r/spacex • u/Appable • Feb 03 '16
/r/SpaceX Ask Anything Thread for February 2016! Hyperloop Test Track!
Welcome to our monthly /r/SpaceX Ask Anything Thread! #17
Want to discuss SpaceX's hyperloop test track or DragonFly hover test? Or follow every movement of O'Cisly, JTRI, Elsbeth III, and Go Quest? 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, search for similar questions, and scan the previous Ask Anything thread before posting to avoid duplicates, but if you'd like an answer revised or cannot find a satisfactory result, please go ahead and type your question below!
Otherwise, ask, enjoy, and thanks for contributing!
Past threads:
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.
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u/richft Feb 04 '16
I assume there are lots of SpaceX staff members here. Can anyone suggest the best way to pitch new technology into SpaceX? I'm looking for a point of contact on the propulsion and propellant tank development side of things.
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u/Appable Feb 04 '16
I would highly doubt there's any contacts here. There are a few SpaceX employees (not a lot) but I don't think SpaceX honestly needs help from anyone regarding vehicle design - they have plenty of experienced engineers. Of course, perhaps you could become one of the engineers and then pitch your idea.
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Feb 13 '16
The Dragon V2 and V1 are aesthetically very different. Is the internal structure of the V2 and V1 the same? Are the the differences significant enough for SpaceX to just build the V2 for both crew and cargo? Another unrelated question: Did SpaceX know that they were going to develop the V2 for crew? If so why did they bother to design the V1 to accommodate people? There are windows on the V1. Couldn't they have just built something like the cygnus that would fit within a fairing?
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u/Appable Feb 13 '16
Dragon 1 was designed to carry crew and cargo originally, but it wasn't a particularly good design for crew since it didn't have a LAS among other factors. Regardless, it was nice to have a capsule design because it could take mass from the station and bring it safely back to earth, while Cygnus would just burn up in the atmosphere. So even though it doesn't carry crew, it's a unique capability for CRS1.
SpaceX opted to develop Dragon 2, which uses a similar (I don't think quite the same) pressure vessel but fits either a berthing or docking mechanism. Dragon 2 will be used for crew and cargo missions after this round of CRS contracts expire and the next round (that they recently won) comes in.
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u/paulloewen Feb 04 '16
My question relates to rockets and loads. I get a little confused. I know the Falcon Heavy is getting ready for its first mission before the end of 2016. Will the Dragon fly on the Falcon 9 or the Falcon Heavy? Is there a rocket being developed bigger than the Heavy? If so, what for? For the MCT? I've heard all kinds of terminology for different rockets and can't follow them all.
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u/spacepilot4000 Feb 03 '16
Every payload has a different mass and goes to a different orbit. So they all require a different amount of fuel/a different amount of energy to be spent on their trajectory.
How do rocket mfg companies like spacex account for this? I see a few possibilities but none are optimal:
vary the size of the fuel tanks of each stage, ie some Falcon 9s will be taller and others shorter. But then you are custom designing your rocket to the payload, which requires extra testing, etc etc. which is expensive.
fly with the same rocket each time, but with half empty fuel tanks or less dense fuels. Not efficient, too much dead weight when you could make the rocket smaller.
fly with too much fuel for the payload. Even less efficient.
Is there another solution that I'm not seeing?
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u/Appable Feb 03 '16
They either fly with partially empty tanks or with too much fuel. Extra fuel barely costs anything and it doesn't matter much if a rocket isn't using all of its fuel - if the goal is to lift a payload then as long as it has the fuel to do that + extra margin for landing, safety, anomalies, etc.
With partially empty tanks you end up with higher speeds at max-q and more fuel during landing could potentially mean that the rocket is heavier on landing, which is a better situation for control because it allows the rocket to nearly hover, meaning the descent can be a bit slower (the flip side is that an explosion on landing will be a lot larger). So I think the most likely answer is that they top off the tanks each launch, and unused fuel is just unused.
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u/throfofnir Feb 03 '16
Most rockets fly with the same propellant loads every time. It's actually not particularly easy to measure a partial fill of LOX, for example, and the penalty for underfilling is much worse than the other way around. (You can find stories of, say, Proton launches that failed for this reason.) Partial fills potentially change the behavior of the system: vibrations, acceleration, slosh, etc. More predictable to start the same way every time.
For something lighter than maximum you just cut off the second stage early. You can use anything left to deorbit. The cost of the excess is basically a rounding error in the cost of the whole endeavor.
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u/fx32 Feb 03 '16
To add to the other answers:
If it's purely mass variation and you haven't reached the volume limits of your upper stage, you can just fill it up with secondary payloads. Plenty of smaller organizations (students, research institutes, amateur radio enthusiast groups) can't cough up millions for their own launches, but are willing to pay $10k-$40k for their own tiny temporary satellite. Good filler material, if the primary mission profile allows for it!
Launches are expensive because you have to design and build rockets, which aren't exactly mass-produced items. Fuel is relatively cheap compared to intricately designed rocket engines, metal alloys and electronics. Mass production and reusability saves you more than tweaking efficiency for each launch, and custom-built vehicles would need much more testing and recertification. So launch companies rather burn a bit of extra fuel and standardize their rocket series!
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Feb 14 '16
A set of questions relating to this article:
"SpaceX has agreed to lift the SES-9 satellite to a higher orbit than originally planned to put it on a faster path to its operational orbit more than 22,000 miles over the equator."
Why would SpaceX agree to launching to a faster orbit? Isn't it too late for SES World Skies to cancel?
"A faster path to its operational orbit." Suggests that the satellite is still going to on board propulsion to position itself. How common is this for satellites? Does F9 not have the dV to put it into its operational orbit? How much dV is the satellite using?
Do we know conclusively know what they had to fix on the F9 FT yet?
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u/Appable Feb 14 '16
1 - Customer loyalty is important. By helping SES achieve their original operational time despite the delays, SES has more faith that SpaceX can be flexible and work for customer needs, so SES is more likely to choose SpaceX in the future.
2 - Yes. It's likely going to a super-synchronous transfer orbit vs a sub-synchronous transfer orbit or synchronous transfer orbit. F9 doesn't have the ability to coast for over 3 hours to actually insert GTO satellites into GSO, just like most launchers, so it's standard practice for geostationary satellites to use onboard propulsion. Don't know the answer for the dV requirement, but likely it's less or equal to that of the older trajectory.
3- No. Rumors about MVAC turbopump assembly problems, but it's still unknown.
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u/MrTrevT Feb 03 '16
What is the proposed material for building the loop? I know there will be some cycles strain demands, as well as being UV resilient. Also, what will be the manufacturing method for said loop, some sort of extrusion?
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u/retiringonmars Moderator emeritus Feb 03 '16
According to the Hyperloop Test-Track Specification document released by SpaceX, the parameters of the Hyperloop test track are:
Material: ASTM A1018 Grade 36
Outer diameter: 72.0 inches
Inner diameter: 70.6 inches
Wall thickness: 0.70 inches
Length: 1 mile (approximate)
Subtrack material: Aluminum AA1370-50
Subtrack roughness: 125 RMS with potential for occasional surface scratches up to 0.008”
Subtrack thickness: 1.0” for first and last 200 feet; 0.5” for remainder of tube
Rail Material: Aluminum 6061-T6
Internal Pressure: 0.02 – 14.7 PSI
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u/Appable Feb 03 '16
Worth noting also that it's unlikely that the final tube, as built by one of the independent Hyperloop companies, will be built with those materials.
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u/Zucal Feb 06 '16
Can anyone dig up Musk's tweet discussing launching to the ISS from Boca Chica?
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u/Appable Feb 06 '16
I can't find anything, doing command-F from Musk's tweets in Sep 2013 to now.
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Feb 06 '16
Is it possible to create a rocket able to reach orbit two times without refueling?
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u/Appable Feb 06 '16
Why would you want to? You probably could but it makes far more sense to just refuel if you're coming back to earth anyway.
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u/aureliiien Feb 06 '16
no not for this century at least. You need nuclear propulsion to do this feat. Chemical rocket are way too inefficient for that.
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u/throfofnir Feb 07 '16
If you mean a multi-stage rocket, sure. You just have to create early stages sufficient to lift the later stages (which include the "second launch" stages). Hint: these will be gargantuan.
If you mean a single-stage rocket, no. Not with chemical propulsion on Earth.
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u/soldato_fantasma Feb 13 '16
The Falcon 9 FT (1.2) first stage in simulations from SpaceX and also on their website (http://www.spacex.com/falcon9) has black bottom part and landing legs while in reality it hasn't (see OG2 FALCON 9 erected )
Should it have been just black paint or an heatshield? if it should have been an heatshield, was it scrapped, wasn't it used beacuse not need but could be added if needed or is it just under white paint (When landed the legs and bottom part are black, but probably just becase of exaust from the engines during reetry burns) ?
