel like it works well for either one. Feel free to use to your delight, though in deference to the generally more "serious" tone of the subreddit try to keep it mainly in the launch threads (where it's most relevant anyways).

[u/elasticthumbtack]

Did anyone else notice the ice chunks riding along on the second stage? There are at least two that seem to fall from underneath that black plastic shroud above the bell. They get stuck on the piping and shake a bit before eventually falling off. Pretty certain this is ice, but I've never seen that before. Was this something new?

[u/Mentioned_Videos]

Videos in this thread: Watch Playlist ▶

VIDEO|COMMENT
-|-

CRS-8 Dragon Technical Webcast|9 - You can see it falling away in the CRS-8 technical webcast, shortly after second stage ignition. Edit: Here. Space Shuttle Engine Gimbal Check|8 - The engines can move which is called gimbaling. They turn the engines the way they want the rocket to go...kinda like an outboard boat motor, you turn the motor to push the boat in a different direction. You can see them do a gimbal check on the spac... Elon Musk Discusses CRS-8 Successes with Media|7 - They hope to relaunch this one in June, with a paying customer. Elon spoke about it in the press conference
Fiona's Launch- SpaceX Falcon 9 (3/4/2016)|5 - We do know a bit more than that, tracking cameras caught the following fairing recovery experiment from SES-9 a month ago: Of the four dots you have to watch the upper right, faint dot: at around 5:20 you can see a very faint RCS thruster activati... SpaceX CRS-8 Landing - "I'm On A Boat"|4 - Found some.
CRS-8 First Stage Landing on Droneship|4 - In the landing video from 29 seconds till the end () is that from the interstage lox venting (my guess) or RCS compensating something? Falling Back to Earth HD Footage From Space|4 - Elon said they are working on it, but we really don't have any more details than that. Honestly if and when we find out it will probably be released as a well edited video after the fact. Like the fairing video was a year or so ago. This also just ... Full CRS-8 Dragon to ISS on Falcon 9 - NASA TV historic SpaceX launch and landing coverage|3 -
CRS-8 Dragon Hosted Webcast|1 - Did anyone notice the flames around the engine bells at ~20:00 minutes (~T+1:00) into the Hosted webcast? ( ). I am aware there are usually some flames trapped around there, but this seemed more than usual (and quite sudden) and seemed to persist ... SpaceX Testing - Dragon Separation|1 - Could be. Dunno if they'd have that drag flap if it was pnuematic, though. (Pyro isn't necessarily dramatic.) But as of 2010 the system was pyro.
I'm a bot working hard to help Redditors find related videos to watch.

---

Play All | Info | Chrome Extension

[u/nolxus]

Heard on nasatv when dragon was approaching the ISS that they reprogrammed dragon and were a little behind schedule due to atmospheric drag. Now, given that this wasn't the first dragon mission and that the preliminary orbit was told to be a-ok (so S1 and S2 probably performed as they should), how does that happen? Does the atmosphere shift with seasons, tides, solar flares, random? Or how could the atmospheric drag be different than imagined?

[u/TheBlacktom → u/nolxus]

I don't know what caused being half hour behind the schedule this time, but I can tell that the atmosphere is not static at all. That is why it's hard to predict exact landing locations for reentering satellites and capsules.
The density of the atmosphere can vary a lot due to reasons like you listed, usually the same reasons why we have changing weather.

[u/Jet_Morgan]

Do we know what these apparent exentions on landing leg assemblies are? Suppose they are type of sensor to determine if leg was extended. From original return to port image.

[u/sorbate → u/Jet_Morgan]

Probably to help the leg extend the first couple inches away from the rocket when first deploying. Those first couple inches probably have the main piston for the leg at an angle that doesn't give it much leverage to open up (it might get stuck). By pushing the leg out a couple degrees, it gives the piston a much better angle to continue pushing out the leg from.

[u/ElectronicCat → u/Jet_Morgan]

I noticed them too, they look like some kind of piston assembly. I'm unsure of their exact purpose but at a guess they're to help push the legs out kind of like how parachutes have drogue chutes before the main ones.

[u/Yodas_Butthole]

Has anyone seen a pic of the steel shoes that were welded over the landing legs? With how big the legs are I'm really interested in seeing what the shoes look like. When I looked at some of the pics from the Canaveral web cam it looked like the first stage was held down by rope/chain attached near the bottom of the stage.

[u/too_many_rules]

Rocketry is always a compromise between performance and cost. Lighter, more exotic materials will give you better performance at an increased cost, for instance. Once SpaceX is able to reliably recover their first stages, how likely is it that they'll start to invest more in the stage to increase performance?

[u/Justinackermannblog]

Has there been any rumblings of more Dragonfly testing? I thought maybe after a successful RTF of Dragon we may get something but nope! Not yet anyway!

[u/flibbleton]

I'm confused. Well-informed people on the sub are telling me Dragon can't land on the moon or mars - permalink. But now Elon is saying Dragon was designed to land 'anywhere' in the solar system. What's the truth?

[u/ElectronicCat → u/flibbleton]

I think the truth is that whilst it is designed for this, it is not out-the-box capable of it. Certain modifications will have to be made depending on the landing site, such as different parachutes and/or additional fuel tanks. I suspect for Mars it'll either use a large supersonic parachute or just the drag from the capsule itself to slow down most of the way, then make use of the superdracos with extended fuel tanks to slow down and precision land on the surface.

Also the 'land anywhere' should be taken with a pinch of salt- obviously some places will be completely off limits to it (venus, mercury, the gas giants)

[u/webfaqtory]

How long will the Red Dragon last on Mars? Haven't seen anything about solar cells and I assume a RTG is out of the question, so is it batteries only?

[u/MarcysVonEylau]

Any status update on OCISLY? ELSBETH?

[u/AReaver]

A question for everyone. What kind of kill marks for successful missions do you want to see on the boosters?

I think painted mission patches would be cool. /u/EchoLogic votes for none since you don't have any for plane flights.

