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Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4376: Nov 15th 2019 at 9:15:47 AM

I found the geosynchronous satellite belt fascinating. There is a truly astonishing amount of real estate in orbit, which is one reason why you can put up thousands of LEO Internet satellites without any real risk of collision, but that one specific orbit (GEO) is crowded enough that it is assigned discrete slots, and once a satellite has gone past its useful life, it has to be moved out of its orbit in order to allow another to take its place.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4377: Nov 15th 2019 at 11:09:35 AM

NASA International Space Station

  • NASA tweets that the 6 hour, 39 minute spacewalk has completed, with all objectives met. The purpose of today's EVA was to prepare for the repairs on the Alpha Magnetic Spectrometer instrument by staging equipment, removing its particle shield, and installing handrails. The next spacewalk will begin the process of disconnecting the original cooling system so that a new, external one can be installed. (official article)

Edited by Fighteer on Nov 15th 2019 at 3:54:16 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4378: Nov 18th 2019 at 11:41:58 AM

Nanoracks Falcon 9 Rideshare

Nanoracks Books CubeSat Rideshare and Habitat Building Demonstration in Single SpaceX Falcon 9 Launch

Expected to fly in late 2020, this rideshare mission will loft a demonstration spacecraft from a company named Nanoracks, whose idea is to repurpose expended upper stages from orbital rockets into habitats. The technology that will be demonstrated is robotic metal cutting in space. They aren't actually building a habitat, but performing proof-of-concept tests.

Riding along will be "eight of Spire’s LEMUR-2 CubeSats". Ridesharing is apparently Nanoracks' core business, but they're expanding with this new idea. I wish them luck and success.

Edited by Fighteer on Nov 18th 2019 at 2:58:48 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4379: Nov 18th 2019 at 1:01:48 PM

SpaceX Starship

From Twitter: It looks like the launch site is clearing in preparation for pressure testing of the tank section of Starship Mk1 in Boca Chica. While this is a routine procedure, there's always the risk of a catastrophic failure, so everyone has to get safely away.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
SeptimusHeap from Switzerland (Edited uphill both ways) Relationship Status: Mu
#4380: Nov 18th 2019 at 2:06:23 PM

So I just found out that Christina Koch is the first person to edit Wikipedia from outer space ([https://en.wikipedia.org/w/index.php?diff=926631603 this edit, apparently]).

I wonder, it was already done on Twitter et al, yes?

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4381: Nov 18th 2019 at 7:42:53 PM

Frankly, I have no idea, but it wouldn't surprise me.

The weird thing about the ISS, and most other spacecraft, is that it doesn't get a direct Internet connection from satellites because they're all pointed at stationary targets on Earth, not at other things in orbit. Even Starlink may not solve that problem.


SpaceX Starship Mk1's pressure tests indeed began today, beginning with site clearing, followed by significant venting and visible changes in the exterior surface of the vessel. The "crinkly" appearance of the stainless steel skin became smoother as internal pressure was applied, much as a crinkled bottle will resume its natural shape when blown into. Starship does not have internal tanks for its main propellant; the skin of the ship is the tank wall. However, unlike the old Atlas rocket, it can maintain structural integrity while not pressurized.

There is a bulkhead separating the oxygen and methane sections, of course, but these don't have to have temperature isolation (unlike kerolox and hydrolox fuels) because their boiling points are similar. It looked to my inexpert eye like they were testing the oxygen tank tonight. This makes sense as you wouldn't want to put methane into the rocket before you have verified everything else, and you most definitely would not want to put fuel and oxidizer together.

It's also possible they tested with an inert gas like nitrogen to avoid any accidental combustion events, although that would require an enormous amount that would need to be trucked in. (Starship holds 1200 tons of fuel and oxidizer fully loaded.) Lab Padre Twitter post, with video link


To provide parity, NASA Spaceflight covers the final assembly and checkout of the first SLS Core Stage prior to its shipment for Green Run testing.

