Design a One Stage Launch Craft?

[idobox]

High efficiency pulsed propulsion device?

[Technical Ben]

Ahem. http://en.wikipedia.org/wiki/Nuclear_pulse_propulsion

[bigglesworth]

Yeah, but how do they refer to the devices that produce these nuclear pulses?

[zmatt]

I'm sorry but dropping nuclear bombs out the back of your spaceship to create propulsion is retarded. it's akin to dropping dynamite out the back of your car to go down the highway. Except dynamite doesn't let off dangerous levels of radiation.

[ikrase]

No. Please do not apply 'common sense' to advanced nuclear aerospace engineering. The Orion Drive was well researched and the heavy 'pusher plate' at the back of the spacecraft would have provided sufficient radiation protection. Often, carrying a nuclear reactor ends up being worse. It is, however, not that great for in-atmosphere launch. Between 0.1 and 10 premature cancer deaths were expected per launch.

[idobox]

I'm sorry but dropping nuclear bombs out the back of your spaceship to create propulsion is retarded. it's akin to dropping dynamite out the back of your car to go down the highway. Except dynamite doesn't let off dangerous levels of radiation.

Because, of course, burning a few thousands tons of rocket fuel mix in 4 minutes, and strapping solid fuel boosters (essential oversized fireworks) to a vehicle is not comparable at all to using explosives.
Explosions are used all the time to propel objects at great speed. It's called a gun.

Thermonuclear explosions are the most efficient propulsion method we have the technology to build, and I think only antimatter can beat it.

[Technical Ben]

What about micro thermal nuclear explosions though? Instead of the tons worth of armour plating and spacecraft, could you make a smaller version? (Or does it just become a liquid nuclear rocket engine then?)

[idobox]

Apparently, they studied the question.
During Orion project, the smallest bombs had a yield of 0.03kT.
Daedalus and Longshot focused on inertial confinement fusion. So not really bombs, since it's the ship itself who compresses and ignite the fuel.

[zmatt]

I'm sorry but dropping nuclear bombs out the back of your spaceship to create propulsion is retarded. it's akin to dropping dynamite out the back of your car to go down the highway. Except dynamite doesn't let off dangerous levels of radiation.

Because, of course, burning a few thousands tons of rocket fuel mix in 4 minutes, and strapping solid fuel boosters (essential oversized fireworks) to a vehicle is not comparable at all to using explosives.
Explosions are used all the time to propel objects at great speed. It's called a gun.

Thermonuclear explosions are the most efficient propulsion method we have the technology to build, and I think only antimatter can beat it.

bid difference between harnessing combustion in a chambers and directing it through a nozzle to create thrust and setting off a bomb beside you and using the blast to push yourself. You aren't even directing the energy, so it will go in all directions and a fair bit will be wasted going the wrong way. Now if you could make a combustion chamber that can hold in a nuclear explosion and direct it out a nozzle like a rocket, you are on to something. That still wouldn't work right because you can't keep adding nuclear reactants into the chamber liek you could in a conventional rocket motor, fission doesn't work that way.

[Winter Man]

Couldn't you just get a little nuclear reactor as a heater, and use super heated water as propellant. Or ammonia, if you're elsewhere in the solar system.

[idobox]

bid difference between harnessing combustion in a chambers and directing it through a nozzle to create thrust and setting off a bomb beside you and using the blast to push yourself. You aren't even directing the energy, so it will go in all directions and a fair bit will be wasted going the wrong way. Now if you could make a combustion chamber that can hold in a nuclear explosion and direct it out a nozzle like a rocket, you are on to something. That still wouldn't work right because you can't keep adding nuclear reactants into the chamber liek you could in a conventional rocket motor, fission doesn't work that way.

It is possible to build directive nuclear bombs as well as building explosion chambers. We are not talking about using tsar bombas as a mean of propulsion, but bombs with yields of less than a kT. A shuttle booster burns 500kT of fuel (not TNT, but I don't have the numbers to convert) in about 110s. That's about 5kT of fuel burnt per s.
You can't easily add fuel to an ongoing nuclear reaction, but with pulsed propulsion, you don't care. You explode your fuel, wait a little bit, then send another bomb/pellet.

Couldn't you just get a little nuclear reactor as a heater, and use super heated water as propellant. Or ammonia, if you're elsewhere in the solar system.

This exists too, and have been studied in the 50, both for rockets and planes. The specific impulse is lower, and the thrust to mass ratio is significantly smaller than chemical rockets. So it is a viable solution for upper stages or once you're in orbit, but not very interresting for takeoff.