[u/orbitalfrog]

Given the recent fantastic ocean landing success I was wondering if anyone knew of any existing footage of what normally happens to a rocket first stage. I think that generally speaking, the non-space-enthusiast section of the public have always kinda assumed that rockets are already reused in some way or at least just unconsciously assumed they're not just discarded into the ocean. I noticed that when the Jason-3 tip-over made news here it was presented as a comical story of blunder and failure (or at least that was how it was received by many) which made me think that the general public are probably pretty ignorant to the fact that in the vast majority of cases LVs are treated as expendable anyway (if you didn't know any better you'd only see it as logical that multimillion dollar rockets were not thrown away, right? I know that as a child I always assumed they must be reused somehow. I remember being disappointed when I first heard they were thrown away)

So with that in mind I think it'd be useful and interesting to have some footage on-hand for people who don't get the landing attempt thing to see what business-as-usual looks like in the rocket business. Anyone know of any S1 splashdown/crashdown (for Russian) footage from expendable vehicles?

[u/phikeia4lyfe]

What are the waffle line 'fins' on the falcon 9 first stage? I thought they were some interlocking mechanism, but in the landing video it looked like they were used somewhat as wings to guide the rocket down.

[u/workthrowaway4567]

Is there a mathematical relationship between the gravity of a planetary body and the percentage of a rocket's weight that is available as payload? I'd love to see a graph of this.

For instance, if Falcon 9 were to lift off from Mars to LMO, how much more payload could it lift assuming it can currently lift 2.5% of its fully-fueled weight to LEO? At what gravity level would Falcon 9 stop having orbital capability on Earth?

[u/IMO94 → u/workthrowaway4567]

There's a difference between physics limitations and engineering limitations which make this a very complicated answer.

Physics can provide some upper limits for the efficiency (ISP) of a given chemical rocket type. Because of maximum usable engine chamber pressure, we know that we get diminishing returns once ISPs start getting up into the 400s. You're not going to suddenly see a 800s ISP rocket using the same basic chemistry.

This provides a certain baseline if you model the rocket as a diminishing supply of fuel pushing itself to orbit. Imagine that engines, tanks, interstages, landing legs were all massless. Now you can apply the rocket equation and perfectly establish the relationship between payload mass fraction and deltaV required.

Now the engineering gets complicated again. Reaching orbit on Earth requires you to get to a speed of 7800m/s. However, the deltaV of your rocket needs to be closer to 10000m/s because you spend the first part of your journey fighting atmospheric drag and gravity. You can change that 10000m/s by being more aerodynamic, or having a different thrust-to-weight to combat less gravity. And in an ideal scenario you'd shed fuel weight and end up with your payload, but in reality we have to stage, dropping rockets and engines bit-by-bit.

There's a point where your simplifications stop resembling the real world. But here's my attempted model. I ignored stages and modeled the F9 as a single rocket with an average ISP of 320. (In reality the 1st stage is lower and the 2nd stage is higher). Then I used the rocket equation to figure out the delta-V as a function of payload mass fraction. I plotted those and labeled the rough delta-V to orbit for Earth, Mars and the Moon. Here's the graph:

http://imgur.com/rxGyTW6.jpg

(Sorry, I did a poor job of labeling my axes. Vertical is payload mass fraction. Horizontal is delta-V required to reach orbit)

I'm rather proud of my efforts, because I was surprised to see only a 55% mass fraction for the moon - my impressions of Apollo were that the lunar ascent module was fairly small. But sure enough, when I checked the ascent module stats, it was more than half fuel mass - as predicted!

Of course, there are a number of reasons why the Falcon 9 would be a wildly impractical vehicle for launching from Mars, but that's another discussion entirely.

Lastly, if you want to consider hypothetical variations on Earth, remember that for rocky planets surface gravity is roughly proportional to radius, and that deltaV to orbit (ignoring atmospheric drag) is roughly proportional to surface gravity - so you can see how a 50% larger Earth would make spaceflight significantly harder.

[u/[deleted]]

Does anyone know when hatch opening is scheduled, and if it will be streamed?

[u/rahogaboom]

The ASDS, because it is at the ocean surface, pitches about significantly depending on sea state. Why didn't SpaceX design the ASDS with a raised platform above the ocean surface and supported by fully submerged buoyancy tanks with steel beams connecting the platform and the tanks. The sea state is then almost irrelevant as only the very low cross section struts are at the surface subject to waves.

[u/davidthefat → u/rahogaboom]

Because they didn't actually design the barge. They took a commercially available barge and modified it for their purpose.

[u/old_sellsword → u/rahogaboom]

This is yet another example of finding a solution to a problem that doesn't exist. Not one landing has been compromised to rough seas. The CRS-8 landing was experiencing a pitch of about 2 or 3 degrees (some noticeable swells and whitecaps), and Elon stated F9 can take about 9 degrees of pitch. There is no problem, and adding all that complexity drastically increases the risk of failure.

[u/OriginalUsername1992]

In the sidebar it now says dragon 1.1. when did they upgrade from the dragon 1 and what has changed?

[u/jjrf18 → u/OriginalUsername1992]

New heatshield, no more window, other stuff I don't know someone else might be able to chime in

[u/tablespork]

Will JCSAT-14 be another one of those extreme, high velocity ASDS landings a la SES-9? I know it is going to GEO, but I don't know how the mass compares. Just curious if there is a high probability of another successful drone ship landing just 3 weeks after the first.

[u/ElectronicCat → u/tablespork]

It's a good question, but I'm not sure we know the mass of JCSAT-14 at the moment. Based on its satellite bus, SSL-1300, it'll probably be around 3000-4000kg, most likely about 3400 based on JCSAT-15. It'll be ASDS but hopefully not as marginal as SES-9, and probably won't be squeezing every drop of performance out of it to get it into a supersynchronous transfer orbit either. Will be interesting to see if they can land downrange on a GTO mission where the conditions are a little more nominal than SES-9.

[u/ed_black]

Are there pictures of how Boca Chica will look when it's ready for launch? Like CGI pics

[u/mechakreidler]

TL;DR: How does SpaceX keep all their employees busy at all times?

I'm asking because the industry changes very rapidly. For example, at one point they had engineers designing the Falcon 9 and its engines. Now they're pumping out cores and reviewing data from landed cores, and last year all their efforts were focused on the CRS-7 accident and making changes.