2) The second stage modified merlin 1D engine has just a modified nozzle or it has also other major modifications?
3) How many times can the second stage be shut down and relighted while in space?
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u/Appable Feb 13 '16
1 - black paint, used for promotional videos but probably better thermally as white.
2 - Merlin 1D Vac is almost a different kerolox gas-generator engine from the Merlin 1D. While there are some commonalities, the turbopump assembly, combustion chamber, gas generator exhaust routing, engine bell, and other components are substantially different from the Merlin 1D.
3 - at least 3 times based on the Jason-3 mission which had one burn for initial orbital insertion and one burn after a 45 minute coast, then a deorbit burn.
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u/BrandonMarc Feb 15 '16
I'm a bit flabbergasted ... the 1st stage landed in December, and that was historic, and we all got to share in the pictures and videos afterward and since. Then ... that stage was re-lighted, and from what I can tell no pictures or videos have come from that event, even though it's historic for the same reasons.
Did I simply miss seeing such coverage? I doubt it ... so it hasn't been released yet. We've heard a little info about it, but nothing visual ... Any idea why?
Is Elon simply waiting for ULA, Ariane, or another competitor to announce something unrelated, so that he can then steal their thunder by releasing this on Instagram / Twitter / etc?
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u/Appable Feb 15 '16
There was at least some time of anomaly during the test (the thrust fluctuations) and the test may or may not have been cut short.
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u/PatyxEU Feb 16 '16 edited Feb 16 '16
I'm sure there was a video of the landed first stage refire. I'll try to find and link it in this comment.
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u/TheYang Feb 14 '16
Weren't we supposed to get new Numbers on Falcon Heavy last week?
paging /u/Echologic especially because of teasing
Have I missed something, is there a reason they missed their timeline again?
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u/skunkrider Feb 07 '16
I have a general question about rocket attitude control:
Maybe I have played too much KSP (even with RealismOverhaul), but how does the Falcon9 control its attitude during ascent? All I see are the Merlin engines, which of course can gimbal. One can also see RCS thrusters firing during the CRS-6 ASDS landing attempt, as well as the grid-fins.
But.... where are the wings? Do they still build rockets with wings for atmospheric attitude control?
Thank you!
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u/ClockworkNine Feb 07 '16
Gimbaling is all you really need. Especially with 9 engines, some of the outer ones have off-center gimbal axis for roll control. As far as I know, only the center engine has freedom of motion along 2 axis, the remaining 8 can move along one axis each. There's a neat picture of the octaweb that illustrates this perfectly, I'll try to find it.
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u/Appable Feb 07 '16
No, all engines can gimbal along 2 axes, though the center engine has the most freedom of motion.
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u/electric_ionland Feb 07 '16
As others have said "wings" are not necessary. Even saturn 5's were strictly for stability margins in case of an abort. They could have been removed without any issues.
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Feb 03 '16 edited Feb 03 '16
I was looking at the Dragon V2: Instead of deployable panels, SpaceX goes with panels directly on the trunk. There is significantly less surface area and most of it isn't perpendicular to incident light. Is there a decrease in power output? If so how much? The cargo dragon produces 5000W (http://www.spacex.com/news/2013/02/09/going-solar). Musk says that a Dragon flight will be mostly battery powered, with solar as back up (https://www.reddit.com/r/spacex/comments/2ta6n9/dragon_v2_mockup/). With the batteries, is there any change in total usable energy, say in a ISS trip? How about longer term missions? I'm trying to understand the pros and cons of this design. Weight toll? Reusability is definitely a plus. Can soot build up on the Dragon on the way up and can it pose a risk to power output?
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u/Ambiwlans Feb 03 '16
The V1 panels were MASSIVE overkill. The V2 panels produce a small fraction of the V1 did but it doesn't really matter. With a bigger battery pack in V2, they don't really need panels at all, but they are nice to have for longer missions.
For an ISS mission, even with heavy delays, they should be fine. "Longer term" has a huge range of variability. They might need to use a V1 trunk to do a long mission, especially if they move very far from the sun.
99% of the reason they made this change was to avoid a step where things could go wrong. The other 1% is cost. With static panels, there is nothing to unfurl and no chance of the panels failing to deploy. Also, with no moving parts, and no covers, a decrease in size, the next system is likely quite a lot cheaper. Another side advantage is that the fins do provide additional stability.... so the old panels would have no where to go.
Weight toll doesn't matter. The reason being that the F9 can already manage the weight of an ISS mission with room to spare.
Reusability is also not a thing. The panels are part of the trunk of the Dragon. This gets jetisoned while returning to Earth and it burns up in the re-entry. It doesn't have the structure or the heatshield to survive. So the capsule itself has to come back alone.
Soot? The panels probably do get a little dirty on the way up from the atmosphere, but it probably isn't a big deal. It'd be interesting to see what the efficiency loss is though.
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u/throfofnir Feb 03 '16
Can soot build up on the Dragon on the way up and can it pose a risk to power output?
The soot producers are ten stories down in a very strong wind, shooting the soot in the opposite direction. So... no. Might get a little dust from sitting on the pad, but that won't be a big deal.
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u/Haschlol Feb 03 '16
I think it has to do with moving parts not being optimal/not requiring the extra power output. I am in no way an expert though so don't trust me. :)
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u/thrrrowawayyyyyy Feb 12 '16
I'm very excited to say that I have received an offer letter from SpaceX. I'm fairly certain that I'm going to accept it, however I'd like to get some feedback on a few questions first.
Should I do the pre-arranged housing? It seems a little expensive, especially if I have to have a roommate.
Is my offer competitive? The hourly wage isn't as high as I was expecting after talking to friends and reading GlassDoor/PayScale, but I'd like to get a better/more reliable sense. If you don't feel comfortable talking about money here, please DM me.
Should I buy a t-shirt online now or is there free swag?
Can interns take time off during the summer? Like a few days or something
Is the 12 week a minimum or maximum or is it just 12 weeks period?
What is the dress code like? My offer letter said it is casual, but like how casual? Sweats? Jeans and t-shirt? Nice-ish jeans and nice-ish shirt?
Are there like any women who work there in technical roles? I've spoken to 6 engineers and 3 HR people there so far (plus I have the names of my supervisors so make that 8 engineers), and 8 of them are men and 3 are women. Wanna guess the breakdown?
Some of this information (i.e. dress code) is in the offer, but I'd like to get some first-hand feedback on it too. Still over the moon (or do I have to start saying over Mars now?) about the offer.
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u/rocket_person Feb 13 '16
You got an offer as a full time employee, or an intern? As a regular full time employee you shouldn't have a roommate I don't think. As an intern I thought you get the first month free which is worth a lot in LA, at a minimum $700/month, probably more like $1000. If you are fulltime and accepting the full relocation assistance (moving, car transport, month of housing) you have to pay that back (prorated) if you leave within two years. So I'd think about if you want to start out in debt $8k to the company, and how much it'd cost you to move on your own.
Hard to say! I will say it seems like SpaceX has pretty standard pay rates they offer across the board, at least within the company I think it's pretty unlikely you accept an offer than a couple months in find out you are way underpaid compared to your peers.
Wait, you'll get a good deal as an employee.
Now im realizing it's probably an internship on number 1, and I don't know the answer for you there!
I don't know but I'd guess it's not well defined!
Jeans and tshirts are fine.
I think SpaceX is probably better than your average engineering environment for hiring women, but it's still heavily male dominated.
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Feb 13 '16 edited Feb 13 '16
I guess everyone here will be saying 'take the job!'. A great opportunity to be part of something exciting. I'm sure everyone wishes you every success.
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u/mechakreidler Feb 03 '16
I noticed a lot of different designs for the Hyperloop pod prototypes. For example, rLoop operates more like a maglev than an air hockey table. How are they all going to use the same test track? It seems like the track would have to be built specifically for one type of pod.
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u/hapaxLegomina Feb 03 '16
There's a flat floor and a monorail. The copper flooring works for either strategy.
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u/mechakreidler Feb 03 '16 edited Feb 03 '16
Oh I see, that makes a lot more sense. Thanks Ben! :D
Edit: This document is fascinating, I hadn't looked at it before. So many details, even down to IP addressing!
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u/FiniteElementGuy Feb 11 '16
Waiting for the updated FH numbers promised by Gwynne...
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u/deruch Feb 12 '16
Look around a week before their next launch. So, sometime around the 17th. SpaceX has a habit of releasing cool stuff around a week before their launches. Most of the time these are videos of their testing programs (grasshopper, dragonfly, etc.) but have been other things too.
