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NASA Orders SpaceX Crew Mission to International Space Station (nasa.gov)
593 points by jkaljundi on Nov 20, 2015 | hide | past | web | favorite | 136 comments

So far, SpaceX has completed 23 launches of both its Falcon 1 & currently active Falcon 9 rocket: http://spacexstats.com/previous.php

They have had two failures: https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_He...

Out of 25 launches is that a safe enough success rate?

The first failure was a secondary payload. The Falcon 9 had less spare fuel than expected because one of the first stage engines failed.[1] The primary (NASA) mission went fine. The secondary mission had a 95% chance of success, but NASA vetoed it.

The second failure was a second stage exploding. Had the payload been a crewed Dragon V2, those inside would have survived. Even without a launch escape system, the Dragon V1 was fine[2]:

> The Dragon CRS-7 capsule was ejected from the exploding launch vehicle and continued transmitting data until impact with the ocean. SpaceX officials stated that it could have been recovered if the parachutes deployed, however the software in the capsule did not include any provisions for parachute deployment in this situation.

Overall, it's a much safer design than the Shuttle. The crew vehicle is on top of the stack instead of along side it. If anything goes wrong, the capsule can GTFO and land with parachutes.

1. https://en.wikipedia.org/wiki/SpaceX_CRS-1

2. https://en.wikipedia.org/wiki/SpaceX_CRS-7

> however the software in the capsule did not include any provisions for parachute deployment in this situation.

That seems like a pretty significant oversight?

It wasn't an oversight. It was intentional. The Dragon v1 is designed solely for cargo. It has no launch escape system and its software does nothing while it's going up[1]:

> The software in this cargo version of Dragon (Dragon 1), Musk explained, is inert on ascent and was not programmed to release the parachute in the event of a failure. Software in the version of Dragon under development for taking people into space (Dragon 2 or Crew Dragon) is programmed to do just that.

While it sounds like simple thing, remote control of the 'chutes would add significant complexity and cost.

1. http://www.spacepolicyonline.com/news/failed-strut-likely-ca...

Also, you generally want as many systems "off" as you can manage during the flight. There's just less that can go wrong if there is less going on.

And remember to set your SCE to aux.

That was actually a very interesting read.


"But Bean, who was sitting in the right seat, just in front of the switch, remembered it from the sim the previous year."

I guess we can forgive Bean for frying the color TV camera, then.

I know what that is!!!!

No one expected Dragon to survive those conditions, so they never bothered adding that code. It's just a cargo ship, so it doesn't really matter.

After having learned in real world conditions that it can handle those sorts they figured, what the heck... might as well add it.

The crewed Dragon (Dragon 2) uses powered thrusters to push itself away from a failing rocket.

Water landings only work if you design for them which is a lot of extra weight. Catching the thing in the air is difficult because you get very little warning and they can land in a huge area.

Net result, failed launches are not really worth trying to recover unless it's people. Though, deploying parachutes may have marginally reduced the risks to a passing boat.

Dragon already lands on water, so there's no technical reason it couldn't do it after a launch vehicle failure, if the event was survivable. Now we know that such a scenario exists, but that was not obvious before.

My understanding is Dragon 1 does not float fully loaded. It can get 3,10 kg ISS used and dispose of 3,10 kg of waste, but only to recover ~2,500 kg. https://en.m.wikipedia.org/wiki/Dragon_(spacecraft)

Make that "3,310 kg ISS" not "3,10 kg"

I believe the difference between up and down cargo is because the trunk is dropped and burns up on entry, only the pressurized capsule itself lands.

> Though, deploying parachutes may have marginally reduced the risks to a passing boat.

Didn't it fall in the range safety exclusion zone, which ships were warned away from?

It wasn't an oversight - they launched the mission with the understanding that their parachute software wasn't ready and the risk was acceptable since it was uncrewed. I seem to remember reading that their parachute hardware was ready to go if absolutely necessary, but they wanted to make sure the software was locked down.

Not necessarily, if there was no reason to recover it

(I'm not sure if there was a reason or not)

Move fast and crash things!

Mercury was flown on Redstone rockets for suborbital flights and Atlas rockets for orbital flights.

Redstone had a success rate of 5/6. [1] Atlas had a success rate of 13/24. [2]

It was certainly a different time, but spaceflight has always been really risky. There has also always been more attention paid to human rated flights during the manufacturing & testing process. I also imagine SpaceX will not be doing first flights of new Falcon 9 variations with humans aboard.

That's not to say it is low risk, but 23/25 considering these are unmanned and largely R&D flights is not bad.

[1] https://en.wikipedia.org/wiki/Mercury-Redstone_Launch_Vehicl...