[edit]
A booster has 500T, not kT of fuel. 500kT of fuel per booster would be absurd.
So they burn 5T per s, which is still a lot, but is in no way comparable to a nuclear explosion.

[zmatt]

It is possible to build directive nuclear bombs as well as building explosion chambers. We are not talking about using tsar bombas as a mean of propulsion, but bombs with yields of less than a kT. A shuttle booster burns 500kT of fuel (not TNT, but I don't have the numbers to convert) in about 110s. That's about 5kT of fuel burnt per s.
You can't easily add fuel to an ongoing nuclear reaction, but with pulsed propulsion, you don't care. You explode your fuel, wait a little bit, then send another bomb/pellet.

Of course not, but I still think it's a highly inefficient way to do it, and there are bound to be better ways.

Couldn't you just get a little nuclear reactor as a heater, and use super heated water as propellant. Or ammonia, if you're elsewhere in the solar system.

Try here. We looked into it in the cold war, but the biggest limiting factor is weight. Reactors are heavy, if you can get around that then they are very promising. They were seeing twice the fuel efficiency of conventional rockets when they shut it down and they were still fairly undeveloped. They have the potential to be very useful.

EDIT:

Apparently they resurrected the idea again back in the 80's during the star wars plan and they were able to get the weighs down to 1,650 kg, but it made 1/3rd the thrust of NERVA.

here are the detailed specs for Timberwind 45
* Diameter: 13.94 ft (4.25 m)
* Vacuum thrust: 99208 lbf (441.3 kN)
* Sea level thrust: 88305 lbf (392.8 kN)
* Vacuum specific impulse: 1000 s
* Sea level specific impulse: 890 s
* Engine mass: 3300 lb (1500 kg)
* Thrust to Weight Ratio: 30
* Burn time: 449 s
* Propellants: Nuclear/LH2

seems throughout the project they were bale to get a thrust/weight ratio of about 30 and were able to keep it for the scaled up models as well. Not as good as liquid fuel rockets, but still very good.

[bigglesworth]

Hmm, why are reactors so heavy? Is it a requirement for power generation?

[zmatt]

Hmm, why are reactors so heavy? Is it a requirement for power generation?

well a bit, but mostly due to the design of the reactor core and the heavy equipment involved. But by the 80's we could get a whole engine down to the weight of a car and produce some pretty good numbers so if given real development it could work.

[idobox]

Of course not, but I still think it's a highly inefficient way to do it, and there are bound to be better ways.

In fact bombs are one the most efficient way to use nuclear fuel. Fat man used about 14% of its fuel, and modern designs are supposed to reach 40 to 50% (it's hard to find actual numbers), while civil reactors usually recycle their bars when 3 to 5% of the fuel has been used.

[Roĝer]

This is not a rocket, but I think it might be an interesting solution to the problem of landing on an arbitrary planet without needing custom parts from the surface:

A portable space elevator. In some designs for an earth space elevator a heavy satellite is launched to geostationary orbit and then unrolls a cable to the surface (moving up in the process to keep the centre of mass at GO). If you could do this on Earth, why not around another planet? It might even be a lot easier because of lower gravity.

So your mothership would be rather massive, with carbon fibre/unobtainium cable taking up most of its mass in a very large cargo hold. Interplanetary travel goes by ion drive powered by your fusion/antimatter reactor, which of course also powers the life support system and winch motor. After orbit insertion a small cable fix unit is lowered at the end of the cable towards the surface, a process taking a couple of days to hours, while if necessary atmospheric decent craft go ahead to secure the area. The cable reaches the ground and is fixed by the advance team, after which cable climber cars can bring equipment and personell down and precious resources up. Also, the atmospheric decent craft can be brough up again by cable. At the end of the operation the cable is winched up again and the mothership prepares for deorbiting.

This gives you a system that can leave the surface at short notice, doesn't require any local resources and can be used multiple times. But it cannot be used on a hostile planet that has mastered atmospheric flight, or even worse, rocketry. Well, at least not without some orbital bombardment and space marine action first.

[zmatt]

Of course not, but I still think it's a highly inefficient way to do it, and there are bound to be better ways.

In fact bombs are one the most efficient way to use nuclear fuel. Fat man used about 14% of its fuel, and modern designs are supposed to reach 40 to 50% (it's hard to find actual numbers), while civil reactors usually recycle their bars when 3 to 5% of the fuel has been used.

