Why were the Bezos and Branson space flights so short?

If you’re going that far, and at zero gravity, why not take few laps around the earth?

Orbit isn’t a question of how high up you are. Orbit is a question of how fast you’re going.

They were high up enough to be in orbit, but they weren’t anywhere remotely close to being fast enough. Neither of their vehicles were capable of going anywhere near fast enough.

Blue Origin got up to three times the speed of sound, Mach 3 and then came back down to earth.

Which is fine for a bit of sight seeing and floating around for a couple of minutes.

To get into orbit requires a much bigger rocket to reach a speed of Mach 33, then later deal with the rather infernal problem of slowing down again when you want to return to earth. It is altogether a much bigger deal and I am sure Elon Musk has pointed this out to these upstarts.

Branson flight was over two hours because it used a regular jet to get up to 50,000 feet, then a rocket plane to up to 50 miles and then glided back down to earth.

It all sounds a lot of fun and hopefully the prices will come down eventually so we can all have a go.

I do wonder what the game plan is for these joy rides. Is it just executive tourism or is there a more ambitious plan?

Why just go up and down? How about to the other side of the world like a ballistic missile…

I doubt all the engineers at Blue Origin or Virgin need Elon Musk (who is not an aerospace engineer) to tell them how orbital flight works. Blue Origin was started as basically a think tank in the year 2000 to study different ways of getting payloads into space, not a ton of money was put into it. Their eventual conclusions were that rocketry is still the best option, and then they started developing a suborbital rocket with the intention of reusability and a high rate of test launches to get data for future development. The New Glenn rocket which is being actively developed would be capable of orbital launches, and they also have worked on craft that could facilitate lunar landings and delivering commercial payloads to space. Blue Origin is a lot later to the game than ULA or SpaceX in terms of actual work done, but there’s no real evidence the people there are stupid people that don’t understand how spaceflight works and need a CEO of a competing company (who again, is not an engineer) to explain it to them. Musk has a BS in Economics and a BA in Physics from UPenn, he did not attend engineering school and has never worked professionally as an engineer in any discipline. He is a smart guy who is involved in a lot of his company’s engineering meetings and acquaints himself deeply with engineering work product, but he is not an engineer personally.

I’m not familiar with Virgin having any aspirations beyond tourism, Blue Origin clearly has bigger aspirations but isn’t particularly close to realizing any of them in the short term.

Virgin Galactic was working on a separate system, called LauncherOne, for orbital satellite launches, but they spun it off into a separate company, Virgin Orbit, in 2017, and Virgin Galactic appears to now be purely focused on space tourism.

Orbit isn’t about getting up high. Orbit is about throwing yourself at the ground–and missing.

By necessity, nothing in orbit around the earth is “at zero gravity” - it’s the earth’s gravity that keeps it in orbit in the first place. If something got high enough to really “escape” Earth’s gravity, it would shoot off into space in more or less a straight line.

You reach orbit by:

  1. Achieving a high enough sideways velocity that you “miss” the earth as you are pulled towards it by gravity.
  2. Achieving a high enough altitude so that you do not need to constantly fight atmospheric drag to maintain that velocity.

The perception of zero gravity in spaceflight is because objects in orbit are in a state of perpetual free-fall around the earth.

Both the Bezos and Branson vehicles achieve only suborbital flight - their maximum altitude and maximum velocity is below both these thresholds required to achieve a stable orbit. They basically pop up and free fall back down for a short period, until the atmosphere gets thick enough to slow them down again.

The traditional illustration is a cannon. Fire the cannon horizontally, the ball falls under gravity and hits the ground. The harder you fire it, the further it goes. But fire it hard enough and the ball flies fast enough that the Earth curves away beneath it as fast as it falls, so it never hits the ground.