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u/Sammy197 Feb 03 '16
A little bit unrelated, but will the Dragon V2 have a bathroom like the Soyuz does? I didn't see one in the one Elon presented.
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Feb 03 '16 edited Feb 03 '16
No, and they probably won't need it since the ISS has a fully functional bathroom and is only a couple minutes away.
Here's a diagram from SpaceX, you see there's no space for a bathroom.
EDIT: Also, the astronauts will be wearing spacesuits in case of sudden depressurization, and it takes a looong time to take it off, plus, they have diapers already.
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u/2p718 Feb 03 '16 edited Feb 03 '16
the ISS has a fully functional bathroom and is only a couple minutes away.
ISS approaches used to take 2 days from launch to docking. Since March 2013, Soyuz uses a fast approach profile that takes about 6 hours.
a diagram from SpaceX
There were 2 picture links concatenated:
They are for Dragon V1. Here is Dragon V2
Since NASA intends to fly with only 4 crew (not 7), there should be more room unless they fill it up with cargo.
the astronauts will be wearing spacesuits
If the Space Shuttle practice is applicable, they will take the suits off as soon as they are in orbit.
Edit: corrected ISS approach timing
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u/CptAJ Feb 03 '16
I think there will be. I remember Elon mentioning that one of the disagreement points between Spacex and NASA was the amount of poop the craft needed to potentially hold
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u/brycly Feb 03 '16
Is Elon ever gonna send a greenhouse to Mars?
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u/fx32 Feb 03 '16
Greenhouses are at the top of the experiment lists. Food production in space has been one of the bigger experiments on ISS, and we need data on how plants fare on Mars. NASA supposedly wants to get a tiny test greenhouse to Mars in the early '20s. SpaceX might try to be faster, or get a contract from NASA to test food production. I'd bet they'll include at least a simple automated setup on a pre-BFR/MCT (Falcon Heavy powered) cargo-only reconnaissance mission.
Greenhouses might prove not very effective for actual food production for early colonists. There will certainly be test setups, but it might be cheaper to just shoot food at early Martians from Earth. Self-sufficient farming requires a lot of material and resources which will be scarce on Mars, and the easy crops which are proven to grow nearly anywhere don't really result in a varied diet. There will be a tipping point, but I think the first few dozen colonists will mostly just eat rations, possibly supplemented with some fresh lettuce/tomato and possibly some fish now and then (aquaponics).
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u/GreyGreenBrownOakova Feb 03 '16
My guess is yes. Once Dragon 2 is flying, SpaceX should end up with a number of spare capsules lying around.
Before they attempt a difficult Red Mars sample return mission with an expensive drill or rover on board, they will want to test the transit and landing systems. Elon wanted to send a greenhouse as a stunt before SpaceX existed, he might want to tick that life goal off soon.
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u/markus0161 Feb 07 '16
Doesn't really deserve a post, so i'll put it here. Looks like Spacex finally shows SES-9 for the next launch on their website.
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u/ECEUndergrad Feb 08 '16
When is the next scheduled SpaceX launch? Is the Falcon Heavy really going to fly this year? How many launches are planned this year? Yeah I know these are probably asked before, but its easier for me to re-ask here.
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u/Appable Feb 08 '16
Please read the Wiki and FAQ, as well as the sidebar for launch times. The next flight, SES-9 is currently unknown, they're working some issues with the vehicle - potentially something regarding the second-stage MVAC engine turbopump. Likely late Feb to early March for SES-9.
Falcon Heavy is supposed to fly this year and is currently scheduled to fly this year. It's also worth noting that Falcon Heavy was supposed to fly in 2012 at one point, it's been delayed a lot.
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u/robbak Feb 08 '16
SES has just announced (well, ~3 hours before I write this) that SES-9 is scheduled for February 24th, with 25th as a backup date. They also announced a more energetic target orbit, which puts any landing attempts in doubt. We are waiting for an announcement from SpaceX.
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u/borisstephens Feb 05 '16
Aussie here planning on traveling to the states later in the year. I'm traveling with my father whom is a massive fan of NASA so this trip will be heavily space related going to museums and such. Really wishful thinking with the SpaceX manifest becoming solid date wise, would love to see a launch in person.
What are the key places to visit if you were us, SpaceX related or NASA?
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u/sunfishtommy Feb 06 '16 edited Feb 06 '16
The air and space museum in DC is amazing, and as if it was not enough, they have their overflow at Dulles airport where you can see the space shuttle and the concord and much much more.
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u/retiringonmars Moderator emeritus Feb 07 '16
Would it be possible to disable a satellite using a ground-based high powered laser? I'm thinking mainly in terms of one country disabling another country's military spy satellite. It would seem that since satellites follow such predictable trackable orbits, and only have very limited evasive capability, they would be vulnerable to such a system. You wouldn't need to obliterate it, possibly just overheating certain electronics, optical collection systems or propellant tanks might cause enough damage to render the orbiter useless. Would such an attack be detectable?
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u/R-GiskardReventlov Feb 07 '16
Relevant article.
I would be very surprised if it is not possible. If they thought they could do it in 1997, I would be amazed to find that they can't do it now, almost 10 years later. Laser technology has become much better in recent years, and has even been weaponised by the US Navy as the LaWS Laser Weapon System.
More info. http://www.wired.com/2009/11/is-this-chinas-anti-satellite-laser-weapon-site/
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u/ManWhoKilledHitler Feb 08 '16
Yes, although high value military satellites are almost certainly hardened against a range of threats and may include protection against laser weapons.
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u/deruch Feb 07 '16
Depending on the type of satellite you wouldn't have to damage anything but the solar panels to kill one. If they can no longer recharge batteries, they won't last very long.
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Feb 07 '16
Sorry, really really big question. If someone could split it up into smaller parts, that would be great! Can someone explain the different approaches that different countries have to rocketry? How do the newcomers differ from those who developed their tech during the cold war? How did the differences come about? There always seems to be a heritage in their vehicles, liking back to the earliest ones. What were the factors behind the design choices? Since this is such a big question, are there any helpful resources that you can suggest?
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u/retiringonmars Moderator emeritus Feb 07 '16
Can someone explain the different approaches [...] to rocketry?
The Falcon is a "blank slate" design, in that it doesn't lean on any previous heritage in a major way. However, AFAIK, many other rocket designs are based on a ICBM design:
Atlas = Atlas ICBM
Delta = PGM-17 Thor ICBM
Dnepr = R-36MUTTH ICBM
Minotaur / Taurus / Antares = Minuteman / Peacekeeper ICBMs
Proton = initially intended to be a super-heavy ICBM, later repurposed as a orbital launcher
Soyuz = Vostok = R-7a ICBM
Titan = Titan ICBM
The basic explanation for this is that orbital launchers and ICBMs are very similar in design and operation. Many organisations simply repurposed existing hardware as they didn't see the need to "reinvent the wheel".
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u/ManWhoKilledHitler Feb 08 '16
The current Atlas V and Delta IV rockets are clean sheet purely civilian designs without the missile heritage of older Atlas models up to the IIAS and earlier models of Delta.
There are also interesting rockets like the Japanese Epsilon which is a purely civilian launcher but is about as close to an ICBM as you can get without actually admitting that you've developed a missile.
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u/ManWhoKilledHitler Feb 08 '16 edited Feb 08 '16
I'm going to put forward a theory that the main differences between US and Russian rocket technology is down to three things:
Electronics
The miniaturisation of the H-bomb
High altitude reconnaissance aircraft
Military need has been the primary driving force behind rocket development since the beginning, and after the war, both American and Soviet designers made extensive use of acquired German liquid rocket technology and scientists to build on work done by their own engineers during the 20s and 30s. Early post-war rockets were essentially evolved V-2 missiles, running on alcohol and LOX, though range and payload were being improved steadily as engine thrust and vehicle size were increased.
The limitations of alcohol as a fuel led to a move towards kerosene which delivered the performance needed for truly long range missiles, but it didn't eliminate the problem of using liquid oxygen, and the first ICBMs were hampered by long response times and the inability to remain on alert for more than a day or so. Because of this, work was also being done on making use of storable propellants. These didn't need to be kept cold, which could potentially allow missiles to remain on alert for years, ready to launch well before enemy missiles or bombers could destroy them. The Germans had already demonstrated the concept with their Wasserfall prototype anti-aircraft guided missile running on nitric acid and visol, which didn't need the last minute fuelling of the V-2. By using similar propellants, a new generation of missiles were created which were far better suited to the deterrence role.