[2] https://en.wikipedia.org/wiki/SM-65_Atlas#Atlas-D_deployment

Well the D was the first operational and it did not have that failure rate that the A,B, and C, models had. I doubt NASA would have ever launched a version that didn't have a high nineties success rate.

That's flat out not true. Take a look at the list of Atlas D launched and look at the failures. The first time they strapped a Mercury capsule to an Atlas D is failed. There was an Atlas D failure in February 1962, and Scott Carpenter rode it for the first manned flight only 3 months later in May 1962.

The day before Walter Schirra launched there was an Atlas D failure.

Two months before Gordon Cooper launched there was an Atlas D failure.

What I don't know is how much they were pushing the limits on the other tests vs the manned flights, or how much more QA they were putting into the manned rockets, but it is certainly not the case that NASA only flew on rockets with high success rates at that time.

[1] https://en.wikipedia.org/wiki/List_of_Atlas_launches_(1960%E...

[2] https://en.wikipedia.org/wiki/List_of_Atlas_launches_(1957%E...

Saying "two failures" is awfully misleading. There was one catastrophic failure and one minor failure. In a hypothetical manned mission, the minor failure probably wouldn't have even prevented the mission from going forward, let alone endangered the crew.

The catastrophic failure is obviously a problem. However, for a manned mission, there is an abort system which is supposed to save the lives of the crew in an event like this. This is not like the Shuttle where if anything goes wrong on launch, everybody is doomed.

To state it more precisely, out of 25 launches, there has been one problem which wouldn't have been a threat, one catastrophic failure which would be survivable, and zero failures which would have killed anybody if they had been manned.

There were at least two catastrophic failures that everyone knows about: Challenger and Columbia.

We're talking about SpaceX here.

Looks like I've misread.

I dug up the number for Shuttle missions for comparison: Out of 135 total missions, 2 shuttles were destroyed in accidents [0].

While it is certainly great to aim for 100% success, it's helpful to remember that astronauts are willing to take measured risks in order to perform their missions, and that we must select rockets/etc from the options available, not from the options we might wish to have.

0: https://en.wikipedia.org/wiki/List_of_Space_Shuttle_missions

Although if you count F9-4 as a failure, you should also count the STS-51-F Abort-to-Orbit as a failure, which brings it to 3/135.

Probably STS-93 too.

These two bring up an interesting philosophical point. Are they successes of failures? To me, it sounds like engineering done right. "Something bad" happened, and yet the vehicle survived and even completed its mission.

Well then it's only 1 spacex failure.

People aren't arguing the merits of success they just want to use the same rules to talk about nasa and spacex

As I recall the original engineering estimate was a 2% catastrophic failure rate - i.e. loss of orbiter - on the Shuttle [1]. Columbia was STS 107. The estimate was spot on. You have to respect the level of engineering involved here.

[1] http://www.amazon.com/Development-Shuttle-1972-1981-History-...

As far as I know neither of those failures would have resulted in loss of crew. One was a partial failure where due to a partial engine failure they didn't make their secondary orbital insertion, and the other was a loss of vehicle that would have been covered by either the crew escape system, or the dragon capsule parachuting to safety.

Once they start to recover the first stage, they'll get a lot more information about how their systems really performed, as opposed to how they think they performed from the telemetry. You can do all sorts of testing on all the returned components, figure out how much of the margin of safety was actually used, and look for fatigue cracks that weren't quite bad enough to result in failure this time round. In principle at least, this could greatly increase the safety of future launches, at least as far as the first stage is concerned.

According to [1], the shuttle program ended with a failure rate of 1 in ~67.5.

1: http://www.popularmechanics.com/space/a6611/us-space-shuttle...

In the context of manned missions, it's unsurvivable failures that are unacceptable.

The original comment was clearly using a stricter standard than that.

I don't think anyone expects to strapping oneself to a rocket that packs the energy potential of a not-so-small nuke will ever be considered perfectly safe. And remember the failures they had would be survivable with the current launch abort system Dragon has.

There was a time sailing across the Atlantic was dangerous.

That's not very fair comparison for rockets. When people fly in B-747, it also has a pretty significant amount of fuel - and energy - aboard, yet safety complaints are rare regarding that.

So the goal for rockets - for now - could be to become as safe to ride as airplanes are. 100% safety is unobtainable, so shouldn't be a requirement.

"So the goal for rockets - for now - could be to become as safe to ride as airplanes are."

