Ship entering atmosphere?

[SJE]

If a TL12 shuttle craft entered an Earth-like atmosphere from space and was going to land nearby to some people on the ground - what would they see and hear and when?

Essentially if we assume it's coming in at speed (but controlled flight) would there be a big sonic boom in the sky? Giant controls? A burning hot heat shield that might be visible at night or day?

 

[Condottiere]

As far as I can tell, there are four choices:


1. Controlled crash, unpowered glide.

2. Controlled crash, powered/rocket.

3. Controlled crash, powered/gravitic.

4. Uncontrolled crash.

 

[SJE]

No, I mean if a regular TL12 shuttle left the space craft and landed on the planet in a controlled landing. So option 3 but it's not a crash- it's just flying down from space, through atmosphere and touching down.

 

[Badenov]

If a TL12 shuttle craft entered an Earth-like atmosphere from space and was going to land nearby to some people on the ground - what would they see and hear and when?

Essentially if we assume it's coming in at speed (but controlled flight) would there be a big sonic boom in the sky? Giant controls? A burning hot heat shield that might be visible at night or day?

So, this is basically how the US space shuttle landed, and gliding the whole way, when it was still running. The sonic booms were well up high in the atmosphere and were not heard from the ground. The shuttle had managed to bleed off the speed by flying flat edge into the direction of motion and then nosed down into normal flight once they were travelling at a normal velocity. So the shuttle landings had nothing like big booms and all the heat shield was very high up in the atmosphere.


If the landing craft is not aerodynamic, you get the below choices:

As far as I can tell, there are four choices:


1. Controlled crash, unpowered glide.

2. Controlled crash, powered/rocket.

3. Controlled crash, powered/gravitic.

4. Uncontrolled crash.

1. This assumes the ship's engines are not running for whatever reason. Or the pilot has made a tactical decision to not use the engines for some reason such as to avoid detection. How controlled this can be is debatable and seems like a DM call based on specifics of the situation.

2. This seems like a weird option at TL12. We actually have recent RL demonstration, though, that a detatched solid rocket booster can land safely and in a controlled way if there is some equipment on the ground that can stabilize the craft once the rocket shuts off. This depends a bit on how you classify a detatched rocket booster as far as aerodynamic performance. I would call it partially streamlined as a cylindrical form factor.

3. I would expect this to be the typical TL12 solution, and as the rocket landing noted above proved, it is entirely possible to bring in a 'partially streamlined' craft under power. A grav is at that point a more agile and controllable rocket.

4. This is the line I would use for unstreamlined craft, such as distributed hulls, where even if you set it down gently, the ship will break up under its own mass.

 

[Condottiere]

Audio wise, rockets tend to make a lot of noise.

Gravitic based manoeuvre drive, we tend to assume a jet whine.

Under the current rules set, if you aren't using gravitic based manoeuvre drive, you'll want streamlined and heatshielding.

Gravitic based manoeuvre drives allows you to control rate of atmospheric reentry, if powerful enough, with any hull configuration.

With unstreamlined ones, you probably want dead calm weather, at a deadslow approach.

 

[kilemall]

Definitely heard the shuttle explosion over Texas.

 

[Takei]

Basically what Condottiere said. A standard TL12 shuttle uses gravitic drives with which you can come in as hot and loud as you like. IIRC an air/raft can reach orbit and come back again, albeit slowly.

 

[aramis]

If a TL12 shuttle craft entered an Earth-like atmosphere from space and was going to land nearby to some people on the ground - what would they see and hear and when?

Essentially if we assume it's coming in at speed (but controlled flight) would there be a big sonic boom in the sky? Giant controls? A burning hot heat shield that might be visible at night or day?

If you're using the 3I assumption of Gravitic thrust...

If all is working right...
Locals: See running lights descending. Hear nothing until it's really close. Then the hum of the craft's power systems, maybe some static-discharges (loud bangs), and the thud of the landing gear.

Passengers: get the "starting our descent, please remain belted in." They feel little, hear only the hum of the ship's systems and the ~200-~300 km/h descent, get the "seats upright and trays put away" after about 5 to 50 minutes of that, feel about a half-Gee extra as it enters the landing pattern, then a loud series of clunk as it lands. Then another as the gantry connects. (Why a gantry? At Tl 8+ worlds, passenger routing control, making it harder for passengers to wander the field.) Then a slow change to match local gravity and pressure, then the doors opening. And, of course, finally, the mayhem of "Please remember to take all your carry ons; your checked baggage will be routed to claim area Z."

If not working,
Locals: a series of multiple booms - the classic double from the supersonic fall, plus a third and maybe a fourth or more as impact happens.

Passengers: 0.1 to Zero G, with increasing brightness of fire outside, followed by between 10 and 1000 Gee terminal impact or a sudden encounter with 3000° K atmospheric plasma. Not certain which is worse. Expect the screaming to start with the plasma getting visible...

 

[Enoki]

If the shuttle is gravitic or otherwise capable of a non-ballistic reentry, then you wouldn't see much of anything from the ground. You have a speck of a ship moving in the upper atmosphere without it generating massive heat. As it reaches the lower atmosphere--on Earth that would be somewhere around 15,000 feet / 5,000 meters--the shuttle would start to become observable visually to someone on the ground not using vision enhancement devices. At that point it would look much like an aircraft would today--a small speck in the sky--that grows in size as it gets closer to the ground.

