GB2467309A - A system for decontaminating a spacecraft - Google Patents

Abstract

A system for decontaminating a spacecraft comprises tubes 6 and tubules 6 which supply gases lethal to bacteria or viruses to all parts of the spaceship which may come into contact with external environments. The tubules may be placed so as to introduce gases to any unsealed parts of the spacecraft. Filters may also be incorporated into all cabin vents and airlock valves to prevent viruses and bacteria leaving or entering the pressurized part of the spaceship. The gases or a radiative phase may also be used within docking collars. A leak prevention system comprises a self sealing system for small leaks and a self destruct system for large leaks. The decontamination system may be fitted to spacesuits which may supply additional hydrogen, to produce an external flame in the event of puncture of the skin of the spacesuit.

Description

SPACECRAFT DECONTAMINATION

This patent refers to methods and apparatus for spacecraft decontamination.

Proper decontamination methods and apparatus for spacecraft, especially probes and manned craft, are specified herein since it has long been known that some bacteria and many viruses can Thibernate" for prolonged periods in a vacuum.

Although some decontamination methods are used today, it will be shown that current procedures and equipment are inadequate and that there is still a real chance that bacteria or viruses may contaminate extra-terrestrial environments.

In order to protect future space exploration, new requirements, methods and apparatus are introduced which are both practical and reasonably inexpensive.

These additional procedures and apparatus are advised for all future space flight.

Most subsystems of any spacecraft comprise delicate electronics and mechanical parts. They are normally made in "clean" room conditions. Clean rooms normally filter the air so that most of the dirt, and sometimes bacteria and viruses are removed too.

Hence most spacecraft sub-assemblies are relatively clean and free from microbial contamination. Most of the sub-assemblies normally receive other decontamination treatments before final assembly, and the "prior art" methods are listed below: 1) Heat treatment 2) Microwave (heating) 3) Ultra-violet (ionisation) 4) X-ray (radiotherapy) 5) Electrostatic ionisation 6) Sound (resonance) 7) Chemical (ozone or cyanide gas) After final assembly, most complete space probes are heat treated. That is, the complete craft is heated to about 100 degrees centigrade for an reasonably long time. This is normally sufficient to destroy all remaining external and internal bacteria and viruses.

After heat treatment, spacecraft are tested to see whether their systems, subsystems and components are working properly. Spacecraft are then stored and transported to the launch site in sealed containers.

However, most launch vehicles (rockets) are fairly large and therefore are not kept in clean room conditions. When the satellite, probe or spacecraft is attached the top of the rocket and surrounded by the nose cone, contamination of the spacecraft is certain because this is done in the normal atmosphere.

Thus, although the sub-systems and complete spacecraft may, at some stage, be completely free of living bacteria or viruses, during launch vehicle assembly and while sitting on the launch pad, contamination can still occur.

Most launch flight times are about 10 minutes. During this time the pressure (of air) in the nose cone matches the ambient pressure at the rocket's altitude.

Thus the rocket nose cone expels air as the altitude rises.

The pressure (of air) starts at 10A5 Pascats (1 atmosphere) and stops a 0 Pascals (vacuum). However, bacteria or viruses within the nose cone may become attached to surfaces of the spacecraft or trapped within It before or during launch.

Most spacecraft are initially launched into an Earth orbit. Once in orbit, the probe (and additional boosters) normally make several circular orbits until the transfer trajectory window occurs.

The additional boosters may then fire and a transfer trajectory, sometimes including a gravity assist is achieved. The boosters may then be discarded, sometimes continuing along a similar trajectory as the probe.

Close to the Sun, the external radiation received by most spacecraft is quite intense because of the lack of attenuation of sunlight and sub-atomic particles by an atmosphere. Thus any bacteria or viruses within direct view of sunlight are normally destroyed.

However, most spacecraft have parts that are protected from radiation by a gold (or similar reflective dense) foil. This foil is not air-tight, because if it were it would balloon during launch. Therefore, bacteria or viruses may manage to survive in the shade provided by the spacecraft's own radiative protection.

During re-entry, space probes use a heat shield to protect them as the kinetic energy of the craft is dissipated. This is normally an ablative material (such as epoxy resin) which is heated to several thousand degrees centigrade by friction in the atmosphere.

As the material burns away, gas is produced absorbing energy, and the gas also provides an insulative layer. The heat shield thus protects the spacecraft from incineration. However, this also means that bacteria or viruses inside the spacecraft are protected too.

Thus, it has been shown that with existing methods, it is possible for spacecraft, especially space probes to transport bacteria or viruses. If probe destinations provide reasonably convivial environments, it may be possible for bacteria or viruses to survive on extra-terrestrial planets.

This would be disastrous for future scientific exploration because it would be difficult to determine whether organisms discovered elsewhere were indigenous.

Even worse, the Earth bacteria or viruses may be better at adaptation than extra-terrestrial organisms, which may result in serious damage to other indigenous ecosystems.