If you could build a spacecraft launch system with the weight budget of a commercial airliner, you could get that reliability. The fuel fraction for the Space Shuttle was about 85%; everything else, structure, engines, equipment, and payload, comes out of the remaining 15%. For an airliner, 60% of the mass is non-fuel. Spacecraft are weight-reduced too far to get aircraft reliability. They're just too fragile. Read NASA's "The Tyranny of the Rocket Equation".[1]

Space travel with chemical fuels out of Earth's gravity well is just barely possible at all. Chemical fuels just don't have the energy density to do the job well. It's necessary to launch huge booster stacks to put a dinky payload in orbit. That's why, after 50 years, space flight hasn't progressed all that much.

Without a denser power source, it will never get much better.

[1] http://www.nasa.gov/mission_pages/station/expeditions/expedi...

> the goal for rockets - for now - could be to become as safe to ride as airplanes are.

The energy an orbital rocket packs is significantly more than the full fuel load of a 747. The required performance is also much higher. Tolerances are much lower (because of the performance).

It'll be quite some time until they get to 747 levels. A worthy goal would be to become as cheap as a 747 at a reasonable safety level. That would be massively disruptive.

A more significant point is that the 747 carries only fuel, the rocket carries fuel and oxidiser, which substantially increases the variety of ways in which things can go interestingly wrong.

With the addition of the crew escape system plus nailing down the causes of their last failure, very much safer than any other manned launcher the US has had in service.

You think it's going to be more reliable than Saturn-V manned stack? Why?

Cherry picking the MANNED Saturn V missions conveniently leaves out the unmanned Apollo 6 test where pogo vibrations borked two of the second stage engines and caused third stage relight to fail.

And if you want to consider the whole Saturn V STACK then you're going to have to consider counting Apollo 13 as a failure. The "payload" for Apollo is, in the end, really just the Command Module.

We're a bit offtopic here :) but let me respectfully disagree.

The whole point of doing testing with rockets is to find what you don't know, validate your assumptions... What you usually don't know is when a thing will fail - and you don't want to learn that in a real mission, so you push the test article to extreme. Another reason to do tests is something which should work - and shouldn't fail - but you can't test that without actually doing a flight test.

So, in my opinion, cherry picking test flights - where things fail routinely, otherwise why testing? - doesn't show you the designed - and updated, with test data - reliability of the system.

Regarding whole stack - I meant the whole thing which lifted off and the part of which reached low Earth orbit. That stack had the pulling safety tractor rocket. But frankly, if I'd consider Apollo-13 flight, I'd assume we have the case of mission abort in a later stage of flight, after which the existing measures were taken to bring back the craft safely. So mission was aborted - just as it would be if, say, Saturn-V grossly misbehaved on 30th second of flight - and the systems worked on safe return.

I don't agree with the premise but as I understand it the crew escape system can work for the entire preflight+flight not just a certain window on the ascent.

That's a hope though, not a fact...

That's an estimate based on engineering analysis and statistics, just like any estimate of reliability.

It's not an estimate based on statistics, because there are no statistics for the system you are talking about. It is a prediction based on engineering analysis, and the prediction for space shuttle reliability was quite a bit better than the actual record turned out to be.

I want SpaceX to succeed as much as anyone (probably more since I work there), but one should not delude oneself into thinking that predictions are fact.

The regulatory and compliance checks for manned missions are considerably more rigorous than for unmanned ones. If you look back, manned missions have historically had much better success records than unmanned ones by the same operators.

Is 25 a sufficient sample size?


But this is space flight, not sex with some celebrity. It's worth far more risk.

Few things that are worth doing are risk-free.

This article from a few years back tries to quantify that answer...


The entire company is firmly focused on return to flight. Sometimes failure can be a great motivator and, ultimately, if used as an opportunity to learn and improve, a good thing.

Humans are a dime a billion. We have no problem slaughtering humans daily in contrived conflict but somehow losing a few furthering scientific understanding is unacceptable.

First, this is an extremely naive view as to what goes into training an astronaut to be sent into space. It's not like we just plucked four random people from the globe and are sending them to space. These are people who are very likely at the top of their fields, have gone through rigorous (and costly) training, and are going up to do very specific jobs. These people are not a "dime a billion", and claiming so is the same as saying that if Elon Musk were to disappear today, that any other person could simply take his place and keep moving his companies forward.

Second, just because there are negative aspects in the world that cause loss of life, doesn't mean we shouldn't be doing everything we can to ensure a safe flight. This is unrelated to the cost aspect mentioned in my first point, but the average person living in the U.S.A is only living as comfortable as they are because modern civilization, for the most part, values safety quite high. It's a poor argument to say "Well X people died yesterday, so we shouldn't care so much about the 4 that might die in a launch".