It’s worth pointing out that for a given payload mass, going 11 times as fast (Mach 33 vs. Mach 3) requires 121 times the kinetic energy. The payload mass will be higher too, since you’ll need more enduring life support systems, and a heat shield for reentry

New Shepard’s engine developed 110,000 pounds of thrust for 141 seconds. The Atlas rocket that put John Glenn into orbit had 341,000 pounds from its booster for 135 seconds, followed by 81,000 pounds for another 600 seconds. Interestingly, the Atlas was only about twice as tall as New Shepard. The difference in total vehicle size would have been much more dramatic if they had been using the same engine technology, but New Shepard’s engine technology is the latest and greatest, and it also burns hydrogen, which has about twice the specific impulse of the kerosene that the Atlas used.

Being in zero G induces disorientation, space sickness and vomiting (there is a reason why parabolic flight planes are nicknamed ‘vomit comet’).

Professional astronauts are extensively trained to deal with that. But for ordinary people, there are only so many minutes of zero-G flight before it stops being funny.

The pollution created by the flight. (I wonder how many miles per gallon they got :slight_smile: )

I understood that reference.

If only it were that simple.

It is that simple. But simple isn’t the same thing as easy. In order to miss the ground, you have to throw yourself really, really hard.

Pretty much the best way to learn the difference between the sub-orbital flight and full on orbital flight is to play Kerbal Space Program.

Indeed. Orbits, interplanetary trajectories, etc… all become a lot more clear after you’ve played some KSP for a while.

Largely bullshit. From the article:

But globally, rocket launches wouldn’t need to increase by much from the current 100 or so performed each year to induce harmful effects that are competitive with other sources, like ozone-depleting chlorofluorocarbons (CFCs), and CO₂ from aircraft.

Commercial aircraft emitted 905,000,000,000 kg of CO2 in 2018. A Falcon 9 launch (which is a much larger vehicle than the Branson/Bezos ones) emits about 480,000 kg of CO2. The number of rocket flights would have to rise from about 100 per year to roughly 1.9 million to match commercial aviation. The difference will become even more significant when methane-powered rockets (like Starship or New Glenn) become operational. And again, that’s for orbital flight, not suborbital (enormous difference in energy use).

Modern commercial spacecraft are cleaner than the Shuttle, (or NASA’s SLS) whose solid rocket boosters put out a lot of pollutants.

Falcon 9 burns RP-1 (Kerosene), so it does emit CO2. But Bezos’s little rocket uses hydrogen and oxygen, so its exhaust is essentially water. It has very little effect on the environment at all.

Blue Origin’s Spaceship Two uses a hybrid rocket motor that burns HTPB (Hydroxyl-terminated polybutadiene) which is a plastic polymer, using nitrous oxide as an oxidizer. It emits some bad stuff, but remember that compared to an orbital rocket these engines are puny and just don’t burn all that much fuel anyway compared to something like a shuttle launch.

SpaceX’s Starship and Super Heavy booster burn Methalox (Methane and oxygen), and do emit significant CO2. However, methane can be manufactured. Using the Sabatier process, CO2 is consumed to make the methane, then later when burned the CO2 is released. Musk has committed to building a fuel manufacturing facility using green power, so the entire Starship system will be carbon neutral in terms of fuel.

Pretty much all hydrogen is produced by steam reforming methane, which isn’t a very efficient process, so hydrogen engines are going to be less efficient (in terms of CO2 emissions) than methane engines for the time being. Of course, long run you can electrolyze water into H2+O2, with the electricity coming from nuclear/solar/wind, and if you need the hydrogen anyway it’s not a terrible way to smooth out electricity demand.

Yeah, I wasn’t thinking about the creation of the hydrogen, but the result of burning it in a rocket. As you say, it’s possible to make it in carbon neutral fashion, but that’s pretty expensive today.

As regards SpaceX, it should hopefully be a moot point in the future, because if Starship is successful they are going to retire their other rockets and only use Starship. So if Musk can actually produce enough ‘green’ methane, SpaceX would be the first company to have a carbon-neutral fuel system for every flight.

Jeff Bezos’ BE-4 engine for the New Glenn and ULA’s Vulcan rocket is also methalox.

I thought hydrogen was a pain in the ass to deal with.

Being the smallest atom, containing it is a problem. It can leak out of almost anything without extra effort to keep it contained.

As such, its benefits are outweighed by it being a real problem to work with. Certainly doable and we do work with it but there are better options, all things considered.