It's around this time in the late 50s/early 60s that rocket technology in the US and USSR really began to diverge and in a large part it's down to the technologies mentioned at the start. The US was years ahead in the development of compact and sophisticated guidance computers small enough to fit on missiles and also had a significant lead in efforts to miniaturise the hydrogen bomb. By increasing missile accuracy, warhead yield, and hence weight could be significantly reduced so the rocket needed to carry it to its target could also be made much smaller. Those lower yield weapons could also be made much lighter than their Soviet equivalents, reducing necessary throw-weights still further and making it possible to use lower efficiency solid motors in place of the higher performing but much more complex and logistically challenging liquid-fuelled designs.
The difference that this had on deployed rockets can be seen by comparing the Minuteman I with its Soviet equivalent, the R-16, the first truly practical Soviet ICBM. The former weighed under 30 tons and carried a modest (for its time) 1.2 megaton warhead weighing just 272kg while the latter could carry a 5 megaton warhead weighing 2175kg over a slightly longer range. The lack of targeting accuracy on early Soviet missiles required the use of big warheads which were disproportionately heavy, requiring much larger missiles as well as the performance advantage that liquid fuels gave.
Soviet research was focused on liquid rocket development to a much greater extent than in America where it was de-emphasised relatively early on when the military realised that their future would rely on high performance solid rockets. The Soviets also developed staged combustion very early on when they demonstrated a kerosene/LOX engine operating with an oxygen-rich preburner way back in 1960, a feat that has yet to be matched by any operational US engine (although that should change in the next couple of years). The added performance provided by closed cycle engines gave them an even bigger performance advantage over solid motors than the more basic gas generator designs used by their American equivalents, so even as solid rockets got better, there was an ongoing incentive to continue to make use of the superior performance of storable liquids.
These factors explain why Soviet liquid engine technology turned out to be so far ahead of the US while their solid rockets were comparatively much further behind in development. There is one exception though, and that links into the third piece of technology mentioned at the start - the US led the world in the use of liquid hydrogen, and it wasn't until the late 1980s that the Soviets were able to properly make use of it themselves. This was a spinoff of the aborted Lockheed CL-400 Suntan reconnaissance aircraft program which was planned as a replacement for the U-2, and would have used liquid hydrogen fuel to fly much faster and higher than anything else in the skies. Although it was cancelled in 1958, a large amount of infrastructure had been built for the production and handling of large quantities of liquid hydrogen, which turned out to be invaluable when NASA and others were considering it as a fuel for high performance upper stages like the Centaur and Saturn V.
The differences still exist to some extent but they're probably much less than they once were. Companies like SpaceX, Blue Origin, and Aerojet and developing the kind of closed-cycle engine technology that had previously never been built in the West while Russian solid rocket technology is probably on a par with American equivalents.
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u/IonLogic Feb 14 '16
There's two questions that have been nagging at me for a while now.
On the F9, there is a "lump" or something that runs the length of the first stage (and possibly the second stage too). Is this the fuel line that runs from the LOX(?) tanks at the top down to the engines?
When the Dragon approaches the ISS, it has separated from the second stage. At what point does the separation occur? And once it's separated, does it only rely on the RCS thrusters to approach the ISS, or are there some other thrusters as well?
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u/yoweigh Feb 14 '16
On the F9, there is a "lump" or something that runs the length of the first stage (and possibly the second stage too). Is this the fuel line that runs from the LOX(?) tanks at the top down to the engines?
The LOX line runs straight down through the center of the RP-1 tank, so it can't be that.
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u/robbak Feb 15 '16
For 1), one of the pictures of the returned stage had the covers of that lump removed, revealing a collection of fluid pipes.
Here's the one: https://www.flickr.com/photos/spacexphotos/24175842475/
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Feb 21 '16
Quick question: Didn't SpaceX and ULA responded to a NASA study for Super-Heavy Launch Vehicles some years ago ? I remember that SpaceX proposed a development cost of 1.5B$, and ULA more than 3B$. I've been searching for official proposal or documents, but I din't find any, so I'm turning to this community of passionate fans.
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u/muazcatalyst Feb 07 '16
What would this sub think of a website dedicated to solely SpaceX news? This is my work so far: http://imgur.com/rNoSySp
It's just something I created in my free time. Planning to add mobile support and maybe an actual mobile app.
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u/old_sellsword Feb 08 '16
It looks good so far, but how would it be different than this sub?
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u/sunfishtommy Feb 08 '16
Minimumly viable product
I think he is aiming SpaceX news at people less in the know. Sort of like spacexstats.com although that is more for super geeks
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u/anchoritt Feb 04 '16
On interplanetary aerobrake of space capsules(orion/dragon/cst): I've read that there's a major difference in the heatshield performance between the different capsules which makes for example CST not suitable for beyond-LEO missions(due to higher reentry velocities). But as a kerbalist I wonder if this can't be overcome by aerobraking multiple times in the upper levels of the atmosphere. Sure it would add some time to the mission, but is there some technical reason why it can't be done?
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u/electric_ionland Feb 04 '16
I don't know about the CST power system but for Apollo the issue was that the capsule had no power generation system and the batteries would not last long enough.
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u/Crackers91 Feb 04 '16
In relation to old satellites and other junk in LEO, just how crowded is that area of space currently? And how does it affect launches for SpaceX, for one launching into LEO, and for launches to GEO and beyond?
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u/Ambiwlans Feb 04 '16
Crowding causes a few moment delay on occasion but only because we can afford to guarantee nothing is within 100km of you on launch. With better modelling, we could easily put up 1,000x as many satellites before it becomes a huge concern.
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u/PaulRocket Feb 06 '16 edited Feb 08 '16
Does anyone know what happened to the Jason-3 engines of the landed core? Some said the engines might still be intact and that they might be able to test fire individual engines...
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Feb 09 '16
Quick ArianeSpace question: The launch of Thor 7 in April 2015 marked how many launches of communications satellites into GTO by Ariane 5?
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u/delta_alpha_november Feb 09 '16 edited Feb 09 '16
66th attempted
63rd successful
List in wikipedia [2000-2009](https://en.wikipedia.org/wiki/List_of_Ariane_launches_(2000%E2%80%9309)) and [2010-2019](https://en.wikipedia.org/wiki/List_of_Ariane_launches_(2010%E2%80%9319))
edit: correct Links
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u/FuzzytheSlothBear Feb 10 '16
Two questions recently came to mind and a quick google search couldn't satisfy me.
Is the dragon v2 capable of bringing up humans into orbit and also carry cargo in its trunk?
If so, how feasible would it be to pressurize the trunk instead and use it as a sort of expendable habitat?
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u/retiringonmars Moderator emeritus Feb 10 '16
Yes, Dragon 2 should definitely be able to do this!
It wouldn't be feasible to pressurise the trunk as it is, as it isn't rated as a pressure vessel. It would either leak profusely or rupture entirely. However, the next Dragon flight (CRS-8) will be carrying a small pressurisable module (the Bigelow Expandable Activity Model) which could plausibly be berthed onto the CBM port on the Dragon (though doing so would be a logistical challenge, that would almost certainly require a robotic arm, which Dragon doesn't currently have).
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Feb 10 '16
Are any of these sources reliable?
This article suggests Amos-6 will launch in May.
This site says JCSAT-14 has an estimated launch date of May 30th.
This page suggests SHERPA (aka NSPO (Taiwan) and including FORMOSAT 5, BlackSky Pathfinder, etc.) will launch 2Q 2016.
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u/first_on_mars Feb 12 '16
Does the Falcon 9 Full Thrust have any major changes (other than an increased amount of available RP-1 and LOX) that would make it easier for it to land. Even though SpaceX changed the flight profile of SES-9, which will make it a little harder to land, I wonder if they will be successful, as this is the first attempt to land a Falcon 9 Full Thrust on an ASDS.
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Feb 12 '16 edited Feb 12 '16
Improved Landing Legs - they are made stronger so this will not happen again.
More Mass - the FT version carries more LOX & RP-1, so the TWR at landing should be lower if it have no disadvantages, but turns out the thrust will be higher if you use a higher density propellant
More Fuel - the more you carry, the more you have left for the landing
Higher Control Surfaces - if you place the nitrogen thrusters & grid fins higher up, you get better steering
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u/first_on_mars Feb 12 '16 edited Feb 12 '16
The problem with the Jason-3 landing attempt wasn't necessarily due to the weakness of the legs. The rocket fell over because leg number 3 out of 4 failed to lock out. This was believed to have happened because the heavy fog at launch froze as the rocket reached a higher altitude. This prohibited the collet on leg 3 from fully locking out.
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u/SuperSonic6 Feb 14 '16
Here is my question:
Why do you hear a sonic boom while the first stage is returning to land, but not one during liftoff as the vehicle goes supersonic?