Edited by Fighteer on Nov 19th 2019 at 9:23:45 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4382: Nov 19th 2019 at 8:17:08 AM

NASA

Ars Technica: One part of NASA seems serious about fostering aerospace innovation

Clearly not referring to the part of NASA working on the Artemis program (snerk), this article is about NASA's Commercial Lunar Payload Services program, or CLPS, which has recently expanded its list of potential contractors to deliver small payloads to the Moon's surface for scientific purposes, with contracts potentially worth up to $2.6 billion through November 2028.

Both SpaceX and Blue Origin are on the expanded list due to their forthcoming rockets, both of which should be able to land on the Moon. The main issue for SpaceX, as outlined in the article, is that its Starship would be significant overkill, as none of the proposed payloads would be anywhere near its theoretical 100 ton capacity.

SpaceX President Gwynne Shotwell called the program "super cool", noting that they are targeting 2022 for Starship's first Moon landing, at least a year earlier than previously expected.

Edited by Fighteer on Nov 20th 2019 at 9:22:05 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4383: Nov 20th 2019 at 6:56:36 AM

SpaceX Starship

According to posted road and beach closures, the next round of Starship Mk1 testing is scheduled for tomorrow afternoon/evening.

Rocket Lab Electron

I missed posting about this earlier in the week, but Peter Beck, Rocket Lab CEO, tweeted an image of what appears to be a finished Electron rocket with new fittings for parachutes and RCS thrusters [1]. This hints that we may see the first recovery attempt as soon as the next flight. It's very encouraging, since reuse is the key to affordable access to space.

.

As a reminder: Electron is too small and has too low a fuel margin to perform a propulsive landing. Instead, the plan is that it will orient itself for aerobraking on reentry, then deploy parachutes once it is lower in the atmosphere. As it descends, it will be caught in mid-air by a helicopter, which will transport it to a recovery ship. I really hope we get footage of these attempts.

Boeing Starliner

From various sources including ULA CEO Tory Bruno, Starliner CST-100 integration continues as planned and the vehicle's orbital flight test atop an Atlas V rocket is still on for NET December 17. [2] [3]

SpaceX Crew Dragon

NASA just tweeted slow-motion footage of the Super Draco thrusters on the Crew Dragon capsule for last week's static fire test. Majestic.

Edited by Fighteer on Nov 20th 2019 at 10:50:40 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4384: Nov 20th 2019 at 3:57:04 PM

SpaceX Starship

So, I appear to have been slightly wrong, or misinformed. Starship Mk1 underwent cryogenic pressure testing today and... it didn't go so well. To be clear, the purpose of these prototypes is to discover the failure states of the design so as to improve later versions. If it works perfectly the first time, they didn't test it hard enough.

In this video from Lab Padre, we can see the upper bulkhead of the rocket blasted off the top, like a bottlecap or overloaded pressure cooker. Except in this case it's a 9 meter diameter hunk of steel, which flew an estimated 500 feet into the air atop a column of super-cold gas.

Scratch one prototype. Elon Musk replied to a query on Twitter, saying that they will move on to the Mk3 design. That said, Mk2 continues construction in Florida, so we may have another chance to see it pop its top.

Edited to add: Per this article by NASA Spaceflight, SpaceX indicated in a statement that:

  • This was a max pressure test, so a failure was predictable, if not desired.
  • A decision had already been reached not to fly the Mk1.
  • The Mk3 construction will be much faster and use the improved design discussed by Elon at the presentation.

No word on the fate of the fairing + nosecone for Mk1, which is still at the construction site.

Edited by Fighteer on Nov 21st 2019 at 9:07:29 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4385: Nov 22nd 2019 at 3:58:14 AM

Slightly off-topic, but I couldn't find another place for it, The Atlantic recently published an article titled "The Long-Forgotten Flight That Sent Boeing Off Course", discussing the events 20 years ago that led to the company's current crisis. Specifically, the blame is pinned on its "reverse merger" with McDonnell, in which Boeing's money bought out the company but its leadership was taken over by McDonnell's, leading to a culture driven by cost-cutting and shareholder value instead of engineering principles.