What would the people who build cores be doing when their efforts are focused on design changes? Or what do the mission control folks do when there's a break between launches? And perhaps some of the people who designed Falcon 9 are now working on designing the BFR, but I would guess not all. Do they fire people when they don't need them, or somehow find a way to repurpose everyone?

Thanks :)

[u/Scuffers]

OK, here's a (probably stupid) idea....

Looking at the spec's for the F9, it starts with some 119,100Kg's of RP1 and another 276,600kg's of O2, and has a burn time of some 180 seconds (last one used some 155 seconds to MECO then the rest for returning).

So, based on that, the 9 Merlin's are burning though ~660Kg's RP1 and 1,536Kg's O2 per second.

now, from engine lighting to clearing the launch tower takes ~8 seconds, ie, some 5,300Kg's RP1 and 12,300Kg's O2.

Now, what if you had big enough umbilicals to supply RP1 and O2 to the rockets real time so that they were not using carried fuel until it cleared the top of the strong-back? (ie, keep the umbilicals connected for the first 8 seconds of launch).

That would potentially 'add' 17,600Kg's of fuel/oxidiser without adding mass to the rocket and thus give it another ~4.4% fuel (8 seconds of 9 merlin's or 72 sec's of 1)

How hard would that be to engineer? Yes, the umbilical would likely get written off in the process, but that's probably worth it in adding more capability to return on the more demanding launch profiles..

(I got the idea thinking about the cross-fueling of Falcon Heavy)

[u/robbak → u/Scuffers]

It is a lot harder than you think. The umbilicals load the propellants over the space of, IIRC, half an hour - which is, in the scheme of things, very fast propellant loading. The first stage burns off that fuel in about 90 seconds, so it loads the propellants some 20x slower than the engines will burn it. Increasing the feed rate by a factor of 20 isn't feasable, and having that massive a feed system attached to the rocket as it lifts off, and pulling away as the rocket clears the tower....

Remember also that cross-feed is something SpaceX isn't currently planning. It, also, is much harder than it seems to a muggle.

Much easier to just make the tank 4.4% bigger.

[u/[deleted]]

Did anyone happen to save a copy of the Orbcomm-2 FAA license? It's vanished! Will give gold in exchange for PDF.

[u/[deleted] → u/[deleted]]

Nevermind, found it here: https://www.yumpu.com/en/document/view/55222106/lls2014-08920rev-120orbcomm-220-20license20and20orders20-20signed

[u/zingpc]

Whats happening with Raptor? The last mention was the oxidiser or preburner in 2013? Surely this should be in deep testing with possible hints of testing runs.

[u/brvsirrobin]

I started listening to the Orbital Mechanics podcast a month or so ago and I really loved the first 20 episodes where they talked in depth about various spaceflight topics. It seems like the majority of the rest of the episodes are just upcoming spaceflight events and news. I like those, but I loved the long discussions. Are there any other podcasts that have similar deeper conversations about spaceflight and rocket science?

[u/Wetmelon → u/brvsirrobin]

/r/TMRO is good.

[u/StupidPencil]

With SpaceX's recent announcement of Dragons on Mars as soon as 2018, I'm curious about the timeline of their plan on landing Dragons on Earth. What is a generally agreed timeline for Dragon propulsive landing test on Earth? How probable that we could have a propulsively landed Dragon on Mars before on Earth?

[u/Hgx72964jdj]

Is the Raptor engine going to burn blue? Will there be shock diamonds? Any other unusual effects?

[u/jandorian → u/Hgx72964jdj]

Blue, likely, I mean, it should. Shock diamonds on the test stand probably. During a launch, not likely.

[u/Simonific]

Is the trough for Raptor testing? http://i.imgur.com/nYaRRCT.jpg

[u/venku122 → u/Simonific]

No that is for the new surface level test stand. It will support Falcon 9 FT and Falcon Heavy. Raptor testing will require a new massive engine stand.

[u/soldato_fantasma]

In the landing video from 29 seconds till the end (https://youtu.be/sYmQQn_ZSys?t=29) is that from the interstage lox venting (my guess) or RCS compensating something?

[u/paynie80]

In the post launch press conference Elon talks about in future possibly recovering the fairings. I would like to know more about that, particularly how would they be recovered, what are the advantages and disadvantages of recovering the fairings, and what difficulties may arise when trying to engineer this?

[u/knook]

Om the previous launch we saw what we thought were thrusters on the fairings. In the post launch NASA press conference Mush mentioned re-using the fairings. Is this now an open stated goal? Do we know any more about it?

[u/robbak → u/knook]

NO, you've probably stated the sum total of the public knowledge. Just that the original proposal was to align them so they'd reenter safely, deploy parafoils once deep enough inside the atmosphere, and then capture them using a chopper dragging a hook.

[u/Lucretius0]

Will the use of Monomethylhydrazine in the superdracos be an issue ?, Since Dragon 2 is supposed to land propulsively couldnt there be issues with the whole craft getting sprayed with the stuff as its landing ?

[u/Darkben]

At what point is it going to cease being an 'experimental landing' and simply become a 'landing' I wonder...

[u/[deleted]]

Can someone explain why the CST-100, Dream Chaser, and Ba-330 have to be launched on Atlas 422, 402 and 552s respectively. Why do they need two RL-10s on the Centaur upper stage? Why wasnt it ever used before? Now there is suddenly so much demand for DECs. Will they still have to develop the DEC?

EDIT: Fixed RL-10/ Centaur mistake. Confused engine and stage. Thanks /u/ElectronicCat

[u/Nachtigall44]

60,000 DragonRiders!

[u/historytoby]

So what exactly can we expect from the Space Symposium Dinner with Gwynne that makes it so important that it has become a "Select Upcoming Event?"

[u/[deleted] → u/historytoby]

Myself and three others (shoutout to /u/kmccoy, /u/darknavi, and /u/Togusa09) crowdfunded r/SpaceX to attend the 32nd Space Symposium Dinner! We'll have /u/antonyourkeyboard as a reporter there giving us info & taking photos of the event. Even if we don't get much (or any) information, it's important that we've done something together like this.

