Launching and landing rockets: A comparison between Blue Origin and SpaceX | Hacker News Reader

Launching and landing rockets: A comparison between Blue Origin and SpaceX

i.imgur.com

This graphic aptly shows the differences in complexity between the two flight plans, but it doesn't show the biggest difference between the two rockets. When the Falcon 9, enters space at the height of 100 km, it is traveling at 5000 km/h with 125 metric tons of payload[0]. Blue Origin's New Shepard, the best I can tell was traveling at ~0 km/h at that height, as it reached apogee at the height of 100.5 km and began falling back to Earth.

According to Musk[0], a first stage of a rocket is judged by the energy it can impart to its payload at the standardized height of 100 km. Merely getting to 100 km is the easy part. The Falcon 9 is able to deliver 120 giga-joules to its payload at the height of 100 km, while performing a return to launch site landing. While it appears the New Shepard had ~0 joules left at 100 km.

[0] - http://www.spacex.com/news/2015/12/21/background-tonights-la...

[1] - https://www.blueorigin.com/news/news/blue-origin-makes-histo...

Amazing, thanks for that explanation.

Potential energy is energy, so it's not quite correct that New Shepard had 0 joules at 100km. At 100km and 0 velocity it'll have about 1 gigajoule of energy per metric ton of mass.

Potential energy is not energy that you can give to a payload unless you want to have it fall 100km back to earth.

Sure, but it's energy that a rocket needs to impart nevertheless.

The point was that the measurement is what it can impart on a payload (presumably one going UP.) So your point doesn't seem relevant.

I think the point was to illustrate the difference in energy requirements for the rocket to impart to the payload.

That said, re-reading Elon's article, he did explicitly say _kinetic_ energy in the 120GJ figure, in which case 0 is the right number for New Shepard at 100km.

This really made the difference clear to me, thanks for the write up.

As @jzila pointed out this didn’t include the potential energy, with that included, the energy comparison becomes more stark.

The Falcon 9 v1.1 weights 557.6 tons and the number floating around for New Shepard is 40 tons. So that would give 496 gigajoules of potential energy for the Falcon 9 and 36 gigajoules of energy for New Shepard.

For a total of energy of 616 gigajoules for the Falcon 9 and 36 gigajoules for the New Shepard.

A more apt comparison is this: A single SpaceX F9 rocket can lift three Blue Origin New Shepards into orbit at 200km altitude (vs merely touching space at 100km) and then come back to land.

Here's a size difference comparison as well: http://i.imgur.com/g2VIKVC.jpg

So it turns out that guy messed up the SpaceX plot (the distance downrange was doubled), and posted a corrected one to reddit: http://i.imgur.com/Z81NgAk.png

Jeff Bezos: "... Welcome to the club!" https://twitter.com/jeffbezos/status/679116636310360067

The best part about that tweet is how Jeff double spaces after a period.

Why is that the best part?

It's sort of a nonstandard punctuation thing, especially on Twitter, where characters are limited and space-saving measures like single spaces after periods are standard.

I'm curious, why does the falcon reverse course after having so much lateral velocity? Why not launch somewhere in Arizona and land in Texas or Florida?

Probably to avoid a path which goes over populated land. Launches almost always go east to benefit from the Earth's rotation, so you want to launch from the eastern coast if at all possible.

Defeats the purpose of landing at the same site where you launch it, and be able to immediately start processing the rocket for re-use and maybe a launch it again same-day.

It's also a great illustration why SpaceX landing on land requires substantially more reserve fuel than a barge landing. (look at the length of the burn at apogee)

For those trying to figure out the importance of who did what first please read . http://www.theverge.com/2015/11/24/9793220/blue-origin-vs-sp...

Please read this Trisell and others who are so concerned about who did what first. http://www.theverge.com/2015/11/24/9793220/blue-origin-vs-sp...

A somewhat tangential question I've had since seeing the landing -- why are these rockets trying to land by themselves, which seems really difficult, compared to say getting the rocket roughly in the right place and then having a robotic arm attached to the ground reach out and grab them?

Two big issues with that. First, the arm would have to grab an attachment point of some sort, so you'd be trying to position the rocket and the hand close together and still enough to lock on. That's a much smaller and tougher target than landing. Second, there's no way you could build a robotic arm and grasping mechanism that's strong enough to hold the rocket once the engine shuts down, while also being nimble enough to reach out and grab it. To even have a chance, you'd need three arms and three attachment points, evenly spaced around the rocket, and coordinated to all grab on at the same time.

This sort of thing works well in space when everything is just kind of floating next to each other, and you only have to deal with very small thrusts to make small position adjustments, and momentum when you try to move things. (Weightless != massless) But down on the surface everything that's not solidly on the ground is constantly accelerating towards the center of the planet, and it takes a lot of force to counter-act that.

What about hard numbers? Anyone has delta-v figures for first stage ascent, velocity both vertical and lateral components at meco, and delta-v for boostback, entry, and landing burns?

This is pretty cool. Is the first stage trajectory to scale here?

Dear Jeff Bezos: Suck it.

Sincerely, Science

The problem that SpaceX has is that Blue Origin did it first. Even if the technical challenges were larger for SpaceX then Blue Origin.

In the mind of the general public that cares, it's all the same thing. The technicalities of a suborbital flight of a small capsule verses an orbital flight carrying a payload is meaningless. They just saw the Blue Origin rocket do it, and then the SpaceX rocket do it, and they looked about the same.

Nope.

SpaceX did it in 2011 w/ Grasshopper - https://en.wikipedia.org/wiki/Grasshopper_(rocket)

Uh, Grasshopper went < .5 miles up, Blue Origin went into space.

They actually had a successful 1km test.

TBF, 1KM is less than 100KM and Falcon 9 Dev didn't successfully land until 2014.

Blue Origin technically went into space for about ~30 seconds. The space officially starts at the Karman line (100 kilometers) and they reached 100.5 kilometers for a split second.

Too bad Blue Origin can't actually put anything into space that stays for a while (such as 11 satellites). The only thing Blue Origin exists for is to give millionaires a thrill ride that lasts a few minutes. BTW, this isn't fanboyism -- I really fail to see how the suborbital rockets will advance humanity's future in space -- whereas getting down the cost to orbit (and remember, leo is halfway to anywhere) is what is going to open up a new future for mankind.

If the millionaire gets out and jumps at apogee, they might stay in space for a while. But that'll use up Blue Origin's market pretty quickly.

And McDonnell Douglas did a vertical hop of a rocket in 1993 with DC-X.

You can continue to down vote me, but none of these examples went into 'space'. Also I reiterate my point, that the average person is not going to know or care that grasshopper went up and down 2440 ft in 2013. Or that others had a rocket that went up a few hundred feet and then landed in 1993. They will remember that Blue Origin just did this and that SpaceX did it second.

You still haven't described what exactly Blue Origin did first, that is so important.

I'm not a SpaceX fan boy, and I am happy Blue Origin is contributing to this space too. However; going straight up and then coming back down is no major challenge. It doesn't impart anything extra to the test. The novel and hard part is the landing. It's quite a shame that Bezos (and Musk, I guess) felt he had to treat it like a competition when actually both are doing cool and hard things.

That said; SpaceX are clearly some way ahead, in that they (rightly) focused on getting stuff to space whilst heading toward the landing tech.

The general public has no idea what Blue Origin is.

In reality, the general public has no idea what SpaceX is either.

Fortunately for SpaceX it doesn't really matter what the general public thinks since they're not buying SpaceX's services.

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