This could explain many things, including the disastrous safety issues with the 737 Max and the insane cost overruns and delays on SLS (and Starliner).

Edited by Fighteer on Nov 22nd 2019 at 9:37:26 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
SeptimusHeap from Switzerland (Edited uphill both ways) Relationship Status: Mu
#4386: Nov 22nd 2019 at 5:36:08 AM

There is an aviation thread in Yack Fest.

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4387: Nov 25th 2019 at 9:22:16 AM

It's the triumphant return of my report on the week's upcoming launches. As always, schedules are subject to change for any number of reasons. Information is from Everyday Astronaut's Prelaunch Previews unless otherwise noted.

  • Nov 25 17:30 UTC: Russia, Soyuz 2.1v/Volga from the Plesetsk Cosmodrome
  • Nov 25 23:44 UTC: China, Long March 4C from Taiyuan
  • Nov 26 21:09 UTC: Europe, Ariane 5 ECA | TIBA-1 & Inmarsat-5 F5 (Global Xpress-5) from Kourou, French Guiana
    • The mission was originally going to launch this weekend but got pushed back a few times, first due to GSE (ground support equipment) issues, then weather.
  • Nov 27 03:30 UTC: India, PSLV-XL | Cartosat-3 & others from Sriharikota
  • Nov 28 07:56 UTC: Rocket Lab, Electron | Running Out Of Fingers from Mahia Peninsula in New Zealand
    • This booster will not make a recovery attempt, but will be used to test survival on reentry as Rocket Lab moves forward with their reusability effort.
  • December 1: China, Long March 3B | SupremeSAT-2
  • December 1: China, Long March 5 | Shijian 20
  • December 1: India, PSLV-CA | RISAT-2BR1 & others

We can expect high-quality livestreams of both the Ariane 5 and Electron launches; I'll post if I find them, although most people in the U.S. will be asleep for the latter.

The next launch from U.S. soil will be SpaceX's Falcon 9 | CRS-19 mission to the International Space Station NET December 4, atop booster B1056.3. This will be the company's 20th mission in 2019.

We are still expecting Boeing's orbital flight test (OFT) for its Starliner crew capsule NET December 17, and SpaceX's Starlink 2 mission in late December. There is no new information on the schedule for SpaceX's Crew Dragon in-flight abort (IFA) test.


Chinese social media showed images of yet another Long March rocket booster falling on houses in the Xichang province (Twitter). The country's launch cadence has been insane lately and they're beating every other nation in sheer volume, although not (yet) with technological sophistication, given that they are still dropping spent boosters on their own countryside. In this case, toxic hypergolic fuel was seen leaking that would seriously contaminate the crash site above and beyond the wreckage itself.

China is supposed to be developing grid fin technology that would let them steer descending boosters away from people, but we haven't seen that deployed yet.

Edited by Fighteer on Nov 25th 2019 at 12:42:16 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
eagleoftheninth Shop all day, greed is free from a dreamed portrait, imperfect Since: May, 2013 Relationship Status: With my statistically significant other
Shop all day, greed is free
#4388: Nov 25th 2019 at 9:35:25 AM

Baikonur isn't too different.

One day, we will read his name in the news and cheer.
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4389: Nov 25th 2019 at 9:41:24 AM

Yes. It's related to geography; neither Russia nor China has a surfeit of accessible launch sites that track over water instead of over land, and both have decided to allow spent boosters to crash randomly rather than invest in steering them. It's a bad image, but frankly their governments seem to have concluded that the value of space launches outweighs the risk to human lives and livelihoods.

Coincidentally (or not), both nations also continue to use hypergolic propellants in the parts of their rockets that could fall on people.

