Small Orbital Craft

[penlu]

If you want to make something simple, then form follows function, right? So, I’ve come up with a thing I call a Small Orbital Craft. It’s a one-seated, simple spacecraft that launches into orbit on top of a twenty-foot, solid fueled rocket, to be docked to the ISS or something else.

The crew cabin itself is only one meter tall, just enough to fit one less-than-six-foot astronaut. It would be oxygenated and maneuvered by the attached service module. Just as a random point, the RCS of the service module is not like that of Apollo’s. It is more like that of the Delta Glider’s rear thruster assembly, a box with holes in it. The RCS can be retracted, and is powered by hydrazine and nitrogen tetroxide.

The basic mission plan is as follows: The craft would launch and fly up to about 180 kilometers using its first stage. It would then turn horizontal and continue firing the remainder of its first stage. After that, it would fire its second in order to circularize its orbit. Final corrections would be done with the ship’s RCS thrusters. RCS would be used again to dock with the ISS or another target craft. At launch, the craft would have a sea level pressure nitrogen/oxygen atmosphere, to be replaced with a pure oxygen atmosphere at 5 psi in space.

In preparation for docking, the nosecone would open on a hinge. Since the currently exposed surface is too small for a typical ISS or Space Shuttle dock, a set of spars with clamps at their tips would unfold from the now flat top of the craft. The span of the unfolded spars would be enough to reach across the dock of the ISS, allowing the craft to attach itself.

In order to transfer from the small ship to another one, an EVA must be performed because of the lack of an access tunnel. The ship would first be depressurized, and an entire half of the cabin would then swing outwards to provide the astronaut access to space. Another couple of random points: the astronaut launches and flies with the suit on, so changing in the small room would be no problem. The suit is not pressurized, either! It’s made out of tight rubber pressing in on the skin in order to simulate air pressure. The only part of the suit that is pressurized is the helmet. Continuing on, the astronaut would first attach an oxygen hose from the service module to the oxygen port of the docked craft before finding and entering an airlock on the ship.

Deorbiting would be done in the same manner as Mercury did it. The craft would then open its parachutes, stored inside the nosecone, and make a landing with retrorockets like Soyuz, ending its long mission. Interesting, no?

 

[eveningsky339]

Sounds like something worth pursuing. It reminds me of the saying about the Mercury program... "Mercury capsules are not ridden, they are worn."

 

[penlu]

Lol, even more so in this case! Also, I left a few things out:

Since the parachutes are in the nosecone, the latch or latches holding it closed will have to be especially strong. I was thinking of... say... 5 latches, one hinge? I don't know.

Another thing is that the two RCS thrusters to the left and right of the pilot have openings on all sides: specifically, one on the top and bottom for pitch, two on each of the front and rear facing sides (relative to the pilot) and another two on the outward facing surfaces. The RCS thrusters in the fron and back relative to the pilot, on the other hand, only have one thruster on the top and bottom. The cabin itself has no control, it's only the service module that rotates the cabin.

The spacecraft, excepting the cabin, is meant for disposal.

And finally, the cabin has a reentry spoiler that will automatically open because of its shape in case of a wrong-way reentry. It will also close due to its geometry, I think.


-----Posted Added-----


Doublepost: Please respond. I want more opinions! Anyhow, I think I'll put up a drawing soon.

 

[Spicer]

Sounds like fun. Hey, I'm willing to try any new spacecraft!

 

[penlu]

Here's my picture of the crew cabin. The rocket is just a fairly nondescript stick with fins at the bottom. The first stage is ~2.5 times the length of the second stage, a little shorter. Rocket length is 7 meters, width of orbiter and rocket is 0.95 meters, service module height is 0.65 meters, and cabin height is 1 meter. Maybe someone could make this? I can barely model at all: Best thing I've done is a fusion engine on ZModeler out of basic components like sphere, torus, etc. I can't code at all. So could someone please make this? Or is it not realistic or feasible, as in such a small rocket can't launch 1500 lbs?

 

[Cobalt]

This is a great idea. This is the kind of thing I was hoping either I, or someone else would make. If you're interested in possibly working together, I can certainly try to model a rough shape out. Small details would have to wait a bit since I'm fairly new to modeling myself, but I'm more than willing to try. PM me if interested, and maybe someone else who's even better than I am can help us, or you finish it.

 

[Danny Ramone]

this is what i was asking about in another thread. I like the idea of a "worn" type spacecraft that would cut down the required size of the launcher.

here is my suggestions:
instead of a docking port on the ship why not add a hanger module to the ISS that the ship could actually fly inside, pressurize then the pilot could exit the spacecraft. a hanger could also be carried inside an orbiter or XR5.

if its really lightweight how fast would it actually re-enter? perhaps some kind of spoiler could be deployed in the upper atmosphere to help slow it down before it gets to hot.

 

[eveningsky339]

I think that if you want to expand on this idea, you could use the small craft in a variety of ways. For example, if you want some sort of "orbital bus" or larger transport, you could find a way to use the craft as a sort of pit. Which can, of course, be undocked in any emergency.