I'm talking about using the force of the explosion to propel you. It seems to me that it is very inefficient. I would rather put my nuclear assets into nuclear thermal rockets, which we have already had work. Right now nuclear pulse "engines" (if you can call them that) have not made it past a PowerPoint. I'm not sure how you would test them either. I mean you can't do it on earth, and carrying all of this into space to test is expensive and probably wouldn't sit well with I dunno, the whole planet.

This is not a rocket, but I think it might be an interesting solution to the problem of landing on an arbitrary planet without needing custom parts from the surface:

A portable space elevator. In some designs for an earth space elevator a heavy satellite is launched to geostationary orbit and then unrolls a cable to the surface (moving up in the process to keep the centre of mass at GO). If you could do this on Earth, why not around another planet? It might even be a lot easier because of lower gravity.

So your mothership would be rather massive, with carbon fibre/unobtainium cable taking up most of its mass in a very large cargo hold. Interplanetary travel goes by ion drive powered by your fusion/antimatter reactor, which of course also powers the life support system and winch motor. After orbit insertion a small cable fix unit is lowered at the end of the cable towards the surface, a process taking a couple of days to hours, while if necessary atmospheric decent craft go ahead to secure the area. The cable reaches the ground and is fixed by the advance team, after which cable climber cars can bring equipment and personell down and precious resources up. Also, the atmospheric decent craft can be brough up again by cable. At the end of the operation the cable is winched up again and the mothership prepares for deorbiting.

This gives you a system that can leave the surface at short notice, doesn't require any local resources and can be used multiple times. But it cannot be used on a hostile planet that has mastered atmospheric flight, or even worse, rocketry. Well, at least not without some orbital bombardment and space marine action first.

That is more than a little beyond our current level of technology, but i think that a space elevator would be a good solution for getting things off earth. Super expensive at first, but it would quickly pay for itself. Lets be honest, using liquid fuel rockets is a less then optimal way of getting stuff off of Earth and into space. if we can do it cheaper and easier we should. And barring some kind of revolutionary breakthrough in propulsion in the next hundred years I think a space elevator would be the best solution long term.

Once getting off of Earth, getting to the Moon, Mars or Lagrangian points is pretty trivial. I would imagine investment in space would explode. Bringing SciFi into the discussion, a recent gundam spinoff had massive solar arrays on space elevators as a way of providing cheap power to most of the globe. So the space elevator had two important purposes. I don't know enough about solar tech to know if putting the arrays in space would be worthwhile though.

[idobox]

I'm talking about using the force of the explosion to propel you. It seems to me that it is very inefficient. I would rather put my nuclear assets into nuclear thermal rockets, which we have already had work. Right now nuclear pulse "engines" (if you can call them that) have not made it past a PowerPoint. I'm not sure how you would test them either. I mean you can't do it on earth, and carrying all of this into space to test is expensive and probably wouldn't sit well with I dunno, the whole planet.

A bomb is just another way to heat reaction mass. The difference is you are not limited by the fusion temperature of your reactor materials.
http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB
Not exactly a rocket, but still fun to read.
Nukes are a mature and well tested technology. Materials able to resist an explosion from a distance were known in the 50s, and I guess there are better ones now. They could have built an Orion ship during the 60s.
http://en.wikipedia.org/wiki/Spacecraft_propulsion#Table_of_methods
This table, although quite incomplete, gives a nice overview of existant and theorized propulsion methods. Pulsed nuclear is easy, efficient and powerful.

[Technical Ben]

Thanks Roĝer. I'll keep that idea in mind for the future. It's a great idea for larger planets, especially those without an atmosphere to produce drag. Mining and resource ships could work that way. Even a Mar transport of some sort.

Will try to get a design up later.

[bigglesworth]

In fact bombs are one the most efficient way to use nuclear fuel. Fat man used about 14% of its fuel, and modern designs are supposed to reach 40 to 50% (it's hard to find actual numbers), while civil reactors usually recycle their bars when 3 to 5% of the fuel has been used.

I wonder; if there were a decent energy storage technology, whether you could have a power station based on detonating bombs...

[Technical Ben]

Well, here's hoping 40% efficiency is allowed for liquid nuclear rockets, as I've taken a little liberty on fuel tank size, rocket size and the lot really.


Shuttle in flight.

Spoiler:

Refuelling in orbit...

Spoiler:

The with this design is that the engines, fuel tank and crew cabin are interchangeable for different tasks or sizes.