According to the present invention there are provided methods and apparatus comprising tubes and tubules that supply lethal gases to all parts of a spacecraft that may come into (chemical) contact with external environments in order to prevent bacterial or viral contamination.

The invention will now be explained in detail, referring to the drawings wherein: Figure 1 shows tubules (6) that allow introduction of toxic gases between the ballistic (1) and thermal (2) layers and into unsealed radiative boxes (3), and additionally wherein radiative layers (5) may be within the pressure (seal) layer (4)..

Figure 2 shows an unmanned space probe (4) within a rocket nose cone (1) designed such that external chemical (2) and/or radiative sterilisation may be used for decontamination.

Figure 3 shows a complete double-hulled manned (3,4) spacecraft designed to allow both chemical (2) and radiative sterilisation of all unsealed sections, with a self-destruct for containment of intermediate leakage.

Figure 4 shows a cabin airlock (3) whereby filters (5,6,7) are introduced to vents and pressure equalisation pipes and whereby chemical and/or radiative decontamination (8) may be used during egress or return.

Figure 5 shows a spacesuit wherein the astronaut may breathe a hydrogen (2) oxygen (4) mix so that small punctures may be ignited to prevent leakage of bacteria or viruses again incorporating a self-destruct contingency (3) for intermediate leakage.

The inlet pipes (Figures 2-2, 3-2) allow lethal gases to be introduced to the spacecraft. The gases, in turn, vent out into the rocket nose cone before launch.

Most launch pads are evacuated (of people) before the launch sequence because they are already hazardous areas. The launch sequence normally takes several hours, and at the start of the sequence decontamination should commence.

The decontamination process comprises pumping poisonous gases into all unsealed parts of the spacecraft that may be contaminated, through inlet pipes, especially behind any unsealed radiative shielding (see Figure 1). The gases diffuse through the spacecraft, then into the nose cone, and then into the atmosphere though the normal pressure equalisation pipes (Figure 2-5).

The most favoured gas is hydrogen cyanide, as it is unlikely that cyario-bacteria would be present in the spacecraft, although several sequences using different gases may be better. It is important that all bacteria or viruses inside any unsealed thermal and radiative protection be destroyed, and for inter-planetary flight it may be necessary to decontaminate nose cones and boosters also.

The thermal and radiative shielding is only be designed to protect the delicate parts of the space probe that are susceptible to extra-atmospheric heat and radiation. This is because, as mentioned above, harmful radiation should also be used to argument chemical sterilisation either from external or internal sources.

In order to guard against any form of contamination from manned spaceflight, other considerations need to be taken into account. The above methods for unmanned spaceflight should still be used, and hence all unsealed parts of the spacecraft must be free of bacteria and viruses by launch time.

Of course, the crew can never be made completely sterile and hence the crew (and subsequently the cabin) will contain bacteria and viruses. These may be reduced to a minimum using antibiotics for the crew and UV/ozone/hydroxide air scrubbers for the cabin [with the added effect of protecting the health of the astronauts'].

Because the exterior of the spacecraft will be decontaminated both chemically (during launch) and using radiation (during Earth orbit) whilst the cabin Is inhabited, by making the cabin's radiative layer inside (or the same as) the pressure layer, solar radiation will further reduce any chance of contamination.

Since the inhabited part of any spacecraft will always contain bacteria or viruses, it is important to consider contingencies against leaks. The most likely cause of leaks during flight is from meteorite strike: most meteorites are very small, no larger than a grain of sand, but travel very quickly (>100,000 mph). Most of these grains can be evaporated using a double hull design (see Figure 3), similar to the design of the Giotto probe.

That is, the outer hull is designed for impact and thermal protection. The inner hull is designed for pressure and radiative protection. Modern materials allow these to be lighter and stronger that those used in the Apollo project. The gap between the outer and inner hull will, of course be decontaminated using the methods and apparatus advocated for unmanned flight above (see Figure 3).

Some meteorite collisions may punch through the outer hull, but the resulting evaporated material will spray harmlessly onto the inner hull (ballistics theory).

If however, the meteorite is sufficiently large, some of the fragments may puncture the inner hull. Therefore self-sealing mechanisms should be employed so that if the inner hull is compromised, it can self-seal within a short time.

[Note that the flash of a meteorite collision is very energetic, which tends to decontaminate the local area of impact.] Very large objects (tennis ball sized) will normally cause catastrophic failure of the spacecraft, since the energy and momentum of the collision are very large.

Any contamination will probably be avoided since the flash and energy from such a collision would sterilise most of the spacecraft, and the destruction of the spacecraft from a sufficiently large explosion would ensure no contamination.

Therefore small and large accidents can be made to be non-contaminating.

However, medium sized leaks that cause contamination may still occur: those that do not self-seal or cause catastrophic destruction of the spacecraft. Because preventing contamination is so important [even taking priority over the safety of the crew] spacecraft may need their own self-destruct capability.