> These are people who are very likely at the top of their fields, have gone through rigorous (and costly) training, and are going up to do very specific jobs

That is irrelevant to the level safety precautions. Unless you were trying to argue that their costly training makes them worth more than other people. I hope that is not what you were arguing.

> doesn't mean we shouldn't be doing everything we can to ensure a safe flight

At some point you have to declare something 'safe enough' since 100% safety is an impossible perfection. Bicycles aren't 100% safe, but we don't go around insisting on multiple backup systems. Personally I do find it curious that the standard of safety for astronauts is so high. The cynic in me suggests its less out of concern for the astronauts and more to do with the publicity fallout that occurs after disasters and the damage to other assets. The optimist suggests its more a concern for all the ground crew and spectators who are also at risk. There is potential for a lot more than 4 casualties when you play with that much fire.

>> These are people who are very likely at the top of their fields, have gone through rigorous (and costly) training, and are going up to do very specific jobs

>That is irrelevant to the level safety precautions. Unless you were trying to argue that their costly training makes them worth more than other people. I hope that is not what you were arguing.

I believe GP was arguing about the "a dime a billion" part. They are not worth more than other people in the human sense, but that doesn't make them any more common. It's just the fact that there are very few people with such qualifications that negate the argument of "a dime a billion".

And I guess it's also true that not any of those billions could be trained to be an astronaut for a myriad of reasons.

> And I guess it's also true that not any of those billions could be trained to be an astronaut for a myriad of reasons.

This is less clear. Even more, the space tourism industry relies on that to be false. To an extent.

Well, in part I agree.

But I think there is (or at least will/should be) a difference between a trained astronaut and a space tourist.

I mean, being an astronaut is more than just going to outer space, isn't it? A space tourist might do a lot of the stuff that astronauts do, but I think there will still be a fundamental difference. Astronauts are there to do research, push the limits on human capabilities, etc.

After all that is settled, then the tourists can come.

Well and think about planes. Planes are already safer than cars, but we demand very high reliability. If 30% more planes crashed and it cut ticket prices by 30%.. some people would make that trade. People do it when buying smaller less safe cars... but we don't like the thought of plane or shuttle crashes.

Of course, for cars you have the added problem of externalities: the bigger `safer' car actually causes more damage to others in a crash.

> Unless you were trying to argue that their costly training makes them worth more than other people.

I would imagine they are to the company that is launching them.

What astronauts are trained to do at the top of their field and what they end up doing are kind of divorced though. They spend an inordinate amount of time turning wrenches really, really slowly.

I think that's like saying that pilots spend an inordinate amount of time sitting in their chair making sure that the autopilot is working properly. The remainder is why they get all of the training that they do.

Divorced, but still related, I think. There are lots of possibilities to die in space, to kill fellow crew members or to seriously damage quite expensive equipment, so one should really know how to, e.g., turn wrenches.

You are making the appeal to common practice fallacy. Even if human death (or sacrifice) is a common occurrence, it does not make it acceptable.

Not only is it acceptable, it is necessary. How do you think our ancestors determined what was safe to eat? As the saying goes, sometimes you need to break some eggs. Now don't get me wrong, I'm neither condoning, nor encouraging, wanton negligence concerning human safety, obviously all possible efforts should be made to ensure it, but sometimes, such as in cases like this, the rewards far outweigh the risks.

Yes. And thousands have died in death camps to bootstrap our modern cariology. We should be grateful to all people who died in the past providing us data and knowledge, and to honor them we should use it in the best way we can, so that no one else has to die.

> How do you think our ancestors

Right, but that doesn't mean we should follow that just because the ancestors did that?

On the opposite, I'd hope for astronaut-level safety precautions be spreading for the rest of society, so everybody could benefit.

This type of comment was and is "a dime a billion"

"Thousands of people die in car accidents every year and..."

It's bizarre that anyone would find this type of comment insightful after all the times its been posted ad nauseam.

Oh, it's a purchasing order. I misread it as a commanding order and thought there's some emergency or something.

Quick guys, to the rocket!

Yay, passed phase 1 readiness review. I am a bit surprised they could pass before they have the inflight abort test but hey this is a huge step forward.

I keep wondering if there will be a program where a group of 5 can hire a pilot/co-pilot and ride in a Dragon Crew into orbit. Spend the day there, and then fly home. If you are re-using the first stage at that point I can't imagine the cost is going to be more than a few million $ for each "astronaut".

I'm assuming NASA is pretty confident in SpaceX's SuperDraco thrusters after the unmanned pad abort test [1].

With regards to the second comment, I can find out if you're interested.