[idobox]

Nice design.
How do you imagine landing on a planet with no atmosphere?
Also, wouldn't it be a good idea to put some kind of air intake for the atmospheric one? That way, you could save for reactant mass while at low altitude.

[Technical Ben]

Oh, not refined the air breather yet. It's more of a 3d sketch. Thanks for the suggestion. I would expect a shuttle landing on earth to be completely different from one used on Mars. One planet had dense oxygen rich atmosphere, one a sparse low reactive atmosphere. One idea was to have different engines strapped to the sides. Add scram jets or solid boosters. To land on a low atmosphere planet, it would either have to land virtically, or use the boosters on the side to help it. Would be like Space 1999 Eagle, and about as unscientific too.

Found another image and article for size comparison too. The Dragon capsule is really small, and allows you to get a crew into orbit with a fraction of the fuel needed for the space shuttle!

http://www.space.com/7930-commercial-ro ... fting.html

Uses a Falcon 9. Now a fat, short version of that could fit a Sci-Fi style "shuttle" no? I think I'll work on folding it in half so it's twice the width, half the height. Then add some wings!

[idobox]

What do you think of the shuttle landing backwards on thin atmosphere planets?
I'm not sure it would be practical, but a shuttle flying backwards at 6km/s, with its reactors at full power to brake, could look pretty awesome.

[Technical Ben]

I'm thinking of giving it some sort of re-entry shielding on the bottom/rear. As it's a low atmosphere, not gonna need a lot of it. Use the entire craft for aero breaking. Plus some chutes, I just realised I forgot them!

[zmatt]

those are actually really cool.

[HopDavid]

What ideas do you have for a one stage space craft for launch into orbit? Lets say to the International Space Station.

Economical single stage to orbit reusable launch vehicles has been the aerospace engineering holy grail for decades.

Propellant to dry mass ratio climbs exponentially with delta V. The 9 to 10 km/sec upleg makes propellant to dry mass ratio very difficult.

Going down, a vehicle suffers terrible abuse shedding 8 km/sec over an hours time via aerobraking.

One of the more plausible schemes (in my opinion) is capturing suborbital vehicles with momentum exchange tethers. Kirk Sorensen has several momentum exchange tether essays on his blog

Capturing a suborbital payload would subtract from a tether's momentum, lowering it's orbit. Catching a payload from a higher orbit would boost it's momentum, raising its orbit. If suborbital catches are balanced with superorbital catches, momentum is exchanged and the tether's orbit is preserved.

With the aid of a tether, 8 km/sec might suffice to attain LEO. For the trip down a ship might re-enter earth's atmosphere at 7 km/sec rather than 8.

A single km/sec advantage would substantially decrease re-entry abuse as well as the propellant to dry mass ratio needed to get there.

[ikrase]

What about different reentry patterns? Has anyone ever tried extremely gradual, multiple hour reentries?

[Kang]

What about different reentry patterns? Has anyone ever tried extremely gradual, multiple hour reentries?

I think one of the problems that you face with that is, that it means you need to burn fuel for multiple hours. Even if you put wings on your craft to enable 'standard' atmospheric control once you get enough airflow, the control surfaces probably won't work with simple mechanical connections.
In theory there is nothing against it and it sure would make a smoother ride to some extend, but the amount of fuel (thrusters, APU and maybe even main thrust) required probably makes a proper heatshield the easier challenge.

[idobox]

what about a giant, very light parachute?
If it's big enough, it should slow you down, even with very thin atmosphere, to the point you don't need a heatshield.

[ikrase]

Problem is it will slow you down a bit, then you will plunge deep into the atmosphere and vaporize. Gradual reentries of any kind can only be done with lifting vehicles.



Could you elaborate, Kang?

[idobox]

Problem is it will slow you down a bit, then you will plunge deep into the atmosphere and vaporize.

That's why you have to use unobtanium film to build it. You need it to be REALLY large. If you launch a feather from space, will it burn during re-entry?

What about a aerobraking in steps?
You take a very elliptical orbit, and everytime you enter the atmosphere, you loose a bit of speed.
I suppose there an issue with that, or we would do it. Something like the vehicle slowing down to the point it simply falls?

Another thought. Today, heat shield simply deal with heat by beeing good insulators, and probably by evaporating.
Would it be possible to extract the heat and radiate it? I'm imagining a system of liquid cooling with a very long radiator behind the craft, or very thin wing-like radiators that have a very small front surface, but a large exchange surface with air. Or maybe something even more exotic, like pumping it into air, with sound waves (it exists, but I don't see how to apply it to a spacecraft), or with a plasma-magnetic-wathever thingie.