Hence in the event of any medium sized collision (that is non-sealable & non-catastrophic), in order to prevent contamination occurring, complete destruction of the spacecraft should be augmented using a self-destruct system.

Since most manned spacecraft allow extra-vehicular activity, airlocks must also include a decontamination phase. Remember that the radiative layer of a sealed spacesuit (and spacecraft) should be inside the pressure layer. This means that not only can a poisonous gas phase be included (see unmanned considerations), but also a radiative phase during airlock pressure equalisation.

In terms of pressure equalisation, most known "ecosystems are very low pressure (for example, Mars) and hence during airlock operation, air is vented to the outside. Thus filters need to be incorporated into the airlock design in order to prevent contamination, both on egress and return (see Figure 4).

It should be assumed that other planets may be capable of supporting life, even if such life forms are primitive (from Earth's perspective). However, for the reasons given above, it is very important that such life should not be destroyed by contamination from bacteria or viruses from Earth (and vice_versa!).

Another exploration example is Titan, where the ambient pressure is 1.5 bar (of nitrogen). Thus pressure equalisation will include allowing Titan "air" into the spacecraft. Thus the decontamination phase needs to take this into account (again both on egress and return). All filters (see Figure 4) must be fine enough to prevent even viruses from passing through, and should be made self-sterilising. [According to previous thinking, on Titan, a sealed spacesuit would not even be required!] Spacesuits can be thought of as small spacecraft and they too must never allow contamination. Remember, destruction of the spacecraft or astronaut has a higher priority than allowing contamination. Thus a self destruct capability will probably be needed for intermediate leakages from spacesuits.

Remember, very catastrophic events will probably not result in contamination because of the energy of such events. However, destruction of the astronaut should be prevented in the event of small leakages, and hence some form of self-seating should be incorporated into spacesuits as well as spacecraft.

Note that leakages from spacesuits will probably be caused by sharp objects causing incisions. Thus the energy of a leakage event will be small and hence will not sterilise the leak. Air may then leak from the suit quickly and therefore any self-sealing needs to be very fast.

One possible solution to this problem is the addition of breathing hydrogen.

Hydrogen is non-toxic but flammable. If a small leak occurs, the hydrogen can be then made to spontaneously combust causing an external flame, thus preventing contamination. Hence self destruction of the spacesuit may not be required for small leaks.

Although normal hydroxide scrubbers are good at filtering bacteria and viruses, since destruction of the astronaut or spacecraft be deemed more important than allowing contamination, with any intermediate leakage, the hydrogen & oxygen mix may also have to be augmented with other self-destruct explosives or incendiaries (see Figure 5).

Finally, as a managerial note, most space exploration is conducted by public civilian organisations and private sub-contractors. These organisations should consider the commercial (and other value) of space flight.

Although most information gathered by space exploration will be of a superficial or inexpensive nature, some findings may be of great value, and that value may be diminished by publishing findings prematurely or publicly.

This is because any organisation engaged in serious space exploration may require that previous findings to have been kept confidential until such time that it is needed. Hence a cautious approach to disclosure is advised.

Claims (9)

1. CLAIMS1. Spacecraft decontamination comprising tubes and tubules that supply lethal gases to all parts of a spacecraft that may come into (chemical) contact with external environments In order to prevent bacterial or viral contamination.
2. 2. Spacecraft decontamination as claimed in claim 1 whereby tubules should be placed so as to introduce gases to any unsealed parts of a spacecraft where normal diffusion is deemed insufficient, especially behind any unsealed radiative shielding.
3. 3. Spacecraft decontamination as claimed in claim 1 whereby the lethal gases comprise one or more gases poisonous to bacteria or viruses, introduced from external or internal sources.
4. 4. Spacecraft decontamination as claimed in claim 1 whereby where possible radiative shielding should be placed inside (or be the same as) the pressure shielding (i.e. sealed) so that either external or internal radiative sources may also be employed to eliminate bacteria or viruses.
5. 5. Spacecraft decontamination as claimed in claim 1 whereby, in manned craft, filters are incorporated, into all cabin vents and airlock valves, that are fine enough to prevent bacteria or viruses leaving or entering any pressurised part of the spacecraft.
6. 6. Spacecraft decontamination as claimed in claim 1 whereby a poisonous gas or radiative phase may also be included within airlocks during pressure equalisation with external environments.
7. 7. Spacecraft decontamination as claimed in claim 1 whereby a poisonous gas or radiative phase may also be included within docking collars prior to undocking.
8. 8. Spacecraft decontamination as claimed in claim 1 whereby leak prevention comprises a self-sealing system for small leaks and a self-destruct system for larger leaks.
9. 9. Spacecraft decontamination as claimed in claim 1 whereby spacesuits may supply additional hydrogen so that in the event of puncture the skin of the spacesuit causes spontaneous combustion to form an external flame.