New Sweet way to reenter?

[joiz]

I was playing orbiter as I usually do, playing today with the model rockets, and I noticed that one of them had huge drag, and when i reentered after crossing the USA (using and SRB as a booster) Thanks to the drag, all the slowing happened in the upper atmosphere and so there where no reentry flames. so if you deployed a huge ballute or something at reentry to make all the slowing happen in the upper atmosphere, maybe you could avoid the kind of thing that shuttle astronauts dread?

 

[the.punk]

Which rocket of model rockets was it?

 

[RisingFury]

I was playing orbiter as I usually do, playing today with the model rockets, and I noticed that one of them had huge drag, and when i reentered after crossing the USA (using and SRB as a booster) Thanks to the drag, all the slowing happened in the upper atmosphere and so there where no reentry flames. so if you deployed a huge ballute or something at reentry to make all the slowing happen in the upper atmosphere, maybe you could avoid the kind of thing that shuttle astronauts dread?

Well, no offense meant with this, but I think the people running the Shuttle Program know quite a lot better what they're doing then you, not to mention that you're relying on a computer program with a rocket that might have bad values

 

[garyw]

I think a ballute has been considered as a heat shield for aerobraking.

As for risking peoples lives with one.... well,

1. Where do you put it?
2. What happens if it fails?
3. What happens if its damaged whilst in the atmosphere?
4. How do you inflate it?
5. What happens if it's accidently inflated at the wrong time?

and so on.......

 

[T.Neo]

1. Where do you put it?

Somewhere on the ship.

2. What happens if it fails?
3. What happens if its damaged whilst in the atmosphere?

What happens when any TPS fails?
Disaster...

4. How do you inflate it?

With compressed gas, a gas generator, etc.

5. What happens if it's accidently inflated at the wrong time?

It won't be. Same thing with the Shuttle landing gear- they don't deploy on orbit accidentally...

 

[joiz]

Well, no offense meant with this, but I think the people running the Shuttle Program know quite a lot better what they're doing then you, not to mention that you're relying on a computer program with a rocket that might have bad values

true about the bad values, but I never suggested that a tube would have that much friction, i said use a ballute, something the shuttle obviously could not do as its a plane (or maybe it could). the shuttle reenters the way it does because it needs cross range for military missions.
it was model rockets by anemazozo or something like that.
if it fails, you can have a backup one, or a capsule that seperates from the main ship that reenters the old way. you store it like a normal chute.
google canadian arrow, they propose using a ballute for suborbital reentry (manned)

 

[tblaxland]

google canadian arrow, they propose using a ballute for suborbital reentry (manned)

I doubt that you could make a ballute that is lighter than a traditional ablative or thermal soak type TPS for orbital velocities. Sub-orbital - definite maybe, but not orbital. The advantage with a traditional type TPS is that shock front set up by the blunt body reentry keeps the hot plasma away from contacting the TPS and significantly reduces the thermal load. A ballute would definitely not set up a strong shock front due to its shape (see http://en.wikipedia.org/wiki/Atmospheric_reentry#Blunt_body_entry_vehicles). That leaves you with two options: 1. Make the ballute large enough that the decellaration occurs very high in the atmosphere and the thermal loads are widely distributed; or 2. Make the ballute robust of enough that it can withstand the thermal loads of decellaration at lower altitudes. Both options would require a lot of mass to work and, if they weigh more than a traditional TPS (I expect they would), would reduce the payload fraction for the launch system.

 

[RisingFury]

true about the bad values, but I never suggested that a tube would have that much friction, i said use a ballute, something the shuttle obviously could not do as its a plane (or maybe it could). the shuttle reenters the way it does because it needs cross range for military missions.
it was model rockets by anemazozo or something like that.
if it fails, you can have a backup one, or a capsule that seperates from the main ship that reenters the old way. you store it like a normal chute.
google canadian arrow, they propose using a ballute for suborbital reentry (manned)

Why? Why have a double reentry system? It's just dead weight. The one that's on the shuttle / capsules works just fine - but of course nobody intended to blow 50 cm holes in it.

 

[joiz]

AHAH! instead of using a ballute, you could increase drag by feathering like SS1 did, except from orbit. that would be really good. no heat.