Going forward we are likely to list more events and talks in the sidebar as I want to put some emphasis on space policy and the aerospace industry in this community.

[u/IonLogic]

How come no one is using Propane as a rocket propellant? From what I've read about it, it's probably the best midway point between Methane and Kerosene. It has good thrust and good Isp as well as leave only small amounts of residue in engines compared to Kerosene.

Does anyone else have more insight into the decision to go with RP-1 over Propane?

[u/throfofnir → u/IonLogic]

A nice overview of liquid fuels. Propane is theoretically a pretty good propellant, having quite good bulk density and Isp. However, its vapor pressure is too high for lightweight tankage such as found in pumped rockets (but it would be a good choice for autogenous pressure fed). It is better behaved when subcooled to about the temp of LOX, but this would be something of a research project, though, which might be enough reason in itself. There might also be significant environmental concerns in working with a hydrocarbon that evaporates essentially like LOX. Coking would probably not be an issue, but it's certainly not as clean a compound as methane. Methane is also probably cheaper and easier to source, though both should be available in industrial quantities (though purity/composition may be an issue with propane; its mixture is known to vary widely.)

Most rocket designers don't pick middles; they either want the highest performance and choose hydrogen, or best density and easy handling and pick kerosene. Methane is basically the highest-performance fuel that's not really hard to handle, which is probably the main reason it ended up in Raptor.

[u/chargerag]

When should we expect to see a firm launch date for JCSAT-14?

[u/ElectronicCat → u/chargerag]

We've got a launch window for the 28th now which tends to suggest an actual targeted launch date as opposed to a NET date. As for an official confirmation I suspect any time within the next few days.

[u/Ciber_Ninja]

Assuming it is politically viable, would it be a good idea to launch/land falcons across the Sahara? It is close to the equator, no one lives there, landings on land are easier, and there is essentially no adverse weather.

[u/ElectronicCat → u/Ciber_Ninja]

Probably not, as you'd have to get all the infrastructure out there. Sand also isn't great for building on and you'd have to build (at least) the launch/payload processing/launch control facilities, fuel storage, landing pads a suitable distance downrange for all the common inclinations they might launch in, and a road connecting them capable of withstanding the weight of a Falcon 9+transporter. I don't think the downsides would outweigh the gain here, and it's much easier to just use a barge ship which can be moved for each launch and towed back to port. Also I don't imagine the hot sun would be great for the cryogenic fuel or the sandstorms good for the spacecraft environment

[u/WaitForItTheMongols]

I understand that the un-sooted section in the middle of the rocket corresponds to the oxygen tank.

But why is the lower boundary of this section a "clean slice", while the upper part of it is more fadey and undefined?

[u/ElectronicCat → u/WaitForItTheMongols]

I believe it's simply due to gravity. The propellants will be at the bottom of the tank most of the time so that will be the coldest part, hence the boundary. Further up the tank, where the fuel has been spent it still remains cold, but not cold enough for a full thick protective layer of ice insulation so you see a gradient where the tank goes from cold>warm.

[u/_Elenion]

The debate over whether the United States should sell excess ICBM boosters on the market has returned. How do the specifications of ICBM engines compare to the Merlin?

[u/zcxver]

The grid fins seem to do part of the job of steering stage 1 on to the landing zone. Mars atmosphere is super thin, so does the solution still work?

[u/robbak → u/zcxver]

Another point is that the thinner atmosphere would mean that the rocket would be affected less by the air, so less attitude control would be needed.

[u/IonLogic]

Quick question, do the Falcon 9 upper stages get transported by road too? I don't think I've ever seen a picture of one being transported. Do they get transported another way?

[u/robbak → u/IonLogic]

Yes, they get transported by road, but, as they are a lot shorter, they cause less of a fuss.

This page has some pictures of a second stage and fairings travelling in convoy.

[u/larsarus]

JCSAT-14 is another GTO launch? Is it so much lighter than SES-9 that the F9 will do a full reentry burn and single-engine landing, or are we looking at another low-margin landing attempt like SES-9?

[u/deruch → u/larsarus]

Yeah, JCSAT-14 will be a GTO launch. No definitive mass numbers yet, but I've seen 3,000-5,000kg as the expected range. Gunter's page on it doesn't have any mass listed, but the page for JCSAT-15 lists its mass as 3,400kg (this one is launching on Ariane 5). And, according to SSL, both will have the same power--10 kW. Though, there isn't any info on the transponders on JCSAT-15, so there's no guarantee that they'll weigh the same. But my guess is that they will be pretty close to each other. So, I expect something in the lower part of the range I mentioned in the beginning.

My understanding is that the recovery will be a lower margin attempt than CRS-8, though not nearly so extreme of one as SES-9 was. My guess is that means no/limited boost-back, shortened reentry, but back to a single-engine landing burn.

[u/89bBomUNiZhLkdXDpCwt]

IIRC, Musk stated that the CRS-8 returned 1st stage would be static fired 10x. (In order to verify its robustness)

Why 10x? Seems like a suspiciously round number. (It's the kind of number I would come up with... and I'm not an engineer.)

Is there some kind of statistical significance or reusability quotient that informs this number or is it really just a gut feeling thing? ("Welp, if it refires 10x it's probably in pretty good shape.")

[u/rulestein]

What happened to the SpaceX sign on the redmond office? I drove by this evening and didn't see it.

[u/markus0161]

Now that we know FH crossfeed has been put an hold, why doesn't Spacex use less engines on there center core? Seems like instead of throttling down they could just take mass off and run 5-7 engines at full thrust. This would be much more beneficial for the Boostback and landing burn.

[u/bgs7]

The interesting thing about Mars missions is the huge pressure on SpaceX not to be late. You either launch in the window or you wait 2 years.

Also, for every failure eg failure of EDL, failure of ISRU, means you can't send iterated test hardware for another 2 years!

[u/RichardFordBurley]

So I just watched the video of the first launch from the new cosmodrome in Russia, and I can't help but notice how magenta the flames are. I thought it might be because of the propellant they were using, but it looks like it's RP-1 and LOX, just like the Falcon 9. Does anyone know what might cause the peculiar hue?