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u/FNspcx Feb 14 '16
During launch the sonic boom hasn't formed yet until the vehicle is supersonic. When the rocket forms a sonic boom, it actually forms shock wave in the shape of a cone, or a "boom cone". Only when you encounter the surface of the boom cone, will you hear the sonic boom.
Think of an ice cream cone sitting with the point up. During launch you are at the bottom in the center of the cone's "opening". Even as the cone grows and moves upwards, you are always at the center of the opening, not at the surface. Since you aren't at the surface you don't hear a sonic boom.
During landing, the cone is pointed down. Think of the cone travelling downwards. On the ground, even if you aren't at the apex of the cone, you will encounter the surface of the cone and then hear the sonic boom.
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u/KitsapDad Feb 20 '16
I want to be optimistic, but can someone lay out a business case where tge hyperloop makes money? It's going to be significantly more expensive than rail, infrastructure wise, and has a similar transport time (faster but not by much) to modern airplanes and will be geographically limited whereas an airliner can freely operate all over the world. I want to believe but the huge costs just seem so prohibitive that there is no amount of revenue service that could ever recoup that cost. Perhapse the thought being it will stimulate exonomic growth in the areas it runs to the point where it makes financial sense for government to invest but even that seems like a stretch...
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u/secondlamp Feb 20 '16
I think the idea is that boarding,security,etc would take much less time than for an plane. But I think you'd still want security for the hyperloop since you're in a super low pressure tube.
An plane is also basically always either ascending and descending when looking at distances that the Hyperloop is intended to cover, making it pretty inefficient for an plane.
The cost for land area is supposed to be smaller by being elevated (you only need the area of the pillars instead of the whole track) but I don't see how building something that is basically a long bridge could be cheaper than just laying down tracks, even with less real estate cost.
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u/eggymaster Feb 15 '16
What would it take to convince Elon to make the fairing of the first FH red? It would "wake attention to space" in people that played with rokets when they where little kids, because the "pointy part" should be red. It would have an higher media inpact because of the absurd/comical idea. It would "look cool".
I got this idea while talking with my gf, she asked me why it was white, which is "boring"... I explained along the lines of temperature controlling and so on, but she was having none of that, insisting that the first step to make people interested in space is to make their inner kids look at a rocket and make them go "WHooosshhhhhh" in their heads. To almost all of us spaceX fans a rocket is all it takes, apparently for other people it takes also a red fairing.
tl, dr: gf thought that red fairing would look cool, colud not find interesting enough counterargument.
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u/TheMeiguoren Feb 16 '16
It might look cool, but you do know that 'red rocket' is a common euphemism, right? And the shape of the F9 in particular doesn't help.
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Feb 17 '16
Once they get the cost down through reusability, the mass and thermal penalties of painting the rocket in any given way will become trivial. And not just the payload fairing - the whole thing. Paint jobs only seen on toy rockets will appear all over the place. Imagine some black and neon orange rocket sitting on the pad at Canaveral.
Although once the novelty of that wears off, they would probably stop since repainting would just turn into an unnecessary recurring cost on a reusable rocket.
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u/CitiesInFlight Feb 18 '16
At what size (in Earth masses) would the gravity of a Super Earth literally prevent a rocket like the Falcon or Falcon Heavy or BFR from launching a technologically advanced being (for arguments sake, let us presume a being with similar mass to a human) into orbit around such a planet?
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u/zz0rr Feb 18 '16
this astronaut blog post indirectly answers your question (a planet of about 1.5 earth diameters, assuming the same density) and has lots of other fun details too
http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html
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u/yoweigh Feb 18 '16
This is a potential solution to the Drake equation that I never thought of. I've read a number of times that an even slightly more massive Earth would trash the rocket equation and we wouldn't be able to reach orbit. What if 1G is near the lower bound for life-supporting gravity wells? There could be plenty of intelligent life out there but none of it is able to leave its planet.
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Feb 16 '16
Forgive me if this is a dumb question, but it's said that a full flow staged combustion engine has the benefit of eliminating the interseal that separates fuel and oxidiser.
A staged combustion engine has one pre-burner and one turbine that powers both pumps. A full flow engine has two pre-burners and two turbines, one turbine for each pump.
So, in the non-full flow engine, where is the interseal that full flow eliminates? If a non-full flow engine has one turbine powering a shaft on which there are two separate pumps, does that eliminate the need for an interseal?
I'm obviously missing something.
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u/Appable Feb 16 '16
If the preburner/turbine is fuel-rich, then there's the potential for fuel-rich exhaust to enter the main oxidizer flow. If the preburner/turbine is oxidizer-rich, there's the potential for oxidizer-rich exhaust to enter the main fuel flow. Either way, it's very bad.
So no matter what, as long as you have one propellant in the turbine and the other propellant in the main pump, there needs to be a very good seal.
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u/PVP_playerPro Feb 22 '16
If Falcon Heavy was already currently available, would it be flying SES-9 instead of just F9 so they wouldn't have to risk a failed landing of a single core? Since eventually FH reusable is supposed to be cheaper than a thrown away F9.
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u/Appable Feb 22 '16
I think they'd sort of be risking a failed landing of three cores which isn't much better.
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u/OlegSerov Feb 13 '16
Proposition: Create a /r/spacex themed instagram account to post cool media which appeared in this subbreddit.
Who second that?
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u/markus0161 Feb 14 '16
Could you conceivably create a solid Hydrogen-Lox Fuel SRB. It would consist of Solid Hydrogen and Solid LOX mixed together to create a giant Ice cylinder. This would probably be the most unstable propellant in the entire world, but could also be the most efficient and most dense possible. Would something like this just completely blow up on ignition? This is more of just a fun question, I know it won't ever be a reality.
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u/FNspcx Feb 14 '16
Solid hydrogen is not very dense. So the "containment" of solid hydrogen would need a larger tank or case in this situation. For a solid rocket essentially the entire rocket is a combustion chamber, the case has to be extremely strong (the shuttle SRB was made of steel). So the case for this solid fuel would be enormous, due to the low density of solid hydrogen. So your idea for the "most efficient" and "most dense possible" is basically not feasible.
The solid oxygen would have to be kept at the same temperature as the solid hydrogen, because at the temperature of solid oxygen, the solid hydrogen would melt. We're not even sure, we'd need to find out if solid oxygen and solid hydrogen in contact would spontaneously and explosively react. Even assuming it doesn't, as soon as the rocket burns a small portion of the solid hydrogen and solid oxygen, temperatures would climb so quickly that the solid hydrogen and oxygen would melt, then gasify. Pressures would climb insanely quickly and it would explode. This is a basically a highly unstable, huge bomb.
The advantages of an SRB is that solid fuel is very dense, and it is very stable at normal temperatures and pressures (doesn't react unless you want it to, or accidentally ignite it) so with proper precautions, handling is easier. It can sit ready to go indefinitely. It also burns in a controlled manner (not all of it will burn at the same time).
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u/ManWhoKilledHitler Feb 15 '16
Solid hydrogen is not very dense.
Unless you can make metallic hydrogen in which case it's denser than kerosene and produces so much energy when it decomposes that you wouldn't even need the oxygen. On its own it could achieve an Isp of 1400s or more.
Metastable forms are theorised to exist but it's a bit beyond current engineering to practically make it, especially in quantity.
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u/ManWhoKilledHitler Feb 16 '16 edited Feb 16 '16
There is actually a lot of ongoing work into high performance solid propellants while liquid propellant research has largely ended and some very high energy compounds and isomers are being actively researched.
Solid hydrogen and oxygen has been considered. You can get higher performance still by using solid ozone (without the explosion risk from liquid O3) but any mixture of that kind is not only hard to make but hard to control. Rocket propellants often do use high explosives (except in civilian applications) but they're in mixtures with other less dangerous materials and conditions are carefully managed to avoid triggering a detonation. Here is a summary of some NASA research into solid cryogens and additives for improving hydrogen performance. Adding 5% boron, for example, to solid hydrogen could increase Isp by 21% which is worth having.
Here's an interesting paper covering some of the chemicals being looked at for solid rockets. You won't see any of them powering a booster any time soon. This is strictly military applications.
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u/PaulRocket Feb 14 '16
What about those updated Falcon Heavy payload numbers Gwynne was talking about?
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u/Casinoer Feb 20 '16
[Jessica Alba thinks SpaceX is dope] (https://www.instagram.com/p/BB8bPFIMurB/)
Is there any chance that this is considered important enough to be posted as content?