[1] https://www.youtube.com/watch?v=1_FXVjf46T8

In-flight abort is a more challenging scenario. If you need to get far from the rocket, you'll have to factor in its own acceleration. The pad won't try to run you over, but an ill-behaved rocket could. Hopefully, the SuperDraco engines will be able to steer the Dragon away from whatever direction the Falcon decided it'd go.

It's really not as hard as you think off, an ill behaved rocket won't be like a balloon flying around in "random" directions, even if there is loss of vector control at the nozzle the existing inertia of the rocket would keep it flying relatively quite straight.

Considering that the capsule still has the inertia from the main engine at the time where the separation/landing boosters fire it doesn't need that much to outrun the existing rocket since it pretty much just needs to get out of it's way.

In-Flight Abort is nice, but this is the 1st and only human piloted craft that has it, even if it will have quite a bit of risk attached to it it's still better than the competition.

> In-Flight Abort is nice, but this is the 1st and only human piloted craft that has it...

Apollo had it - at least for during the first stage.


Mercury had it. Gemini (and Vostok) had ejection seats. Soyuz has it, but it first flew well after the Apollo's first used them.

That's not correct. The maximum acceleration of a Dragon mission has been 5G, so if you abort at that time you need 5G just to get your butt off the launch vehicle. You can't abort sideways.

The abort system for the Dragon capsule provides 4.5G of acceleration (human dragon space flight will not reach 5G, don't mix in cargo launches, irrc SpaceX said that the nominal max acc. for human flight will be below 3G similar to an STS launch) and it does kinda abort side ways, as soon as it clears the main rocket it tilts and gets the heck out of the way because it's quit important to be as far away from the rocket as possible in case it explodes (also to prevent any chance of rocket derby catching with the capsule during decent) and out-running it upwards isn't a possible in the long run.

If the point is to abort, you can't rely on the engines being throttled down to the accel limit -- you have to be able to successfully get out of any reasonable scenario and the engines running away does not seem unreasonable. (I don't know exactly what the abort requirements are, but the point is just that it's not easy.)

Also, during an abort scenario, the aero drag is pushing Dragon back onto the launch vehicle, so you actually need more thrust to overcome that, too. (Although that obviously depends very strongly on the dynamic pressure at which you abort.)

I don't disagree, but SpaceX has proven (at least, I think) that they can programmatically handle vectoring multiple craft in close proximity with their barge return attempts.


If there is anyone that can pull this off at this fast pace, it's these guys.

BTW, if I ever charter a flight to the ISS, I'll have the Pan Am logo painted on the spacecraft.

That was an excellent demonstration, and the static firings seem to have gone as expected as well. I would guess that the in flight ejection is mostly about being able to maintain both an escape route and the capability to execute it during an unplanned orientation divergence and rapid disassembly :-). Given the low cargo capacity (100kg) it seems like the 'trunk' is dedicated to the eject capability.

As for finding a space tourism company, I'd be interested if anyone had approached SpaceX with that as a business plan. I would certainly consider investing in something like that given the right team and opportunity.

Well at that point where there is demand for travel into space create a destination station for them to stay at and get more for their millions.

When this mission occurs, it will be particularly historic, because we are at a point in history that is similar to the human spaceflight gap that existed between the Apollo program and the Space Shuttle program in that the U.S. does not currently possess this mission capability.

It will also be symbolic for Americans: an American flag was presented to the ISS crew during the STS-135 mission (the final Space Shuttle mission). It is awaiting return by the next mission that is launched from the U.S.

> It will also be symbolic for Americans: an American flag was presented to the ISS crew during the STS-135 mission (the final Space Shuttle mission). It is awaiting return by the next mission that is launched from the U.S.

I find it very interesting how the human sense of belonging to a group carries on as we keep, as a society, moving forward.

Arguing in favor of, or against it is not really what concerns me, but instead just observing how we change as we move closer and closer to the possibility of having to leave those old notions aside. I guess that's why it's common in sci-fi to have people born in other world have no sense of belonging to the Earth.

Probably a lot of the reasons for making it a big deal to return the flag in a US-launched vehicle has to do with PR, but still I can imagine that both engineers and astronauts will be very proud of making that happen nonetheless.

If we do have to leave Earth-based nationalities and nationalisms behind, I'm quite confident we will find new arbitrary group identities to hold on to. The human tribal impulse is very strong.

This one is gold. Thanks for sharing it.

It's another confirmation to what I already suspected.

That robot/alien overlords will have no pity on the human race.

Much more significant than nationalism is the fact that SpaceX is a private enterprise. Private space ventures are our only hope for purposeful success, sustained expansion, and the conquest of space.

> Much more significant than nationalism is the fact that SpaceX is a private enterprise.