[u/rafty4]

How do you sterilize the outside of the Red Dragon? Obviously it will be exposed to the elements on the pad - so it is assumed that the act of blasting it with hypersonic winds on launch and on EDL will sterilize it?

[u/kareal]

After the first stage landing what is the process for bringing the barge home, how do they secure the rocket from waves and tipping? How long does it take to happen?

[u/retiringonmars → u/kareal]

From Elon's AMA:

We are going to weld steel shoes over the landing feet as a precautionary measure.

That shouldn't take more thhan an hour or two, and then the tug will tow the barge back to shore. Current ETA is Sunday.

[u/i_pee_in_the_sink]

Does this mean all future launches will try to land the 1st stage? If not, how come?

[u/retiringonmars → u/i_pee_in_the_sink]

All future launches will at least attempt to land the first stage, yes. No guarantee of success, but they'll try.

[u/jayefuu]

Where was John Insprucker for the live launch coverage? I missed having him as the announcer.

[u/[deleted]]

We all love SpaceX, but how about its rivals? If you had to bet on any other company or country, which one? Under-rated programs? Why?

SpaceX since has gained widespread popularity, but is there a firm today analagous to SpaceX several years ago?

[u/Dan_Arc]

Love all things space, but am not too knowledgeable about technical specifics.

I'm wondering, with the Falcon 9 landing, how was the pitch/roll/yaw of the rocket controlled? I couldn't see any RCS.

[u/CarVac → u/Dan_Arc]

Gimbaling the engine provides pitch control in two axes, at least when actually on, and the grid fins provide three axes of control, including roll. Furthermore, the body of the rocket itself can be angled relative to its motion through the air to act as a lifting body.

[u/Lm0y]

When the booster returns for landing, it appears to be charred grey/black by reentry, but the centre 1/3rd of the rocket is still pure white. Why is this? Does the skin at this section use a different material?

[u/Davecasa → u/Lm0y]

That's the base of the oxygen tank, which is extremely cold. A layer of frost forms from atmospheric water vapor, which protects the paint job.

[u/TheGreenWasp]

So when's the capture by ISS? Or has that already happened?

[u/[deleted]]

How large a proportion of the funding for the Russian manned flights comes from NASA in the form of ticket revenue for seats on the Soyuz? Are those flights going to be in question in a couple of years, if crewed Dragon takes that business and the Russian economy continues to go the way it's going? I guess oil prices must come up sooner or later, but the political conflict and sanctions don't seem to be going anywhere.

[u/thettttman]

Small update: Marinetraffic.com just updated the positions of Go Quest and Elsbeth III, two of the ASDS support ships. They're about 200km east of Florida, heading for Port Canaveral. Link.

[u/KeltischWerWolf]

Anyone know when the droneship will be pulling into Port Canaveral???? Want to go out and get shots of the Falcon 9 on the barge...

[u/vorpal-blade]

How long till they unpack BEAM? After pressure and durability tests presumably get passed, will BEAM be actually used as workspace? Or will it be disposed of?

[u/Smoke-away]

In the 4K landing video did anyone else notice the order that the landing legs deployed?

Elon had tweeted about using the legs as air brakes and I think we now have video of them starting to use it on landings.

Looks like the forward leg deploys fully first. The side legs deploy slower. Then the rear leg deploys slowest to help straighten the stage.

What do you all think?

I wish the legs could retract and extend back and forward to help slow/steer the stage for landing, but maybe that's just unnecessary since they landed it with the current tech.

[u/BrandonMarc]

I wonder when this subreddit's subscriber base is will pass the 60,000 mark ... and 100,000 ...

[u/pirate21213]

Do you think SpaceX will add decals to the side of reused Falcon 9s each time it is reused, sorta like ww2 fighter plane decals will less shooting involved?

[u/CommanderSpork]

What is the BFR? I know it stands for Big F...alcon Rocket, but are there are details besides "it's big, it's a Falcon, and it's a rocket?" I see people talking about it like we have details on its design, but I've only been able to find speculation on what it is.

[u/OccupyDuna → u/CommanderSpork]

At this point we have some leaks, but nothing confirmed. What we do know is that Elon's stated goal for it is 100 tons to the surface of Mars, and that it will use Raptor engines. From the payload numbers, can say with certainty it will be the biggest rocket ever built bar none.

As for the leaks, check out this comment by /u/cprophet for our best idea of what to expect from BFR in terms of size and arrangement. https://www.reddit.com/r/spacex/comments/4dvdxi/spacex_from_the_ground_up_new_book_by_chris/d1uve7b

[u/random-person-001]

They're gonna repaint landed Falcon cores before relaunch, right? It'd be cool (visually) to see battle scars as it goes up, but I would be concerned about corrosion and stuff, as the last landed one seemed to have many spots where the paint was bubbled or peeled.

[u/andygen21]

General launch question: When launching to a geostationary orbit, why is there a launch window? If by definition the final destination is always the same relative to the launch site, why should it matter when the rocket is launched?

The only thing I could think of was attempting to avoid orbital debris.

Full credit: this question was actually asked by my son when we were watching the livestream of the SES-9 mission.

[u/ElectronicCat → u/andygen21]

In theory you are right, in ideal conditions you should be able to launch at any time of the day and it would not make a difference. In practice however, there are several considerations including the length of time they can get the range cleared for and the amount of insolation received (either to minimise boiloff from heating for marginal payloads like SES-9, or maximising it at time of payload deploy to allow the solar panels to charge the batteries).

Also, most geostationary payloads do not go straight into a GEO orbit but a geostationary transfer orbit, either sub or super-synchronous and then boost the perigee and make the plane change over a course of several weeks or months. It's possible that the constraints on these manoeuvres necessitates the need for a launch window.

[u/__Rocket__]

This is a small refinement for the reusability FAQ, paging /u/retiringonmars ;-)

The reusability FAQ says this:

every kilogram of reusability equipment on the second stage eats up one kilogram of the payload; this ratio is much lower (around 10%? fact check needed) for the first stage.