Edited by Fighteer on Nov 25th 2019 at 12:42:49 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4390: Nov 25th 2019 at 11:28:01 AM

Double Post: Here's a full news article from Space News about the China booster thing. Some takeaways:

  • The main rationale for Chinese launch sites to be inland was fear of strikes by the U.S. (or the U.S.S.R., for that matter) against coastal or border sites. It doesn't say if Russia has the same situation.
  • Both China and Russia post mandatory evacuation orders for civilians who are potentially in the drop path of spent rocket parts and they are advised not to approach potentially toxic debris.
  • China is, in fact, actively developing and testing steering technology for its boosters; however, the Long March 3C rocket involved in this latest incident has not been fitted with that technology yet.
  • China is also looking into first stage reuse and a concomitant switch to less toxic kerosene and liquid oxygen for propellant.
  • China is also developing coastal launch sites but has not yet made massive use of them.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
eagleoftheninth Shop all day, greed is free from a dreamed portrait, imperfect Since: May, 2013 Relationship Status: With my statistically significant other
Shop all day, greed is free
#4391: Nov 25th 2019 at 11:53:04 AM

The Baikonur site in southern Kazakhstan was the closest to the equator they could build it in the USSR without bumping into major settlements. The Vostochny Cosmodrome is being constructed in the Russian Far East so that Roscosmos won't have to depend on leasing Baikonur from the Kazakh government - it's 51° North versus Baikonur's 46°, and fairly close to the Sea of Okhotsk (though probably still going to leave a long overland debris trail).

Edited by eagleoftheninth on Nov 25th 2019 at 11:59:17 AM

One day, we will read his name in the news and cheer.
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4392: Nov 26th 2019 at 9:32:38 AM

Ariane 5 ECA | TIBA-1 & Inmarsat-5 F5 (Global Xpress-5)

Liftoff: November 26, 2019 21:08 UTC (5:08 PM EST).

For those interested in watching this launch live, the stream will be broadcast from Arianespace's official Youtube channel. The direct link is not active yet. Everyday Astronaut also has a preview with details. I'll edit this post before liftoff if I find the livestream.

The mission is a rideshare to geosynchronous transfer orbit (GTO), lofting communication satellites from Inmarsat and Egypt's TAS. The Ariane 5 rocket is not designed to be recoverable.

If I recall correctly from past launches, the primary stream will be in French; I don't know if there will be English commentary available.

Edited by Fighteer on Nov 26th 2019 at 12:33:35 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4393: Nov 26th 2019 at 3:10:00 PM

The Ariane 5 VA 250 launch was successful. I was too busy to post the livestream, but all I can find on Youtube now is this short video of the launch sequence. Oh, well.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4394: Nov 27th 2019 at 6:32:43 AM

Looks like Arianespace posted a short recap of the launch, here. You can see liftoff, booster separation, stage separation, fairing deployment, and vehicle deployment. I'm not sure why the liftoff footage is so dark compared to the tracking camera shots; either they used archive footage or there's a filter on some of the cameras to avoid the image being blown out by the intensity of the SRB exhaust.


Meanwhile, Scott Manley posted a video inspired by the Chinese booster debris news report, talking about the evolution of the Long March rocket family from its first days as converted ICBMs to today. It's quite good and I recommend watching it.

Some things that I either didn't know or didn't remember: China is already in development of a reusable first-stage booster using kerolox propellant, and they are a working on a heavy lift vehicle capable of carrying 100 tons to LEO and doing interplanetary missions, although it is not expected to enter service until at least 2030.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4395: Nov 28th 2019 at 5:27:49 AM

India and China both had recent successful launches:

  • China: Long March 4C | Gaofen-12, November 27
  • India: PSLV-XL | Cartosat-3 & others, November 27

Upcoming missions:

Rocket Lab | Electron | Running Out Of Fingers

New liftoff: Nov 29 07:56 UTC (2:30 AM EST) from Mahia Peninsula in New Zealand

The launch was pushed back by one day for "payload readiness" issues. As a reminder, the first stage of this Electron rocket is equipped with technology to allow it to attempt atmospheric reentry, but will not itself make a recovery attempt. The data gathered will be crucial to the company's work on reusability.