Noise-wise? There'd be some wind noise it generates dependent on speed. I really have no idea how its engine(s) would sound as that's dependent on how they work.

 

[Spinward Flow]

If a TL12 shuttle craft entered an Earth-like atmosphere from space and was going to land nearby to some people on the ground - what would they see and hear and when?

The answer varies with propulsion options.

With NO propulsion used ... so basically an aerobraking atmospheric entry and glide slope to the landing zone ... you're looking at something akin to a NASA Space Shuttle or SpaceX Starship type of atmospheric entry profile (lots of compression heating plasma high up to bleed off orbital velocity). The main difference between the two entry profiles is the "glide slope vs belly flop" option for scrubbing off as much velocity as possible before making contact with the world surface (in a controlled or uncontrolled manner) for a touchdown.

WITH propulsion used, all kinds of alternative options for entry profiles become possible.

Simple gravitic (or other reactionless) thrust makes it possible to "geosync in low orbit" and effectively "hover down" from 100+ km above the world surface in a controllable way. So a constant descent rate of 100 kph would be able to descend from the "edge of the atmosphere" in about an hour at what amounts to ground vehicle freeway speeds. Nothing dramatic or impressive ... although the views out any windows would no doubt be spectacular.

Reaction (rocket) thrust could potentially do the same thing as the gravitics, but at MUCH higher expense (in reaction mass to generate the necessary delta-v). For most reaction mass thrusters, the sheer inefficiency relative to gravitic "reactionless" thrust makes the notion something of a non-starter, but in an emergency condition would remain an option. Needless to say, a reaction thrust drive will have a "louder signature" than a gravitic one, but that's about it (aside from the consumption of reaction mass needed for the maneuver).

These options are not even mutually exclusive.
A streamlined hull could use inertial aerobraking to scrub off a portion of orbital velocity and use gravitic thrust to scrub off the rest of the orbital velocity, resulting in a quicker descent through atmosphere in a controlled manner.

As far as "observers on the surface at the landing zone" are concerned, they're only going to be able to witness anything that happens within their view of the horizon.

If you're wanting to make a "low signature" descent and touchdown, your best option is going to be to avoid aerobraking (since that makes a bright streak moving rapidly across the sky) entirely and due a pure gravitic power descent from orbit (basically "stop" relative to the surface while in orbit to achieve geosynch and then descent vertically on gravitic thrust only). It will take longer to complete the maneuver than an aerobraking approach, but it will have a much lower signature that can be easily "not seen" (or just not noticed) by any observers on the world surface.

 

[Rupert]

If you're wanting to make a "low signature" descent and touchdown, your best option is going to be to avoid aerobraking (since that makes a bright streak moving rapidly across the sky) entirely and due a pure gravitic power descent from orbit (basically "stop" relative to the surface while in orbit to achieve geosynch and then descent vertically on gravitic thrust only). It will take longer to complete the maneuver than an aerobraking approach, but it will have a much lower signature that can be easily "not seen" (or just not noticed) by any observers on the world surface.

With a streamlined ship and reactionless thrusters and/or gravitics 'stopping' and descending can be quite fast. No more than 15 minutes to lose orbital velocity (at 1g), and then accelerate downwards to 1000 km/h or so and 5-10 minutes to ground level, all without a sonic boom. Without streamlining the descent will need to be much slower and more cautious.

The most dangerous part of the procedure for a streamlined ship would be the losing of velocity whilst still at orbital altitude (because that's inviting a collision with objects still in orbit), so the pilot would probably drop the ship's orbit to the point where there's enough atmospheric drag that anything unpowered would de-orbit quickly but not so low that buffeting and heating are noticeable, and then slow to a stop (thus anything colliding with the ship while it slows won't be doing it by accident).

For low-profile de-orbiting, do all this over an uninhabited part of the planet (if there's such a place) - over oceans or polar ice caps is often a good choice, and then fly to the objective at high sub-sonic speeds and moderate altitude (too low and collisions with local aircraft or flying creatures becomes more likely, too high and you can be seen from a great distance). When close, lose altitude and speed and sneak in (your ship does have terrain avoidance radar, etc., I hope).

All this still works with TNE-style HEPlaR thrusters or 50s SF style atomic torches, because they have the fuel efficiency to burn for hours, but they'll probably be much, much louder so the in-atmosphere transit may as well be supersonic (choose altitude based on how much annoying locals with sonic boom vs being seen matters).

 

[Grav_Moped]

I wrote an EDL (Entry, Descent, and Landing) scenario for the Rangent Play-by-Post, using a Type T Patrol Cruiser.

The relevant part starts here. (with the orbit/atmospheric entry theme by "Air" -- subequent posts actually narrate the trip down.)

 

[agorski]

With a streamlined ship and reactionless thrusters and/or gravitics 'stopping' and descending can be quite fast. No more than 15 minutes to lose orbital velocity (at 1g), and then accelerate downwards to 1000 km/h or so and 5-10 minutes to ground level, all without a sonic boom. Without streamlining the descent will need to be much slower and more cautious.

Yes, I don't think a meteoric descent would be chosen. Reminds me of how an air/raft would get to orbit and back.