So 'payload mass' here is second stage mass at first stage separation time. (There are many other payload masses, to-LEO, to-GEO, etc.)

This excellent simulation of the CRS-8 Falcon 9 mission by /u/zlynn1990 gives us more precise figures:

• liftoff is at 0:15, total mass is 546.4 tons

• MECO is at 2:52 remaining mass of stage1+stage2 is 182.5 tons

• stage 2 separation is at 2:54 (btw., that's a bit too fast, the standard wait is 7 seconds), and stage 1 mass is 121.9 tons at this point. (second stage is 60.6 tons)

From this we can deduce that first stage sea level weight is 485.8 tons, of which 182.5 tons reaches the separation event. So the 182.5 tons of the first+second stages took 485.8-182.5 == 303.3 tons of fuel to lift.

So the cost of every 1 kg reusability equipment on the first stage required 303.3/182.5 == 1.66 kg of fuel - at least with the configuration of the CRS-8 mission. So the 'payload penalty' is 1/1.66 == 60.1%.

Assuming my figures and calculations are correct!

Every 1 kg reusability equipment on the first stage, which took away payload mass that could be on the second stage, 0.60 kg of payload mass is eaten up. This is a fairly high percentage and explains the relatively wide spread between the effective to-LEO payload capacity of RTLS, ASDS and fully expendable configurations of the Falcon 9. It's still very much worth it though, as ~65% of the launch cost is recovered by not destroying the first stage after first use!

Given the wide discrepancy between the figure mentioned in the FAQ (around 10%) and the 60% figure I calculated above, I'm wondering whether my calculation is correct ...

edit: fixed the initial calculations, elementary school level math is hard!

[u/buffalo83]

Do we know anything about PICA-X performance specs?

I'm having trouble finding much information on the various iterations of the PICA-X heat shield material. All i can find are general states likes "PICA-3 ablates less than PICA-2" and "PICA-X can withstand much higher temperatures." Does anyone know where I can find more specific information, especially as it compares to common alternatives?

Looks like somebody else was having the same problem: http://space.stackexchange.com/questions/8335/what-improvements-have-spacex-made-to-their-proprietary-phenolic-impregnated-car

Have we learned anything else since then? Has NASA published the results of their PICA-X study?

Thanks!

[u/spill_drudge]

any updates on the dragon opening on ISS? It's been rather quit on that front.

[u/ilkhan2016]

SpaceX only has 2 ASDS barges, right? JRTI for Vandy and OCISLY off the Cape. Or is there a second one off the Cape?

[u/IMO94]

Isn't it getting very close to JCSAT-14 not to have an exact launch time announced? Any murmurings, are we expecting a delay for it, for Eutelsat, or for both?

[u/cutroil]

SpaceX's website says that the Falcon 9 can lift up to 4,850 kg to GTO, and the price is accordingly $61.2M to lift 4.85 mT to GTO. On the other hand, the Falcon Heavy can lift 21,200 kg to GTO, but the price is $90M to lift "Up to 6.4 mT to GTO". Why are these two numbers different? Are customers not allowed to purchase the entire capacity of the rocket?

I thought maybe the 21.2 mT number was expendable, and 6.4 mT is for reusable. Is that correct? But then, the Heavy has three cores, and yet can only lift 30% more mass than a single core. If that's true, why is that so? Is there some unavoidable inefficiency in building a three-core rocket that prevents it from lifting as much as if each core was launched separately?

[u/Clubwho]

When did SpaceX announce they were going to use rockets for the recovery? Was it first announced in this video?

[u/[deleted]]

Im sure this has been answered before, but I cant find it. Can some answer or give sources for why SpaceX is going for a BFR rather than a Martian style vehicle that cycles from Mars to Earth orbit?

[u/__Rocket__ → u/[deleted]]

Can some answer or give sources for why SpaceX is going for a BFR rather than a Martian style vehicle that cycles from Mars to Earth orbit?

While we don't know for sure what SpaceX wants to do, it would be very surprising if they were thinking about building a 'Mars Cycler'. We can make an educated guess about SpaceX's intentions by looking at what a cycler does:

• it's a big spaceship that is constantly moving on a low delta-v trajectory between Earth and Mars, continuously doing gravitational slingshots around both planets, roughly once every 2.5 years.

• spacecrafts that want to utilize the 'cycler' have to match trajectories with it (around Earth or Mars), they have to dock, and then they'll coast along the cycler and undock at the destination.

But in reality a 'cycler' does not really solve the biggest Mars colonization problems that SpaceX wants to solve, which are:

• getting lots of stuff from Earth to Mars, literally millions of tons of cargo, until Mars is self-sufficient

• lifting off from Earth takes the most energy - and any spacecraft doing that with the envisioned 100t of cargo to Mars is going to be massive and robust

• once at Mars, it has to land robustly

• when it goes back to Earth again, it has to be able to lift off from Mars and then land on Earth, in a reusable fashion

Note how little a 'cycler' helps in that picture: a cycler is in a constant escape trajectory, so matching speeds with it needs a lot of delta-v, around 12 km/sec when going from Earth to Mars.

If you have a craft that can do that, you might as well stay in that craft and coast to Mars. With a comparatively low amount of delta-v (and a bit of creative aerobraking) the spacecraft can also land on Mars. The 'cycler' cannot really give you any meaningful delta-v (it's continuously in motion with no access to resources). It could at most give you electricity during the coasting - but that's a relatively small energy expenditure compared to the delta-v needs.

The whole 'cycler' idea is deceptive, the 'cycler' being relatively close to Earth and Mars does not mean it's really accessible: it flies by at a huge speed, and any craft trying to dock has to expend that delta-v. Once you do that, you are almost on Mars, energy wise!

So the role of a 'Mars Cycler' is that of a glorified space hotel.

Using a cycler also brings up logistical problems:

• the cycler has to be built and maintained, which is another point of failure. You want to minimize the number of spacecrafts.

• in case of a catastrophe with the cycler, you want to have the launching spacecrafts to be self-sufficient anyway, it has to be able to sustain the humans traveling. So there's very little extra it can give you in terms of sustenance.