So were Douglas, Grumman, North American and Rocketdyne. Those were the companies that put men on the Moon.

So too is Orbital Science, which has been launching satellites on a commercial basis for 30 years.

There's nothing 'significant' about the status of SpaceX as a company.

SpaceX is significantly disrupting the entire launch industry right now.

— If it’s that important a project, why doesn’t the government undertake it?

— Here’s the reason: The vast amount of brains, talents, special skills, and research facilities necessary for this project are not in the government. Nor can they be mobilized by the government in peacetime without fatal delay. Only American industry can do this job.

Destination Moon, 1950 (Loosely based on the book The Man Who Sold the Moon by Robert A. Heinlein, written 1949, published 1951)

I've been out of the loop. Has SpaceX flown any more rockets since their rocket blew up?

No. Return to flight is scheduled for early December (ORBCOMM OG2). Specific time has not been announced yet.


This might be seen as the tipping point in commercial space ventures. With SpaceX running LEO operations, NASA/Roscosmos can focus on the planets next.

Good news on that! The Falcon Heavy is tentatively scheduled to have its first flight in April-May 2016. The Dragon v2 capsule is designed for powered landings, which is how the in-flight abort thing works. Combine the two, and fiddle with the configuration a bit, and you can land in a whole lot of desirable parts of the solar system. Want to send a Mars rover? They're calculating that they can deliver 2-4 tons of payload to the surface of Mars. Want to send an unmanned mission to the moon, or Europa? Ditch the parachutes and add extra propellant to make up for the lack of aerobraking. And so on -- it could be an incredible boon for planetary science.

LEO is the most difficult part. I bet NASA and Roscosmos will have tons of company up there.

LEO is the most expensive part, but we know how to do it pretty well at this point. Landing something big enough to carry humans on Mars, on the other hand, is a problem we haven't solved yet.

Landing won't be the hardest part - any Earth-rated capsule with rockets like the human-rated Dragon can do the last leg provided you are leaving Martian orbit with some rocket to slow you down. You may need parachutes to slow the craft to the point the rockets can make their part. Curiosity was complicated because they didn't want to touchdown on rockets.

Now, accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive for a year outside the Earth's benevolent magnetic field and having enough fuel to accelerate back to Earth (even assuming we'll throw out the interplanetary craft and get to Earth on a capsule) is quite an impressive engineering feat. I'm inclined to suggest that, instead of building a vehicle like that we build one or more cyclers that will orbit the Earth-Mars-Sun system periodically and astronauts would only need to reach them in order to get back and forth. This way we pack all shielding for the long-duration trip into the cyclers and astronauts only need to carry the consumables they'll use. Since reaching them would be time-critical (they won't stop), I would suggest building a similar one that could be stationed in Martian orbit to serve as a fallback plan in case a crew misses the one cycler and has to wait a couple months for the next bus home. These two spacecraft are, essentially, space stations with clever orbits we could maintain with regular resupply missions just as we do with the ISS, but we'd need beefier rockets because the delta-v is the same as a craft going to Mars (because that's what it's doing). Luckily, we'd only need to accelerate the resupply craft - living space is "free" after the first burn.

I am uncertain if these craft are more or less complicated than building and landing the Mars ascent vehicle (much worse than landing a crew capsule, for sure). This sounds very complicated to me.

> accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive ... and having enough fuel to accelerate back to Earth ...

You don't need to ship enough fuel to return to Earth in the same trip as a manned crew.

You can send orbital depots for return fuel and ascent\descent vehicles ahead of time in unmanned missions. This could be done multiple years in advance.

When you are launching the crew and interplanetary habitat, you only need to bring enough fuel for a one way trip.

It's true, and a clever approach. Since the orbiting propellant depots on Mars would have gotten there with engines, the simplest approach would be to dock the Mars departure vehicle (which could just be the service module of the Mars ascent vehicle) and dock it to the propellant depot and use it as a propulsion stage to match the trajectory of the next cycler passing by. Docking that vehicle with the cycler would allow any extra fuel to be used for trajectory corrections. As long as the mass you are adding to the cycler has propellant and an engine, there is no big issue with adding it.

LEO by far isn't the most difficult part, not if you are aiming for moon/inter-planetary transport. LEO is ridiculously easy to get too, The ISS is at 340KM, GEO orbit is 35,000 you can put payload in LEO with "amateur" rockets, GEO/HEO is a completely different story, it's extremely hard and you need a heck of a rocket to do it with any substantial payload.