Reusability is the key to reducing the cost of space access going forward, and many nations/companies are now working on it following SpaceX's example, including Rocket Lab, ULA (with their Vulcan), China, etc. I'm particularly interested in Rocket Lab's solution because SpaceX attempted aerobraking + parachutes with Falcon 9 and abandoned it. Electron is much smaller than Falcon 9, however, and should be able to survive reentry conditions better.

Livestreams: Rocket Lab official Youtube channel, Everyday Astronaut. Unfortunately, I'll be asleep at the time.

SpaceX | Falcon 9 | CRS-19

Liftoff: December 4, 2019 17:51 UTC (12:51 PM EDT) from SLC-40 at Cape Canaveral

These are becoming routine enough that I don't feel the need to labor over the details, but some last-minute changes were made to the mission that are worth mentioning. It was originally going to fly on B1056.3, marking the third flight of that particular booster, but it was swapped to B1059.1, a brand new one, with B1056.3 going to SpaceX's next mission: JCSAT-18/KACIFIC-1, NET December 16.

Also, for unknown reasons, this booster will perform a drone ship landing rather than a return-to-launch-site (RTLS), although it will be very close to shore. It will be only the second time a CRS mission has used a drone ship landing, after (I believe) CRS-17 had to land offshore because the landing pad was closed for investigation due to the Crew Dragon explosion in April.

For more information on the science payload of this resupply mission, go here.

We're still expecting Crew Dragon's in-flight abort test and a second Starlink launch in December, so SLC-40 and LC-39A are going to be busy over the next few weeks.

Russia | Soyuz 2.1a | Progress MS-13 (74P)

Liftoff: December 6, 2019 09:34:00 UTC (4:34 AM EST) from Baikonur Cosmodrome, Kazakhstan

It seems a bit unusual to me to have two ISS resupply missions this close to each other, but I presume everyone involved knows what they're doing.

Edited by Fighteer on Dec 6th 2019 at 12:02:41 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4396: Nov 29th 2019 at 5:37:32 AM

Rocket Lab | Electron | Running Out Of Fingers

The launch was aborted due to issues with ground systems. We're waiting for the new target date. (Twitter)

Update: Per Peter Beck, Rocket Lab CEO, there was an issue with the stage 2 umbilical that will require a pad recycle, pushing the launch out "a few days". [1]

Ars Technica Rocket Report

Just in time for Black Friday reading, here's Ars Technica's Rocket Report. Stories covered that I haven't previously discussed:
  • Virgin Galactic's new chairman has been discussing the company's future as a point-to-point commercial transport provider rather than just space tourism. The main problem is that their current vehicle only has a range of 100 mi (160 km). (Ars)
  • Richard Branson's Virgin Orbit sought approval from Cornwall, England to build a spaceport there, but faced unexpectedly vehement opposition from local protesters. (Cornwall Live News)
  • A public company from Australia named Titomic says it has 3D printed a 5.5-meter rocket in less than 28 hours using titanium powder, and claims it can scale up to a full-sized rocket in 165 hours. Pretty nifty if they can also put engines on it. (InDaily)
  • Vandenberg Air Force Base in California, US has been trying to attract new launch business since it's been losing a lot of market share lately. Vandenberg is suited mostly for launches to polar orbit, with equatorial launches going from the east coast of the U.S. (Noozhawk)
  • The ESA is already eyeing upgrades to Ariane 6 after it goes into service about a year from now. This rocket will replace the venerable and distinguished Ariane 5. (SpaceNews)
  • The U.S. Air Force is going to revise its selection criteria for national security launch providers after Blue Origin protested. The USAF is preparing to award two five-year contracts in mid-2020. (SpaceNews)


Bonus news: The LEGO NASA Apollo Saturn V model is on sale today. (Official site)

Edited by Fighteer on Nov 29th 2019 at 2:18:07 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4397: Dec 2nd 2019 at 6:08:41 AM

International Space Station

With nothing better to do, right now I'm watching the NASA TV live feed of the Alpha Magnetic Spectrometer repair spacewalk, the third of four scheduled EVAs. [1]

As a reminder, this instrument detects cosmic rays and has been an invaluable source of science data, but is at the end of its design life as its cooling systems have failed. Rather than build and send a new one, a decision was made to refurbish the device in-situ, despite it not being designed with this in mind. It is the most sophisticated repair job ever performed in space.