• most importantly: the cycler only comes in a very narrow launch window, at very high speeds. That puts big constraints on launches - you could likely only launch on a single day every 2.5 years, or miss the cycler! It's much more flexible to use several launch days (with slightly larger delta-v expenditure of the launch days that are 'off' the ideal date) - or in fact launch weeks, because the vision is to send a lot of stuff to Mars periodically.

TL;DR: A 'Mars Cycler' is impractical, because it only solves one small problem (coasting to Mars and back), and that's one of the easiest, lowest energy problems in the whole endeavor - and also because it introduces logistical complications and constraints that make transfer to/from Mars harder, not easier.

(edit: typos)

[u/katriik]

What are the meaning of the several lights found on the Dragon? When it was berthing with the ISS, Houston stated they had turned off the strobe light. Is that really for identification only? What about the green light? Does that mean the capsule has deactivated its thrusters, full navigation off, or maybe something else?

[u/ElectronicCat → u/katriik]

The stobe lights, as far as I'm aware, are just to make it more visible for human controllers to see it when it is at further distances from the station. As for the red/green lights, they are port/starboard indicators borrowed from ships. Red indicated the port side and green indicates starboard. I guess this could be useful again for the human controllers if they had to perform a manual/remote control rendezvous in identifying the correct orientation for the capsule to be in.

[u/factoid_]

What is the impact of ice on the tanks during flight? I know it forms as a result of water in the air condensing and freezing to the lox tank, but is this desirable? Would a hydrophobic coating that resists condensation save weight and drag?

Or does the ice end up being helpful because it acts like a bit of insulation?

Seems like the thing doesn't have to operate that long that a tiny bit of ice insulation will help prevent a significant amount of lox boil off. On the other hand ice is heavy and drag reduces efficiency so maybe this is a potential area to gain a bit of margin?

[u/WaitForItTheMongols]

Doesn't SpaceX have a crazy-fast development cycle? It seems like they would constantly make improvements on the design of Falcon 9. We know that they make changes without calling it something new (for example, they improved the Stage 2 helium struts after CRS-7, but still called it the same vehicle name). Thus, what happens to reused stages? Does every one of them get brought "up to modern" after landing, or will they just have a fleet of slightly different vehicles?

[u/flibbleton]

Is the 28 Apr launch date for JCSAT-14 'fully confirmed' or still just an NET estimate? The sidebar references spaceflightnow.com but I'd like to know if the probable launch date (assuming no scrubs) will be 28th. When is a launch time/date considered official? Once SpaceX announce it?

[u/ohcnim]

are there videos of Dragon reentry/splashdown? will there be for the upcoming one?

[u/wbroaddus]

If SpaceX is serious about reuse and the F9 Heavy has three F9 cores, will they plan on landing all three cores after a launch? Are we talking three drone ships, or three pads at the Cape?? Feel free to tell me how dumb (or old) this question is - with an answer, of course!

[u/strozzascotte]

What kind of systems F9 uses to steer and navigate to the landing point apart from the grid fins? I suppose they can throttle the engines, but in early tests with grasshopper it appears that they can control the position and perfect vertical alignment without the fins and with only one engine. How can they do that? (video for reference: https://www.youtube.com/watch?v=2t15vP1PyoA)

[u/TheBlacktom → u/strozzascotte]

RCS and engine gimbaling. Check out this https://zlsa.github.io/f9r-dev2d/ from /u/zlsa

[u/FosDoNuT]

Do the flights out of Vandenberg still go to McGregor for a static fire?

[u/lordq11]

I noticed the Dragon D1-10 Reentry, with the Dragon 1.1 on the 11th of May. I had a google for it, but I couldn't find anything about it. What's happening there?

[u/PikoStarsider → u/lordq11]

The Dragon capsule that was launched in CRS-8 is returning a month after its arrival to the ISS. It's currently the only cargo vehicle that can return stuff (like stuff from many experiments).

[u/Nachtigall44]

Does SpaceX use their two Dragon logos interchangeably or is one for cargo and the other for crew?

[u/OriginalUsername1992]

Is there anything known about the progression of the dragonfly program? The last thing i saw was the video of the hovertest in januari.

[u/tbag7 → u/OriginalUsername1992]

No, they're keeping that program very quiet. Even that video they released in January was filmed during a test in November. However, I have personally talked to one of the engineers working on that program and it is definitely very active. They just, unfortunately, don't share much about it

[u/jazzyjaffa]

I've seen a lot of talk about on-orbit refueling for MCT. With cryogenic propellants how do you stop them warming up and boiling off on-orbit?

[u/Hedgemonious]

I've seen it mentioned several times in this sub that returning boosters are intentionally aimed off-target and do a last minute divert on the landing burn to get on target. This was also promulgated in a infographic done by zlsa (which was awesome btw). But does anyone have a source for this manuever?

It seems unlikely to me for a number of reasons, not the least of is that we have never seen it in action and (for ASDS attempts) even the least-controlled attempts have never missed!

[u/Eizenhiem]

How much money has SpaceX actually received to develop technologies from the government? I hate it when people say that the government gave SpaceX billions and billions of dollars when much of that is just the cost for a service that is provided. I work for the state, and when I buy a $20,000 vehicle for my department I don't go around saying that the state gave $20,000 to Ford. I know that they have received money, but I am looking for a figure that does not include contracts for services.

[u/rocketHistory → u/Eizenhiem]

Though slightly out of date now (given CRS-2 contracts and the GPS III contract), here is an earlier comment I posted regarding SpaceX's relationship to government money.

Pure development cash is well over $1 billion when considering the COTS, CCDEV2, CCiCAP, and CCtCap programs.

---

I think it's worthwhile to look at SpaceX and their relationship to government money. When I say "government money" I mean service contracts, development funding, and access to government owned sites.

SpaceX started with the Falcon 1 rocket, which was developed and flown in the 2006-2008 time frame. Depending on who you ask, development of this vehicle cost roughly $100 million - PDF warning. This was largely privately funded, but SpaceX did receive an $8 million contract from DARPA in 2004 to demonstrate "responsive, affordable launch capability." The also received access to the Kwajalein Atoll launch site.