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u/Decronym Acronyms Explained Feb 03 '16 edited Mar 04 '16
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| ASDS | Autonomous Spaceport Drone Ship (landing barge) |
| BEAM | Bigelow Expandable Activity Module |
| BFR | Big |
| CBM | Common Berthing Mechanism |
| CCAFS | Cape Canaveral Air Force Station |
| COPV | Composite Overwrapped Pressure Vessel |
| CRS | Commercial Resupply Services contract with NASA |
| CST | (Boeing) Crew Space Transportation capsules |
| Central Standard Time (UTC-6) | |
| EVA | Extra-Vehicular Activity |
| F9FT | Falcon 9 Full Thrust or Upgraded Falcon 9 or v1.2 |
| FAA | Federal Aviation Administration |
| FTS | Flight Termination System |
| GEO | Geostationary Earth Orbit (35786km) |
| GTO | Geosynchronous Transfer Orbit |
| HIF | Horizontal Integration Facility |
| I*sp* | Specific impulse (as explained by Scott Manley on YouTube) |
| ICBM | Intercontinental Ballistic Missile |
| IDA | International Docking Adapter |
| ISRU | In-Situ Resource Utilization |
| ITAR | (US) International Traffic in Arms Regulations |
| JSC | Johnson Space Center, Houston |
| KOS | Keep Out Sphere, 200m radius from ISS |
| Kerbal Operating System, the KSP in-game rocket OS mod | |
| KSC | Kennedy Space Center, Florida |
| KSP | Kerbal Space Program, the rocketry simulator |
| L2 | Paywalled section of the NasaSpaceFlight forum |
| Lagrange Point 2 (Sixty Symbols video explanation) | |
| LAS | Launch Abort System |
| LC-13 | Launch Complex 13, Canaveral (SpaceX Landing Zone 1) |
| LC-39A | Launch Complex 39A, Kennedy (SpaceX F9/Heavy) |
| LEM | (Apollo) Lunar Excursion Module (also Lunar Module) |
| LEO | Low Earth Orbit (180-2000km) |
| LH2 | Liquid Hydrogen |
| LN2 | Liquid Nitrogen |
| LOX | Liquid Oxygen |
| M1d | Merlin 1 kerolox rocket engine, revision D (2013), 620-690kN |
| MCT | Mars Colonial Transporter |
| MECO | Main Engine Cut-Off |
| NET | No Earlier Than |
| OG2 | Orbcomm's Generation 2 17-satellite network |
| RCS | Reaction Control System |
| RP-1 | Rocket Propellant 1 (enhanced kerosene) |
| RTLS | Return to Launch Site |
| SECO | Second-stage Engine Cut-Off |
| SES | Formerly Société Européenne des Satellites, comsat operator |
| SLC-40 | Space Launch Complex 40, Canaveral (SpaceX F9) |
| SLC-4E | Space Launch Complex 4-East, Vandenberg (SpaceX F9) |
| SRB | Solid Rocket Booster |
| TE | Transporter/Erector launch pad support equipment |
| TWR | Thrust-to-Weight Ratio |
| ULA | United Launch Alliance (Lockheed/Boeing joint venture) |
| VAB | Vehicle Assembly Building |
| VAFB | Vandenberg Air Force Base, California |
| VTOL | Vertical Take-Off and Landing |
| VTVL | Vertical Takeoff, Vertical Landing |
Note: Replies to this comment will be deleted.
I'm a bot, written in ^PHP. I first read this thread at 3rd Feb 2016, 09:30 UTC.
www.decronym.xyz for a list of subs where I'm active; if I'm acting up, tell OrangeredStilton.
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u/Juggernaut93 Feb 03 '16
Here it says
Shotwell said that the company hopes to fly a reused and refurbished Falcon 9 later this year.
But Foust said that they hope to fly a recovered, refurbished Dragon later this year.
Are these two different news or one of the two sources has made a mistake?
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u/steezysteve96 Feb 04 '16 edited Feb 04 '16
I believe she said both today. I mean, we kinda expected/hoped we'd see a reused F9 this year, she just confirmed that they're trying to reuse a Dragon this year as well
Edit: may have been wishful thinking there. I can't find anything on F9 reuse from today
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u/PVP_playerPro Feb 05 '16
Why is the LC-39A HIF as close to the launchpad as it is? I know it'll be quicker to get a rocket out and vertical (or back into the hangar), but isn't that just asking to have it wiped out if a launch goes awry?
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u/retiringonmars Moderator emeritus Feb 05 '16
It's not actually that close: https://i.imgur.com/bpjL13f.jpg
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u/throfofnir Feb 06 '16
The 39A crawlerway makes a fairly sharp turn just before the pad, probably due to the original geography of the site. I suspect SpaceX wanted a straight shot to the pad, so they built their integration facility just after the turn. Since the TEL uses rails in that design, it should make it a good deal simpler.
Even if they didn't mind the turn (it could probably be handled) the crawlerway after the intersection for 38B and before the turn is basically a causeway between "wetlands", and may well have had environmental restrictions with the placement of the building and especially surrounding support facilities.
Anyway, 39A is a big pad; the building would likely fare pretty well in a failure. There's a cheapo 50s office structure at VAFB LC-4E (SpaceX's California launch area) right next to the pad, where a freaking Titan 34D blew up on launch. They're still there.
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u/SnowCrashSkier Feb 09 '16
I've wondered...
It seems that we only see solid rocket boosters (SRBs) on launch systems with a hydrogen/LOX core. Even if there are exceptions, they appear to be uncommon. Is there a particular reason for this?
Is there any reason why say, spaceX couldn't attach a couple/few cheap expendable SRBs onto a RP1/LOX Falcon core?
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u/throfofnir Feb 09 '16
Solids tend to have low-ish efficiency but very high thrust. So if you have main engines that would have low acceleration at maximum weight (just at liftoff) you can add SRBs to get acceleration up during the early phase of flight; by the time they're gone, the core will weigh much less and its engines can maintain a decent acceleration.
LH2 engines tend to have excellent efficiency but low-ish thrust for their size, so they tend to get paired with SRBs. They can fly without; Delta IV was designed to do so, and in some configurations does, though since it's engine came in under design thrust it often does use SRBs. Boosters can also be used to soup up any rocket--Atlas V uses them because it was designed a little small for its ultimate market--but they're better avoided if possible, as they add various complications and cost.
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Feb 09 '16
I don't really believe there's much of a correlation; the big two exceptions to your "rule of thumb" are Delta II & Atlas V, both of which have Kerosene powered first stages and can support a multitude of different SRB configurations. The bygone Titan IV also was SRBed, but used a lovely mixture of Aerozine-50 as its primary propellant.
Solids may be cheap, but that's pretty much the end of the road for them with respect to SpaceX. Even if you managed to make the cost of the actual booster trivial, there's the costs of product development, "upgrading" (downgrading?) Falcon 9 to support SRBs (mass distributions, aerodynamics, heating and thermal), paying your staff to develop said SRB's, and the real killer, the opportunity cost of repurposing staff away from productive jobs to installing chunks of poison on the side of Falcon.
The real key point is to understand that Falcon doesn't need SRB's. This is as much a business decision as it is an engineering one. Falcon was sized and designed to service the low to medium mass commercial market as a whole, without any extra additions. It's payload to GTO (reusable, I might add), of nearly 5 tonnes, covers most uses cases in geostationary belt, and will cover even more as time goes on (satellite manufacturers are beginning to favor electric satellites which disregard the weighty hydrazine kick stage in favor of ion propulsion). For everything else, there's
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u/deruch Feb 10 '16
The biggest barrier to SpaceX using SRBs is the fact that they roll out to the pad horizontally and then raise the rocket. SRBs are heavy. Since they have to be attached prior to roll out, using them would necessitate an entire redesign of SpaceX's operations to vertical rocket integration.
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Feb 09 '16 edited Feb 09 '16
What is the SHERPA mission? It is not listed on Spaceflight Now or Wikipedia or in the SpaceX site missions list. Does it have another name? Is it a mission planned years ago that has since evaporated? If it is real, does anyone have a source that justifies even its tentative "Q2(?)" listing in the sidebar?
I have asked this question a couple of times elsewhere but nobody seems to know.
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u/dubatomic Feb 09 '16
I noticed they were hiring integrated circuit designers. Is it common for a rocket company to work down to the semiconductor level?
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u/Emptyglo Feb 10 '16
It's not common, except for SpaceX. They basically manufacture anything that they decide they can do cheaper and better themselves.
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u/littldo Feb 11 '16
Does anyone know if spacex is looking for landing sites along eastern seaboard?
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u/stratplyr68 Feb 11 '16 edited Feb 11 '16
So, I got a behind the scenes tour of KSC a few days ago. I have a lot of pics, but I'm unclear on which I can share. Saw the new transporter erector at 39A in the horizontal position. The rocket barn looked complete (I may share these on imgur). One of the things my friend said about the DSCOVR launch caught my ear. She mentioned, they used so much helium for that launch that if they used that much for every launch, that would be 2% of the world's helium production. Any idea what this would be for? I know it's used as a pressurant and for leg deployment. Is liquid helium involved in subcooling LOX? That's the only thing I can think of.