[Kang]

Problem is it will slow you down a bit, then you will plunge deep into the atmosphere and vaporize. Gradual reentries of any kind can only be done with lifting vehicles.



Could you elaborate, Kang?

Provided that your spacecraft has a heatshielded side you will want to point that very side in the direction of travel. For a vehicle designed to generate lift in atmospheric conditions this is almost certainly the case and in fact gets even harder, since you have to control the angle of attack precisely to balance drag, gravity and lift. Of course that control is also necessary for a blunt-ended capsule, but the precision needed is far less and since there will hardly be any lift. Now controlling that angle of attack during reentry requires you to either fire reaction control system thrusters, the way a spacecraft is turned around in space, or - once you reach a sufficiently dense atmosphere - using normal aircraft control surfaces (although that probably shouldn't happen until you are through the reentry phase).
The problem is that that angle isn't set up once at the beginning of the procedure and just left like that, but it has to be adjusted and re-adjusted throughout the reentry to accomodate for increasing atmospheric pressure, consider later calculations about the projected landing spot and -for a long maneouvre- even compensate for curvature of the earth.
While each correction is fairly short and not much of a problem you have to take into account that the frequency and duration of the thruster bursts are not terribly depending on the desired reentry angle, as long as you are within the envelope the craft was designed for. That means that for a very shallow entry that takes five times as long as a regular one, you might have to use up four times as much thruster fuel.
An exception of course is a skip reentry, which is a short aerodynamical breaking at a shallow angle from which your craft 'skips back up' like a stone on the water; you'd still need to correct attitude for each 'skip' but since you'd be out of the atmosphere in between you would have long gaps with no necessity to act. You would lose a little speed with each skip and then eventually go for a steep entry. I'm not sure if that could be what you meant?

P.S.: I hope this made any sense. It's fairly late here and I've stumbled over language more than once while typing.

[ikrase]

I see, although our nuclear powered shuttles should not need APU fuel. I think that you actually do use atmospheric surfaces during reentry. I also heard of magnetic control surfaces that might provide more surface for the weight, and not burn off.


Idobox: Yes, if you drop a feather it will burn. There are TWO kinds of reentries.

Ballistic: Fast, high deceleration, very hot. Can only be done with ablative heat shields. Must be precisely aimed to avoid bouncing or burning up. This was done by all space capsules. Reentry vehicles are spheres (i.E. Soviet space probes, Soviet Vostok capsule) , saucers(I.E. US Mars Probes) , rounded cones, or inverted cones( i. e. Mercury, Apollo, Gemini, Soyuz). They are somewhat steerable if conical, but not very. Essentially, these are aimed so that they dig far enough into the atmosphere that the drag will slow them down enough to not exit it again, and they they plough deeper and deeper, loosing speed until they eventually fall to the ground at terminal velocity, which is roughly 400 km/h for Earth. Cheap, simple, not versatile, good for expendable things. Spacecraft geometry approximates a rock, and drag is roughly constant.

Lifting: Slower, medium deceleration, much less hot. Can be done with ablative sheilds, insulating/capacitative shields (i.e. Space Shuttle), or radiative shields (some experiments). Aiming is theoretically less precise but the spacecraft requires constant control with thrusters and surfaces. The spacecraft uses lift to keep itself from ploughing into the lower atmosphere. The force keeping it in the air gradually changes from inertia of orbit to aerodynamic lift (this happens sometime around mach 4-7?) and the drag is VARIABLE. The reentry vehicle MUST be shaped like an airplane or lifting body. (which can, confusingly, include saucer shapes). They are very steerable: this is called cross range and in the case of military spacecraft and the Space Shuttle is quite high. I belive that controlling a lifting reentry is within the bounds of human ability (keep the heat meter in the green zone, but don't jerk or you'll fly into space) whereas you need a nav computer or ground control to aim a ballistic reentry.



If you drop a feather from orbit into the very upper atmosphere, it will be moving at around 7-8 km/s but the air will be so thin that it won't burn at first. However, it will slow down a LITTLE BIT, but still be traveling at 6 km/s. THe lower speed lowers the orbit (remember that atmospheric forces are very low compared to inertia, even for a feather) so that it will plunge into the lower atmosphere while moving at close to orbital velocity, and will burn up.

If one drops a large rock, the profile will be similar. it may vaporize slowly enough that there is some left when it reaches the ground. You can find an angle at which the burn up is minimum, small enought that one can use an ablative heat sheild around a capsule.