Now from GEO/HEO to anywhere else it's quite easy to get because you are pretty much near the escape velocity so it takes almost no delta-v to get pretty much anywhere you want in the solar system, at least as far as getting to a higher solar orbit goes as the closer you get the faster your solar orbital velocity is so using that speed to get even to the edges of the solar system takes very little energy. If we talk about say a mars shot then most of the energy in that trip goes to 2 things, getting to high earth orbit, and then slowing down for a mars capture the amount of fuel needed to do the martian orbit transfer is almost negligible.

The concept of LEO being "ridiculously easy to get too" is mad.

No amateur rocket has made orbit or even come close. The difficulty of building a vehicle to make LEO is not comparable to building one to raise altitude once in orbit. LEO to GEO is less than half the delta-v of surface to LEO. It is routinely done by satellites alone. The only reason getting to GEO is particularly hard is because you have to get to LEO first.

You are right about transfer to Mars, though.

What amateur rockets can put payload into LEO?

https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Tea... Their "go fast rocket" got to about half the altitude of Sputnik so if you got the cash you don't need to scale "go fast rocket" up by that much to put a cube-sat / micro-satellite up there.

It only takes 2 km/s to get to 100 km altitude on a ballistic hop. But the gravity pulls you down.

It takes a 8 km/s horizontal velocity just to stay in orbit. That is in addition to the 2 km/s to just get to the right altitude.

So just by speed ratios orbit is 5x the difficulty of a space hop. In reality rocket scaling is exponential (you need more fuel to carry more fuel...)

Anyway, I do think nowadays "amateurs" actually could build orbital rockets with budgets in the low millions class. Modern electronics and GPS make it a bit easier than a few decades ago.

GPS receivers have US-government mandated speed and altitude cutoffs to prevent this scenario. A nice writeup on bypassing them is here: http://www.wired.com/2013/09/bypassin-us-gps-limits-for-acti...

  US-government mandated
GPS receivers "capable of providing navigation information at speeds in excess of 600 m/s" are actually covered under the Missile Technology Control Regime. (category II 11.A.3.b.1) http://www.mtcr.info/english/MTCR-April2011-Technical-Annex....

The MTCR has 34 members, basically the G20 minus China and India. Since the MTCR doesn't have any provisions for enforcement, (It's "an informal and voluntary partnership") its US equivalent is the International Traffic In Arms Regulations Act. (Category XV, Section c, if you want to read how the US statute words it. In imperial units, of course, just to make things simple.)

Here's a great graphic on delta-v needed to get all over the solar system (including various orbits), by the way.


It's a toll map. :-)

The difference between such a ballistic trajectory (1/5th of escape velocity) and LEO is huge.

>you don't need to scale "go fast rocket" up by that much

My napkin math says you need at least 2 orders of magnitude more fuel mass which classifies as "a lot"

Not sure what your math is, but mine is about 20% larger rocket to get to 160KM and have enough speed for orbit, at least as far as cube-sats that can skip on the atmosphere for a bit go. There's also https://en.wikipedia.org/wiki/Copenhagen_Suborbitals with their plans for a manned suborbital flight, their rocket (although it blew up) could also be used as a base for amateur orbital flights. I'm not entirely sure what is so surprising here, it's a question of money at this point, but amateur rockets are quick close to being able to reach space, this doesn't mean that they will be commercial viable or even viable for any non-anecdotal use.

What's surprising is that amateur rockets can reach space on suborbital trajectories but none of them come even remotely close to orbit.

Altitude is the easy part, relatively speaking. Getting the speed for LEO is the hard part. The GoFast rocket you linked to has demonstrated up to 4,200MPH. Low earth orbit requires about 17,000MPH.

That factor of ~4 requires massively larger rockets, because the rocket equation is cruel. Each incremental increase in final speed requires an exponential (actually using this word correctly, for once) increase in the amount of fuel. Fuel in return requires more hardware like tanks and engines, which means yet more fuel is required, etc.

Edit: using RP-1 as the fuel in a single stage, getting to 4,200MPH requires that 45% of your total rocket mass be fuel at launch. Getting to LEO requires 94% of the mass to be fuel.

Yes I understand it quite well, ~20% scale up which is 20% longer, and 20% wider is quite a big change in mass. The big problem is either staging or being able to shift it to a shallow enough trajectory and get enough velocity, but it might be solvable if you can do a zoom climb type launch from an aircraft similar to how Pegasus/SpaceShip One do it. https://en.wikipedia.org/wiki/Pegasus_(rocket)

How is a 20% scale up going to get you anywhere close to the extra dv needed? 20% on each dimension is still only 70% more rocket, where you need something more like 10x more rocket to make that leap.

That's 1.2^3, or 70% more... not even close. Also remember that making the rocket bigger also increases the dry mass, which further increases the fuel requirements.