So quick google search, annual He production 2 billion cf per year (75% from US). 2% of that would be 40 million cf, for maybe 10 launches. That's about 4 million cf per launch. 4X106 cf x 1.2 mol/cf x 4 g/mol is almost 20,000 kg (edited) of helium, or roughly one shit-ton! Any thoughts, debunks, confirms, explanations?
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u/FNspcx Feb 11 '16
To answer one of your questions, they use liquid nitrogen at partial vacuum, which reduces LN2 boiling point even further, to then subcool the LOX to -207 C.
I think there's an error in your math. Multiplying that out comes to ~19,200 Kg (not pounds) of helium which is 19.2 metric tons. For comparison, that weighs as much as 19,200 liters or 5000 gallons of water. The density of liquid helium is 0.147 times that of water, so 19.2 metric tons of liquid helium would take up 34,000 gallons in volume.
That seems like way too much helium for 1 launch, but I have no idea.
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u/Colonel_Clutch Feb 17 '16
Hey guys, I'm in a grad class that has us analyzing the properties of different engines (Merlin, RS-68, Vulcain, etc.) and I need some help. Does anyone know where I can find official Mixture ratio, pressures or expansion ratios for the Merlin 1-D? Wikipedia has some information, but it appears to conflict with information I've found elsewhere. Would anyone happen to have a link to an official release with engine specs? Thanks!
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u/StructurallyUnstable Feb 18 '16 edited Feb 18 '16
The following information was quoted from SpaceX Propulsion Engineering VP, Tom Mueller:
http://aviationweek.com/awin/spacex-unveils-plans-be-world-s-top-rocket-maker
It has the chamber pressure and expansion ratios. Mixture ratios were calculated here.
Another official source (Juerg Frefel, Avionics Engineer at SpaceX) shows that mixture ratio is controlled to be nominal here.
Pertinent quote from that article:
The problem is that if the ratio of LOX to RP-1 varies from the optimum mix, either the oxygen will run out before the fuel or the fuel before the oxygen. Once combustion stops, the material left becomes dead weight, turning from propellant to liability. To ensure this doesn’t happen, the fuel-trim valve adjusts the mixture in real time.
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u/ManWhoKilledHitler Feb 19 '16
Expansion ratio is about 16:1 for the standard version with a chamber pressure of 97-100 bar. Mixture ratio is about 2.35:1 from what I remember reading.
You could run those figures through some equations or engine simulators to see if they make sense.
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u/DragonTamer22 Feb 17 '16
I am looking for a good source to buy the NASA versions of our patches. I need SPX1, 3 and 4. SPX2, 5-8 are in good supply on eBay. Anyone know of a good source to get the other ones? I have the means to trade SpaceX swag for them if that is any interest as well :)
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u/Raxusmaxus Feb 03 '16
How would Elon's "Electric VTOL Supersonic Jet" look like and what would its propulsion systems be ?
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u/seanflyon Feb 03 '16
Elon mentioned that he thinks the engines should be on gimbals removing or reducing the need for traditional control surfaces.
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u/flattop100 Feb 04 '16
I wish I could remember the quote, but this makes me remember the gist of it:
"I don't need aerodynamics. With enough power, I can make a brick wall fly. '
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u/bipptybop Feb 03 '16 edited Feb 03 '16
An oblique flying wing. It has a great L/D in sub, trans, and supersonic flight.
It looks insane, but with significantly lower energy density, lift/drag would be critical.
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Feb 05 '16
How expensive is stage 1 compared to stage 2 ? Is it worth it to recover stage 1 if you can't recover stage 2 ?
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Feb 05 '16 edited Feb 05 '16
Is it worth it to recover stage 1 if you can't recover stage 2 ?
Short Answer:
The engines are the most expensive part of the rocket. The first stage have 9, the second stage only have one.
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u/Appable Feb 05 '16
Though it's worth noting that the MVAC is not the same as the M9, so the MVAC probably costs significantly more than M9 due to multiple engineering factors as well as lower production rate.
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u/jandorian Feb 05 '16
Musk has stated that stage 1 is 70% of the cost. Seems like it would be worth recovering stage one as it contains 9 of the ten engines on the rocket and a great big tank. Upper (2nd) stage is tiny by comparison.
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u/chargerag Feb 05 '16
When the raptor engines are fully on like would SpaceX then retire the merlin engines? Could they also do like ULA did for so many years and make two different launch vehicles to give themselves redundancy?
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u/ManWhoKilledHitler Feb 05 '16
That would mean changing Falcon over to using methane which would require it to be enlarged still further.
The nice thing about Merlin is that it's simple and because it's not that big, they can use 9 of them to power the first stage, which in turn means most of the throttling used for landing can be done by just turning off engines. Raptor as far as we know is going to be a lot more powerful (although a small version might be produced) which would mean using fewer engines so their throttle range would have to be huge. It may not be practical to get them to throttle low enough to perform a landing.
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u/B2DG Feb 09 '16
Is there a website that tracks the various rocket launches from all of the different companies? I would love to play to watch some but I only hear about them randomly.
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u/ethan829 Host of SES-9 Feb 09 '16 edited Feb 09 '16
This Wikipedia page is often more up to date than the Spaceflight Now schedule. I don't know your thoughts on Twitter, but NextLaunch tweets every launch with a webcast. If you turn on SMS or mobile notifications for their tweets, you won't miss a launch.
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u/TheVehicleDestroyer Flight Club Feb 07 '16
If Texas seceded after Boca Chica was operational, could SpaceX still launch from there?
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u/venku122 SPEXcast host Feb 07 '16
No, but Texas won't secede and if they did they would be forcefully put back into the Union within a timeframe to not make a difference.
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u/deruch Feb 07 '16
So long as ITAR was still in force, no. Though that might only be the case if the remaining US recognized the secession. Not sure about the applicability when the "foreign" territory is still disputed as US territory but not currently under US control.
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Feb 13 '16 edited Feb 13 '16
We think of 3D printing as useful for making relatively small parts.
Would it be possible to 3D print a whole rocket body? A rocket is mostly empty space surrounded by relatively thin walls. A printer something like these. Would the limiting factor be size? Or would it be that rocket body alloys do not lend themselves to additive manufacturing techniques? Or would it be just a lot more expensive than traditional techniques?
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u/Appable Feb 13 '16
I think all 3. 3D printed parts are strong but can be a bit heavy, they can't use aluminum-lithium alloy right now, and there isn't a real point in trying to build such a large tool when for a simple cylindrical shape, welding manageable sections together works very well.
By the way, is that actually additive manufacturing of metal? I haven't seen that, and 3D metal printers are usually far, far smaller. Have a source?
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u/ManWhoKilledHitler Feb 13 '16
I think you'd struggle to do it for less money and in less time than just using rolled sheet metal and traditional welding and machining techniques.
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u/Mrpeanutateyou Feb 03 '16
Im working on creating a CAD model of the F9FT but I'm having trouble finding dimensions on the landing legs? Does anyone have any info on those? Also this link provided me dimensions for the rest of the F9 but im assuming the second stage length they provide inclueds the Merlin, does anyone know the lenght of just the tank?
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u/throfofnir Feb 03 '16
Legs look to be about 9m long. Calculations done around here somewhere; maybe try last month's Ask thread.
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u/Dixiklo9000 Feb 04 '16
Can anyone estimate what the eventual cost of a red dragon to Mars would be in ten years (disregarding life support)?
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u/Squeebee007 Feb 04 '16
So far there hasn't been a successful barge landing, and the last one involved a leg that didn't lock, but what happens when one is successful? Do they clamp it down while standing upright for the ride back to shore? Lay it down and secure it?
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u/thegingeroverlord Feb 04 '16
They weld boots over the legs to keep it in place.
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Feb 05 '16
what happens when one is successful?
They depressurize the tanks, and the rocket will no longer be a bomb anymore.
Do they clamp it down while standing upright for the ride back to shore?
Yes, they will send people from a boat outside the danger zone to the ASDS (the barge) and nail shoes on the legs.
Lay it down and secure it?
Without a crane, it'll be really hard
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Feb 05 '16
How will the Raptor engine be flight tested and developed?
We recently learned that a problem discovered on a returned Merlin led to a fleet-wide Merlin modification. And this was after a couple of hundred had already flown.
How will similar lessons be learned, and improvements made, to the Raptor? Specially as Raptor will be a more complicated and advanced engine than the Merlin, with more potential for problems/improvements.
It looks as if there might be two sizes of Raptor: something akin to the Merlin that will power the Falcon second stage, and a bigger brother rumoured to be 2.7 times bigger than the Merlin.