The first spacewalk removed the instrument's cover and shielding, and installed a scaffold for the astronauts to work from. The second cut the existing cooling lines. This third spacewalk is installing the new cooling unit and connecting its lines to the old system. The fourth, scheduled for Dec 7, will complete the work.

Edit: The spacewalk concluded successfully.

Edited by Fighteer on Dec 2nd 2019 at 1:07:54 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
dRoy Professional Writer & Amateur Scholar from Most likely from my study Since: May, 2010 Relationship Status: I'm just high on the world
Professional Writer & Amateur Scholar
#4398: Dec 3rd 2019 at 6:28:45 AM

Edit: Never mind, I found the answer I was looking for: escape velocity.

Edit 2: Okay wow now I feel like a jerk. XP

Might as well as put up the original question, which was: what's the altitude from where objects start to drift out of space and never return to earth?

Edited by dRoy on Dec 4th 2019 at 12:00:27 AM

Continuously reading, studying, and (hopefully) growing.
Fighteer Lost in Space from The Time Vortex (Time Abyss) Relationship Status: TV Tropes ruined my love life
Lost in Space
#4399: Dec 3rd 2019 at 6:41:40 AM

[up] Your confusion is understandable, and stems from thinking of the problem in the wrong terms. Some basic concepts, in no particular order:

  • "Space" is defined, rather arbitrarily, via the Karman Line at 100 km above the Earth's surface. This has no real meaning other than to be able to say that something or somebody "went to space". There is still atmosphere up there, and the Earth's gravity is still almost as strong as at the surface.
  • Similarly, something can be quite far away from the Earth and still be gravitationally bound to it. We have satellites in geosynchronous orbit (GEO) at precisely 35,786 km; even the Moon, at 384,399 km, is part of the Earth's gravitational system.

So, what defines "leaving the Earth"? It's not distance, but velocity. How fast you are going determines whether you will leave Earth behind or remain in orbit (or fall back down, if you for some reason decided to go straight up).

The minimum velocity to remain in low Earth orbit (LEO) is approximately 7.5 km/s. This is horizontal velocity, not vertical. An object in orbit is still falling towards the ground, but it's going sideways fast enough to miss. That is, indeed, a good colloquial definition of "in orbit" that makes the The Hitchhiker's Guide to the Galaxy ironically accurate. You fall, but miss the ground. note 

There's a physics equation that you can use to calculate the "escape velocity" of any body, based purely on mass and radius. I won't copy it here, but this Wikipedia article can explain in detail. For the Earth, at the surface, it is about 11.186 km/s. That is, if you lift off and accelerate until you are going 11.2 km/s relative to your starting point, you are no longer gravitationally bound to the planet.

Of course, it isn't as simple as going straight up. Losses to atmosphere and gravity on the way up mean you need a lot more actual delta-V, and that takes a very big rocket. That gets into more complicated answers about orbit raising and other mechanics that are beyond the scope of this conversation.

Summarized in a simple way: it's not about how high you go, but how fast.


Edit: Oh, well... I'll leave this up regardless, since I spent a lot of time typing it out. cool

Edited by Fighteer on Dec 3rd 2019 at 9:57:31 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
dRoy Professional Writer & Amateur Scholar from Most likely from my study Since: May, 2010 Relationship Status: I'm just high on the world
Professional Writer & Amateur Scholar
#4400: Dec 3rd 2019 at 6:59:23 AM

Hey, I still appreciate your well-researched and explained reply. smile[tup]

Continuously reading, studying, and (hopefully) growing.

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