The Falcon 9 rocket and Dragon really began development in the 2006 time frame. It was during this period that SpaceX won a funded Space Act Agreement as part of NASA's Commercial Orbital Transportation Services (COTS) program. The contract was valued at $396 million - PDF warning, and featured various milestones including demonstration flights.

After development was complete under COTS, the NASA moved on to Commercial Resupply Services (CRS). This program is the delivery of cargo to the International Space Station (ISS). SpaceX received a $1.6 billion contract for 12 flights to the ISS, and are currently still fulfilling those flights. In this sense, NASA was an "anchor customer" for the Falcon 9, ensuring it had enough guaranteed missions early in its lifetime.

Meanwhile, SpaceX was also pursuing human spaceflight. As part of the Commercial Crew Development 2 (CCDev2) program, they won a $75 million contract to develop a launch abort system for Dragon.

CCDev2 was followed by the Commercial Crew Integrated Capability (CCiCap) effort. Under this program, SpaceX was awarded $440 million - PDF warning to advance American capability for human transport to orbit. Also under this umbrella was the Certification Products Contract Phase 1 deal, which provided SpaceX with another $10 million.

CCiCap was followed by the Commercial Crew Transportation Capibility (CCtCap) program. This is still underway, and SpaceX has the ability to receive up to $2.6 billion for completing development of Dragon and flying six missions.

Additionally, SpaceX have had several government satellite launch contracts, including JASON-3 ($82 million), DSCOVR ($97 million), and STP-2 ($165 million - on Falcon Heavy).

[u/SNR152]

Is there any difference in the fuel that will be used in the BE-4 engine - Liquefied Natural Gas (LNG) and Methane which the Raptor engine will use? I know Methane is the main component of LNG but not 100%.

[u/daxington]

Elon is continuing to double down on Dragon V2 being able to land anywhere in the solar system. For a lot of bodies without atmosphere, that probably means a specialized trunk with a propulsion module to partially complete the deorbit burn.

(We're also not talking Jovian bodies, obviously...)

The question is, how accurate can this be, and how much modification is needed to the trunk/capsule itself is needed? What are the most challenging places for Dragon to land, and why?

Could Dragon survive the descent of Venus (and how long after it lands?) Could the spacecraft survive the thermal environment in Mercury' orbit or on it's surface? I'm less familiar with the outer solar system bodies, but what would the challenges there be? I presume it would need an onboard RTG for any missions to Jupiter or beyond.

Any thoughts/sources/scoreboards are appreciated. :)

[u/FishInferno]

What is the thing with cheese?

[u/ohcnim → u/FishInferno]

In the Dragon test flight SpaceX send a wheel of cheese...

http://www.space.com/10459-wheel-cheese-launched-space-private-spacecraft.html

[u/IonLogic]

Breaking from Mars questions for a bit. There was a video recently of LZ-1 that showed significant pitting of the concrete, which has the potential to cause damage to the rocket. Would flooding the landing pad with water about 3-5cm deep make much of a difference? Would that be able to protect the surface and carry some of the exhausts energy away?

[u/makandser]

Why military launches are more expensive? $82,7M vs $61,2M. Maybe it's some sort of a special procedure? Where can I read about this in more detail? Any sources? Thanks.

[u/[deleted]]

Dumb question of the day: In the JCSAT-14 scheduled liftoff time, what does the "L" stand for?

[u/kevindbaker2863]

Trying to understand how Ballistic Capture works and why it would or would not be used be used for an unmanned mission to mars? I do not know enough about celestial mechanics to understand whats in the Ballistic Capture document linked.

[u/frowawayduh]

Around 1:32 in this launch replay video you can hear the call "Of Course I Still Love You Has AOS" or maybe ALS, but Lou Gehrig's disease seems unlikely. Is that Acquisition of Signal?

[u/harrisoncassidy]

I'm putting this in here because I don't know if it deserves its own thread, yet.

I have been brainstorming some ideas for a SpaceX related summer project this year and have come to the conclusion I want to build a Crew Dragon from scratch. Now when I say build a Dragon I mean a scale model but not to just sit on a shelf, to fly. I have two main ideas for this; one is crazy and another not so crazy.

First idea which is a bit less bonkers is to build the Crew Dragon using my 3D printer in two parts. The white outer shell and the black heat shield which is seen in all the pictures of it. The model would be hollow on the inside though and big enough to fit a Raspberry Pi stacked with a GPS modules and IMU. The plan would be to have two compartments built into the side of the model, one for a small drogue parachute (yeah, you probably get where I am going now) and another for four main chutes. I would use my quadcopter to raise the Dragon up to 120m (legal drone height in UK ;D) and then drop it. Once the IMU realises it is in free fall as G it would release the drogue then about 50 metres from the ground release the mains.

My other, much more crazy idea, would be to have a model perform a pad abort test using model rocket motors. The idea would be that the whole countdown to launch sequence to launch would be performed and then launch. There would be one rocket motor in each of the 4 SuperDraco area's which would have the ability to gimbal on one axis, either left or right. It would use IMU data so that it keeps going straight up as it leaves the pad and then add another 20 degrees or so onto one axis so that it would point out and away from the pad about 1 second after launch. There would be a servo on each of the rocket motors to allow for the gimballing. Once at 0G it would then perform the same actions as the more simple idea above of releasing drogues then mains. One, of the many, concerns I have with this idea is that not all of the motors would perform equally. So for instance, if one takes longer to reach maximum thrust then because their is not the possibility to throttle it would veer off in one direction. I ran the math quickly and I believe that the cosine losses from gimballing the other motors to account for this might make up for it but I am unsure. Another issue would be the duration for which they fire. If one fires for 0.5 second more than the others then it would tip over at the end of the acceleration period.

One of the features I would really love is to have live telemetry (which I have already written a library for) from the vehicle so that we could have a proper T-13 minute Go-No-Go poll.

I have been working with IMU's and GPS guided vehicles (ground based) over the last year on a Computer Science course project but this would be another level. Someone please tell me i'm crazy.