 

[TSPenguin]

To quote Wikipedia refering to Burt Rutan:

However, it is important to realize that the velocity attained by SpaceShipOne prior to reentry is much lower than of an orbital spacecraft, and most engineers (including Rutan) do not consider the shuttlecock reentry technique viable for return from orbit.

 

[joiz]

maybe not for a plane, but what about a capsule? think of a real shuttlecock, the little hard thing at the end is where the capsule would be, that should be big enough!

 

[whitewatcher]

The Russians experimented with extreme ballistic coefficients:

http://www.astronautix.com/craft/irdt.htm

I think this way of re-entry is pretty cool because you reduce peak heat loads. Of course, you must get rid of the same orbital energy, but you have more time for surrounding (residual) atmosphere and radiation to cool down your ship's surface.
Maybe the theoretical minimum system mass is similar to current reentry systems, but you can probably have lower margins in the inflatable system. Effects like catalysis currently create larger errors in the numerical models for standard reentry whereas ballistic effects are well understood.

 

[Sky Captain]

What about using wings to counter the gravity and stay in an upper atmosphere longer to reduce speed without too much heating. In Orbiter it`s possible to reenter XR series without exceeding 600 degrees hull temp simply by lowering AOA to stay in ~ 60 - 70 km altitude during most of the reentry time and going lower when your speed has dropped to 2 - 3 km/s.

Why such a tactic is not used to reenter real space shuttle?

 

[garyw]

What about using wings to counter the gravity and stay in an upper atmosphere longer to reduce speed without too much heating. In Orbiter it`s possible to reenter XR series without exceeding 600 degrees hull temp simply by lowering AOA to stay in ~ 60 - 70 km altitude during most of the reentry time and going lower when your speed has dropped to 2 - 3 km/s.

Why such a tactic is not used to reenter real space shuttle?

Because in the real world the atmosphere doesn't cut off at 200km.

Entry is a very different beast in the real world compared to Orbiter, you have friction, Laminar flow and turbulent flow to think about.
You can't just "hover" around the 60-70km mark in the real world without significant heating. The shuttle structure would not handle it.
The shuttle is designed to enter the way it does. Please don't compare entry in the real world to that in Orbiter.

 

[Sky Captain]

Because in the real world the atmosphere doesn't cut off at 200km.

Entry is a very different beast in the real world compared to Orbiter, you have friction, Laminar flow and turbulent flow to think about.
You can't just "hover" around the 60-70km mark in the real world without significant heating. The shuttle structure would not handle it.
The shuttle is designed to enter the way it does. Please don't compare entry in the real world to that in Orbiter.

I know it`s different I just thought doing most of the braking in higher altitude where air is less dense would cause less heating.

 

[tblaxland]

Why such a tactic is not used to reenter real space shuttle?

It does, except that vertical speed is controlled so that it does not go positive. Guidance for skip re-entries is much less precise than for a full atmospheric re-entry (Urwumpe posted on that somewhere recently). Also, there is a trade-off between payload fraction, size of wings and weight of TPS. That is an optimisation function that I will leave to the experts.

 

[garyw]

I know it`s different I just thought doing most of the braking in higher altitude where air is less dense would cause less heating.

You still have to get from up there to the ground, gravity will accerlate you and you get heating.

Remember, top speed of the shuttle is achieved AFTER the deorbit burn!

 

[tblaxland]

You still have to get from up there to the ground, gravity will accerlate you and you get heating.

The shuttle does level out somewhat at about 60km in a nominal reentry. I can't find the graph of it just now.

EDIT:

 

[Sky Captain]

I just searched about proposed Skylon spaceplane and it turns out it is going to use somewhat similar reentry trajectory as I thought where reentry will occur at altitude between 90 and 60 km thus avoiding the high heating and necessity for heavy and fragile Space Shuttle style TPS system.

http://www.reactionengines.co.uk/skylon_vehicle.html
http://en.wikipedia.org/wiki/Skylon

 

[joiz]

yeah, I agree with sky captain, von braun proposed reentering lifting body like ships heading back from the MOON not just orbit, they would reenter for 6 hours instead of 3 minutes, so the heating would be so minimal an X-15 could handle it.