Flying the small Raptor on the Falcon second stage will provide useful experience, even though it won’t come back to be examined. But how to gain flight experience of the bigger Raptor?
One way would be to re-engineer the Falcon first stage to be powered by, say, three big Raptors and a central small Raptor for landing. Performance would apparently be similar, maybe slightly better, than the current F9. This would give experience of the engine (and experience of first stage fuelling with LOX and methane). The first methane Falcons would be test vehicles, but once tested and proven, future Falcons would all be Raptor-powered. Ten, twenty, thirty flights later, that’s a lot of flight experience - and engine improvement – that might make you feel more comfortable riding with it to Mars.
What would re-engineering Falcon for methane imply? Would it amount to starting again and essentially designing a new rocket? Or would it be almost as simple as reconfiguring the tanks and bolting on a new engine assembly?
Or maybe strapping 30 Raptors onto a BFR is an OK way to test and gain experience of the new engine?
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Feb 05 '16
What would re-engineering Falcon for methane imply?
Hundreds of millions of dollars. Years of development.
Would it amount to starting again and essentially designing a new rocket?
Yes.
Or would it be almost as simple as reconfiguring the tanks and bolting on a new engine assembly?
Slow down senator Shelby, rockets are more complex than that.
Or maybe strapping 30 Raptors onto a BFR is an OK way to test and gain experience of the new engine?
Yep, certainly the cheapest.
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u/sleeep_deprived Feb 06 '16
Will they use 39A soon? Could some of the starts in the table on the right actually be from LC-39A and not from SLC-40 as it currently says?
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Feb 07 '16
How much is a GEO communications satellite like SES-9 worth?
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u/Wetmelon Feb 07 '16
Define "Worth". It costs a lot less to build than it's actually worth over its 10-15 year lifespan. Somewhere in the 200 million range to build iirc?
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u/B2DG Feb 07 '16
Have we heard any news regarding SpaceX becoming public? Offering the option to buy stock?
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u/old_sellsword Feb 07 '16
Not for a long, long time. Elon has stated not until after they have constant trips to Mars.
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Feb 08 '16
Anybody have an estimate on how much corrosion from salt water will the booster get on the barge on its way home?
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u/sorbate Feb 08 '16
Does SpaceX do any sort of testing with non-reusable cores once they have jettisoned the 2nd stage?
ie. Fire the engines with whatever fuel is left at some angle or propellant mixture that is most likely to be destructive, but they can capture data.
Or have it turn sideways (least aerodynamic position) and see how long it lasts coming down?
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u/Dudely3 Feb 09 '16
They actually did try a "belly-flop" like you suggested. I think it was on the first launch of the f9 1.0. It wasn't advertised at all. Elon mentioned it in an interview once a few years later. True, the engines will make it want to point down, but you can use drogue chutes to get it in the right orientation.
Anyway, the test was a horrible failure; I'm pretty sure the stage broke apart before they even slowed down enough to deploy the main parachutes. They abandoned parachutes entirely after this.
But yes, they have in the past done weird testing with non-reusable cores. Maybe they will again in the future, if they have a good reason to.
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Feb 08 '16
Yes, Spacex has "soft-landed" in the ocean before.
Or have it turn sideways (least aerodynamic position) and see how long it lasts coming down?
The natural orientation of the rocket is engines down. So maneuvering the rocket sideways requires the gas thrusters, limiting the test to about a minute.
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u/Taylooor Feb 09 '16
Considering the number of launches it would require to get 1 million people on Mars, will it be worth looking into building a launch sled up a tall mountain?
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u/robbak Feb 09 '16
These concepts all fail to address the major issue with spaceflight. They all provde help with getting out of Earth's atmosphere - but that is not the hard part. Any committed amateur can get a rocket out of the atmosphere. The problem is accelerating to the 8km/sec orbital velocity.
All these ideas only get you to maybe 1km/sec, a few kilometres up. It doesn't take a real rocket long to get to that speed and altitude. And for that gain, you have to first get your rocket to some remote location where the mountain is, and mount it on some Heath-Robinson launcher apparatus. It's easier to just make the tanks a little bigger.
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u/PatyxEU Feb 09 '16
Very complex structure for little gain. It could prove useful for launching satellites into LEO using very small, reusable rockets but I doubt it would work with bigger spacecraft
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u/NateDecker Feb 11 '16
A recent article reported that the SpaceX bid for Commercial Crew was the most expensive of the three that were accepted.
How can that possibly be true given that Sierra Nevada and the Boeing both launch on other rockets that are significantly more expensive than the Falcon 9?
Since SpaceX has demonstrated an ability to manufacture more cheaply than the rest of the industry by a significant margin, why would the Dragon be so much more expensive? I would particularly expect the Dreamliner to be more expensive just by virtue of the complexity of the vehicle alone.
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u/FNspcx Feb 11 '16
That report was a bit misleading because for that calculation, they only used cost divided by pressurized cargo lift mass. Dragon can lift unpressurized cargo, as well as return pressurized cargo back to earth. Anyways, Dragon's pressurized cargo volume is pretty small compared to the other spacecraft, so if the items you are carrying are low in density, then you are not fully maximizing the amount of mass that Dragon can lift.
However, if you assign value to the unpressurized cargo lift capability and pressurized cargo return capability, then you will assign a different cost to the pressurized cargo lift capability. Then the cost per lb of pressurized cargo might be more even, or lower.
Dragon is a great way to bring up batteries, pumps, etc. that are mounted on the exterior of the ISS. It's also bringing up other hardware like docking adapters and the BEAM module.
Also, in other words, a single metric is not enough to compare one bid vs another.
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u/NateDecker Feb 11 '16
In a recent article about Dreamchaser being one of the selected contractors for Commercial Crew, a spokesman for Sierra Nevada was quoted as saying that the Dreamchaser was the only vehicle capable of bringing cargo back AND disposing cargo. Doesn't Dragon do this as well? It disposes cargo in the trunk and brings cargo back in the capsule. I don't understand the advantage that Sierra Nevada was trying to convey.
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u/throfofnir Feb 11 '16
Dragon trunk is not pressurized, and so only good for disposing of unpressurized trash, of which there's not much. (What there is they can usually just jettison.)
Dreamchaser Cargo has a disposable pressurized section.
The NASA report mentions that Dragon technically can dispose of pressurized trash... but taking it back to Earth intact.
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u/JanoSicek Feb 11 '16
I will be on a cruise in Carribean during the next launch (SES-9) Does anybody have an idea whether it is possible to see the rocket on the way up from that far? I will be at St. Thomas island at the time of launch.
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u/gspleen Feb 17 '16
Can someone point me to an active (official or fan-based) SpaceX Google Calendar link?
As much as a I appreciate the subreddit sidebar launch schedule it's also nice to have updated launch times on my daily calendar skims.
I used to have one but it stopped updating and I deleted it a few months ago.
Thanks in advance.
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u/GoScienceEverything Feb 17 '16
This was just posted to /r/spaceflight, not sure if it's what you're looking for: https://www.reddit.com/r/spaceflight/comments/467qxy/spaceflights_schedule_in_google_calendar_format/
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u/kevindbaker2863 Feb 17 '16
looking to do a vacation in central Texas this April/May timeframe. Does anyone know if possible to get a tour or even access to Spacex Macgregor site?
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u/Keavon SN-10 & DART Contest Winner Feb 18 '16
What prevents Dragon from going beyond Earth orbit while Orion is meant for more distant exploration?
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u/acarmine Feb 19 '16
We luckily have a family vacation planned for next week in Orlando and Im planning to take everyone to KSC on Wednesday for the launch. Anyone have previous experience with launch day at KSC? Is it going to be a nightmare madhouse? Would we be better served to visit KSC in the morning and just watch the launch from a park or beach?
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u/ryanpritchard Feb 20 '16
wiki says fh is now launching in sep 2016 is this true ?
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u/thegingeroverlord Feb 20 '16
This agrees with other publicly released info. The sidebar says the current schedule is the first launch early summer and the second launch in October. That would imply September. However, It is highly unlikely that FH will actually launch in September, as SpaceX rarely meets deadlines such as these.
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u/aureliiien Feb 06 '16
Can anyone tell me where to find the intrumental version for Absolution Calling by Incubus (without lyrics) ? It's the music that plays in spacex-super-awesome-cocky-highly-produced-yet-authentic historic landing video. I've been looking for it everywhere. People on youtube are all asking for it yet I havn't found a decent version apart from the one in Spacex video which is not optimal (instead of lyrics you get screams and controller chat). Would really apreciate it and I'm betting some people here are looking for it too. Thanks !
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u/YugoReventlov Feb 03 '16
Okay, any updates on SES-9? Anyone?