Now let's consider dropping a paper airplane from orbit. (THIS WILL NOT WORK IN REAL LIFE). The paper airplane will slow down a little bit like the feather, but its lift will be high in relation to it's inertia, and will hold it up in the upper atmosphere where it won't burn up, and it can slow down gradualy and spiral in. This is a lifting reentry. A very, very unrealistic one.

With all current spacecraft, lifting or ballistic, you are still riding a fireball.

[Soralin]

Now let's consider dropping a paper airplane from orbit. (THIS WILL NOT WORK IN REAL LIFE). The paper airplane will slow down a little bit like the feather, but its lift will be high in relation to it's inertia, and will hold it up in the upper atmosphere where it won't burn up, and it can slow down gradualy and spiral in. This is a lifting reentry. A very, very unrealistic one.

What do you mean it won't work in real life?

http://seattletimes.nwsource.com/html/n ... ace28.html
http://www.airspacemag.com/space-explor ... plane.html
http://boingboing.net/2008/01/17/paper- ... to-be.html

Japanese scientists and origami masters hope to launch a paper airplane from space and learn from its trip back to Earth.

"It sounded like a simply impossible, crazy idea," Suzuki said. "I gave it some more thought, and came to think it may not be ridiculous after all, and could very well survive if it comes down extremely slowly."

A large spacecraft such as the Space Shuttle can reach speeds of up to Mach 20 (over 15,200 mph) when it re-enters the Earth’s atmosphere, and friction with the air heats the outer surface to extreme temperatures. The much lighter origami aircraft, which the researchers claim will come down more slowly, is not expected to burn up on re-entry.

Although the paper is coated with a heat resistant material, and it can survive at 400 degrees F + and at mach 7 in a wind tunnel.

[idobox]

However, it will slow down a LITTLE BIT, but still be traveling at 6 km/s.

Are you sure of these numbers?
When you drop a feather at sea level, you get a terminal velocity of maybe 1m/s, compared to a few hundreds for a rock. I understand drag will be very small in thin atmosphere, but if there is enough drag that the feather burns, inertia and weight will be almost negligible, and the feather will quickly slow down.

I don't know how to compute the surface to mass ratio where stuff stops burning in the atmosphere, but there must be one.

[Kang]

I see, although our nuclear powered shuttles should not need APU fuel. I think that you actually do use atmospheric surfaces during reentry. I also heard of magnetic control surfaces that might provide more surface for the weight, and not burn off.

Yes, I guess the control surfaces have their use, but that's probably at a rather late stage in the reentry. For them to have an effect you need a proper airflow over the wing, which initially isn't desireable for craft like the Space Shuttle that you'd want to slow down rather quickly after all. If I remember correctly the main portion of lift during that phase is generated by the fuselage as a whole, not strictly as a wing effect.

Of course making the shuttle nuclear powered solves the issue, since that means you have virtually unlimited energy at your disposal, which in turn might eventually even enable you to use a very powerful momentum wheel or even a magnetic device provided your target planet has a magnetic field. Those system are in widespread use today for satellites, but especially the magnetorquers make for awfully slow control.

[ikrase]

Paper reentry vehicle? AWESOME!
The fact that it's a lifting vehicle is, I think, quite significant here. A nonlifting vehicle traveling at Mach 7 at 60 miles will plunge, and then heat (although not as intensely).

Drag is extremely low in orbit, and a significant issue is that once some speed is lost, the amount of drag is also lost until the object sinks deeper.

[Technical Ben]

No idea as to what to do with re-entry, but how about this design? To land, it would re-enter bottom first, and use it's engines to slow down. Else it could use inflatable heat shields, then parachutes.
The crew capsule is it's own life pod. It releases in an emergency. It could also land with no atmosphere, as it does not rely on aero breaking. So like a giant moon landing craft.



It's still a lot larger than anything you would expect to see in Star Trek, but comparable in size with something from Star Wars.
If launching from earth, it would need to refuel in orbit to land again I guess. But if landing first, could you then launch again without refuelling? It's already been done from the moon right, could we do the same from Mars?

[Kang]

But if landing first, could you then launch again without refuelling? It's already been done from the moon right, could we do the same from Mars?

I don't think so. It wasn't done exactly like that on moon, although various early concepts for a lunar lander went for something looking a lot like your craft, but concerns about weight and fuel had all of those concepts discarded. In the end you could have it do it by cutting a bit on the same corners as for having a single stage craft in the first place: assuming fuels of much higher efficiency.