 

[astrosammy]

if its really lightweight how fast would it actually re-enter? perhaps some kind of spoiler could be deployed in the upper atmosphere to help slow it down before it gets to hot.

This could also be solved with an inflatable heatshield to increase the drag. Or parachutes that survive the heat of reentry.

 

[penlu]

An orbital hangar is a good idea, but most current ships don't have that sort of thing on them. The dock should be kept, but that idea is worth looking at... maybe it could dock that way in the ships that actually have such a port? Lol, in Orbiter it wouldn't make much of a difference anyways. Someone should make an addon that would allow you to pressurize, say, the cargo bay of something and allow astronauts to EVA inside of it with infinite oxygen. Or something.

Too bad the ship's too small for a rescue module! You would have to have 3 in order to evacuate a Soyuz!

I didn't think of the reentry speed problem, but if Mercury was so small, how did they do it? Would using an ablative heat shield help? Or possibly letting the service module out behind it on a tether and using it as a parachute? Remember: no ejection seats!


Oh yes, I left out a couple of things:
One was that the pilot would obviously have to sit scrunched in a ball. I measured my dad up, and he fit. He's about 5.5 feet tall, so.
Two was that the pilot seat should be able to be gimballed so he is in the "sitting up" position and the "lying down" position. I thought that if you were scrunched up so much, it would hurt to look up out of the docking window.


-----Posted Added-----


Zomg best solution for the fast reentry problem: How about just lowering the orbit to maybe 80 kilometers? There's enough air there to slow the craft gradually down to a gentle flight through the atmosphere. I downloaded a Skylab addon and I undocked the Apollo thing from it. I fired a burn to deorbit like how Soyuz does it, a Hohmann to 25 kilometers. And I didn't even see any flames! It was actually rather disappointing.

 

[ar81]

I do not see the point of having an orbital hangar.
A docking port and EVA mission seems fine.
The cost of transporting such a huge facility to space does not seem too cost-effective.

 

[n122vu]

I do not see the point of having an orbital hangar.
A docking port and EVA mission seems fine.
The cost of transporting such a huge facility to space does not seem too cost-effective.

Agreed. If I'm not mistaken, the goal here is to propose a low-cost, low-resource, possible near-future craft. An orbital hangar would not be currently feasible IMHO, especially for the ISS.

Would be interesting to see an opening nosecone that also houses parachutes & their pyro.

 

[ar81]

Cost per unit = (Fixed cost + Number of units * Variable cost per unit) / Number of units

Cost is a non linear function.
You may think units are flights.
Variable cost is direct cost per flight.
Fixed cost is a fixed bill composed by overhead costs that do not depend on number of flights.

 

[penlu]

n122vu is not mistaken. To come up with this, I followed what I thought would be logical for a company or developing country's attempt to space.

 

[Andy44]

One of Greg Burch's addons is a pressurized hangar module which can house a small vehicle, IIRC. I think it has animated doors and stuff.

 

[penlu]

An orbital hangar really isn't neccesary, though. If there's already one, I might try that, but there is currently no existing real orbital hangar. And what if the doors failed? Explosive decompression is painful without a space suit.

The only problem with doing an EVA mission immediately after arrival in orbit is that vomiting in a spacesuit can be fatal. The reason NASA doesn't allow astronauts to EVA directly after arriving in orbit is that the astronauts could become spacesick in their suit. Clogging up air filters. Since the vomit is floating everywhere, including in your throat, the risk of inhalation and asphyxiation is also extremely high. Maybe an autopilot to bring the astronaut automatically to the airlock?

 

[Deke]

Well you've got a buck.

So you've got yourself a Buck Roger.

PM me details on this. I'll ring 'er out up around Earth when it's ready.

 

[Danny Ramone]

I just thought a hanger would be good for orbiter as the cost effectiveness would be negated.
Still might be something worth trying.

Im just trying to think outside the box seeing as the entry wouldnt be through the docking port maybe there is another way of docking.

My other point on re-entry was me thinking out loud wondering if anyone had made steps towards solving the "re-entry problem" i.e. having no need for heat shields. I thought a lighter craft like this might be good, especially if it had a spaceship one like spoiler to slow its descent. Or the inflatable spoiler sounds good.

 

[tblaxland]

[2 cents]
Instead of your fancy docking port spar arrangement you could just equip the nose cone with a grapple fixture. The station arm could then grapple your craft once it is station keeping nearby. Your astronaut could then do his EVA over to the airlock. The station arm could even move your small orbital craft (SOC?) close to the airlock for him.

This is the technique that will be used by the real-life Japanese HTV, except that the station arm will bring the HTV over to a CBM port.
[/2 cents]

 

[penlu]

Hey, that's a good idea. But what if they needed the arm for something else while the crew are still aboard? They wouldn't just let the ship drift, so it has to have some sort of docking capability. Right?

And I just got another idea on the reentry problem. How about a heat shield that unfolds from a jettisonable ring? For some reason I think a heat shield would burn up. I'll put a picture up.