The difference in ISP between a liquid-fueled rocket (say 450s for LH2/LO2, 350s for RP1/LO2) and solid propellant (250s) makes a huge difference to your prop fraction. To get, say 8km/s delta-v, just plug it into the rocket equation:

LH2/LO2: 6.1 initial/final mass. RP1/LO2: 10.3 solids: 26

Staging can help this a bit, but the basic fact remains. It's very difficult to get useful payload to orbit with solids.

I'm not sure what your math is because you're not showing us any. But it sure doesn't agree with mine.

Math is done with numbers, so let me give you actual numbers. You can double-check these against https://en.wikipedia.org/wiki/Orbital_speed#Tangential_veloc....

Standing on the surface of the Earth your potential energy relative to infinity is −62.6 MJ/kg. If you were standing still 160 km up, you've added roughly 1.6 MJ/kg. (You climbed 160,000 meters against a force of 9.8 Newtons per meter.)

To then go into orbit you have to add a sideways velocity of about 7800 m/s. Apply the famous kinetic energy = 0.5mv^2 and going into orbit requires 30.4 MJ/kg of energy. That's 19x more energy than is required to get to altitude!

But it gets worse! If you're going to go into orbit, you need to think about getting down. Going up we go straight up out of the air and then add sideways velocity. Going down we let the atmosphere do most of the work of slowing us down. But in order to survive that you need a much more rugged device with a heavy heat shield. You're now both doing more work per mass lifted AND you're lifting more mass!

But we're not done with the bad news. A fundamental fact about rockets is that you have to lift the fuel you use later in the launch. That means that as you're increasing the final velocity you're getting an ever-decreasing ratio of energy expended to useful kinetic energy for your payload.

Put it all together and actual rocket scientists have told me that it is about 100x easier to get to orbital altitude than it is to actually get into orbit.

That said, LEO is the half-way point. Getting into LEO takes about as much energy as it does to launch from LEO entirely out of Earth's orbit.

A 160km altitude cubesat would require a minimum 7.8km/s of delta-v. Anything less than that and it will burn up in the atmosphere after a few orbits. GoFast Rocket achieved a top speed of 1.6 km/s (3580 mph).

It needs to go 4 times faster, and no, a 20% larger rocket won't cut it. 20000% larger by mass would be more like it. It also needs a 2nd stage burning liquid propellant with high specific impulse which is way, way harder to build than a dumb solid propellant rocket.

Noone (not even governments) has been able to send a single stage rocket to orbit.

Israel and India use 3 stage HTPB solid rockets for space launches you don't need to have a 2nd stage liquid fuel rocket to get to orbit.

Also 20000% larger by mass? want to be a bit more serious? if you scale this rocket by 35-40% you get to about the size of the first stage of the Shavit solid fuel space launcher which is a commercial space launcher.

You do understand how scaling works on 3 dimensional objects right?

10000% by mass is a more accurate figure and since you like dimensional scaling, that's 364% scaling.

The GoFast Rocket weighs 350kg. Scaling it by 35% (1.35 ^ 3) would make it weigh 861kg. The rocket you mentioned weighs between 30 and 70 _tons_.

I'm not sure you understand how anything works.

> I'm not sure you understand how anything works.

Based on my previous conversations with this guy, this seems to be a recurring pattern. I do hope that he's using these conversations to recognize and fill in the holes in his knowledge. :)

What good does it do to scale something up to the size of the first stage of a four stage rocket? Those other three stages are pretty important to that whole putting-stuff-in-orbit business.

Edit: I see Shavit can also launch in a three stage configuration. My overall point remains.

LEO difficulty is mostly speed, not height. SpaceShipOne flew above 100 km - but it's a long way to reach Vostok-1 performance, as delta-V for SS1 is more than four times less than for Vostok-1.

A honest hint: spend some hours in Kerbal Space Program. It does wonders for one's intuitions about rockets and its calibration with reality.

I'm surprised they would do this while the previous launch was still a failure and SpaceX has not shown a series of unmanned flights with a reliability as good as what the Russians offered. That would seem to be the benchmark for manned flights.

As pointed out in the article, this is basically a direct consequence of the commercial crew program:

"The contracts call for orders to take place prior to certification to support the lead time necessary for missions in late 2017, provided the contractors meet readiness conditions."

There is plenty of time for NASA to back out if either of the companies don't meet the milestones.

Three years late better than never. Bush promised 2014 private LEO launches when ending the shuttle program in 2007.

I can't help but feel, his success is somehow related to how awesome his name sounds!

I came up with pretty cool names before. Not an active ingredient in success :)

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